by Schalk Schoeman, Rersearch Extension Manager, SAMAC
The polyphagous shot hole borer was positively identified on macadamias in the South Coast during March this year. Various bark borer species were observed on macadamias since 2014 and their incidence has been increasing every year since then. This situation is not unique and other countries with subtropical climates such as Australia and the USA (Hawaii) recorded similar increases. Climate change and more particularly small but incremental increases in mean ambient temperatures have been blamed for this phenomenon. In countries such as Canada, the effects of global warming are much more noticeable in the form of receding glaciers and increases in CO2 emissions due to thawing of permafrost and peat bogs. In this context beetles that normally require 2 years to complete their life cycles can now do so in less than a year. This has led to exponential increases in the numbers of an indigenous species with the concomitant destruction of thousands of hectares of pine forest.
The danger posed by these insects is that some species can transmit an ambrosia fungus which rapidly aids in killing a tree. This fungus blocks the vascular bundles of a tree and if sufficient beetle numbers are available, they will overwhelm the defences of the trees leading to rapid death. While the fungus/beetle association is of high interest to academics as it is possibly the first steps in the evolution of social behaviour in beetles most farmers are less exited when these uninvited guests show up on the farm. Nature will in time balance this situation out but what can we in the meantime do in South African macadamia orchards to minimise the impact of these destructive beetles.
It is said that these insects prefer stressed trees, so keeping trees as healthy as possible should be the first and obvious defence method. Stressed trees, especially in the early stages are not easily discernible and drones equipped with stress sensing cameras could provide an appropriate solution for early detection.
According to literature, some beetles are attracted to ethanol or turpentine, but due to the volatile nature of these compounds, they are unfortunately unsuitable for long-term surveillance.
Scouting teams should be specifically trained to be on the lookout for these pests and the best method will be to look for secondary symptoms such as dead or dying leaves as well as fine sawdust particles collecting in the crotches of the main branches as well as around the base of these trees. Noodle like projections consisting of fine sawdust can often also be seen on basal stem portions while some beetles make more open holes that is often very difficult to see. These openings are very small (and are therefore easy to overlook (± 1mm) and are scattered throughout the trees. Tree mortality can be very rapid as there is possibly an ambrosia fungus associated with at least some these insects.
In the case of a positive identification, sanitation measures in the form of tree destruction should immediately be carried out. Trees should not be dragged through the orchards as beetles could escape into previously undamaged parts of the orchards. Affected stems should be cut into smaller pieces and immediately destroyed by burning. Stems of surrounding trees should be sprayed with a mixture of a general fungicide such as propconazole as well as an insecticide such as chlorpyrifos as a preventative measure.
Growers with infested trees should immediately contact SAMAC as it is important to keep record of all infected locations to ensure that this problem is timeously and efficiently addressed. An important strategy for this group of pests is early detection and rapid response time as established colonies are often very difficult to manage once they are established in an orchard.
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The economic importance of the moth complex is often vastly underestimated as growers often tend to only take notice of the direct kernel damage reported by various kernel processing facilities. Typically, this type of damage seldom exceeds 5% which is accepted as a general action threshold in lieu of a more scientifically based value.
The shells of most macadamia cultivars begin to harden after mid-January and any nut borer/false codling moth larvae already present in the husks of infected nuts find it impossible to penetrate this seemingly impenetrable barrier. These larvae then feed on the husk tissue and in so doing they sever the vascular bundles connecting the nuts to the plant. Because the embryo is compromised, these nuts drop prematurely and are often reflected in processors reports as immature. Damage induced by these insects may also cause nut drop during the early part of the season and estimates of average crop losses of up to 15% are probably realistic. Of course, there are big differences between various cultivars with 816, 788 as well as most of the hybrid cultivars being preferred.
It is important to note that only the egg or recently hatched larvae can be controlled with conventional pesticides. Fortunately, the egg laying peak at the end of the premature nut drop phase (during late Nov/early Dec) is well synchronised which would be he time to apply a pesticide with an ovicidal or larvicidal activity. Once the larvae have burrowed into the nut they are effectively out of reach of any insecticide.
MOTH BORER COMPLEX ON MACADAMIA
Spray coverage is of the utmost importance as these insects prefer to oviposit in the darker and denser areas of the tree. Chemicals must be applied so that both areas of the nuts facing away from the spray rig as well as areas facing towards the spray rig are equally covered in fine droplets. High spray volumes do not necessarily equate to good coverage, in fact quite the opposite could be true. Over spraying will in most cases result in run-off with most of the pesticide ending up off-target (orchard floor).
Fortunately, there are a considerable amount of alternative environmentally sensitive methods that can be used to control this pest complex such as:
A range of products containing entomopathogenic viruses, nematodes, bacteria, and fungi. Except for the nematodes all products have to be sprayed and are therefore subject to problems highlighted above.
Various mating disruption products are also available, but these products are expensive as well as species specific. Make sure that you are targeting the correct specie before selecting this as an option
Inundative releases of the parasitoid Trichogrammatoidea cryptophlebiae is a very target specific method of control but its efficacy depends on the number of broad-spectrum products used in the orchard at the time.
Any spray against this complex from January onwards (when larvae are most visible in the nuts) are largely ineffective as generations overlap to such a degree that only a small portion of the new eggs and/or larvae are affected. Please be very critical when a spray is advised during this period.
