Part of the MPC field day group at Tweebreena orchard discussing gully erosion management

Featured topics were:

• Working safely near overhead power lines in orchards
• Canopy management – tree removal at ‘Tweebreena’
• Nut in shell drying using a ‘Bungay style drying system’
• Erosion control

Working safely near overhead power lines

Michael Dall from WorkCover addressed the danger to macadamia growers when working near power lines in their orchards.

There is a Code of Practice – Work Near Overhead Power Lines available to macadamia growers, setting out the permitted safe working distance which must be maintained from power lines.

The Code illustrates various voltages of power lines and the critical factors which apply. The code is available from the local office of WorkCover or on line at www.workcover.nsw.gov.au

Canopy Management

Using tree removal the Jones family embarked on a canopy management plan to introduce light back into their mature trees and onto the orchard floor.

The orchard has two plantings with two different densities. The first in the early 80’s was on a 10 x 5 metre spacing and has 246, 508, H2, 344 and 741 varieties. The second planting in the early 90’s was planted at 8 x 5 metres with 344 and 660.

The close spacing of this second planting caused trees to compete for light, creating tall trees with hollow centres and little canopy growth near the base due to lack of light penetration.

These trees have expanded to cover the inter-row space which introduced problems of loss of ground cover, soil erosion, and an orchard floor that remains wet through harvest with a subsequent major reduction in yield.

Greg Jones said: “Work to remove every second tree in every second row (25% tree removal) in the 8 x 5 blocks began in 2010.Thinning of the remaining rows will take place at a later date. Little sunlight reached the orchard floor in the 8 x 5 blocks and production was very low. These areas did not dry-out during harvest and harvesting was very difficult in the wet conditions. ”

“Since the tree thinning” said Greg, “we now have a lot more sunlight in the trees and on the orchard floor, ground cover is returning in the form of weeds and some grass and the ground dries out much better. We have planted smother grass in these areas as there is now plenty of light to allow it to grow. The trees are producing new shoots and are opening up and filling in the space from where the trees were removed.”

The removed trees were stacked up and then taken away by Surfmill contracting for free as part of the co-generation power plant at Broadwater Sugar Mill.

This first stage of tree removal was a big job, with trees cut and tractors used to haul the felled trees out. To make the job easier and to retain the wood chip as a mulch on the farm, David Jones recently bought an 18 inch self powered chipper and a medium sized excavator with a grab to feed it. The remaining 8 x 5 blocks will have 25% of the trees removed by felling with chain saws. After felling it will be chipped, with the wood chip spread under the remaining trees.

“After we finish the 8 x 5 metre blocks we will probably start on the 10 x 5 blocks. We will see how this work goes and then make our decision based on the results”, said Greg Jones.

Nut in Shell drying.

David Jones (centre) describes his Bungay style macadamia drying system and how it has assisted in post harvest quality retention

Tweebreena a 40 tonne ‘Bungay style’ macadamia drying system

“We had to hold the nuts in the outside blowdown silos for far too long before we could resort during wet weather. As a result of the nuts stored and remaining wet, we had a reduction in quality from brown centres, discolouration and mould. This new system dries the nuts quickly and efficiently and we can get them to the factory for processing with the original quality retained. The bins hold about a week’s harvest” said David.

Air recirculated through the four by ten tonne bins is sourced from just under the roof in the dehusking/machinery shed. Dry air is pumped by fan in the base of each bin through the nut bed where it accumulates moisture from the nuts.

When the circulated air accumulates to a pre determined moisture level, an exhaust fan purges some moisture laden air from above the nut bed. During purging new dry air is introduced and the cycle re-commences. If the introduced air is not sufficiently dry to be effectively used, a bank of electrical elements in the intake duct is turned on by the system. Heat expands the air which can carry a higher level of moisture. The elements may be in use for as little as 60 seconds in this process. When the nuts reach a pre determined moisture level the computer controlled system closes down.

The original ‘blow down’ silos are now only used for pre delivery storage of dried nut in shell.

Erosion Control.

Trees had been planted across a steep gully at the rear of the orchard prior to purchase by David. This gully traverses the tree rows for some 250 metres and carries a lot of water during a heavy rainfall event. Trees planted in the gully shaded the ground and as a result, grass died out.

With no protection, the gully eroded and the area became very difficult to manage and caused problems for harvesting.

The gully restored following damage created by soil erosion

With assistance from Gerry Ryan of the Catchment Management Authority (CMA), a plan to reconstruct the gully was formulated.

In 2009 trees were removed from the gully allowing sufficient light to reach the gully base so grass could regrow.

