44 



CIRCULAR 2 7 0, U. S. DEPARTMENT OF AGRICULTURE 



to spray for the second brood in August, spraying should be delayed 

 until after the crop has been harvested, or nicotine sulfate (40 percent 

 nicotine) in the proportion of % of a pint to 100 gallons of water, to 

 which is added 2 or 3 pounds of soap in solution, should be used in 

 order to avoid getting too much lead arsenate on the fruit just before 

 it is harvested. 



Pear Leaf Worm 



Round or oval holes, half an inch or more in diameter, are some- 

 times found in pear leaves late in April or in May. A close examina- 

 tion will usually show a green 

 worm stretched along the 

 edge of each hole, feeding on 

 the leaf (fig. 52). This is a 

 pear leaf worm (Gymnony- 

 chus calirfornicus Marlatt). 

 The young worms first make 

 small holes in the leaves, 

 gradually enlarging the holes 

 as they feed around and 

 around them. A single worm 

 will consume about one- 

 fourth of a Bartlett pear leaf 

 during its life, and when the 

 worms are numerous the 

 trees may be partially defoli- 

 ated. This insect occurs 

 throughout the Pacific North- 

 west and in California. 



LIFE HISTORY 



The adult insects are saw- 

 flies similar in appearance to 

 those of the pear slug, but 

 somewhat more slender and 

 with some yellowish mark- 

 ings. They emerge from the 

 ground early in April and cut slits in the lower surfaces of the partly 

 unfolded leaves, in which the eggs are laid. The wounds often cause 

 the leaves to become deformed. The small green worms hatch in 10 

 days or 2 weeks and feed as described above. Growth is attained in 

 about 4 weeks, when the mature worms, which are about one-half of an 

 inch long, drop to the ground and spin tough brown cocoons among the 

 leaves or in the soil within an inch or so of the surface. Here they 

 remain until the following April, as there is only one generation a year. 



Figure 52.— Pear leaf worm: A, Injury to 

 leaf; B, egg in tissue and young larva 

 feeding (X 12); C, full-grown larva (X 6). 



very easily controlled by the use of lead 



CONTROL 



The pear leaf worm is very easily controller ^j ..^ 

 arsenate in the proportion of 2 pounds to 100 gallons of water, applied 

 just after the petals have fallen. This is the same as the usual calyx 

 application for the codling moth. 