In the first part one of this series of articles we have focused on the identification and selection of good quality trees, which in my opinion is one of the most critical steps in macadamia farming. Placing an order for tree should, in all cases, precede the land preparation phase of setting up a new orchard. That being said, imagine that you will receive your top-quality trees in three months’ time, there is a certain amount of soil preparation work that needs to be done, but where do we start? Well seeing that all farms are different, it will depend on a range of factors, but most importantly we will have to take into account what type of soil macadamias like to grow in.
Macadamias like to grow in soils that are:
Well drained
Highly aerated ‘
Well structured
Rich in organic matter
Low in plant available Phosphorous
Slightly acidic in nature
Considering these components, it seems rather logical that we should start our soil preparation practices by doing a thorough examination of the soil chemical and physical properties. In general soil physical properties are assessed by means of in field inspections of the proposed planting area. As a consultant, I typically ask farmers to dig a range of soil profile pits from which we can gather the following information:
The effective rooting depth or soil depth
The soil type that we are farming
The soil texture and structure
Are there any signs of wetness or a shallow water table?
In most cases, you don’t need to be a consultant to figure these things out, by digging a soil pit you can easily asses the aforementioned points as follows:
Effective rooting depth
Macadamias, require a soil that has an effective rooting depth of at least one meter.
The picture on the left is of a deep red soil, which is uniformly red up to a depth of >1m and is suitable for macadamia production.
The soil on the right has an effective rooting depth of around 35 cm and in most cases, it is not recommended to plant macadamias on these soils without making further adjustments to these soils. When assessing a soil for effective rooting depth, measure the depth of soil that does not have distinct changes in color.
Soil type and texture
Macadamias prefer well drained soils and as a result soils that have a high clay percentage are not recommended. Coarse textured soils are always preferred above fine textured soil in macadamia.
Take a handful of soil, wet it, and work it to the consistency of dough;
Continue to work it between thumb and forefinger and make a mud ball about 3 cm in diameter;
• Soil texture can be determined by the way the ball acts when you throw it at a hard surface, such as a wall or a tree.
• If the soil is good only for splatter shots (C) when either wet or dry, it has a coarse texture; • If there is a “shotgun” pattern (D) when dry and it holds its shape against a medium-range target when wet, it has a moderately coarse texture; • If the ball shatters on impact (E) when dry and clings together when moist but does not stick to the target, it has a medium texture; • If the ball holds its shape for long-range shots (F) when wet and sticks to the target but is fairly easy to remove, it has a moderately fine texture; • If the ball sticks well to the target (G) when wet and becomes a very hard missile when dry, it has a fine texture.
Signs of wetness
Macadamias absolutely hate it when their roots are standing in water or when the get exposed to extended periods of water logging. Soils that have signs of wetness should therefore be avoided when planting macadamias
When examining the soil pit look for yellow and grey colors in the soil profile. In general, these colors are indicative of soils that have been poorly oxygenated as a result of poor drainage and standing water. When you see red colors, these are usually good signs and the soils are oxygenated and well drained.
Following the soil physical inspection, it is critical to do a soil chemical analysis. These tests might be slightly expensive, but in the long run they are invaluable, seeing that most of the corrections that need to be made to the soil need to be made at the start of the tree’s life cycle. These test can be done at a range of laboratories and you typically need to get the soil analyzed for the following:
– Soil Texture
– Soil pH
– Extractable Phosphorous
– Extractable Potassium
– Organic Matter
– Sodium Content
– Calcium Content
– Zinc Content
– Magnesium Content
– Cation Exchange Capacity
Most of these components will be in a standard soil analysis. Nevertheless, once the soil analysis is received, a grower needs to consult with an agronomist to decide which soil ameliorants and nutrients should be added to the soil. Certain elements need to be added in the soil before the trees are planted, simply because certain nutrients do not move in the soil and if these elements are not added at the start, we will struggle to get the chemical soil balance correct in the future. Mobile and immobile soil elements are summarized in the following table:
Following the physical and chemical examination of the soil, a grower needs to make some decisions regarding the preparation of the soil. Put simply, the grower needs to decide how they want to prepare the soil before planting, in particular should the soil be ripped and should I plant my trees on ridges? Before we get into these details the simple soil preparation process is as follows:
Land Clearing
Deep Ripping
Ridging
Discing
The following needs to be considered when preparing the soil:
Deep Ripping – In general, the soil should be loosened to a depth of at least 800mm using experienced contractors. It is also advised that soil be cross-ripped as this will ensure that no compaction is present when to trees are planted. Remember that you will never have the opportunity to cross rip the orchard again.
Ridging – Ridging is something that needs to be assessed on a case by case basis. When soils are shallow or poorly drained there is no other option as to ridge, as trees need an effective rooting
depth of 1 meter. When soil is deep and well drained ridging should be considered carefully. Ridging has various advantages and disadvantages.
Advantages
• Soil compaction is confined to the interrow.
• Creates more room for roots.
• Creates a favourable water environment for roots.
• Controls disposal of excess surface water.
Disadvantages
• Results in increased soil drying.
• Makes the placement of organic matter on the soil impossible
• Becomes increasingly difficult to harvest mechanically, especially if ridges were constructed incorrectly.
• Creates potential erosion problems by channeling rainwater.
Discing – Discing is essential whether you are mounding soils or not. Discing allows the large clots created in the soil preparation process to be broken up and allows for a fine soil bed to be prepared. The finer soil bed creates better contact between the soil and the tree roots and ensures tree success. Furthermore, discing can be used to successfully incorporate pre-plant fertilizers and soil ameliorants into the topsoil.