Large chunks of crushed rock were spread across the gully to revert the base shape from a ‘V’ to a dish shape. Rocks were then covered with soil.

The area was rolled and seeded with millet, which grew rapidly and held the soil in place. Straw bales were fixed in place across the gully at 24 metre intervals on tree lines to slow the flow rate of water during rainfall. Then on June 3rd 2010 the area was drenched by a rainfall event which delivered 200mm in a few hours. Much of the work held firm. There was however a trench formed down the centre of the gulley and several holes formed that corresponded with the tree rows where the soil may have been less compacted.

To fix the damage the holes and small trench were filled with soil using a tracked ‘Bobcat’, re-rolling the area, laying a jute mat and sowing a grass mix to stabilise the soil.

The jute mat was used because it gives temporary protection to the soil surface until the grass establishes. If there is heavy rainfall while the gully is regressing, the run off water will flow over the upper surface of the mat and not scour out the soil.

The jute mat covering is 4.0metres wide (two widths of 2.0m mat were used) and runs for the length of the gully. At the time of the field day the grass mix had started to germinate and there were grass shoots starting to protrude through.

The jute mat and seedlings emerging through it

Gerry Ryan from the CMA said “the mat has to be well pinned down to a smoothed soil surface to ensure that the grass seed germinates and grows through the mat, thus holding the mat in place. If the soil surface isn’t smooth, the seed germinates and grows under the loose mat, not through it. This causes the mat to be lifted by the grass and may become less effective in stopping soil erosion”. The jute mat should rot away in about six months, leaving the grass to hold the soil in place.

The block of trees that the gully runs through may now be harvested without the difficulty that has been experienced.

Did you know that the Northern Rivers CMA has grants available for works such as repairing this gully? To find out more contact Gerry Ryan at the CMA on 02 6627 0170.

MPC would like to thank the Jones Family for hosting this field day and showing us the changes they have been making on the farm. We also thank them for sharing their experiences and knowledge with all of us

There are 2 files that need to be downloaded below:

1. The instruction file that outlines the method that is used and the factors impacting upon the accuracy of the results. CLICK HERE TO DOWNLOAD

2. The macadamia sorting calculator which is an excel® based spreadsheet which is used to calculate the estimated quality and value of sorting. CLICK HERE TO DOWNLOAD

The information required to use the calculator is the total estimated kernel recovery of the nut sample to be sorted, the average time taken to sort a tonne of NIS, a payment table from your processor and a sample of NIS that you will simulate a sorting with.

Technical Requirements

The macadamia sorting calculator requires Microsoft Excel® (testing has been performed on Excel version 97 and up on various Microsoft operating systems).

The software has calculated cells which are locked. Before carrying out any calculations it is best to check that the input information cells are clear and you are entering new figures. If previous figures are left in the input cells the calculations will not be accurate for the new sample analysed.

The original sorting calculator software has kindly been provided by Industry and Investment NSW (formerly the NSW Department of Primary Industries) and MPC acknowledges their assistance in this regard.

Well this tool will allow you to see if your main consignment and a consignment of ‘floaters’ was worth more than having left them mixed together.

By knowing the quality and weight of individual consignments, a weighted average of the quality can be calculated if they were left as one.

To use this tool you will need to have Microsoft Excel® installed on your computer.

To use this calculator fill in your individual consignment quality results and the program will calculate a weighted average of quality if the individual consignments were delivered as one. The Gain/Loss from sending as separate consignments or leaving as one is also reported.

Click here to download our assembling quality reports XLS file

More than 60 people attended the MPC field day on September 8th at Lance Emery’s farm. The focus of the day was on the work Lance has undertaken to improve his orchards sustainability by using green waste mulch and compost to cover exposed roots. This has improved soil health, provided erosion control and given a good orchard harvesting surface.

This day featured demonstrations of a steam weeder, an alternative to herbicide use, and three different machines available for spreading mulch and compost.

MPC growers enjoying a BBQ lunch at the end of the field day

Steam weeding

The Field Day started with a demonstration of steam weeding by Karen Muir from Weedtechnics. (www.weedtechnics.com).
Steam weeding causes plant cells to rupture and die. It is a contact control method that only kills the parts of the plants it contacts. Therefore to get good control, it is best to target young weeds and initially frequent applications are necessary.
The steam for the applicator is generated by a diesel powered boiler. The boiler demonstrated uses 9.0L of diesel /hour. Travel speed is determined by the height of the growth being sprayed, with the initial application applied at approximately 1.5km/hr. Once into a program, this can be increased to 6km/hr.

Delivery of the steam for weeding can be carried out manually using a steam lance or mechanically with a circular applicator or a combination of fixed lance and circular applicator (see photos below and over the page).

