Plants affected
Plums, gages and damson fruits.
Symptoms
Ripening fruits contain a pinkish-white caterpillar up to 12mm long and may be misshapen. The area around the fruit stone has many small, orange-brown pellets, which are the caterpillar’s excrement. A resinous gum around the stone is due to a physiological disorder and should not be confused with plum moth damage. Fruit damaged by plum moth often ripens prematurely but those ripening later generally show a much lower level of infestation.
Biology
The adult moth lays eggs on developing fruitlets in June-July. After hatching, the caterpillar tunnels into the fruit and feeds around the stone. When fully fed in late July-August, the caterpillar emerges, overwintering under loose flakes of bark. It pupates in the following spring.
Control
None of the pesticides available to home gardeners for use on plums is effective against this pest. On isolated trees, use of a plum moth pheromone trap may result in enough males being caught to prevent some females mating, resulting in fewer viable eggs being laid. These traps, which are available from most garden centres, should be hung in the tree in mid-May when the adult moths are emerging.