Family Gelechiidae

Phthorimaea operculella (Zeller) Potato moth

This insect is mainly a pest of the subtropics. However, infestations also occur in temperate regions. The larvae burrow into potato leaves, stems and tubers and are particularly damaging to tubers in store. Damaged potato tubers are often invaded by fungi and mites, and the remaining tissue then rapidly decomposes. Damage is also recorded on other members of the Solanaceae, including aubergine and tomato. On tomato, significant damage may result when the larvae bore within the leaves, stems and developing fruits. This pest is not established in the British Isles, although it is known to occur occasionally in association with imported produce.

BIOLOGY

Adults tend to be active from April to October. Under suitable conditions, there may be six if not more overlapping generations annually (10°C being the threshold for larval development). Adults usually lay their eggs in cracks or crevices on potato tubers, tomato stems and so on. The eggs usually hatch within a few days. Larvae then bore into the plant tissue to form silk-lined galleries from which, as development proceeds, frass is ejected. Larvae are usually fully fed in

Fig. 280 Forewing of potato moth, Phthorimaea operculella (xl5).

2-3 weeks. They then emerge to pupate in narrow, whitish cocoons formed on potato sacks and other available surfaces. New adults appear within 2-4 weeks, depending on temperature.

DESCRIPTION

Adult 10-12 mm wingspan; forewings mainly yellowish-grey, peppered with black spots (Fig. 280); hindwings grey, with long hair fringes. Egg oval and pearly-white. Larva up to 10mm long; body white, suffused with pinkish dorsally on each segment; head, prothoraclc plate and anal plate brownish-black.

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