The circular applicator is designed to allow it to revolve around tree trunks and thus completely eradicate all weeds and grass from between the trunk area.

The steam has an immediate effect on the appearance of the grass and weeds in that they appear blackened by the heating effect of the steam. It was explained that the steam heat has very little effect on the beneficial micro/macro organisms within the soil as the heat from the steam doesn’t penetrate into the soil unless the weeder remains in the one spot for a long period of time.

Karen Muir from Weedtechnics showing how the steam weeder works

The steam weeder using the circular applicator

Long grass in a tree row treated two weeks before the field day

A section of a tree row with long grass was treated two weeks prior to the field day and the results were viewed on the day. The demonstration area showed the steam weeder had a good result in knocking the grass down. To improve the result, a follow-up application would be ideal. For the best results the weeder needs to be used frequently initially to counter the regrowth of weeds and grass from viable plant systems that remain in the soil.

The steam weeder appears to be a useful method for controlling grass and weeds in a macadamia orchard and with some modification to improve the application system for macadamia orchards could be a valuable tool.

Lance Emery’s story

Lance is an inventive farmer prepared to think outside the square. He’s developed some innovative orchard practices to improve soil health and soil erosion control.
Lance’s results are dramatic – no exposed roots, a fibrous root system that binds the soil and mulch together, a surface that is easy to harvest from and a high microbial diversity in the soil. His orchard practices are a credit to Lance’s hard work, dedication and love of his farm.

No chemical fertilizer

Most people are surprised upon seeing Lance’s healthy trees when he tells them he hasn’t used chemical fertiliser (excluding trace elements and agricultural lime) for nineteen years.

“In 2004 I started to work on a problem in my orchard that resulted from ‘stem flow’ washing the soil out from between the trunks of the trees with-in the tree row. This erosion exposed the trees surface roots and made harvesting difficult with nuts being lost in the trench between the trees and caught under the tree roots” said Lance.

Lance thought he might be able to fill this trench in with recycled organic material and turn the trench into a mound. After searching around for a viable source of material, Lance found a good supply at his local council.

In the first year, Lance spread chicken litter and then the recycled material over the top by hand. After seeing the results of putting this material down, he then purchased a Wallaby Spreader to make spreading easier. The material was not ideal and was difficult to spread with the spreader. To overcome this problem, Lance initially thought of a double conveyor design but was convinced by a machinery manufacturer to install a pair of spinners to the end of the spreaders conveyor system. This allowed him to place the material exactly where he wanted it along the trunk line of the trees. The draw back was that it was a slow process. Today Lance is still working on modifications to the spreader, to make it run faster.

There was an unexpected benefit from the placement of the mulch down the tree row, with the mulch material acting as a barrier to water movement sideways, slowing surface water runoff on side slopes. Mobile silt was caught by the mounds and actually built up on the tree row. From this work Lance now has a mound down his tree rows which was described by someone as a “hard sponge” – you can squeeze the material but when you try to pull it apart it won’t separate easily due to the large number of roots in it.

Lance Emery discussing his method of soil health improvement using mulch under his trees

Lance now uses annual applications of about 20.0kg of chicken litter and 15 kg mulch per tree which continues to create a low mound of rich dark soil across the tree root system. When the surface is disturbed, surface feeder roots become very obvious. This soil abounds with life and earth worms are very easy to find.

Trees continually fed with nutrients

Lance has found since starting this system his orchard production has stabilised. “I can now expect no more than about a 5.0t variation in my crop from one season to the next and I think it is because my trees are continually being fed with nutrients from the decomposing mulch and chicken litter and they don’t get stressed easily”.

Husk is used in areas of the orchard where the trees look like they may need a bit extra nutrition or on individual trees that are not doing as well as others.

Diversion drains a key part

The installation of diversion drains throughout the orchard has also been a major part of Lance’s work to overcome soil erosion. These drains serve 2 purposes – to carry the bulk of the surface water away from a tree block – and to stop water entering another block in the orchard. These drains have helped prevent damage from occurring when there are heavy rainfall events.

Limb removal is carried out across the farm to allow the regrowth of grass on the orchard floor to reduce soil erosion. In the oldest block of trees, they have now regrown to a point that the grass has retreated to all but the best lit areas in the block.
As a result, Lance is now preparing to remove every second tree in every second row of this block. He has prepared for this operation by experimenting with ringbarking the trees that he intends to remove, hoping that they might crop well once more before loosing their leaves. Lance see the loss of leaves from the trees to be removed as making the trees easier to handle when they are cut down and a bonus to the biomass that will be left behind in the orchard.

