Movement and Oviposition of Wheat Bulb Flies

Abstract

Water traps examined weekly were used to assess the activity of adult wheat bulb flies during the oviposition period in late July, August and eariy September. Traps were placed at various distances up to 1 mile (1-6 km) from known sources of infestation at Whittlesey, Cambridgeshire and at Rothamsted. Most flies were caught down wind from possible emergence sites and few were caught more than ^| mile (^0-4-0-8 km) away. The distribution of flies between traps was similar in both the first and second halves of the trapping period. At Whittlesey there was a significant positive correlation between the number of flies caught in a trap and the number of eggs laid in the field containing the trap. SUMMARYMethyl-bromide (1 lb/100 sq. ft), applied as in commercial practice, gave an increase in yield of both grafted and ungrafted tomato plants in glasshouse soils naturally-infested with root diseases. Grafted plants greatly outyielded ungrafted plants on treated and untreated soil where phytophthora stem and root rot was present. The efl"ect of the gas on corky root rot varied in the experiments and, on one nursery, control of the disease was not reflected by increased yield.

Rainfall as a mortality factor in the Sorghum Shootfly, Atherigona soccata Rond. (Diptera, Muscidae)

“…In spite of the presence around the study site of a "wild" shoot fly population of unknown size, our data show a significant correlation between rainfall and decrease in adult numbers; a loss in trap efficiency due to reduced sunshine and possibly to an arrestant effect of rain (MILES 1951, BARDNER et al 1968), also occurred.…”

Use of oviposition trays to estimate numbers of wheat bulb fly Leptohylemyia coarctata eggs

“…Tray samples can be taken more rapidly than core samples and, because of the smaller bulk of soil, also require less time for processing in the laboratory. Bardner, Lofty, Huston & Maskell (1968) have shown that most flies do not travel more than 0-8 km to oviposit so that areas found to be at risk are unlikely to change rapidly…”

Forecasting egg populations of wheat bulb fly, Delia coarctata (Fall.), from catches of adult females in water‐traps

“…In both years, four traps per field were used, each one being placed in a different part of the field. This was a practical number to visit and an irnprovem.ent over the one trap per field used by Bardner et al (1968). It also allowed reasonable estimates of a total catch to be made when some traps were upset during cultural operations.…”

“…They then fly to bare soil, either fallow areas or between rows of plants, to lay eggs. Wliile studying dispersal over a limited area in East Anglia, Bardner et al (1968) placed a single white water-trap at each of 15 potential oviposition sites and recorded the numbers of flies caught during July and August. In September, egg populations at these sites were estimated from soil-cores.…”