By Dr Garth Cambray
A small indigenous predator patrols an
organic citrus tree looking for pests to eat.
For years, organic agriculture in South Africa has largely been perceived to be a fringe activity followed by a group of eccentric farmers for whom profit is not a major objective. The Sundays River Organic Growers association has not fallen into this category, but is rather adopting a mainstream alternative approach while creating real sustainable wealth for Africa
Currently the association based in the Sunday's River Valley of the Eastern Cape of South Africa represents 140 hectares of citrus with an annual output of 150 000 export cartons, 60 permanent staff and 150 additional seasonal staff.
Keith Finnemore, the owner of Rosedale organic citrus farm, a member of the Sundays River organic Growers association, has pioneered this approach on the piece of land on which a pioneer of sustainable biotechnology in South Africa, Professor Peter Rose (whose family second name is Dale, hence Rosedale) grew up. Keith Finnemore and Peter Rose have adopted similar approaches to the use of biotechnology in ensuring a cleaner environment with cleaner food and water in what has become a key focus area in biotechnology in South Africa.
Some of the oldest applications of an understanding of biotechnology are in agriculture. The composting process employs microbes to break down complex plant components into less complex components, freeing up trapped nutrients and releasing them into the environment for a new generation of plants to use. For compost to work well, biodiversity is important - the more different microbes in a compost heap, the more different genetic toolboxes your compost heap has in order to break down different complex molecules. Keith Finnemore has, over the years, actively encouraged the biodiversity of microbes in his soil by the careful use of composting procedures which encourage this development.
In the Sundays River Valley, the specialised indigenous vegetation in that area is adapted to periods of drought followed by occasional wet periods. During droughts, biomass such as plant leaves, dung etc, fall on the ground, and then during wet periods extremely vigorous microbial activity rapidly converts this biomass to compost allowing the cycle to continue. It follows that the best source of microbes adapted to the Sundays River Valley are those already living there in the wild.
In non-organic citrus farming, farmers spray a barrier patch of ground between the bush and the orchard with herbicide to create a clear, barren, 'no life land' between the crop the and the wild - a sort of siege mentality agriculture. Keith Finnemore has over the past 5 years allowed these barren strips to be replaced by grasses, indigenous plants and some weeds, allowing nature to slowly penetrate back into his farm.
One of the bigger problems in the early years was scale - scale insects are farmed by ants, and ants like open barren land to run around on between the trees. By allowing small natural groundcovers to reclaim the ground below his citrus trees, Keith has made the land unsuitable to ants. The result - whereas scale was his number one problem 5 years ago, it is now only a problem in the one or two places where the ground has not been completely covered over with natural plants again.
As an additional tool in the toolbox to control scale, Keith Finnemore uses a small wasp parasitoid, Aphytis melinus, which lays its eggs under the scale cap. The eggs hatch and the larvae eats the scale, killing it, and then emerges to go and mate and kill more scale by laying eggs.
One of the biggest threats to a healthy Aphytis melinus population is the application of conventional pesticides, which kill the wasps. Hence, in organic citrus cultivation a decent population of these wasps develops and persists until the problem is under control. From this point onwards it is important for the farmer to monitor scale levels and supplement Aphytis melinus populations when needed - normally in spring.
In South Africa, one of the biggest citrus pests is the false coddling moth. This small moth lays its eggs in fruit, and due to the fact that the moth is not endemic to many of our export markets, the presence of even a single moth found in a shipment of fruit will result in that shipment being rejected by authorities in countries such as Japan and Europe. For organic growers, this poses a big problem as the possibility of a false codling moth surviving in fruit which has not been sprayed with toxic chemicals is higher.
In the 1990s Dr Sean Moore, began research with Professor Don Hendry of Rhodes University's Department of Microbiology, Biochemistry and Biotechnology to develop a viral pesticide for the false codling moth. Later this research resulted in the founding in 2004 of Riverbioscience which now produces and markets the CRYPTOGRAN™ viral pesticide - a certified organic viral treatment to stop false codling moth. The virus is a granulovirus and is applied to trees as a spray and infects false codling moth larvae causing them to die. Being a virus it is entirely specific to its target host, the false coddling moth larvae and does not affect any other caterpillars. Keith Finnemore uses CRYPTOGRAN™ to control his false coddling moth population.
It is also important to note however that as the undergrowth has restored itself in his citrus orchards, more and more small predacious insects and birds have begun to inhabit the land below the trees. False coddling moth have to pupate on the ground, and thus as more hungry mouths are living below the trees, the chances of survival have decreased for these insects, hence CRYPTOGRAN™ plus maintaining insect biodiversity in the soil below the trees is proving a far more effective control than the expensive and toxic agrochemicals used in non-organic agriculture. In non-organic agriculture it is important to remember that pesticides kill both target insects such as the false coddling moth, and non-target insects such as the predators of the coddling moth. There are always less predators than prey - hence, by destroying both, one creates a very healthy environment for reinvasions by the pest (the coddling moth). In this light, organic agriculture helps to reduce the problem of the coddling moth by restoring the predator prey balance.
As a beekeeper, one of the greatest problems with citrus is that when it flowers the non-organic farmers normally spray incredibly toxic chemicals on the trees when the majority of the flowers are pollinated to control pests called thrips. This has disastrous consequences on the bees often resulting in tainted honey and hive deaths.
Organic farmers such as Keith Finnemore represent a haven for beekeepers as they can rest assured that thrip will be controlled with agents that do not hurt the bees. At Rosedale a fungal pesticide containing spores of Beauveria bassiana (Mycotrol GH-OF and Mycotrol GH-ES) is used to control thrips. This fungal pesticide also reduces populations of locusts. Other controls which are used in times of extreme need are sulphur and natural plant product pesticides such as neem and pyrethrum. The neem tree, a close relative of mahogany is native to India. Natural pyrethrum is extracted from the Pyrethrum daisy flowers. The major production of natural Pyrethrum is in Africa with Kenya and Tanzania accounting for most of the world production.
To many people, if you mention the words Botrytis, it will stir dim memories of something some wine aficionado said about a bottle of sweet wine. Botrytis fungi are typically a problem in citrus during wet springs, when the humid conditions and dampness encourage vigorous growth of the fungi. Fungal growth on the surface of fruits in early stages causes the fruit to get big ridges on it, which reduces its value, and specifically its export acceptability.
To control Botrytis, Keith Finnemore already had the ideal tool - biodiversity in his compost. A simple compost tea, made with Rosedale's rich natural microbial populations was sprayed onto the crop, and the thousands of different bacteria used up whatever nutrients were on the surface of the fruit and created an environment that was unsuitable to the growth of Botrytis. And in that way a very interesting loop in the history of biotechnology in South Africa was closed. Professor Peter Rose, the first Professor of Biotechnology in South Africa has always proposed that there is no point wasting time and money engineering special microbes in South Africa as we have sufficient biodiversity that if we look in the right places, we can find microbes that already do the job for us already. And Keith Finnemore has brought that philosophy to fruition on Rosedale farm producing high quality organic export citrus, in a way which will be sustainable forever.