F. R. Pethekbridge 365 



Plot D. Crop in 1919 — Mangolds and cabbages. 

 Wheat drilled November 20th. 



No frit fly larvae found. Fairly bad attacks of wheat bulb fly in 

 patches. 



Plot E. Crop in 1919 — Mangolds, swedes and turnips. 

 Wheat drilled December 18th and 19th. 



No frit fly larvae found. Fairly bad attacks of wheat bulb fly in 

 patches. 



In the above experiments the only loss of crop from frit fly was after 

 Italian rye grass ploughed in during the autumn. The ploughing in of 

 the rye grass before harvest (i.e. bastard fallowing) prevented a loss of 

 wheat from the attacks of frit fly. 



On Plot B tufts of buried rye grass were dug up during the winter 

 and examined for frit fly larvae at intervals of about a month. 



On January 7th a large number of frit fly larvae were present in the 

 rye grass, and many of the shoots were not decayed. 



On February 6th a few frit larvae were found to be attacking the 

 wheat plants, but large numbers were still present on the rye grass. 



Throughout February and March the attack on the wheat gradually 

 became worse, whereas the number of larvae in the rye grass gradually 

 became fewer. April 7th was the last date on which frit fly larvae were 

 found in the buried rye grass. By this date much of the rye grass was 

 decayed, but a few shoots seemed to be suitable as food for the larvae. 



Pot Experiments. 

 These experiments were carried out in 5 inch pots in the laboratory. 



No. of 

 Pot Procedure Remarks 



1 Tuft of rye grass (dug up from Plot B) con- 2 plants attacked on March 16th 



taining frit fly larvae buried in soil in pot. 9 plants attacked on April 17th 

 Wheat sown February 16th 



2 9 frit fly larvae from buried rye grass placed 3 plants attacked on March 26th 



near seedling wheat plants on February 6th 



3 Small pieces of rye grass containing 6 frit fly 3 plants attacked on March 26th 



larvae buried near seedling wheat plants on 

 February 2nd 



4 8 frit fly larvae from buried rye grass placed 2 plants attacked on March 3rd 



near seedling wheat plants on February 9th 



5 7 frit fly larvae from buried rye grass placed 3 plants attacked on March 26th 



near seedling wheat plants on February 16th 



6 4 frit fly larvae from buried rye grass placed 1 plant attacked on March 26th 



near seedling wheat plants on February 2nd 



2 more added on March 3rd 3 plants attacked on April 1st 



1 more added on March 25th 



Examination of the attacked 

 plants showed that the damage 

 in all cases was [due to frit fly 

 larvae 



