54 



CIRCULAR 270, U.S. DEPARTMENT OF AGRICULTURE 



dark brown, emerge when the fruit buds are swelling and beginning 

 to show green. After a feeding period of about 3 weeks the egg-laying 



period begins, and this 

 lasts another 3 weeks. 

 The eggs are very small, 

 whitish, and kidney- 

 shaped, and t?hey hatch 

 in less than 2 weeks. The 

 young are white and simi- 

 lar to the adults in shape 

 (fig. 64). They develop for 

 about 3 weeks, then drop 

 to the ground, burrow in- 

 to the soil, and construct 

 small cells a few inches to 

 3 feet from the surface. 

 Here they remain dormant, 

 changing late in the fall to 

 adults, which emerge the 

 following spring. The 

 pear thrips is thus active 

 on the trees for only about 

 2 spring months and is 

 dormant in the ground the 

 rest of the year. 



CONTROL 



The pear thrips may be 

 controlled by thoroughly 

 spraying the trees during 

 the first warm weather 

 after the buds have begun 

 to show green. Later 

 sprays may be needed 

 when the blossom buds be- 

 gin to show white and just 

 after blooming. The trees 

 should be examined some 

 days after the first spray 

 has been applied; if there 

 is an average of one or 

 more thrips to each bud 

 at this time, the later 

 sprays are advisable. For 

 prune and plum trees an 

 oil emulsion or a miscible oil 

 suitable for dorm ant spray- 

 ing (p. 68) should be used, 

 2 gallons to 100 gallons of 

 water, to which is added 1 

 pint of nicotine sulphate 

 (40 percent nicotine). Con- 

 trol by cultural means has not been successful, because many of the 

 young are too deep in the ground to be reached by cultivation. 



Figure 63.— Prune twig showing deformed leaves and poor set 

 of fruit caused by the pear thrips. 