IIn conclusion, preparing the soil for planting is a critical step in setting up the orchard for success. Using a horticultural consultant to assess your soil before planting could prove to be priceless in the long-term, and an experienced macadamia consultant should be able to provide you with good soil preparation plan.
Loading soil with biochar allows farmers to cut way back on irrigationAt high applications levels, researchers found that biochar can not only soak up a lot of carbon, but also reduce the need for irrigation by almost 40%.
Biochar – the charcoal product used to enrich agricultural soil and trap carbon—may have a hidden commercial benefit for farmers: it could lock moisture in the soil and save on gallons of costly irrigation.
The coarse, black material, made by combusting wood, grass, and other organic materials under low-oxygen conditions, helps to sequester carbon in the soil. Biochar’s major benefit in this regard is that it doesn’t easily decompose, meaning it can become a reliable long-term carbon sink. Its application to farmland soils is recognized as one way to turn agriculture into a force for climate mitigation, helping it redress some of its immense emissions damage so far.
Biochar also reduces the need for fertilizer by enriching the soil, and gives soils the capacity to soak up excess water, which can cut the risk of runoff that strips vital topsoil off the land.
But while experts have been aware of these environmental benefits for some time, the researchers on the new BCG Bioenergy study say that not as much attention has been devoted to how these advantages could translate to benefits for farmers – especially considering that they’re the ones who need to be motivated to spread biochar on their land. That’s where their research comes in.
They examined several studies which explored how biochar increases the water-holding capacity in the soil: that’s a measure of how sponge-like soil is—or in other words, how much water it preserves for plants to slurp up, later on. This meta-analysis revealed that adding biochar to sandy soils, in particular, has notable benefits. They also showed that larger particles of biochar, instead of a finely-crushed medium, made soil more absorbent, partly because it makes the ground more porous and available for storing water.
When the researchers then followed up this analysis with a field trial on a small test plot of farmland, they were able to show that, at high applications in the soil, biochar can reduce the need for irrigation by a strikingly large amount: almost 40%.
Based on this discovery, the researchers identified regions across the United States where sandy farm soils infused with this product would result in large water savings. These are spread mainly across the north, north east, south east, and western parts of the United States—places where, in many cases, there’s a heightened threat of drought. Discover more: How climate change could shorten pregnancies
The researchers conclude that investing soil with biochar would enable farmers to cut back on irrigation that could save them huge amounts of money. “There’s a lot of biochar research that focuses mostly on its carbon benefits, but there’s fairly little on how it could help stakeholders on a more commercial level,” they say.
To remedy that, they also used their findings to develop a formula that farmers can use to calculate the precise water-saving potential of adding biochar to their land.
One caveat to the study is that farmers would need to apply biochar at much higher rates than is currently typical, to achieve similar savings. Though even at lower quantities on sandy soils, it would bring water-saving benefits. The researchers also note that despite the focus on sandy soils in their study, biochar could bring substantial benefits in other types of farmland too: most of the studies they examined just happened to focus on sandy soils.
Biochar may also have other, subtler benefits for farmers. Consistently dry soils can cause stress in plants that compromises their resilience to disease, and their productivity as well. So shoring up water reserves in the soil through biochar may be good for farmers’ bottom lines in other ways: it could help to create the conditions for healthier crops that require fewer costly pesticides, and which produce higher yields and generate more profit.
In any case, agriculture now accounts for 80% of the United States’ water consumption—a massive amount that will need remedying, under the threat of climate change and increasing drought. Farmers are going to need to use whatever sustainable resources they can to bring that consumption down. Biochar—which already brings many other environmental co-benefits—is at least one viable candidate to add to that toolbox.
The Effect of Pesticide and Fungicide Application on Apis mellifera (honey bees)
In the previous article we looked at one of the challenges that face beekeepers in South Africa which is theft and vandalism of their bee hives.
The second and very serious challenge that beekeepers face is directly related to the farming practices of the sites where the bees are situated. It is fully understood that in order to protect crops from weeds, fungi and pests farmers have to use chemicals and pesticides. As the target of many of these chemicals are insects, it has to be taken into serious consideration that most beneficial pollinators are also insects, including the African honey bee Apis mellifera scuttelata that occur in the summer rainfall areas of South Africa.
There is now widespread consensus that pesticides are having a devastating effect on the sustainability of pollinator populations which is much more than just the effect it has on honey bee colonies. Numerous scientific studies have been done across the globe to ascertain why pollinator and honey bee populations are decreasing at such an alarming rate. Many of the pesticides and chemicals implicated in these effects on pollinators are regarded as “safe” to use even when honey bee colonies are present.
As a beekeeper I am in no way an expert on chemicals or pesticides, but the devastation and economic losses incurred by colonies being poisoned are sadly felt all too frequently. Seeking to understand how chemicals and pesticides are affecting our colonies are an ongoing and difficult task for beekeepers. Constant development of new chemical and pesticide formulations make it very challenging for all parties seeking to minimise risk to pollinators to keep up with new releases and their effects. In addition, any discussion of findings and/or interpretations of the effects of pesticides/chemicals can be potentially contentious. I believe however that it is necessary to consider as much information as possible in order to guide our actions to have as little impact on the ecology of our area as possible. This is a compilation of my own desktop research in order to understand the effects of pesticide and chemicals on my colonies. The losses caused are very real.
Pesticides that have sub-lethal or chronic effects on the colony’s health are even more devastating to the sustainability of our colonies as they slowly deteriorate over a period of weeks or even months. In this way acute toxicity is almost preferred as the forager bee will die before making it back home which means that the queen bee, brood and nurse bees are not affected and the colony survives. Alternatively, when the bee takes an insecticide back to the colony through contaminated pollen or nectar or even on its body, it can potentially contribute to widespread colony death.
