Janine Erasmus
South African company Du Roi IPM is at the forefront of the commercial application of an innovative chemical-free method of controlling agricultural pests.
Based in Letsitele, just east of Tzaneen in the province of Limpopo, the company breeds beneficial bugs for use in commercial farming, a method known as integrated pest management (IPM). It specialises in the control of pests in the grape and citrus industries: the red scale insect and several species of mealybug, both of which can devastate crops if left to proliferate.
South Africa produces a range of top-quality agricultural produce, particularly citrus and wine for export. Du Roi MD Felix Hacker says that while IPM has been used for many years, this has mostly been on individual farms and not on a commercial basis.
Established in 2000, Du Roi is the largest commercial insectary in South Africa. The insects bred there are natural enemies of red scale and mealybug: the predatory ladybird beetles Chilocorus nigritus and Cryptolaemus montrouzieri, and the parasitic wasps Aphytis lingnanensis and Coccidoxenoides perminutus.
Sensitive to the environment
IPM is an ecologically sensitive approach to pest control that can significantly reduce or even eliminate the use of chemical pesticides. The process brings together a range of complementary pest-control methods that include natural predators, pest-resistant crop varieties, cultural practices such as crop rotation, and the strategic use of pesticides. The goal is to produce the best results with minimal damage to the environment.
Organically grown foods – foods grown without the use of synthetic fertilisers or pesticides – are increasingly in demand by health-conscious consumers. Du Roi products, Hacker says, fit easily into an organic programme, as they are completely biological. He adds that pest control is only one facet of the crop-management process; fertilisers and fungicides would also need to be biological in nature for foods to be qualified as organic.
While good for the environment, the use of beneficial insects also makes good financial sense, says Hacker.
“National and international restrictions placed on certain chemicals minimise the chemical options for growers and thus open a door for the use of beneficial insects,” he says.
“Added to this is the overuse of certain chemicals, which has lead to pest insect populations developing resistance to these chemicals and thus not being controlled adequately. Beneficial insects on the other hand, being biological in nature, would adjust to changes in the pest insect population survival mechanisms.”
The risks of chemicals
In the citrus industry there is currently great pressure to reduce the use of chemical pesticides. While the use of toxic chemicals to control pests on many kinds of crops is well established, a January 2008 report in Business Report revealed that some citrus farmers have admitted to using pesticides merely for cosmetic reasons, in order to produce better-looking fruit.
More than that, the chemicals are a risk to those working on the farm. While pesticides were once applied by hand pump, today they are dispersed by airborne crop sprayers or tractors, exposing farm workers to far larger amounts of more powerful chemicals. The Food and Allied Workers’ Union and similar organisations have lodged complaints when necessary, but have found that in general the safety of workers is not a high priority.
All pesticides in South Africa are controlled by the Fertilisers, Farm Feeds, Agricultural Remedies and Stock Remedies Act 36 – but this dates back to 1947. Expert opinion is that the technology has outgrown the legal requirements.
Professor Leslie London, the director of Cape Town University’s School of Public Health and Family Medicine, explains that it’s not only workers are at risk through direct exposure to pesticides: their families can be indirectly exposed through pesticide drift or contact with residues brought home on clothing. Pesticide drift is commonly found in areas such as the Western Cape, a centre of fruit and wine farming, which experience strong winds. Those most at risk are farm workers and people living in informal settlements, which often encroach on farmland.
Pesticide poisoning can be either acute or chronic, says London. Acute effects range from liver, lung and kidney poisoning to damage to the nervous system or brain, and may be fatal. Chronic poisoning damages the immune, reproductive and nervous systems, affecting memory, cognition and thinking and causing personality change. Some pesticides may increase the risk of cancer.
With this in mind, Du Roi aims to provide cost effective, integrated biocontrol to a range of agricultural and horticultural industries so that the needs of both nature and industry are met – and exposure to dangerous chemicals is minimised or even done away with altogether.
A patient approach
“Contact chemicals have a very different mode of action to that of the beneficial insects,” says Hacker. “Results with contact chemicals are fairly immediate and pest insect populations are knocked down quickly. The release of beneficial insects requires a bit more patience as the results only start showing one to two weeks after release.
“In citrus, for example, there are many other pests for which there are no commercially available biological solutions, so the growers still have to make use of chemicals during certain parts of the season.
“However, restrictions on allowable chemical residues on fruit prevent growers from using certain chemicals closer to picking time. At this stage the fruit is still vulnerable to insect damage and outbreaks can be successfully controlled by beneficial insect releases.
“Beneficial insects can also be used successfully in a preventative pest control programme with early season releases and close monitoring of pest insect populations.”
When an infestation of mealybug or scale breaks out, farmers buy the necessary bugs from Du Roi and release them in the affected vineyards or orchards, where the host-specific predators attack and devour the pests. They will only eat their specific prey, so if these are absent they simply die off.
Breeding the bugs
To produce the beneficial insects, the scale and mealybug pests are first bred in a controlled climate, using butternut squash as a substrate. Once they are established the ladybirds and wasps are raised, in their millions, on the pests. These are then packaged and shipped according to demand.
Beetles are supplied in paper packets containing 50 per packet, Aphytis wasps, which are about 2 mm long, come in tubs of 10 000, and C perminutus wasps, which are only about 3 mm long, are supplied in matchboxes containing around 3 000 pupae for citrus plantations, and 1 500 for vineyards.
To stay ahead of technological developments, Du Roi works with the Citrus Growers’ Association as well as several national and international research and academic institutions such as the universities of Pretoria and Stellenbosch, Citrus Research International, and the Agricultural Research Council.
The company has clear-cut plans for expansion. These include going into production with various undercover crops – produce that is grown with the main crop but planted only after the main crop is established – as well as selling internationally recognised products which it will import and support technically.
Hacker adds that Du Roi is also involved in a production agreement with another company to produce an insect virus for the control of a major pest that attacks various fruit crops. The virus is bred within cultures of the pest insect, from which it is then extracted and processed so that it can be applied in liquid formulation as if it were a chemical.