There are also many other different ideas and innovations that Lance has undertaken on his farm. All of these have been aimed at improving the farms sustainability, both financially and environmentally. It is a credit to him and something he should be tremendously proud of.

Lance with his modified Wallaby spreader

One of the newly constructed diversion drains following tree removal prior to revegetation

This article provides a brief overview of the management of spotting bugs (Amblypelta spp.) in macadamias, including the identification of the pest, the types of damage caused and the control strategies used.

Key points are:

• adult spotting bugs can feed on fully mature nuts, as they secrete enzymes when feeding that allows them to penetrate the shell;
• late season damage often does not show up on macadamia shell, but the kernel has been damaged. This late season damage is often called “blind stings”;
• a good monitoring program is critical allowing you to determine when there is activity occurring in your orchard and apply control strategies as needed;
• spotting bugs will continue to feed in an orchard until there isn’t any food available or a more appealing food source emerges;
• you only need small numbers of spotting bugs to have significant amounts of damage;
• the aim of a spotting bug management program is to reduce the population early in the season, so numbers do not build later in the season.

Introduction

Spotting Bug is the general name used to describe the fruit-spotting bug (Amblypelta nitida) and the banana-spotting bug (A. lutescens lutescens). Both of these insects attack a wide variety of horticultural crops, including avocado, custard apples, lychee, mango, passionfruit and pecans, as well as many native and ornamental fruit and nuts. Spotting bugs are not the only bug species that attack macadamia but they are the most perennial problem in all growing areas.

Spotting Bug feeding on Murraya paniculata berries NSW (courtesy I&I NSW)

What do they look like?

Adult spotting bugs are yellow-green-brown in colour and about 15mm long. There are 5 nymph stages (called instars), with the early stages being ant-like, orange-brown in colour and with prominent antennae. Later stages are greener in colour and have wing buds. A distinctive feature of the nymphs is that the second last joint of the antenna is black and flattened. It is rare to see spotting bugs in trees, as both adults and nymphs are very alert and if they fear being seen they will hide behind fruit or leaves. They also have the ability to drop down to the ground quickly to avoid being found.

Life cycle stages of fruit spotting bug nymphs and adults. From Macadamia problem solver and bug identifier © The State of Queensland, (2003)

Banana spotting bug nymph. From Macadamia problem solver and bug identifier © The State of Queensland, (2003)

When are they present?

Most damage to macadamias occurs between September and February, with some of the thinner shelled and later varieties being attacked all year if spotting bug is left unmanaged. Spotting bugs are able to penetrate fully hardened shells due to the long stylet (microfine syringe like feeding tube) and powerful enzymes they release while feeding. This late damage can show up as a ‘blind sting’, as you can not see the damage on the outside of the shell but the kernel is damaged. Blind stings are difficult for growers and processors to detect until after the shell is cracked.

Research by Industry and Investment NSW (I&I NSW) at the Centre for Tropical Horticulture (CTH) Alstonville, over several seasons and on several crops, has been able to link chemicals in flowers with movement of female fruit spotting bugs. These chemicals are known as “semio-chemicals or karimones” and they signal to the adult bug populations that the macadamias are about to develop nutlets. This is very important as the semio-chemcials allow the spotting bugs to know that if they now enter a macadamia orchard and lay eggs, food for their developing nymphs will be plentiful.

Eggs have been collected in spring from the flowers of many crops, including mango, lychee, and avocado but none more than macadamia.As very few eggs are laid, a small number of spotting bugs can do considerable damage. This makes an effective monitoring program a crucial part of spotting bug management.

Eggs of fruit spotting bug laid on early stage macadamia florets August/September 2009 at CTH Alstonville (courtesy I&I NSW)

Typical fruit spotting bug cycle for macadamias. Note the months indicated for a particular active can vary depending upon seasonal weather conditions and crop growth stages.

The aim of spotting bug management is to reduce the population pressure early in the season. This reduces the number of eggs that hatch and the number of adults and nymphs available to damage your crop.

There are two to three generations of spotting bug during the macadamia nut development. The first egg laying usually occurs in August/September and the second in October/November, with it taking approximately 42 days for a spotting bug to develop from an egg to an adult.

Once an adult, spotting bugs can live for up to six months. During the main summer period the adult bugs are far more mobile in the orchard and can invade and leave areas quickly. As a few spotting bugs can do considerable damage, this makes breaking their breeding and feeding cycles crucial.

Normally two applications of a registered insecticide 4 weeks apart during the spring build up and one just prior to Christmas removes the threat for the older Hawaiian varieties. However when poor nutset occurs in the September flowering we often get a season with summer and/or autumn flowering (like 2010) which can immediately start another cycle for the spotting bug. This virtually keeps them in the macadamia orchard all year resulting in higher damage.