Many farmers regard some pesticides as “nontoxic or bee friendly”. How the toxicity of these chemicals are generally measured is to determine what the acute exposure dose would be to cause 50% of the exposed population to die (LD= lethal dose). Nontoxic therefore does not mean that no bees die, just that a much higher dose is required to kill 50% of the test population.
Use of Organophosphates (OPs), Methylcarbamates (MCs) & Pyrethroids (pyr)
According to Dr Hannelie Human Neonicotinoids are neurotoxic insecticides and even field-realistic sublethal doses result in impaired navigation, homing, and olfactory learning in honeybees. It disrupts neural pathways and thermoregulation processes, and in addition decrease foraging and flight ability. This class of insecticide is highly toxic to honeybees in very small quantities via synergistic interactions between multiple stressors. Exposure to these chemicals can affect the entire colony and future generations since they are highly water soluble and therefore have the potential to contaminate non target flowering plants and weeds in addition to the target crop (Human H 2020, Personal communication, 12 October).
It has been shown in recent studies that honey bees experience a learning and memory impairment after ingesting even small doses of the often used insecticide chlorpyrifos, potentially threatening their survival. Chlorpyrifos is a highly neurotoxic organophosphate pesticide used worldwide on crops including macadamia. Exposure to this chemical may be reducing bees effectiveness as nectar foragers and pollinators. Both the lethal was well as sub-lethal effects on bees need to be taken into account.
In other studies it has been found that exposure to sub lethal doses of insecticides known as pyrethroids including permethrin, which is often used on macadamia orchards, may reduce honey bee movement and social interaction. The functioning of a healthy honey bee colony relies on all its members being able to perform all of the necessary duties, such as foraging for food and communicating with other bees. If sub lethal exposure to pesticides affect or reduce the ability for movement, social interaction and feeding of bees, it could potentially impact the whole colony performance and/or survival.
Fipronil is one of the main chemicals blamed internationally for the spread of colony collapse disorder among bees. It has been found by the Minutes-Association for Technical Coordination Fund in France that even at very low nonlethal doses for bees, the pesticide still impairs their ability to locate their hive, resulting in large numbers of bees getting lost with every foraging expedition which may negatively affect the development and maintenance of colonies. Fipronil has also been found to be highly toxic to fish and aquatic invertebrates.
In some other studies it has been found that the fungicides may be having a more profound effect on bees than previously thought. It is especially true when a cocktail of chemicals is used. Fungicides especially affect brood development by reducing the micro-organisms that ferment bee bread and therefore make it palatable to the young developing brood. This makes our modern farmland a very inhospitable place for bees. Insecticides are meant to kill insects, so people have been really interested in how insecticides kill beneficial insects. But fungicides are not meant to kill insects, so they’ve often been passed over.
What can farmers do to minimise the effect of their pest control programmes on pollinators?
Pesticide application to any blooming flowers should be avoided as honeybees are attracted to all types of blooming flowers including weeds and cover.
If blooming flowers absolutely must be sprayed with pesticides, they should be sprayed in the evening or night hours as bees are not in the field at that time.
If aerial spraying is required, spray planes should not turn over fields containing blooming crops or weeds. Ground application is generally less hazardous than aerial application because there is less drift and smaller areas are treated each time.
Limit the contamination of water sources. Bees drinking water which contains pesticides can be very hazardous to them, even water on foliage or flowers.
The following are some classic signs of Bee Poisoning:
Large numbers of dead and dying honey bees in front of the hives
Increased defensiveness (caused by most insecticides)
Lack of foraging bees on a normally attractive blooming crop (most insecticides)
Abnormal jerky, wobbly, or rapid movements; spinning on the back (organophosphates, organochlorines, and neonicotinoids)
Forager disorientation and reduced foraging efficiency (neonicotinoids)
Immobile, lethargic bees unable to leave flowers (many insecticides)
Regurgitation of honey stomach contents and tongue extension (organophosphates and pyrethroids)
Performance of abnormal communication dances, fighting, or confusion at the hive entrance (organophosphates)
Bees seeming unable to fly. Bees move slowly as though they have been chilled (carbaryl).
Dead brood; dead, newly emerged workers; or abnormal queen behaviour, such as egg laying in a poor pattern (carbaryl)
To minimise the effect on pollinators and especially honey bee colonies, the following are recommended:
Consider alternatives to pesticides. Well-planned, integrated pest-management programs often are less dangerous to pollinators and other beneficial insects than last-minute efforts to suppress pest outbreaks.
Treat only when necessary by doing scouting – look before you shoot! Scouting and economic thresholds ensure that pesticides are used only when their benefits (the rand value of crop loss prevented by pesticide use) are greater than the cost of the pesticide and its application. In this equation, also weigh the value of pollination to your crop and the value of hives to beekeepers.
Treat only the areas where necessary – NO COVER SPRAYS
Always use minimum risk pesticides – Use insecticides that are least toxic to bees. Choose the least hazardous insecticide formulation.
Do not apply pesticides unless absolutely necessary whilst there are still flowers in the orchard. This is difficult where several cultivars are present as flowering periods differ.
