CONTROL OF THE GRAPE-BERRY MOTH. 7 



and infested berries in the different experimental plats and in the 

 adjacent untreated check plats. Counts of infested berries in each 

 of the different plats were made the first season from four 40-pound 

 crates of harvested fruit. In all plats in a single vineyard, the crates 

 were taken from the same relative positions. During the following 

 seasons a count was made from all of the fruit from 12 to 25 vines. 

 These vines were taken at intervals throughout the length of each 

 plat so as to include all conditions, and in the same relative positions 

 in all plats in the same vineyard. 



eliminating vineyard conditions favorable to the grape-berry moth. 



Winter Exposure. 



Protected situations in vineyards, along hedgerows, fences, or 

 woodlots, and low-lying spots, are invariably more heavily infested by 

 the berry moth than are the less protected portions of the same vine- 

 yard. On the other hand, exposed knolls seldom are infested heavily. 

 This variability in infestation, according to Johnson and Hammar, 

 is due to protection afforded to hibernating insects and the conse- 

 quent reduction of winter mortality. Goodwin attributed the heavier 

 infestation in low-lying spots to washing of cocoons in winter. 

 Observations by the writer confirmed both these conclusions and 

 also indicated that wind at the time of flight of moths is a factor, 

 as moths drift with the wind into these low-lying spots. 



Of these factors causing heavy infestation, one at least, whiter 

 protection in a vineyard, can be regulated more or less by artificial 

 means. The importance of this factor was tested during the winter 

 of 1915-16. 



Different lots of cocoons, collected in the fall of 1915, were placed 

 in cylindrical baskets of 20-inch wire mesh and wintered in vine- 

 yards in protected and in exposed situations, and also in the insectary 

 yard under a covering of leaves held in place by wire screen. To 

 forestall accidents each lot was divided into two baskets. In May, 

 1916, the cocoons were removed and placed in rearing jars. Table 

 1 shows the effect of the different conditions upon mortality: 



Table 1. 



-Percentage of emergence of the grape-berry moth hibernating in exposed and 

 in protected situations. 



Lot No. 



Situation. 



Number 



of 

 cocoons. 



Number 

 of moths 

 emerged. 



Emer- 

 gence. 



I. 

 II. 

 III. 



In vineyard, naturally exposed; crest of windswept knoll 



In vineyard, naturally protected by brush and drifted snow. . 

 In vineyard, artificially protected by covering with 2 inches 



350 

 360 



150 

 350 



20 



86 



45 

 154 



Per cent. 



5.71 



24.05 



30.00 



IV. 



In insectary yard, artificially protected under "leaf blanket". 



44.00 



