WHAT YOU NEED TO KNOW ABOUT THE RECENT AFRICAN ARMY WORM (ARMY WORM) OUTBREAK IN UGANDA!
The Ministry of Agriculture, Animal Industry and Fisheries (MAAIF) yesterday announced the outbreak of the African army worm of the species Spodoptera exempta in 18 districts that of; Luwero, Mukono, Mukono, Wakiso, Katakwi, Bukedea, Bugweri, Serere, Busia, Bugiri, Mityana, Kiryandongo and Namutumba.
The outbreak was first reported by our neighbors Kenya in their own backyard and now as it stands, the devastating pests have crossed to Uganda.
The African Armyworm also known as nutgrass armyworm, is a species of moth of the family Noctuidae. The larvae often exhibit marching behavior when traveling to feeding sites, leading to the common name “armyworm”.
The caterpillars exhibit density-dependent polyphenism where larvae raised in isolation are green, while those raised in groups are black. These phases are termed solitaria and gregaria, respectively. Gregariacaterpillars are considered very deleterious pests, capable of destroying entire crops in a matter of weeks.
The larvae feed on all types of grasses, early stages of cereal crops (e.g., corn, rice, wheat, millet, sorghum), sugarcane, and occasionally on coconut. The solitariacaterpillars are less active and undergo much slower development.
The species is commonly found in Africa, but can also be seen in Yemen, some Pacific islands, and parts of Australia. African armyworm outbreaks tend to be devastating for farmland and pasture in these areas, with the highest-density outbreaks occurring during the rainy season after periods of prolonged drought. During the long dry seasons (“off-season”), the population densities are very low and no outbreaks are seen.
CONTROL AND MANAGEMENT
Cut grass weeds from bordering fields. Remove weeds regularly to reduce breeding sites and shelter for armyworm. However, if fields do become infested leaving grass weeds until the caterpillar have pupated or been controlled may help to reduce damage to the crop, since caterpillars may feed on weeds. Remove all plant debris after harvesting. Variety selection
Some maize varieties are more susceptible to attack than others, e.g. Katumani, a dry land variety grown widely in Eastern Kenya. These varieties are most at risk where probabilities of armyworm infestation are high. Ask your neareat agro shop for resistant varieties Tillage
Plough and harrow field thoroughly. Turning the soil exposes armyworm pupae to desiccation and natural enemies. . Habitat Management ManagementAvoid burning and overgrazing of grasslands, which are the natural habitat and food store of the caterpillars. Burning often causes outbreaks because as soon as temperatures rise, eggs are laid in large quantities on the fresh new grass. No oviposition occurs at temperatures less than 20degC. Also if their natural habitat and food is unavailable they will attack other crops (HDRA). An outbreak is more likely to occur if crops have been fertilised with high quantities of nitrogen as this causes green, sappy growth, which is very attractive to armyworm caterpillars. Biological pest control
Natural enemies should be encouraged by maintaining natural surroundings with plenty of breeding places for them, including trees and shrubs.
Many birds, toads, lizards, small mammals, insects and spiders prey on the African armyworm at different stages of its life cycle:• Lacewings, predatory wasps, parasitic wasps, flies, and spiders attack armyworm caterpillars.• Night birds and bats feed on the African armyworm moths.• Birds (storks and crows) may decimate small outbreaks but have little influence on larger ones.
Biopesticides (including botanicals/plant extracts and microbials) such as Neem, Pyrethrum and Bt should be applied if larvae are at or above threshold levels and preferably when caterpillars are approximately 12 to 20 mm long, namely before most damage has occurred. Once caterpillars are mature, that means they are 30 to 35 mm long, they will have done most of their feeding damage and it would no longer be economical to apply a biopesticide.
Biopesticides should be applied in the evening since armyworms prefer to feed at night.Precautions: It is important to follow all precautions and directions listed it on the label when using a commercial biopesticide(or a pesticide) and ensure that the product is registered for armyworms on the specified crop. Pay particular attention to the required water volume to be used. Best control is achieved when using the highest water volumes. This applies to pesticide and bio-pesticide use for all pests/crops.
NeemTrials carried out in Tanzania showed that both neem seed and leaf extracts could be used to kill armyworms. Even though neem extracts are as effective as SpexNPV and synthetic pesticides, their use is only practicable in small holdings.The high bulk of neem needed and high transport costs means it is not feasible to use it on a large scale.
Dosage: 50g of neem powder per litre of water. This solution is then sprayed on infested • Spray the neem water directly onto the crop using a sprayer or straw brush.
There are different physical methods mainly practicable in small holdings:• Plough a deep ditch. Keep it filled with water. This method is helpful, when caterpillars are found to be moving towards your field from the adjacent fields.• Another method is to dig a deep ditch with vertical sides to trap the caterpillars and prevent them from crawling out. Dig a hole, a diameter of a fence post, in every 10 meters within the ditch. Caterpillars are lured to congregate in the holes. Collect and properly dispose the trapped caterpillars• Make pitfall traps – see image below• Use light traps. They can provide useful information about the population of moths and therefore of caterpillars. Light traps help to predict if there is going to be an outbreak. However, light traps attract many other insects, including other moths. Therefore, it is very important to be able to recognise moths of the African armyworm. Use of light traps is primarily a tool in monitoring. In addition, a wooden tripod with a kerosene lantern is a ”light trap” locally improvised.• A tripod made of wooden poles (bamboo) is constructed with a lantern (kerosene) hanging in the middle over a bowl of water. The lantern is a fire hazard so the tripod must be secure, and the lamp must be hung so that the wood does not catch fire.• Hand picking of caterpillars. This is only practicable in very small plots
April 12, 2022