STUDIES ON OSCINELLA FRIT LINN.

Data, collected in Sweden during the year 1927, indicate the existence of considerable variation in extent of infestation of the grain of different varieties, sown at the same time. Also they suggest that sterility or "blindness" of grain may be a varietal character.     

STUDIES ON 08CINELLA FRIT LINN

As the result of studies on Oscinella frit during the years pro to 1928, it was considered that an attempt might be made to solve economic problem presented by this fly by hybridization of oats, i a resistant variety as one parent.
The technique adopted is described and the experimental data show that resistance to attack is an inheritable character (or complex characters), although difficult of precise measurement. Further, shown that agricultural quality and resistance to attack are not in patible.
Wet weather conditions during the flight of the fly have a marked effect in limiting the extent of damage to the crop.
It is suggested that varietal differences in extent of attack ma due to varietal differences in crude fibre production or depositio silica, both tending to increase the larval difficulties and there for resistance of the plant.
I have great pleasure in acknowledging the readiness with w Dr Hunter of the School of Agriculture, Cambridge, has given me benefit of his experience; also, the valuable criticism which Mr J. C. F. Fryer, of the Ministry of Agriculture Pathological Laboratory, Har-penden, has always placed freely at my disposal.     

EXPERIMENTS ON THE MODE OF ACTION OF DIELDRIN SEED-DRESSINGS AGAINST SEEDLING ATTACK BY THE LARVAL FRIT FLY, OSCINELLA FRIT L

Experiments with dieldrin seed-dressings were done to see whether the conditions favouring their action against wheat bulb fly larvae apply also to frit fly.
Experiments with oats and wheat in boxes and a small field trial with oats showed that fewer newly hatched larvae were killed when dieldrin-treated seed was sown deeply than when sown 1/4 - 1/2 in. deep; shallow sowing probably puts the insecticide where the larvae are likely to meet it before they attack the plant. Kill was never complete even with dieldrin applied at almost forty times more than the highest rate normally used. This is partly because some larvae hatch from eggs on the plant and these, unlike those from soil eggs, can enter the shoot without touching the seed dressing.
Even in the most favourable circumstances (large doses of dieldrin applied to the shallow-sown seed and the plant at the one-leaf stage at the time of attack) there was little evidence that frit fly larvae are killed inside the shoot by systemic action of dieldrin translocated from the seed. This is not because the pales which normally surround the oat seed impair the uptake of insecticide, or because of any other factor specific to oats. Frit fly larvae also survived in wheat from seed dressed with doses of dieldrin that can kill almost all wheat bulb fly larvae by systemic action. Possible reasons for this difference are discussed.     

THE EFFECTS OF SPRAY TREATMENTS ON INFESTATION OF THE OAT CROP BY THE FRIT FLY (OSCINELLA FRIT L.)

Criteria are given for the timing and assessment of the effect of sprays on experimental plots, based on biological observations at Silwood Park from 1950 to 1955 and on previous work.
A preliminary experiment on small plots in 1952 indicated that 'blanket spraying' with DDT and parathion throughout the life of the crop gave protection against both tiller and grain attack. A more detailed replicated plot trial in 1953 showed that for oats planted on 22 April two carefully timed tiller sprays with parathion reduced tiller infestation from 31 to 3%. Six panicle sprays at weekly intervals reduced a heavy grain attack of 60% to 13%. Dieldrin was also effective but significantly less so than parathion. Much of the damage to the crop was caused by weed growth following initial loss of the primary oat shoots.
In 1954 and 1955 two and three parathion sprays were applied to 2-acre fields in order to study recolonization. Despite almost complete control of the tiller generation, a normal evenly distributed infestation of the panicles was found.
It is concluded that good control of the tiller generation may best be achieved by a spray programme based on knowledge of the phenology of the fly combined with that of the crop. The first general emergence in early May is likely to be critical.
Reinvasion of a sprayed crop may take place within 4–5 days and panicle infestation may not be causally related to tiller infestation in the same field.