Studies on Oscinella frit Linn: Notes on the resistance of cereals to infestation

Abstract

Resistance of the oat plant to infestation by the frit fly is not correlated with either carbohydrate or silica content. By increasing the number of eggs placed on an oat variety, proved to be resistant in the field, its resistance can be reduced below that of the most susceptible type, the inference being that resistance is indirect and due to some form of plant attractiveness which determines extent of oviposi‐tion. Oviposition studies in the held show that oviposition on susceptible varieties of oats, such as Victory and Star, is three times as great as on resistant types, such as Summer and Spet; selections from crosses between susceptible and resistant types, intermediate in resistance, receive a proportionate number of eggs, resistance being inherited. Some oviposition data for wheat and barley are included. Fly orientation is not controlled by either chemotaxis or hydrotaxis, but is influenced by stereotaxis; negative results have so far been obtained from phototaxis studies. Trie resistance to infestation in the field of twenty‐two named varieties of oats is compared with that of a standard variety; none is so resistant as Summer, while Richland Iowa 411 and Eagle approach Sandford in possessing moderate resistance. The marked difference between Victory and Summer in regard to stem infestation in spring is not extended to the grain infestation, no marked difference being observed. Susceptibility to sterility of grain shows significant differences, and there is an indication that segregation may be transgressive. Late nitrogenous dressings have no effect on extent of either grain infestation or sterility. The recovery capacity of Sandford almost equals that of Gris de Houdan, a good tillering variety. Maize exhibits varietal differences in extent of resistance to attack. The protective effect of D.D.T. is considerable, but not complete.The essential statistical analyses have been lodged with the Librarian of the British Museum. A statement of significance of result means significance at the 1 % point of distribution.