EXPERIMENT STATION BULLETINS. 293 



THRTPS ON OATS. 



.1 R. H. PETTIT. 



*Special Bulletin No. 38. 



From all parts of the state, complaints are coming in with respect 

 to the condition of the oat crop. The last week has seen a notable 

 change in the outlook. The young oats in a large part of the state 

 have suddenly become as if stricken by blight, the outer leaves turn- 

 ing yellow and afterwards reddish until, after a little time, the field 

 appears as if badly rusted. A closer examination shows that there 

 are few if any rust pustules and the appearance on the surface is just 

 enough different from that produced by rust to raise a doubt as to the 

 real cause of the difficulty. 



Careful examination with the aid of a powerful lens shows the culprit 

 to be a minute insect called a thrips, very small, and very quick in 

 its movements, jumping like a flea when disturbed and disappearing 

 completely. These little creatures have narrow wings with fringes of 

 long hairs instead of the ordinary form of wings. They scrape the 

 surfaces of the oat leaves and cause them to become withered and to 

 turn yellow and die. Now, this little creature has never before been 

 seen in numbers by the writer and it is very difficult to judge just 

 what will be the outcome of the infestation. If one might judge by 

 the behavior of its relatives one would expect the condition to improve 

 after one or two good rains, since thrips, in general, thrive in hot, dry 

 weather, and do not do well when it is moist. However, it seems to 

 be quite serious in places where there has been a fairly good supply 

 of rain. The larger the plants are, the better they fare. 



Now, there seems to be nothing one can do to check the trouble at 

 this time. If it were possible to stimulate the growth of the plants in 

 any way it would be a benefit, but such a course seems to be impossible. 

 All plant life seems to be more susceptible to insects when plants are 

 in poor condition for any reason, and the backward, cold, wet spring 

 furnishes a very sufficient reason for the lack of vigor and resisting 

 power which they should have to help repel the invaders. 



•The reports of the South Haven Sub-Station, and of the Upper Peninsula Sub-Station, both of 

 which appeared in the ri907 Report as No. 38, are now numbered in the series of special bulletins 40 

 and 41, respectively, and hence these numbers will not appear in the 1908 Report. 



