Pest control |
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Affected by stinkbugs
Graeme Whyte, GFNC development and client manager, says“ Damage to kernels that are supplied to processing factories impacts the farmer in a number of ways. The first is that 60 to 80 % of the damage to kernels delivered for processing in the northern regions of Limpopo and Mpumalanga, is due to stinkbug infestation. Areas like KwaZulu- Natal are less affected by stinkbug but the increasing percentage of unsound kernel being delivered, shows that their stinkbug population is growing too.
“ The unsound kernels can be converted into macadamia oil, but the margin for farmers is far lower. Either way, there is no sensible reason to incur preventable damage.
“ There is also a cost to the farmer related to the need to sort and eliminate unsound kernels in the factory. If stinkbugs attack the kernels early in the season, the nut carries a dark brown mark that optical sorters can pick up automatically. Later in the season, however, the mark on the kernel is very pale. Sorting then has to be done manually, which adds cost to the production process.
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“ In addition, the higher the percentage of sound nuts delivered to a factory, the faster they can be cracked. In one of our factories, for instance, we can crack up to 70 tons of sound kernels a day. When we have to sort high unsound kernel, production can drop to 20 tons a day. This means that the cracking costs we are obliged to charge our suppliers increases.
“ And, when factories are less productive, they’ re able to take on new supply at a slower rate. So, farmers can’ t bring their product in as quickly as they would like. The ultimate flow of product to market is slowed down, impacting sales and, therefore, farmers’ profits.
Cost-free and environmentally responsible
“ When you consider that pest control via bats and birds is free – all you have to do is put up bat boxes in bat friendly areas and grow indigenous bush next to your orchards – then there really is no downside to doing the environmentally responsible thing.”
GFNC has made available to the research project orchards on two of its own farms owned by Green Farms Director, Alan Whyte, in the Levubu area. Three of its suppliers, Fritz Ahrens, Jaco Roux, Alistair Stewart and his farm manager
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Branden Jardim, all in the Levubu, Thoyandou and Louis Trichardt areas, are also participating in the project. Researchers Valerie Linden and Sina Weier have put up 48 cages around trees on the six farms.
One set of cages keeps birds and bats from feeding off the insects on and around the trees. A second set enables both bats and birds to access the insects day and night. The third set of cages is closed in the evenings, to exclude bats and nocturnal birds. And the fourth set is closed in the day time, to exclude birds that are active in the day.
The nuts from the caged trees are then sampled to establish the percentage of damage caused by insects under these controlled conditions.
Linden and Weier have been trained at the GFNC sampling facility at its Levubu factory to identify the specific types of damage caused by the various insects.
Weier is also focusing on the feeding patterns of the bats and birds, using their droppings to establish which insects they are feeding on in the orchards that are part of the study. This information will enable farmers to provide the right environment for encouraging
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specific bird and bat species to develop colonies around their orchards.
Feeding on stinkbugs
“ Before we started the study, we knew that the bats were feeding on false codling moths and stinkbugs,” says Linden, whose focus is the caged trees.“ We’ ve since established that certain species will also feed off the stinkbugs and that the bats will catch the insects in the air and take them off the leaves of the trees. Various species of birds have the same habits.
“ Based on this behaviour, and the kernel damage patterns we’ ve seen this season, it’ s clear that the bats and birds make a definitive contribution to reducing crop damage. Where bats and birds were excluded from the trees, kernel quality dropped.
“ We expect that biological control through the use of bats and birds will reduce the need for farmers to spray their trees. In turn, this will cut their production costs. And, because they will have less kernel damage, a higher percentage of their crop is able to be processed for export. Taken together, the savings on costs and the ability to market more of their crop will make their operations significantly more sustainable.
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SABI | APRIL / MAY 2017 37 |