This insect is a widely distributed and locally common pest of damson and plum; infestations are often also abundant on Prunus spinosa. The larvae, known as 'red plum maggots', feed singly within the flesh of developing fruits, and often cause premature ripening and fruit drop. Unlike fruitlets attacked by larvae of the fruitlet-mining tortrix moth, Pammene rhediella (p. 222) and plum sawfly, Hoplocampa flava (p. 251) wet, brown larval frass accumulates within the fruit and is not ejected from the feeding gallery during larval development. This pest is of particular importance in years when fruit set is light and in conditions favourable for development of a noticeable second generation. Second-generation or late-developing larvae are a particular problem as they often occur inside harvested fruits. Even very small numbers of infested fruits may be sufficient for processors to reject crops at the factory.
Moths are most numerous from mid-June to mid-July, but may occur at any time from the end of May to September. Eggs are laid singly on developing fruitlets. The eggs hatch in about 2 weeks and the young larvae then burrow into the flesh to begin feeding. Larval development lasts for approximately 5 weeks. Fully fed individuals vacate the fruits from late July or early August onwards. They then spin cocoons in sheltered positions on the bark of host trees, overwinter and pupate in the spring. Under favourable conditions, early-developing larvae may pupate immediately and give rise to a partial second generation of adults in August or September. Second-generation larvae complete their development in the autumn.
Adult 11-15 mm wingspan; forewings dull purplish-grey, with darker but obscure markings, and irregularly suffused with ash-grey; hindwings brownish-grey (Fig. 290). Egg 0.7 x 0.6mm,
flat, oval and translucent. Larva up to 12 mm long; body reddish (early instars whitish); head dark brown; prothoracic plate and anal plate light brown with darker markings; anal comb present but with a weakly sclerotized base (cf. that of Pammene rhediella, p. 222). Pupa 6-7 mm long, light brown.
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