ALWAYS follow the instructions on the label
Mixing pesticides with sugar will attract bees
Do not spray in conditions where spray can drift onto hives or fields supporting bees
Avoid tank mixing insecticides and fungicides
Remember fungicides also affects bees as it limits the fermentation of pollen making it useless to the bees and can even lead to starvation of brood dependent on pollen protein
Apply insecticides in late evening or night when bees are not foraging (generally between 8 p.m. and 3 a.m.) Evening applications are less hazardous to bees than early morning applications. Warm days and nights and full moon conditions can extend the foraging period; therefore applications may be necessary later in the evening under unusually warm conditions.
Do not apply insecticides when cool temperatures or damp conditions are expected after treatment. Residues will remain toxic to bees for a much longer time under these conditions.
Contact the beekeeper at least 48 hours in advance to inform him or her of your pesticide application plans so he/she can confine or move the colonies before pesticides are applied and losses incurred.
Always notify neighbouring farmers in order that their bees and beekeepers can also be protected
Remember: A WET BEE IS A DEAD BEE
Honey bee recovery from pesticide poisoning
If a honey bee colony has lost many of its foragers, but has sufficient brood and adequate stores of uncontaminated pollen and honey, it may recover without any intervention. Move bees to a pesticide-free foraging area if available. If sufficient forage is unavailable, feed them with sugar syrup and pollen substitute, and provide clean water to aid their recovery. Adding probiotics and trace minerals to your artificial feed may assist the colony to recover. Protect them from extreme heat and cold, and, if needed, combine weak colonies.
If the pesticide has accumulated within pollen or nectar stores, brood and workers may continue to die until the colony is lost. Many pesticides freely transfer into beeswax, and you may consider replacing the comb with new foundation, drawn comb from unaffected colonies, or shaking the bees into a new hive and destroying the old comb. Artificial feeding with added probiotics and trace minerals in the sugar syrup and pollen substitute may assist the colony to recover. Replacing brood comb on a regular schedule (typically 3 to 5 years) may prevent accumulation of pesticides to lethal levels in brood comb wax.
In 1962 Rachel Carson wrote the book Silent Spring. She introduced the world to the dangers of pesticides that started the Global Environmental Movement, but now more than 50 years later, we still seem to be ignoring the dangers of pesticide use. Can we still claim ignorance? We need to see the bigger picture that everything is connected – when there are no longer what we consider “pests” there might be nothing left at all.
The health of our environment is in our hands…. We can all make a difference
Casida JE, Durkin KA (2013) Neuroactive insecticides: targets, selectivity, resistance, and secondary effects. Annu Rev Entomol 58
The summer rains came early this season but the rain also brought a reason for great concern for the macadamia growers in the form of possible flower diseases. Flowering this season was extremely good, but the rain came at a time when many flowers were only a few days (5-10 days) past the full bloom stage and very susceptible to blossom blight. Some flowers were fortunately further developed with many flower remnants falling from the racemes just as the ovaries began to swell. These flowers are not susceptible.
In South Africa blossom blight is caused by the fungus Cladosporium cladosporioides. Symptoms: Diseased racemes are covered with olive grey patches of mycelia and abundant spores. The fungus is present every year and the significance of the disease is dependent on weather conditions prevailing during the susceptible flower stages. Orchard epidemics can occur when rainy weather prevails for three or more days and temperatures range from 20 to 25°C during this period. As these weather conditions were experienced the past few weeks severe blossom blight epidemics occurred in many areas, sometimes irrespective of preventative sprays applied.
In trials the ARC-TSC conducted under the leadership of Maritha Schoeman, the effect of spraying were compared with non-spraying in terms of fungal presence and nut set. A total of 1920 racemes were monitored during the season at six production sites, on cultivars 816 and Beaumont. Sprays were applied by the growers when flowers were fully extended and have just started to open and again three weeks later. At the first rating it was evident that spraying did reduce the presence of fungal growth on the racemes from 75% to 0% at five of the producers. The reason for the lack of reduction at the one producer was because the fungicide was applied as a light cover spray compared to a full cover spray at all the other producers. Results clearly showed that fungicides had an effect on the fungus. At the second rating of the disease, when nuts were ± 20 mm in diameter and withered flower parts and unset nuts had already fallen, fungal incidence decreased significantly even in the unsprayed blocks (20% vs 75% at first rating). The reason for this is that there were little dead or dying tissue left for the fungus to live on.
There was a fair amount of fungus present in the unsprayed trees, and zero in the sprayed trees but there was not a huge difference between sprayed and unsprayed blocks in terms of nut set. These results hinted that the fungus is maybe of little importance, but this needs to be confirmed. There is still a lack of adequate knowledge about the disease and its influence on nut set in particular.
Spraying should only be done preventatively if there is a moderate to severe disease risk for flower blight and the aim is to apply fungicides so that it systemically penetrate flowers before they enter the stage were flowers have been open for 5 to 10 days. If a disease epidemic occurs and a large portion of the flowers are in the stage where all flowers on the raceme have already been opened 5-10 days, it is too late to begin spraying. During dry seasons disease control are not warranted at all.
Sprays should be considered on a site by site basis and at most sites, intervention will in most seasons not be required. Pruning or thinning out of trees is extremely important allowing more sunlight into the trees, thus rendering conditions inside the orchard unfavorable for disease proliferation, at the same time promoting flowering and nut set.
In Australia, Botrytis cinerea is the main cause of Blossom blight and Cladosporium to a much lesser extent. Researchers there also found that due to a lack of adequate knowledge about these diseases, attempts to control raceme blights with fungicides during severe outbreaks have mostly not been successful. They also found an absence of Botrytis blight during disease conducive periods when heavy rain actually stripped all the dead flower parts from the raceme leaving no dead or dying tissue for the fungus to live on.
