Prevention and Management of Fall Armyworm
There are a number of ways to try to manage Fall armyworm in maize and other crops, but because Fall armyworm is a new pest to Africa, none of them are guaranteed to be effective and research is going on to develop more effective solutions.
However, the approaches listed below are believed to be the most effective.
Recommendations vary between countries.For more precise recommendations on what might work in your area, talk to your extension agent and other experts.
Cultural and manual practices
- Intercropping and crop rotation with non-grass species such as cassava can reduce crop damage.
- Handpick and destroy egg masses and larvae, or collect and drop larvae in hot water.
- Killing one caterpillar prevents the appearance of more than 1500-2000 new caterpillars within less than four weeks.
- Using good quality seeds can increase plant vigour and potentially reduce damage.
- Eliminate grassy weeds in maize fields and nearby as they provide shelter and food for the pest.
- Avoid late planting.
- Put a handful of sand (mixed with lime or ash), sawdust, soil, or grit in the whorl of attacked plants to kill bigger caterpillars.
- Use balanced fertilization to boost plant vigour. In maize, the recommended fertilization rate is 200 kg of NPK at 15:15:15 per ha—but this varies depending on the country.
- Remove and destroy all crop residues.
- Do not move infested plant materials to areas where the pest has not been reported.
Biopesticides
- Biological pesticides, including Bt (Bacillus thuringiensis) sprays are an option in some African countries, though they are not always available or affordable for small-scale farmers. In some countries, governments may provide subsidies or fund spraying programs. If available, apply 1 sachet per 15-litre knapsack of these products twice a week at three-week intervals.
- Neem-based products
Chemical control
Carefully observe your maize to check if there is significant damage. If you decide to use insecticides, try to rotate insecticides with different modes of action to avoid the pest developing resistance to individual insecticides or groups of insecticides. In the list of insecticides below, that would mean rotating products with different IRAC (Insecticide Resistance Action Committee) codes.
For example, in one cycle, you could spray Alpha-cypermethrin (group 3A); in the following cycle, you could change to chlorpyrifos (group 1B), so that you don’t use an insecticide with the same mode of action in consecutive cycles.
A variety of insecticides might be effective against Fall armyworm, including products which contain:
- Alpha-cypermethrin (Pyrethroids, group 3A)
- Chlorantraniliprole (Diamides, group 28)
- Chlorpyrifos (Organophosphates, group 1B)
- Diazinon (Organophosphates, group 1B)
- Diflubenzuron (Benzoylureas, group 15)
- Trichlorfon (Organophosphates, Group 1B)
- Emamectin benzoate (Avermectins, Milbemycins, group 6)
- Indoxacarb (Oxadiazines, group 22A)
- Lambda-cyhalothrin (Pyrethroids, group 3A)
- Lufenuron (Benzoylureas, group 15)
- Spinetoram (Spinosyns, group 5)
- Spinosad (Spinosyns, group 5)
Spraying Guide:
- Spray early in the morning or late afternoon, when the caterpillars are most active. Pesticides must be applied at the correct dose.
- Ensure that the spray gets into the whorl, as this is where the older caterpillars are.
- Avoid spraying under adverse environmental conditions such as high winds or when it is raining, as this will reduce the effectiveness of the chemicals.
- Control is best if all farmers in an area apply controls.
- Fields that aren’t controlled act as breeding grounds for the insect and a source of re-infestation.
Important note:
- Farmers need to know that broad-spectrum pesticides will also kill the natural enemies that control Fall armyworm.
- Managing Fall armyworm with insecticides is made more difficult by the caterpillar’s tendency to hide within the whorls and reproductive parts of the host plant, where it is difficult for insecticide sprays to reach them.
- For this reason, the crop should be sprayed as soon as the pest is noticed on exposed leaf surfaces, and during the early development stages of the larvae.
Caution: Pesticides are poisonous. When using a pesticide, always wear protective clothing and follow the instructions on the product label, including dosage, timing of application, and pre-harvest interval. It’s also important to avoid spraying pesticides near bodies of water, and to avoid spraying at times when bees are actively foraging.
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The above article was adapted from @Farm Radio International resource pack @CABI. All rights reserved