Once adult spotting bugs enter your orchard (or are bred in your orchard) they will not move onto another crop until the food source dries up (i.e. nuts start to fall at harvest) or they find an alternative food source that is more attractive.
If your early season management stops the nymphs from maturing and the adults from reproducing and feeding, you will reduce the potential for late season damage, which is very difficult to see or remove from your nut in shell (NIS). Good monitoring is crucial to ensure you detect any populations of spotting bug and so apply control strategies only when necessary.

What does the damage look like?

Damage caused by fruitspotting bug depends upon the stage of development of the nuts. I&I NSW carried out a series of experiments between 1997- 2005 at CTH Alstonville, where they caged macadamia nut racemes for an entire season. Fruit spotting bugs were released into the cages at different stages of the season, to ensure nut damage.

This series of experiments showed that all early season damaged nutlets basically dropped from the raceme up to November. After this time nuts continued to be damaged but less and less fell off the tree. The visible symptoms of damage follow this same pattern, with less and less damage obvious until late in the season spotting bug damage is only visible in the kernel. There are also occasions where small nymphs feed only on the husks. The following photos show the damage caused at different stages of development.

Typical fruit spotting bug damage symptoms

All images below are form Macadamia problem solver and bug identifier© The State of Queensland, (2003)

Spots on a young nut.

Sectioned nut showing lesions on the inside of the husk (nut removed)

Sectioned developing nut showing damage to soft shell and developing kernel

Shell damage

Kernel damage

Can spotting bugs feed on fully mature nuts?

Unfortunately yes. Due to the long proboscis (feeding tube) that fruit spotting bugs have and the secretions they exude from it, they can penetrate fully mature nuts. In some orchards they attack late in the season (January to early February) and damage the kernel.

Caged racemes from 344 and A16 trees with fruit spotting bug introduced for a weeks feeding during the month labeled. January feeding on both varieties left dark welts in the forming shell, March feeding still visible in the kernel but not on the shell. (courtesy I&I NSW).

The damage does not show up on the outside of the shell, but the kernel is damaged. This makes it difficult to remove these damaged nuts on a sorting table. (

Green vegetable bug (Nezara viridula) is also able to feed on mature nuts, although it will not usually breed in the crop (like fruitspotting bug). Green vegetable bug has even been found to feed on dropped nut if left unmanaged. Green vegetable bug invade from pasture legumes, soybean or passionfruit crops and also have many weed hosts (especially black berry nightshade). It is much easier to control if the weed management is good on your farm. This damage also does not show up on the outside of the shell.

Both types of bugs have the potential to make significant proportions of the crop worthless quickly, and as a result, careful monitoring is required to determine if late season bug activity is present in your orchard so that appropriate control strategies can be carried out.

Fruit spotting bug feeding directly through the shell to create a blind sting (left) (courtesy I&I NSW). and the typical blind sting damage found in macadamias (right). Note the absence of damage on the shell (courtesy MPC).

Are there variety preferences?

Research at CTH Alstonville has found that there are varietal differences in the levels of fruit spotting bug damage found. Generally, thinner shelled varieties have been found to suffer higher levels of damage than thicker shelled varieties. This means that you’re monitoring and control strategies may need to be different for particular varieties, especially late in the season. In thin shelled varieties, if spotting bug is not controlled, crop losses over 80% per tree are not uncommon, with an average of around 30-50% being observed most years.

Monitoring and action levels

A small number of adult and nymphs can do a lot of damage. This makes monitoring and timely control strategies crucial for spotting bugs. It is best to monitor trees from all areas of the orchard, but it is important to pay particular attention to trees adjacent to bushland and ‘known hotspots’. Experienced scouts and many researchers have found that spotting bugs will infest the same areas consistently each year. Most orchards tend to have these areas, but only good spatial crop records will provide this information.

The conventional approach is to look for green fallen nuts with internal fresh damage. From December onwards it is important to collect nuts from the tree for damage, as nuts damaged from this time onwards will not be aborted.
The current protocol is as follows:,

Early in the season, sample at least 10 freshly fallen nuts from each tree (and from December onwards sample nuts from the tree). The number of trees examined will vary, but you need to ensure you sample enough trees to determine if spotting bugs are present or absent. One option is to monitor 10 trees in known hotspots and then examine trees randomly across the remainder of the block. You must ensure a minimum of 35 trees are monitored in this arrangement.

To monitor for damage, cut open the nut and separate the husk, shell and kernel. Examine each part for damage. Spotting bug damage appears as a brown lesion on the inside of the husk. There may also be crinkled areas on the developing shell or the kernel is shrunken. The following photos show some typical damage symptoms seen while monitoring.

