Alabama argillacea

Scientific Name Alabama argillacea (Hübner, 1823)
Common Names English: Cotton leafworm; Spanish: Gusano medidor del algodón; German: Amerikanische Baumwollblattraupe; Portuguese: Curuquerê do algodão
Description A. argillacea is a tropical species, native to South America und Central America. It cannot survive the winter in temperate climates. The adults are good fliers and migrate each spring in large numbers from the cotton-growing areas of Brazil northwards, sometimes as far as southern Canada.
The adult moth has light brown wings that span about 25 mm (0.97 inch). The caterpillars are up to 40 mm (1.57 inch) long, green or brownish with black and white stripes. They have a characteristic pattern of black dots on each segment.

Biology

Damage

Semi-transparent windows are found on the leaves, resulting from feeding of the worms on the lower surfaces of the leaves; the mesophyll is completely removed, and only the cuticle of the upper surface remains. Later, the leaves are skeletonized and the larvae may completely defoliate the cotton plant, usually beginning on its lower parts and moving upwards. When the foliage has been almost fully devoured or if population pressure is high, squares and young bolls may be attacked, too.

During its development, a single caterpillar will consume up to 120 cm² (18.6 square inch) of leaf surface, about ¾ of it as the last instar. Even infestations that are less dramatic than this will lead to a lower number of fruiting branches, smaller plants and therefore reduced yield, due to a large reduction in photosynthetically-active tissue.

Lifecycle

The eggs of A. argillacea are laid singly, usually on the undersides of leaves in the upper third part of the plant. After 3-10 days, the larvae hatch and migrate to the lower parts of the plant, where they find better-quality food in the form of young leaves, as well as greater protection against climatic adversities and natural enemies. As they develop, they pass through 5 - 6 instars in a timeframe of 2 - 3 weeks, then they return to the uppermost parts of the plant, where they pupate.
The pupation takes place in a cocoon, built from one or several folded leaves held together with silk strands. The adult emerges 1-2 weeks later. After a pre-oviposition time of 2-4 days, the female starts to lay eggs, altogether about 500 in its lifetime of up to 4 weeks.
The adult moths are active mostly after midnight; during the day, they only fly up when disturbed.

Occurrence

Agricultural Importance

In Brazil, A. argillacea is considered one of the most important pests of cotton. In other countries, its impact varies between regions and years: yield losses of about 66% have been reported.

Control

Integrated Crop Management

The cotton leafworm is often very effectively parasitized by natural enemies. This should be considered in the choice and application of pesticides.

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