Wheat bulb fly, Leptohylemyia coarctata Fall., and its effect on the growth and yield of wheat

Abstract

SUMMARYIn two experiments done in successive years to compare the growth and yield of Cappelle wheat either protected from or exposed to attacks by larvae of wheat bulb fly, the plots were previously fallowed, but egg laying was prevented on half of each plot by using Polythene soil covers. In the first season wheat was sown at the end of October, November and December and in the second season in late October and in early January, when there were two sowings, one with and one without a spring application of herbicide. The infestation rate was 1·1‐1·7 million eggs per acre, typical of a moderate attack. Larvae had little effect on the yield of October‐sown wheat as the plants had two shoots each when first attacked and few were killed. On plots sown late, yield was decreased by up to 22%, as plants had only a single shoot when attacked and many were killed.The main effect of wheat bulb fly was to reduce the number of ear‐bearing shoots by killing plants and restricting the production of new shoots. Surviving plants partially compensated by producing more ear‐bearing shoots with heavier ears and slightly heavier seeds than normal.Killed plants were not distributed uniformly but were often in patches several feet across. Wheat on the attacked plots ripened more slowly and unevenly than on the unattacked plots.Weather affects the growth of the plants and activity of the larvae and thus partly determines percentage shoot survival.

The Use of Insecticidal Seed Dressings as a Means of Decreasing a Population of Wheat Bulh Fly (Leptohylemyia coarctata(Fall.))

“…With the comparatively low degree of attack there would have been little competition between larvae for access to the plants and it seems likely that larval invasion was at random, with little preference for well tillered plants. Previous workers (Raw, 1954;Bardner, 1968) have shown that the number of shoots present at the time of larval invasion influences the survival of the larvae as they migrate from the egg to the host.…”

The stage of maize, with respect to floral initiation, most vulnerable to infestation by stem borer,Chllo partellus(Swinhoe) in India

“…This will hinder the formation of the bud. But once the bud is formed, growth has started, and even if destroyed the bud may be replaced and further growth again takes place (Bardner 1968). Leaf injuries may be greater in a crop of about 2 weeks, or 5 days before bud initiation, because the leaves are more tender than in older plants.…”

Impact ofHalotydeus destructoron Crop Seedlings at Different Plant Developmental Stages and Levels of Moisture Stress

“…However, when mites were introduced at later growth developmental stages (canolaÑthird true leaf stage; wheatÑGS14), plants were generally unaffected by mite feeding damage. This pattern highlights the susceptibility of early growth stages to herbivory with limited ability to compensate immediately after germination; however, as plant growth proceeds they become increasingly tolerant to attack (Bardner andFletcher 1974, Trumble et al 1993). Similar patterns have been shown previously on wheat.…”

“…Similar patterns have been shown previously on wheat. For instance, wheat seedlings with a single shoot are much more easily killed by the wheat bulb ßy (Leptohylemyia coarctata Fall) than older seedlings with two or more shoots (Bardner 1968).…”