Protection of winter wheat against orange wheat blossom midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae): efficacy of insecticides and cultivar resistance.

BACKGROUND: In 2012 and 2013, Sitodiplosis mosellana (Géhin) flights occurred during the susceptible phase of wheat development in Belgium. The protection against this midge afforded by various insecticides was assessed in infested fields on four winter wheat cultivars (susceptible or resistant, and early or late heading).

RESULTS: The insecticides sprayed at the right time reduced the number of larvae in the ears by 44-96%, depending on the product. For Julius, the cultivar (cv.) most exposed to S. mosellana in 2013, the mean yield gain resulting from insecticide use was 1558 kg ha(-1) (18%). In the same year, insecticide use resulted in a yield gain of 780 kg ha(-1) (8%) for the cv. Lear, in spite of its resistance to this pest. The link between yield and number of larvae counted in the ears was a logarithmic relationship, suggesting an important reduction in yield, caused either by the damage inflicted by young larvae that died at the start of their development or by the activation of costly reactions in plants.

CONCLUSION: The study showed that, in cases of severe attack, the timely application of insecticide treatments can protect wheat against S. mosellana, and that even resistant cultivars can benefit from these treatments.