Why pesticides have failed to fight armyworms

Government recently announced a resurgence of the Fall Army Worm (FAW). By April 14, the pest had spread to 41 districts across the country, ravaging cereals such as maize, millet, and sorghum and pasture for livestock. 
The pest could feed on more than 80 plant species and cause yield loss of about 75 percent, making it one of the most destructive crop pests. Notably, the pest prefers maize because it has big stems and leaves in which it can hide.

Controlling FAW is critical because cereals are a major source of food and income for most households.  According to the Uganda Bureau of Statistics (UBOS), over 3.6 million households derive their livelihood from maize alone. Furthermore, Uganda’s foreign exchange earnings are at stake. In October - December 2021, Uganda exported maize and sorghum worth $38.1m (Shs135b) and $26.3m (about Shs93b) respectively, to the East African Community countries. 
When FAW was first reported in Uganda in 2016, UBOS and the Food and Agriculture Organisation estimated that the invasion caused a yield loss of 450,000 metric tonnes, worth $192m  (Shs685b) during the first cropping season of 2017.
The government spent over Shs4.5b to procure pesticides and undertake a mass sensitisation programme.

 However, the use of pesticides was not effective since the pest persisted in some areas. The ineffectiveness is explained by challenges related to accessibility and affordability of the pesticide, knowledge of correct use/mixing, consistency of use and the possibility of the pesticide not reaching the pest during spraying. Also, the sensitisation programme had a low coverage.
Majority smallholder farmers could not afford to buy the pesticide, others could not mix the pesticide appropriately, given the high illiteracy rates.  

Smallholder farmers use ordinary knapsack sprayers used in vegetable gardens, which have low pressure, thus the pesticide is unable to reach the FAW larvae hiding lower in the maize plant leaves.  Despite the previous shortcomings, the government is again advocating for use of pesticides as the first line of defence in the current FAW outbreak. 
Ministry of Agriculture reported that about Shs600m has been spent to procure 23,000 litres of pesticides, 100 motorised pumps and 200 sets of protective gear have been distributed to the affected districts. However, these items are for demonstration purposes, implying that much of the burden of controlling the pest will be borne by farmers.
 
A litre of the recommended pesticide costs around Shs20,000 in the urban markets and it is sufficient for only one acre, yet smallholder farmers have an average of 2 acres under cereal production. Like in the first outbreak, affordability of the pesticide is likely to be a major constraint in controlling FAW.
Government needs to complement the use of pesticides with other approaches such as the “push-pull” technology (PPT). With this technology, the cereal crop is intercropped with specific legumes while Napier grass is planted around the border of the garden. The legume produces an offensive smell that repels the pest while the Napier grass releases a chemical stimulus that attracts the pest, thus drawing it away from the cereal crop. 

PPT was developed by the International Centre of Insect Physiology and Ecology (ICIPE) and field experiments using PPT in Kenya, Uganda, Tanzania and Ethiopia revealed that FAW infestation and plant damage was 87 percent lower in the plots where PPT was used compared to maize monocrop plots. 
PPT technology is affordable for smallholder farmers because locally available plants are used. PPT also increases soil fertility due to nitrogen fixation by the legume plants, conserves moisture and enhances soil organic matter which prevents soil degradation. 

In addition, Napier grass and the legume plants provide high value animal fodder that increases milk production which creates an alternative stream of income for farmers. Besides FAW, PPT has successfully been used to control other caterpillars and witch weed that affects maize, sorghum, millet and rice,  a reason for us to embrace it . 

The writer, Medard Kakuru , is a research analyst at Economic Policy Research Centre, Makerere University