Some typical damage symptoms seen while monitoring

Sectioned nut showing damage to the soft shell and developing kernel

Spots on a young nut.

Sectioned nut showing lesion on inside of husk (nut removed) and Nut with glucose rich exudates on the surface that appears after fruit spotting bug feeding

Note figure above shows the glucose rich exudates which osmotically flows to the surface of the nut after the fruitspotting bug has fed on the macadamia nutlet (courtesy I&I NSW). (Other images from Macadamia problem solver and bug identifier © The State of Queensland, (2003)).

Control options

Unfortunately there aren’t any effective bio-control agents commercially available, but research work has commenced into this area. The aim of the research work is to reduce our dependence on chemical control for this pest.

Chemical Control

The currently registered chemicals for the control of fruit spotting bugs are shown in the table over (correct as of 22nd September 2010). Please note that the listing of a chemical here does not mean that MPC or I&I NSW endorses its use or recommends the product. All users of agricultural chemicals must be trained and all applications must be made in accordance with label directions.

Currently Registered chemicals for spotting bug(s) control.

What about biological control?

There are some known predators and parasitoids of spotting bugs. Unfortunately there aren’t any effective biological control agents commercially available, but research has commenced into this area. The aim of the research is to find a way to establish both parasitoids/predators for the adult and nymphal stages and also the eggs.

A multi facetted approach to spotting bug management will be the topic of future research and a proposal is currently being developed with a number of horticultural industries. This project will look at a range of issues surrounding bio-control, including the mass rearing of a range of egg parasitoids and adult and nymph predators that are known to attack spotting bug (or potentially attack them) but haven’t been successfully reared in large numbers.

As a precursor to this project, a small Voluntary Contribution (VC) project is being undertaken by Bio-resources PTY LTD to look at mass rearing systems for fruit spotting bug. Mass rearing spotting bugs is crucial because many of the known parasitoids are spotting bug specific. To be able to rear the parasitoids in large enough numbers for release into orchards, you therefore need a good supply of spotting bugs. Spotting bug has proven difficult to rear in captivity and so this project will look to find ways to improve this situation.

Where can I access further information?

The following is a list of information sources:

Macadamia Growers Handbook

This reference book contains a large amount of information on all aspects of macadamia production. The section on spotting bugs is very useful.

Macadamia problem solver and bug identifier

This book contains high quality photos and information regarding the identification of nearly all problems encountered in a macadamia orchard.

BioResources Pty Ltd

This website provides information on the new research project investigating the feasibility of a range of parasites for fruit spotting bug. There are some excellent photos on this website. www.bioresources.com. au/FSBbiocontrol

References

Brimblecombe AR (1948) Fruitspotting Bug as a pest of macadamia or Queensland nut. Queensland agriculture Journal 67: 206-211.

Ironside DA (1981) Insect pests of Macadamia in Queensland QDPI publication 81007.

Miles PW (1987) Plant sucking bugs can remove the contents of cells without mechanical damage. Experimentia 43. 937-939.

Miles PW & Taylor (1994) Osmotic pump feeding by coreids. Entomologia experimentalis et applicata 73: 163-173.

Huwer R.K., Maddox, C.D.A. and Purdue, I.M. (2008). Workshop – Pest & Disease Management: Progressing IPM and tackling options for FSB – the next big problem Proceedings of the Australian Macadamia Society Conference 30 October – 1 November 2008.

Acknowledgements

Photographs of fruit-spotting bugs and nut damage by courtesy of Agri- Science Queensland, Dept of Employment, Economic Development and Innovation, www.dpi.gov.au (formerly DPI&F, QLD); © The State of Queensland, (2003).

In this short video, Stewart Edmonds provides an overview of some good ideas he has instigated in his sorting shed to improve productivity.

Article by Jim Patch – Agricultural Liaison Officer

Orchard soils throughout the harvest period of 2009 have been saturated for extended periods. This warm and wet soil environment has been ideal for the growth and development of phytophthora cinnamomi, a plant disease that is regularly seen in macadamia and avocado orchards in Australia ( Greek: Phyto – tophthora; meaning plant- destroyer).

The real cost to the Australian macadamia industry is not fully understood at present. This disease needs careful monitoring and management prior to the next warm dry spring period when excessive nut/leaf drop may be encountered from water/nutrient stressed trees.

What is Phytophthora cinnamomi?

P. cinnamomi is a water mould. It thrives in warm moist soil conditions. The mould growth consumes the host plant tissue (mainly plant roots) causing areas in the host plant that appear to be rotten e.g. root rot.