With the first heavy rain to follow from now on, dead tissue will also be stripped from the racemes leaving no dead tissue for the fungus to live on. The application of any kind of fungicide at this stage is not recommended as it is deemed too late.
We often get asked the question “how old will my macadamia trees get”? Well, no one is really sure, but what we do know is that they will be around to feed our grandchildren when taken care of. The real question that we need to ask ourselves is will our trees be able to produce above average yields for the next 40 years? Well, as most consultants (the good ones at least) would tell you is that it depends. On what you may wonder? It depends on a range of factors including water, nutrition, tree health etc., but none of these factors are as important as starting with good quality trees and a well prepared and planned orchard. In most orchards that we encounter, especially the ones that collapsed directly after planting, the biggest problems are often related to poor quality trees, poor planting techniques or an unfortunate combination of both. It is therefore essential to ensure that you have good quality trees and that you plant these trees correctly.
So what is a good quality tree?
This is the same as asking what is the best vehicle to have, and there is not a single right or wrong answer when it comes to tree quality. There are , however, a few things that you need to look out for when buying and receiving trees.
Good trees should:
Be fairly uniform in size and color
Be free from any nutrient deficiencies
Be free from pest and diseases
Have well developed root systems and an abundance of new white root growth
Have a strong graft union
Have a fairly straight stem
Be at least 60 cm tall
Not be grafted too high (>60 cm) or too low (<10 cm)
Have a well-drained medium which is preferably free from soil
Bad trees usually:
Lack uniformity in size and color
Have a range of nutrient deficiency
Have a range of pests or diseases
Have poorly developed root systems
Have poor graft unions
Have crooked or damaged stems
Are too tall (>1.5 m) or too short (<50 cm)
According to the South African Macadamia Industry standard, the following points should be noted when purchasing trees:
Avoid trees that are stunted, pot-bound or infested with pests or infected by a disease. To ensure the orchard gets off to a good start, select vigorously growing trees free from nutrient disorders, insect pests and disease with a good healthy root system. Buyers should look closely for:
• A healthy well-formed root system that is not spiralled or twisted.
• A root system that has masses of very fine roots throughout the potting mix.
• A potting mix that is well-drained, friable, and free from waterlogging and hard compacted clods.
• Healthy, vigorous, well-formed growth with dark green foliage/plant leaves.
• A minimum of 150 mm of hardened new growth above the graft. This should consist of at least two growth flushes with a strong graft union.
• Trees that are free from insect pests and diseases.
When examining the roots the following scenarios are unacceptable:
It is highly recommended that you visit the nursery from which you have ordered your trees multiple times before the trees arrive on your farm. During these visits you should investigate root development, tree color and size, and try to gauge the number of trees allocated to your order to ensure that your trees that have been ordered are in the nursery. You should also ask your nurserymen the following question on a regular basis:
1. Are my trees still on track for the agreed upon delivery date?
2. Can you confirm the cultivars and rootstock used in my batch of trees?
3. Could you please let me know well in advance if there are any problems with regards to the grafting success rate?
4. Have my trees been pruned/manipulated as per our agreement?
5. Would you mind if I bring my consultant to your nursery to come and inspect my trees?
In conclusion, growers are advised to order trees well in advance of their proposed planting date to avoid any disappointment in tree quality. Most growers are desperate for trees, which is understandable, but waiting an extra six months for your trees could be the difference between a orchard yielding 5 tons/hectare every year for the next 50 years and an orchard that struggles to yield 2.5 tons/hectare in a good year. Selecting a good quality tree is one of the most important things that a grower can do to ensure that they are setting up their orchard for future success.
When it comes to managing water and nutrients in macadamias, we are often left with two options. We either have to spend a fortune on high-end equipment to help us manage our resources or we simply neglect to monitor water and nutrient use. Fortunately, some basic and inexpensive tools are available to help growers manage these critical components of the production system. Wetting front detectors (WFD) were developed in response to low adoption of existing irrigation tools. Prof. Richard Stirzaker describes a WFD as a switch, which alerts the irrigator that a front of a given strength has passed a given depth in the soil. The WFD comprises a specially shaped funnel, a filter and a mechanical float mechanism (Figure 1).
FIGURE 1 FullStop Wetting Front Detector (WFD). The funnel part is buried in the soil with the black tube protruding above the soil surface. When a wetting front reaches the detector, a red indicator pops up. Detectors are usually placed in pairs, about one third and two thirds down the active root zone.
When rain falls or the soil is irrigated, water moves downwards through the rootzone. The infiltrating water converges inside the funnel and the soil at the base becomes so wet that water seeps out of it, passes through a filter and is collected in a reservoir. This water activates a float, which in turn operates an indicator flag above the soil surface. There are no wires, no electronics and no batteries.
According to Prof. Stirzaker, If the soil is dry before irrigation, the wetting front will not penetrate deeply because the dry soil absorbs most of the water. A long irrigation would be needed to activate a detector. However, if the soil is relatively wet before irrigation, it cannot store much more water, so the wetting front penetrates deeply (Stirzaker 2003, Stirzaker and Hutchinson 2005).
He further notes that knowing how deep a wetting front moves into the soil is critical for irrigation management. If a crop is given frequent but light sprinklings of water, the wetting front will not go deep and the WFD will not be activated. Much of the water will evaporate from the soil surface. If too much water is applied at one time, the wetting front will go deep into the soil, perhaps below the rooting depth of the crop, wasting water, nutrients and energy.
