October, '22] wadley: strawberry leaf-roller 357 



generation hibernate before pupating, and that in long seasons a small 

 fifth generation may develop. Adults of the first generation appear by- 

 June 1, and those of the second generation begin appearing about July 

 10. In Iowa there are at least three generations and probably a partial 

 fourth. The cool weather of late September and October appears to 

 cause a cessation of pupation, and the larvae then present hibernate. 

 After the intermission between the over-wintered and the first generation, 

 all stages can generally be found in the field at any time until fall, though 

 more abundant at some times than others. This is due to length of 

 oviposition period and variation in development. 



Injury 



Usually only a few larvae may be found in a strawberry patch, and 

 injury is very slight. In many cases, however, more or less damage 

 is suffered by the plants, and occasionally a patch is found in which 

 many or all of the plants have been killed. More than one larva to 

 a plant will injure it noticeably. Injury is more severe in dry weather, 

 since the plants have then less power of recovery. The writer has been 

 unable to find the species in Kansasonany plant other than strawberry. 



This leaf -roller shows marked fluctuations in numbers, due to numer- 

 ous parasitic enemies of several hymenopterous and dipterous species. 

 Winter cold, lack of food when larvae are numerous, and disease also 

 reduce its mmibers. 



Outbreaks are usually rather sudden, local and short, lasting a season 

 or less, though the species may be troublesome for several years in one 

 locality. The grower can therefore undertake control measures, 

 knowing that if the plants can be protected for the time, the leaf -rollers 

 will soon diminish in abundance. The first generation is usually 

 most injurious, but later generations often do considerable damage, 

 especially in new plantings. 



Control Problem 

 Control by spraying is based on coating the leafage with poison, which 

 will kill the young larvae as they begin to feed. The older larvae are 

 usually safe in their folded leaves. As all stages are present together 

 during the summer, larvae and pupae present at the time of spraying 

 will mature and deposit eggs for several weeks afterward. Some of these 

 eggs will be deposited on unpoisoned foliage, since the plants will have 

 put forth new leaves and rains will have washed off some of the poison. 

 These conditions make it impossible to secure complete control with a 

 single application under field conditions. When the first generation 