What does Phytophthera do to macadamia trees?

P. cinnamomi causes damage to the roots and collar area of macadamia trees. This damage weakens or kills the tree. Phytophthora produces many different types of spores throughout it’s lifecycle. Figure 1 shows the lifecycle of phytophthora. Wet, moist soils with low levels of oxygen favour the growth and reproduction of phytophthora and this is when the greatest level of infection can occur.

The symptoms of phytophthora are rarely seen in wet weather. This is because the damage to tree roots is not evident as there is plenty of soil moisture available and the tree is not suffering stress. Once the weather turns warm, the tree is actively trying to take up soil moisture but there is a small amount of a healthy root system left and so cannot take up enough water or nutrients for its needs. This causes the tree to stress and the symptoms become evident.

After a long period of wet weather and as we head into spring, the potential for phytophthora affected trees to be seen is very high.

Visible Symptoms

Trees of all ages will have leaves that become yellow and chlorotic to brown in appearance (figure 1) and there may be excessive leaf shedding and bare canopy. Lesions may appear in the bark of the root and trunk area and may extend into the limbs. A common symptom is heavy suckering from the rootstock of a tree. Mature trees may become heavily stressed when soil moisture levels are reduced and excessive nut shedding may occur in warm/hot dry periods in spring and summer.

How does the mould spread throughout the orchard?

Phytophthora moves about by producing different types of spores. Depending on the spore type, spores have the ability to live for periods of between a few weeks to years. Spores may enter a tree through damage to the trunk, damage to exposed surface roots or through healthy roots in water logged soils. When P. cinnamomi has entered a host plant, it grows by producing microscopic filaments called mycelium. The mycelium may grow from one macadamia tree to the next through the intertwined roots of neighbouring trees. Movement may also come about by the movement of spores in runoff water. Spores may be transported on machinery or by other similar means throughout the orchard, or in surface water during rainfall events.

Figure 1. A phytophthora affected tree.

Figure 1. Lifecycle of Phyotphthora cinnamomi. (source Griffith-Jones, 2001)

How can phytophthora be controlled in a macadamia orchard?

It is best to use multiple options for the control and protection of trees from phytophthora. A mix of the following will give you the best results.

Cultural Practices.

Exclusion and sanitisation. Prevention is the best possible control strategy, although it can be difficult as very few macadamia orchard sites are now free from the disease. However grower due diligence may assist in protection of young macadamia trees, e.g. Only plant trees from a nursery that uses soilless potting mixes. Avoid potting mixes with a soil component which may harbour phytophthora. All potting mixes should be heat treated to kill pathogen spores. Divert surface water from neighbouring sites away from the orchard.

Orchard Design. Areas of the orchard site that may become water logged for extended periods should not be planted. Areas that may be marginal should be mounded to avoid the risk of tree roots being waterlogged. Ensure that water is not trapped within the planted tree rows by the mounds. Irrigation systems should be designed to avoid overwatering. This can be achieved by watering blocks together that have similar water requirements and water infiltration rates.

Organic Amendments and Mulching. The best method to protect established macadamia trees is to concentrate on creating a healthy soil environment in the orchard. A healthy orchard soil will have soil properties that favour good tree growth and do not favour the development of phytophthora. A healthy soil may protect the macadamia trees by suppressing P. cinnamomi through the activity of soil borne micro organisms such as fungi and bacteria.

P. cinnamomi appears to be suppressed in rainforests by high levels of organic material which can also be replicated in part in macadamia orchard soil. Organic amendments and mulching is recommended as mulching stimulates plant root development, increases nutrient uptake and decreases evaporation from the soil. Mulching also increases soil – water holding capacity, reduces water runoff, reduces rain drop splash, facilitates drainage, regulates soil temperature, and provides a high level of nutrients for soil microbes. The avocado industry struggles with the same pathogen. Their industry is advised to set up irrigation sprinklers so they do not spray directly onto the tree trunk and skirt the trees high enough to allow adequate air flow to create a dry under tree environment. As the pathogen requires moisture to replicate and waterlogged soils benefit its spread, orchards need to be well drained and not over irrigated. Phytophthora is inhibited by alfalfa meal, cotton waste, soybean meal, wheat straw, chicken manure and urea.

Apply organic amendments such as animal manures and compost to help improve soil structure and fertility. Nutrients in organic matter (especially nitrogen) break down slowly and are released over time in plant useable form. Ammonia and volatile organic acids released by decomposing organic matter kill Phytophthora and the residual organic matter stimulates competitive and antagonistic micro organisms in the soil. Avoid inputs of material which contain excessive levels of ammonia which can cause root damage. The addition of compost or mulches should not reduce the ability of moisture and air to enter into the soil and root system.

