Napomyza carotae Spencer larva Carrot miner

This species is a minor pest of carrot, the larvae feeding in the leaves and the roots. Leaf mines are of little or no consequence. However, mined tap roots may become malformed; attacks are of greatest importance on early crops. Although larval damage tends to be restricted to the uppermost part of the root and is relatively superficial, the overlying tissue eventually collapses to produce obvious, irregular scars which open out as the root grows (cf. carrot fly, Psila rosae, p. 181). Such damage tends to predispose the roots to invasion by pathogens, especially in wet conditions, and is a particular problem on crops in store. Although well established in parts of continental Europe, including Germany, the Netherlands and Switzerland, in the British Isles, where it was first reported (in East Anglia) in 1974, it is rare and not of pest status.

BIOLOGY

Eggs are laid in the leaves or stems of carrot plants. The adult females also make pale, rounded feeding punctures in the foliage, each c. 0.5 mm in diameter. After eggs have hatched, the larvae mine downwards within the mid-rib, petiole and stem; except in mature plants, the larvae also invade the roots. Pupation takes place within the mine. Adults occur from May to June, and from August to September; in some situations, there may be a partial third generation in October. The winter is passed in the pupal stage.

DESCRIPTION

Adult mainly grey or black; wings 2.7-3.1 mm long, the genus differing from Phytomyza (q.v.) by the addition of another cross-vein; legs black with yellow knees. Larva up to 6 mm long, white; mouth-hooks with main axis set more or less at right-angles to rest of mouthparts, and each with several small teeth; posterior spiracles borne on distinct projections and each with a double row of about 20 minute pores (cf. carrot fly, Psila rosae, p. 181). Puparium 4.5-5.5 mm long, white, slender; posterior spiracles brownish-black, each borne on a short projection.

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