Furthermore, the WFD retains a sample of water which can be extracted via a tube using a syringe. This can be analysed for its salt or nitrate concentration using simple tools such as nitrate test strips and an Electrical conductivity (EC) sensor. Monitoring EC or nitrate levels can tell you more about irrigation management than measuring water content itself. For example, nitrate levels will drop sharply if over-irrigation occurs (Stirzaker and Wilkie 2002). Depending on the quality of the irrigation water, EC levels will gradually rise during periods of under-irrigation (Stirzaker et al 2004, Stirzaker and Thomson 2004).
Of particular interest to most growers will be watching the videos of Prof. Stirzaker explaining these and other useful irrigation and nutrient management tools in his own garden:
These tools and many other, reasonably priced and practical tools, are explained in great detail on the Virtual Irrigation Academy (VIA) website (https://via.farm/). VIA is a global community that aids farmers and communities to learn how manage water and nutrients to grow more food.
Why are these tools so useful in macadamia production systems?
Macadamias have shallow root systems and are particularly sensitive to overwatering. The sensitivity to overwatering is not only linked to the increased risk of root rot (Phytophthora), but also to the fact that nutrients are leached passed the rootzone. Using simple tools such as a WFD, macadamia growers would be able to monitor that both water and nutrients are not going past the rootzone, which will not only help them use resources more efficiently but could potentially increase both yield and quality. Furthermore, these tools are reasonably priced, practical and user friendly and could therefore be used by an array of macadamia grower.
For more information regarding these and other tools, please feel free to contact the folks on the VIA platform, or to contact myself (theunis@darwinhort.com).
References
Stirzaker RJ and Hutchinson PA (2005). Irrigation controlled by a Wetting Front Detector: field evaluation under sprinkler irrigation. Australian Journal of Soil Research (in press)
Stirzaker R, Stevens J, Annandale J, Maeko T, Steyn J,Mpandeli S, Maurobane W, Nkgapele J & Jovanovic N(2004). Building Capacity in Irrigation Management with Wetting Front Detectors. Report to the Water Research Commission No. TT 230/04.
Stirzaker R and Thompson T (2004). FullStop at Angas Bremer: A report on the 2002-3 data to the Angas Bremer Water Management Committee Stirzaker RJ (2003).
When to turn the water off: scheduling micro-irrigation with a wetting front detector. Irrigation Science 22, 177-185.
Stirzaker RJ and Wilkie J (2002). Four lessons from a wetting front detector. Irrigation Australia 2002 conference, 21-23 May, Sydney.
The plight of the honeybee is a global concern. The agricultural sector is heavily reliant on bee pollination (some industries more so than others), impacting on crop quantity and quality i.e Blueberries that have virtually unmarketably small fruit without adequate pollination. As the sector expands to meet market demands (both national and global), it is progressively demanding more from managed bee services. It has been proven that both the quantity and quality of fruit set on Macadamia trees improve when the flowers are well pollinated. The main pollinator specie used on Macadamia orchards is honey bees.
There is a misconception amongst both farmers and public alike about what beekeeping is about and how easy and lucrative the industry is to operate in. South Africa is not a bee forage friendly country and apiculturists are struggling to maintain the industry. (More about this in the upcoming instalment on Beekeeping and the challenges that face the industry part three). There is a real risk that there will not be enough healthy bee colonies to service the agricultural industry, in terms of pollination services, in the very near future, especially with the rapid increase of target orchards, especially Macadamia and Avocado.
This situation is compounded by the incredibly high rate of theft and vandalism experienced by virtually all large and commercial beekeepers, but also with the many smaller beekeepers. It is almost an industry norm for commercial beekeepers to have to absorb between 25 – 30% losses due to theft and vandalism. Although this industry is by no means the only one affected by this scourge, it has a serious knock-on effect for clients of beekeepers, the agricultural sector. Having those type of losses make providing enough swarms for pollination demands difficult and also affects the price that has to be charged for this service The estimated loss (in terms of equipment and existing honey harvest loss; swarm replacement value; and potential pollination and honey production earnings) is between R3500 – R4500 per hive. This is significantly higher than what most people realise.
Although much of the vandalism (where honey is stolen and hives damaged in the process) is performed by non-beekeepers for personal use and resale, the theft of hives is increasingly becoming a huge problem. This happens especially just before or during the pollination season which gives rise to the assumption that this is perpetrated by either other beekeepers of farmers that want to use these swarms to rent out for pollination services or for pollination of their own orchards.
Due to the scale of the problem, insurance of beehives are almost never an option due to high premiums if the insurance company is willing to provide cover. Several methods to limit theft are implemented such as cameras, tracking devices, concrete hives and steel cages but one can rarely protect all your sites and assets. The Department Agriculture, Land Reform and Rural Development (DALRRD) has implemented a registration system for all beekeepers whereby a permanent registration number is issued and registration is compulsory even if you only have one beehive. Currently registration has to be renewed every 24 months with updated details as stipulated by the Agricultural Pest Act 36 of 1983 and Control Measures Relating to Honey bees No. R1511, (https://www.sabio.org.za/wp-content/uploads/2020/03/R1511-of-2019-Beekeeping-Control-Measures.pdf) Each beehive belonging to the farmer or beekeeper is also required by law to be marked with the relevant registration number. This will enable beekeepers to be able to positively identify their property if stolen. At the same time the owner can be located if needed. It is strongly advised to brand or router the number onto the hive which makes removing it by thieves much harder as paint can just be sanded off. Should hives with an existing registration number be purchased, the new registration number should be added in addition to the old number and DARLLD notified of the purchase using the available registration form.
