PEST MANAGEMENT DECISION GUIDE: GREEN LIST Black armyworm on maize Spodoptera exempta Black armyworm; African armyworm; Nutgrass armyworm Prevention Monitoring Direct Control l Grow less susceptible varieties if available l Monitor immediately after germination and check weekly for l For small farms, hand pick caterpillars l Plant early to try and avoid severe damage by symptoms. and eggs and destroy them by crushing second generation armyworms l Check for armyworms late evening/early morning. They often feed or feed to chickens or ducks l Avoid planting close to overgrazed grasslands at night and hide under debris during the day l Dig a 30 cm deep trench with vertical which provide food and refuge for caterpillars l Look for caterpillars in field margins, low areas where plants have sides around the field to trap marching Black armyworm; dorsal caterpillars. Collect and destroy them surface of larva, showing l Remove weeds such as Amaranthus and grassy lodged, beneath plant debris around the base of plants, underneath markings (©Rikus Kloppers/ weeds since they are food for young caterpillars, plant leaves and on young, soft shoots and stems l Apply neem. Seed extract: 50g/L water PANNAR Seed (Pty) Ltd, with a little soap. Greytown, South Africa) and keep other weeds to provide shelter and l Monitor closely when rains come after a long period of drought, food for natural enemies causing grass growth. l Apply Pyrethrum: Grind Pyrethrum l Encourage the presence of natural enemies l Look for chewed leaves making the crop look ragged. Only the flowers into a dust, use pure or mix with such as birds, toads, lizards, small mammals, midribs are left in severe cases a carrier like talc or lime, then sprinkle over plants insects and spiders, by planting trees and l You may find dark specks of frass from caterpillars on plant stems shrubs and leaves l Or use Pyrethrum powder: 20 g l If armyworm is suspect in the field, plough and powder/10 L water. Soap can be l Caterpillars: When young: <1 cm long; white to greenish with an added to make the substance more harrow field thoroughly before planting to orange head. When old: up to 3 cm long; grey-green to black; expose pupae to natural enemies and effective but it is not vital. Apply Black armyworm; underside of velvety black shiny head; inverted V-shaped mark on head; white/ immediately as a spray. larva, showing true-legs (in desiccation yellow strips along the sides and the back. anterior region) and pro-legs l If available, place egg cards with l Do not over-fertlize the soil since too much N l Black armyworm can be confused with Fall armyworm. See (©Rikus Kloppers/PANNAR can cause green, sappy growth which is Trichogramma wasps that will hatch Seed (Pty) Ltd, Greytown, information on Fall armyworm for description of the caterpillar. attractive to armyworm caterpillars and then parasitise and kill armyworm South Africa) l Adults/moths: Stout-bodied, 1.4-1.8 cm long, wingspan of 3 cm. eggs (read and follow label l Rotate maize with non-cereals such as legumes Forewings dark brown with distinctive grey-black markings. instructions) since these are less susceptible. Avoid crop Hindwings white with dark veins. Emerge from pupae in soil which l If available, apply product based on S. rotation with alternative hosts such as barley, are brown-black, 1-1.4 cm long, smooth and shiny. teff, oat, millet, sorghum, wheat. exempta nucleopolyhedrovirus l Consider action when 10-25 % of plants show signs of feeding (SpexNPV) against larvae (read and l Remove and destroy all plant debris after damage follow label instructions) harvesting to reduce the food source for armyworm l When older, about 3 cm long, caterpillars eat large areas of leaf Adult female S. exempta edges, leaving leaf midribs, or eat entire leaves, direct control may (museum set specimen) not be effective (©Georg Goergen/IITA Insect Museum, Cotonou, Benin) Note: Pesticides may be available to control this pest. Please check with the Ministry of Agriculture in your country to find out which pesticides are registered in your country and the local restrictions for their use. CREATED/UPDATED: September 2017 LOSE LESS, FEED MORE PRODUCED BY: Plantwise Plantwise is a CABI-led global initiative www.plantwise.org.