Contarinia tritici Kirby Yellow wheat blossom midge

Infestations of this widely distributed midge occur on wheat and, less frequently, barley and rye but are rarely of economic significance. The larvae attack the floral parts (stigma and styles) (cf. orange wheat blossom midge, Sitodiplosis mosellana, p. 176), and usually prevent pollination and, thus, grain development. Heavily infested ears have a flattened appearance.

BIOLOGY

Adult midges, although short-lived, sometimes appear in vast numbers over cereal crops in about mid-June. Eggs, typically in batches of up to 30, are laid in the developing but unhardened florets, as soon as the developing ear is exposed (i.e. when the leaf sheath has split: Growth Stage 51); the females do not deposit eggs in hardened florets. Eggs hatch 7-10 days later. The larvae then feed gregariously, sometimes several hundred in each infested ear, and complete their development in approximately 3 weeks. (The yellowish nymphs of cereal thrips, Limothrips spp., also occur in the ears of developing cereals, see p. 92 et seq, and these are sometimes mistaken for midge larvae.) Fully grown larvae eventually 'jump' to the ground and enter the soil; they usually emerge from the ear ahead of those of Sitodiplosis mosellana (larvae of both species sometimes occur together). Under very dry conditions, the larvae can become trapped within the glumes but they often emerge in numbers following a shower of rain. A few larvae may pupate whilst still within the glumes; others which have succeeded in reaching the ground may also pupate (without forming cocoons). Such individuals give rise to a partial second generation of adults that deposit eggs on Elytrigia repens. The majority of larvae, however, spin cocoons in the soil and either pupate in the following May or early June (typically, first emerging from their cocoons and moving closer to the soil surface) or remain in diapause for up to three seasons before eventually pupating. Winter mortality of larvae is often considerable.

DESCRIPTION

Adult 2-3 mm long, lemon-yellow to dusky-yellow, with relatively large, black eyes and dusky wings. Egg minute, golden-yellow and translucent; sausage-shaped with a long stalk. Larva up to 3 mm long, yellow, tapered anteriorly and blunt posteriorly, the penultimate body segment with a pair of chitinized tubercles; sternal spatula with a rounded, bifid tip (Fig. 246b).

Building Your Own Greenhouse

Building Your Own Greenhouse

You Might Just End Up Spending More Time In Planning Your Greenhouse Than Your Home Don’t Blame Us If Your Wife Gets Mad. Don't Be A Conventional Greenhouse Dreamer! Come Out Of The Mould, Build Your Own And Let Your Greenhouse Give A Better Yield Than Any Other In Town! Discover How You Can Start Your Own Greenhouse With Healthier Plants… Anytime Of The Year!

Get My Free Ebook


Post a comment