What can farmers especially those that rent hives for pollination, do to help? According to the above-mentioned Control Measures, hives are to be marked with the permanent registration number of the beekeeper and no unmarked hives should be allowed. Also: “(Clause 9) No person may utilise the services of a beekeeper for the purposes of carrying out any beekeeping activities unless the beekeeper is in possession of a valid registration certificate issued in terms of control measure 2 (1)”
It is therefore imperative to obtain the registration certificate from the prospective pollination/beekeeping service provider and to ensure that the hives placed are all clearly marked with that registration number. Should that beekeeper have purchased or sub contracted hives marked with another number, proof of such purchase/sub contract rental should be at hand. If there is doubt, the validity of registration can be confirmed with DALRRD.
After speaking to several other beekeepers, members of the SABIO Board, inspectors of DALRRD and members of the SA Police, we request that farmers allow (or even request) spot inspections by the inspector of DALRRD accompanied by a SABIO Board Member and/or local commercial beekeeper (if available) on their property to ascertain that pollination service providers are registered and that no stolen bee hives are used. This will greatly assist the industry as a whole by making it harder for the criminal element to get away with the crime of hive theft.
Beekeeping and the challenges that face the industry part one
By Inge Lotter 4 September 2020
The plight of the honeybee is a global concern. The agricultural sector is heavily reliant on bee pollination (some industries more so than others), impacting on crop quantity and quality i.e Blueberries that have virtually unmarketably small fruit without adequate pollination. As the sector expands to meet market demands (both national and global), it is progressively demanding more from managed bee services. It has been proven that both the quantity and quality of fruit set on Macadamia trees improve when the flowers are well pollinated. The main pollinator specie used on Macadamia orchards is honey bees.
There is a misconception amongst both farmers and public alike about what beekeeping is about and how easy and lucrative the industry is to operate in. South Africa is not a bee forage friendly country and apiculturists are struggling to maintain the industry. (More about this in the upcoming instalment on Beekeeping and the challenges that face the industry part three). There is a real risk that there will not be enough healthy bee colonies to service the agricultural industry, in terms of pollination services, in the very near future, especially with the rapid increase of target orchards, especially Macadamia and Avocado.
This situation is compounded by the incredibly high rate of theft and vandalism experienced by virtually all large and commercial beekeepers, but also with the many smaller beekeepers. It is almost an industry norm for commercial beekeepers to have to absorb between 25 – 30% losses due to theft and vandalism. Although this industry is by no means the only one affected by this scourge, it has a serious knock-on effect for clients of beekeepers, the agricultural sector. Having those type of losses make providing enough swarms for pollination demands difficult and also affects the price that has to be charged for this service The estimated loss (in terms of equipment and existing honey harvest loss; swarm replacement value; and potential pollination and honey production earnings) is between R3500 – R4500 per hive. This is significantly higher than what most people realise.
Although much of the vandalism (where honey is stolen and hives damaged in the process) is performed by non-beekeepers for personal use and resale, the theft of hives is increasingly becoming a huge problem. This happens especially just before or during the pollination season which gives rise to the assumption that this is perpetrated by either other beekeepers of farmers that want to use these swarms to rent out for pollination services or for pollination of their own orchards.
Due to the scale of the problem, insurance of beehives are almost never an option due to high premiums if the insurance company is willing to provide cover. Several methods to limit theft are implemented such as cameras, tracking devices, concrete hives and steel cages but one can rarely protect all your sites and assets. The Department Agriculture, Land Reform and Rural Development (DALRRD) has implemented a registration system for all beekeepers whereby a permanent registration number is issued and registration is compulsory even if you only have one beehive. Currently registration has to be renewed every 24 months with updated details as stipulated by the Agricultural Pest Act 36 of 1983 and Control Measures Relating to Honey bees No. R1511, (https://www.sabio.org.za/wp-content/uploads/2020/03/R1511-of-2019-Beekeeping-Control-Measures.pdf) Each beehive belonging to the farmer or beekeeper is also required by law to be marked with the relevant registration number. This will enable beekeepers to be able to positively identify their property if stolen. At the same time the owner can be located if needed. It is strongly advised to brand or router the number onto the hive which makes removing it by thieves much harder as paint can just be sanded off. Should hives with an existing registration number be purchased, the new registration number should be added in addition to the old number and DARLLD notified of the purchase using the available registration form.
What can farmers especially those that rent hives for pollination, do to help? According to the above-mentioned Control Measures, hives are to be marked with the permanent registration number of the beekeeper and no unmarked hives should be allowed. Also: “(Clause 9) No person may utilise the services of a beekeeper for the purposes of carrying out any beekeeping activities unless the beekeeper is in possession of a valid registration certificate issued in terms of control measure 2 (1)” It is therefore imperative to obtain the registration certificate from the prospective pollination/beekeeping service provider and to ensure that the hives placed are all clearly marked with that registration number. Should that beekeeper have purchased or sub contracted hives marked with another number, proof of such purchase/sub contract rental should be at hand. If there is doubt, the validity of registration can be confirmed with DALRRD.
After speaking to several other beekeepers, members of the SABIO Board, inspectors of DALRRD and members of the SA Police, we request that farmers allow (or even request) spot inspections by the inspector of DALRRD accompanied by a SABIO Board Member and/or local commercial beekeeper (if available) on their property to ascertain that pollination service providers are registered and that no stolen bee hives are used. This will greatly assist the industry as a whole by making it harder for the criminal element to get away with the crime of hive theft.
