Armyworm mystery deepens in Union

January 4, 1929

THE Rhodesian “armyworm” (Laphygma exempta Wik), or “army mystery worm” as it is sometimes termed in the South African Union, has put in an appearance in numbers in at least two districts, namely Hartley, including Gatooma sub-district, and Shamva. Considerable damage to maize is reported.

The last big outbreak of this pest was in January and February 1926.

This caterpillar is the young stage of an inconspicuous night flying moth, and has no connection with the migratory white butterflies which commonly fly steadily in a south-easterly direction for days on end during the early part of the wet season.

The eggs are laid in clumps on the food plants and are covered with down from the parent moth.

They hatch in a few days (minimum three) and the caterpillars feed up rapidly. The period of development has not been ascertained accurately in Southern Rhodesia, but it is probably about three weeks in the summer.

When fully fed, the caterpillars enter the soil and change to the pupa stage, from which the bulk of the moths emerge in a fortnight or less in the summer. Outbreaks rarely last for more than about 10 days after the caterpillars are noticed.

LESSONS FOR TODAY

◆ As the summer cropping season progresses, so too the dangers of pests (the African armyworm and fall armyworm) that cause immense damage to economically cultivated cereals like maize, sorghum, including vegetable crops and cotton.

◆ The armyworm is one of the worst enemies of Zimbabwe’s agricultural industry to achieving food security since they cause extensive damage to crops. It is also present in a number of Southern African Development Community countries: Namibia, South Africa, Mozambique, Malawi and Zambia. ◆ Native to North America, the armyworm got their name from their behaviour of moving across fields in army-like fashion. While the larvae consume available food sources, they migrate as an army to new host plants.

◆ Mitigation measures are led by the Department of Plant Protection Services Institute under the

Department of Research and Specialist Services.

◆ In 2019, Dr Unesu Ushewokunze-Obatolu said the fall armyworm is one of many “transboundary outbreaks” Zimbabwe has been fighting in the past years: “The Government’s approach to managing fall armyworm outbreaks has been to train extension officers and raise awareness among farming stakeholders, to contain and manage fall armyworm outbreaks.”

◆ Seed Co, a leading seed company, through Wendy Madzura, said insect pest control is a critical element in increasing productivity: “Insect pests have the potential to greatly reduce the surface area of the crop, which then reduces photosynthesis, resulting in reduced yields . . . Effective insect control is characterised by correct and timely identification.”