Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Relations between phenology and food-plants in the wheat gall-midges Contarinia tritici (Kirby) and Sitodiplosis mosellana (Gehin).

Abstract

Further field and laboratory investigations on the biology of Contarinia tritici (Kby.) and Sitodiplosis mosellana (Geh.) in northern Germany, where the midges infest wheat and rye, are reported [cf. preceding abstract, etc.]. When pupae were kept at 15-25 deg C in the laboratory, the adult emergence of C. tritici extended over 30 days, with a sharp peak at 10-14 days. Emergence of S. mosellana extended over about 50 days, with a broad peak at about 25-45 days. In the field in 1971, emergence of C. tritici took place from early June to 10th July, with a peak at about 4th-8th June (when the air temperature was high and soil moisture content low) and a lesser peak at about 25th June. In S. mosellana, emergence took place from about 5th to 25th June and in the first half of July, when temperatures were again high and the soil moisture content falling.The relation of the occurrence of the midges to their main food-plants and their time of flowering was investigated in 1969-71. In areas where wheat is the main crop, with only a small amount of rye, the latter is scarcely attacked by S. mosellana, but in the Weser-Ems area, where only rye is grown, infestation is sometimes heavy [cf. RAE/A 55, 860]. S. mosellana infests winter and spring wheat about equally. The peak flight period of C. tritici is also fairly closely related to the time of appearance of the wheat flowers, and early varieties do not escape attack. Adults of both species that emerge after wheat has virtually finished blooming oviposit on very late ears and on couch grass (Agropyron repens). The Pteromalid Pirene penetrans (Kby.) was found parasitising S. mosellana on both wheat and rye.