April, '17] KELLY: GREEN-BUG OUTBREAK 237 



widespread, but indications in the fall of 1907 were that, in the spring 

 of 1908, there might be a heavy infestation or general outbreak, should 

 the spring be cold and backward as it was in 1907. The wheat fields 

 were surrounded by blue grass in which Toxoptera were plentiful in 

 November, 1907, and where they remained till the following spring. 

 The fall was rather warm, the winter was not very severe, and it was 

 not surprising to find as many as forty to fifty half-grown to adult 

 aphids on a plant in early February and March, 1908. 



The aphid showed up in abundance in the spring of 1909, in south- 

 western Oklahoma and northern Texas, where they did a lot of damage 

 and threatened an outbreak, but here the parasites were present, and 

 these, together with continued warm weather and considerable rain 

 throughout April and May, held the pest in check. 



Several wheat and oat fields in eastern Oklahoma were rather badly 

 damaged in the spring of 1911 and in one or two fields, as much as 

 twenty-five to fifty acres had been devastated. The oats were rather 

 large at this time, and were heavily infested, many plants turning 

 brown and dying. Owing to the downpour of rain on the night of April 

 8, the aphids seemed to be rather scarce, many of them being buried in 

 the soil. A careful investigation all around this infested territory indi- 

 cated that the insect must have been in that immediate locality since 

 fall, 1910, as it would have been very difficult for them to have come 

 from a distance, on account of the territory being more or less sur- 

 rounded by timber, with wide sections of timbered land between this 

 section and other cultivated sections. There was considerable blue 

 grass growing near the fields, along the fence rows, which contained a 

 number of aphids, and it is probable that the grass was more or less 

 responsible for theh' passing the winter and getting an early start. 

 May 5, these fields were practically free from the pest, and the plants 

 were making a good growth. The heavy beating rains during April 

 evidently cleaned the aphids ofi' the plants. Inquiry among the farm- 

 ers revealed the fact that there were considerable volunteer wheat 

 and oats throughout the vicinity during the summer and fall of 1910. 

 In one field where the volunteer oats were very plentiful all through the 

 summer and fall, the Toxoptera gained such headway that they cleaned 

 up the wheat, the field being seeded to oats early in the spring of 1911, 

 and the oats being devastated. In this outbreak, then, there seems 

 to be further indication that the volunteer oats and wheat were 

 directly responsible for their presence in the fall, and continued 

 presence in the spring. The rains in April and early May were 

 responsible for their destruction, and from all indications the parasite 

 Aphidius festaceipes was not a controlling feature, although present in 

 large numbers. 