Cover crops.

Organic matter may be increased by growing cover crops in the inter row. Cover crops provide nutrients, increase soil organic matter, improve aeration and provide food for soil organisms. Cover crops may reduce orchard temperatures by 1-2°C in summer and protect feeder roots near the surface from drying out or being effected from excessive heat. Sweet smother grass is presently being used very successfully in many macadamia orchards but there are many other grass species that macadamia growers may use to suit their growing region.

Chemical treatments

The use of chemical treatments to aid in the control of phytophthora has been found to be beneficial. These can be applied to give a fast response while other long term protection and prevention strategies such as improving soil health are carried out.

Research has shown that timing of any application of Phosphorous acid is critical. Tree roots do not receive nutrients whilst a tree is flushing as nutrients are moving up the tree towards leaves and twigs. When the flush has hardened, carbohydrates and other products start moving down the tree to the roots. This is the best time to apply your applications.

Always apply the chemical as directed on the label and follow all safety precautions outlined on the label.

Foliar Application

Apply Phosphorous Acid (Phos.Acid) to the foliage when the leaf flush has just hardened in early spring and autumn.
Application rates are:-
400g/L Phos. Acid: Apply at a rate of 2.5mL to 3.0mL product per litre of water. Apply 7.5 to 10.0L of spray solution per tree.

600g/L Phos. Acid: Apply at a rate of 1.7mL to 2.0mL product per litre of water. Apply 7.5 to 10.0L of spray solution per tree.

620g/L Phos. Acid: Apply at a rate of 1.6mL to 1.9 mL product per litre of water. Apply 7.5 to 10.0L of spray solution per tree.

Do NOT apply to trees under severe stress or during hot weather.

Trunk Application
Research work is presently being conducted on trunk application using Phosphorous (phosphonic) Acid(eg. Phospot 400® and Agri-Fos 600®). The results of this work to date have been encouraging.
The rate being used for bark painting in this experimental work is 20% acid, i.e. Agri-Fos 600® is 1L of product and 2L water. Phospot 400® is 1L of product and 1L water.

The penetrant Pulse® is also being added to this bark application to assist the translocation of the potassium phosphonate throughout the tree. The rate of Pulse is 20ml of Pulse in 1L of mix.
This mixture has been applied to the trunks by spraying from the ground to the first limbs of the trees. The use of Pulse for foliar applications is not recommended as it could cause leaf burn to trees.

References:

Diversity and Management of Phytophthora in Southeast Asia. Drenth, A and Guest, D I. Australian Centre for International Agricultural Research. Canberra. 2004.

Soil Environmental Factors and Their Relationship to Avocado Root Rot. Menge, JA. and Marais, LJ. Department of plant Pathology, University of California, Riverside. CA92521.

Strategies to Control Phytophthora cinnamomi Root Rot of Avocado. Menge JA. Department of plant Pathology, University of California, Riverside.CA92521

Biological control of Phytophthora Root Rot of Avocado with Microorganisms Grown in Organic Mulches. Jefferson, L. da Costa, S, Menge, A Casale WL. Department of plant Pathology, University of California, Riverside, CA, USA. 2000

Phytophthora Root Disease. Griffith-Jones. 2001

What is phytophthera cinnamomi?
Tasmanian Department of Primary Industries, Parks, Water and Environment www.dpiw.tas.gov.au/inter/nsf/

Fruitgrowers’ Newsletter-p9, Spring 2007

Phytophthora in Macadamia, Akinsanmi, O and Drenth, A. Australian Macadamia Society Journal p49-50, July 2008.

Growers have used Lepidex® for the control of flower caterpillar and reported that the results have been poor. This is believed to be as a result of alkaline hydrolysis. Alkaline hydrolysis causes certain chemicals to breakdown rapidly when they are subjected to high pH conditions.

For example, adding Lepidex® to water at a pH of 8 will cause 50% of the product to breakdown in 63 minutes. This means that the chemical concentration is less than what is needed to give good control. To overcome this problem a product such as LI700® can be added to the tank solution. This product buffers the pH and reduces the breakdown. It is a good idea to test the pH of the water you wish to use for spraying to determine whether or not you need to add a buffering solution like LI700®. Like all other sprays, coverage is crucial for the best results with Lepidex®.

If the pH of your water is low or you add a buffer to reduce the pH, then adding copper based products has been found to cause phtyotoxicity problems in some crops. Research work is being undertaken to test whether macadamias are susceptible to this problem. As a result it is best not to add copper to a tank solution that has been buffered to reduce the pH until this research work has been completed.