CONTROL OF GRAPE-BERRY MOTH. 5 



The winter is spent in the pupal stage in cocoons (PI. I, fig. 2) 

 which the larva? spin in grape leaves the previous fall. These leaves 

 are the ones that fall early and become soft and sodden on the ground 

 (PL II, fig. 2) and remain under the trellis during the winter. In 

 the spring, previous to and during grape bloom, moths (PI. I, figs. 

 4, 5 ) begin to emerge from the overwintering pupa?. This emergence 

 gradually increases and continues at a high point for about 3 weeks. 

 The moths begin to deposit eggs on the young grapes about 4 days 

 after emergence and the eggs hatch in from 4 to 6 days. This first 

 brood of larva? or worms usually is not seriously destructive, though 

 first-brood infestation amounting to as much as 30 to 35 per cent 

 has been observed. The average length of the feeding period of this 

 brood of larva? is 23 days. When mature the larvae migrate to grape 

 leaves on the vines and spin their cocoons on them. From the cocoons 

 moths emerge in about 13 days and begin laying eggs about 4 days 

 later. The eggs of this second brood are placed on the nearly full- 

 grown grapes and are easily found where the infestation is heavy. 

 Before the eggs hatch they appear as creamy-white raised dots on 

 the green grape berries, but after the larva? leave the eggs the egg- 

 shells appear as glistening white spots. This brood of eggs hatches 

 in from 4 to 6 days and it is the resultant brood of larva? that, if 

 allowed to develop, does the greatest damage to the grape crop. 

 (PI. II, fig. 1.) The larva? of this brood feed for a long period and 

 usually leave the grapes just before harvest. They spin down to the 

 ground and make their winter cocoons on old decayed grape leaves 

 under the trellis. In the case of a cold fall many larva? do not leave 

 the grapes but are harvested with the grape crop. This condition 

 prevailed in the fall of 1917 to an unusual degree and the result was 

 a lighter infestation in 1918. 



RELATION BETWEEN SEASONAL-HISTORY DATA AND CONTROL 



MEASURES. 



The control experiments recorded in this bulletin are based on ex- 

 tensive field observations and on life-history studies conducted each 

 season. The data shown in diagram form in figure 1 are sum- 

 marized from the complete seasonal-history data. In determining 

 the hatching periods of the larva? 4 days are allowed from the 

 emergence of the moths to the deposition of eggs and 6 days for in- 

 cubation of the eggs. These are average figures from many obser- 

 vations extending over several seasons. 



It is seen in figure 1 that in 1916 and 1917 a few larva? had hatched 

 before Concord grapes began to bloom and in 1918 that the dates of 

 first hatching and beginning of bloom are coincident. In each sea- 

 son the first-brood larva? were hatchins; in large numbers for about 



