ORCHARD INSECTS OF THE PACIFIC NORTHWEST 5 



they ordinarily hatch in 6 or 7 days. The worms often remain in the 

 fruit for more than a month in the fall, and many of them are still 

 there when it is picked. They may leave the fruit before it is packed, 

 and for this reason large numbers of wintering worms in their cocoons 

 may be found in picking boxes and packing sheds. 



The codling moth is very sensitive to variations in temperature. 

 In the warmer localities there is often a partial third generation, but 

 at greater elevations and along the coast there is no third generation 

 and the second generation is smaller than elsewhere. In any locality 

 the yearly abundance of worms varies greatly, as it is dependent on 

 weather conditions. Winter temperatures of —15° F. or colder kill 

 some of the overwintering worms. Probably the most important 

 effect of temperature occurs during May and June, when large num- 

 bers of first-brood eggs are laid if the weather is warm, but the number 

 is greatly reduced if it is cold or rainy. Thus an early, warm season 

 produces many worms, but a late cool season has the opposite effect. 

 The fruit grower should therefore study weather conditions as well as 

 conditions in his orchard and plan his spraying schedule accordingly. 



CONTROL 



Spraying the fruit to protect it from the codling moth is not always 

 sufficient if the infestation is severe. In such cases supplemental 

 measures are necessary. The trees should be scraped thoroughly 

 to remove all the loose bark under which cocoons might be spun. 

 Bands of corrugated paper, treated with a mixture of beta-naphthol 

 and oil, 2 may then be placed on the trees not later than the first week 

 of June. Many worms will spin cocoons in the bands and will 

 be destroyed by the chemical. The bands should be removed and 

 burned the following winter and fresh ones applied the next year. 

 This method will often destroy over half of the worms that leave the 

 apples. In pruning, trees should be kept open enough to permit 

 all parts to be sprayed thoroughly. Each cluster should be thinned 

 to a single fruit and all wormy fruit removed and destroyed. Worms 

 that have spun cocoons in picking boxes and packing sheds should 

 be destroyed or the resulting moths prevented from reaching the 

 orchard. The boxes may be placed in a shed that is kept tightly 

 closed during the spring and summer to prevent the escape of the 

 moths, or boxes and sheds may be sterilized. 3 



Maximum efficiency is not so easily attained in spraying for the 

 codling moth as in spraying for other pests, because more sprays 

 are necessary, and the time of application is more important, since 

 a spray applied at the wrong time may be largely wasted and the 

 fruit left unprotected when large numbers of worms are hatching. 

 Other orchard operations, such as irrigating, cultivating, thinning, 

 and the handling of alfalfa cover crops, should not be allowed to 

 interfere with the spray schedule. It is more difficult to determine 

 the proper time for applying codling moth sprays than for apply- 

 ing any of the other sprays used by the fruit growers of the Pacific 

 Northwest, as the time differs from year to year. 



2 Information on how to make and use these treated bands may be obtained from the Bureau o Ento- 

 mology and Plant Quarantine, U. S. Department of Agriculture, Washington, D C. 



3 Information on a method of sterilizing boxes with steam may be obtained from the Bureau of Ento- 

 mology and Plant Quarantine, U. S. Department of Agriculture, Washington, D C 



