The Gulu Agricultural Development Company (GADC) in northern Uganda works with tens of thousands of smallholder farmers who produce organic cotton. Organic production is often challenged by the large numbers of pests which attack the crop, notably the African bollworm, aphids and various species of sucking bugs. However, help is at hand in the form of the naturally occurring organisms or ‘natural enemies’ that prey on these cotton pests – such as ladybirds, lacewings, and parasitic wasps. These natural enemies can be very effective in keeping the numbers of pests down. By encouraging these natural enemies into the crop and helping them to survive there, farmers can prevent pest numbers from reaching economically damaging levels.
So how can farmers encourage these natural enemies into their crops? One approach is to use ‘food sprays’, based on a mixture of sugar and yeast or maize. These sprays, which mimic the scent of the prey, can be used to attract the natural enemies into the crop early in the season so that they are ready for action when the pest numbers start to increase. The use of food sprays was first developed by Dr Robert Mensah of the Australian Cotton Research Institute, who worked with the UK Pesticide Action Network to adapt them for use by smallholder farmers. Trials in Benin and Ethiopia have found that the sprays can be very effective in controlling pests and increasing yields, and therefore in increasing farmers’ income.
Field testing with smallholder cotton farmers
To see whether these positive results would also apply in Uganda, AgDevCo supported GADC in testing food sprays with smallholder farmers during the 2019 cotton season. Forty of the company’s lead farmers were provided with food sprays, made from four different combinations of yeast, maize, sugar and molasses. The farmers applied the first spray when the cotton plants were very young in order to attract the beneficial invertebrates into the crop early in the season. They then checked their cotton once a week and used an identification manual to count the number of pests and natural enemies they saw, re-applying the food spray if the pests outnumbered the natural enemies by more than two to one.
It quickly became clear that the food sprays were having a major impact. The plots that had been sprayed were found to have larger numbers of predators and lower numbers of pests than control plots where the sprays were not used, demonstrating that the food sprays can tip the balance in favour of the natural enemies. At the end of the season, the yields from the sprayed plots were significantly higher than from the control plots – with the difference ranging from 20% to 65%, depending on the particular spray used. As the sprays were made from cheap, locally-available materials, the increases in yields were more than enough to outweigh the cost of producing the sprays and hence to produce a net return for the farmer. Almost all the farmers involved gave positive feedback on the sprays, commenting that they found them very easy to use.
Although these initial results look very promising, this isn’t the end of the story. Having demonstrated that smallholder farmers can use food sprays effectively, GADC and AgDevCo will be carrying out more rigorous trials in the 2020 farming season. In particular we’ll be assessing whether farmers themselves can produce the sprays cost effectively, and will compare the efficacy and cost/benefit ratios of the various formulations. As always when introducing innovations to smallholder farmers, we need to be very confident about the benefits and clear about the costs before we can recommend that adoption is scaled up.
If the initial positive results are borne out, there’s no reason to think that the use of food sprays should be restricted only to cotton. We already know that planting maize or sorghum near cotton can reinforce the efficacy of the sprays by providing habitats for natural predators – so we’d like to look at whether the food sprays can also help to protect those crops as well. Food sprays could well turn out to be a significant step forward in enabling smallholder farmers to improve their yields in a sustainable and cost-effective way, without the use of hazardous and expensive chemicals.
AgDevCo’s Smallholder Development Unit is supported by the Mastercard Foundation and UK aid.