16 



CIRCULAR 2 7 0. U. S. DEPARTMENT OE AGRICULTURE 



markings. The eggs are laid during June and July, each female deposit- 

 ing all of her eggs in a single mass, unless disturbed. These eggs hatch 

 the following spring. 



CONTROL 



The most effective means of controlling the leaf roller is by destroy- 

 ing the eggs with an oil spray in the spring before they have hatched. 

 Any of the emulsions that are satisfactory for scale control may be 

 used for this purpose. Light infestations may be treated with an 

 emulsion containing 4 percent of oil, as this kills most of the eggs, but 

 for serious outbreaks, when large numbers of eggs are on the trees, 

 the strength of the dilute emulsion should be increased so that it con- 

 tains 5 or 6 percent of oil. Spraying should be done during the first 

 settled period of mild weather. It should not be done just before a 

 rain or when temperatures lower than 25° F. are likely to occur within 

 a few days, as there is danger of injury to the trees under those condi- 

 tions. Neither should it be delayed until the eggs have begun to 

 hatch. Severe infestations that have not been sufficiently controlled 

 by this means may sometimes be lessened by the use of lead arsenate 

 in the proportion of 4 pounds to 100 gallons of spray just at the time 

 the buds begin to separate in the clusters. 



Red Spiders 



Eed spiders or mites do great damage to apple and pear trees, much 

 of it difficult to measure. They feed by withdrawing the contents of 

 the leaf cells, including the chlorophyll, thus causing a whitening or 

 mottling of the leaves. Apparently this chlorophyll is not replaced, 

 becomes browned or bronzed as a result of mite 

 attacks. In irrigated orchards the leaves sel- 

 dom drop, but in nonirrigated orchards com- 

 plete or partial defoliation frequently results. 

 Pear foliage is affected in somewhat the same 

 way as apple foliage. The leaves, particularly 

 on Anjou, Winter Nells, and Bosc, often brown 

 and dry up during the first extremely hot 

 weather in the summer. While this condition 

 is probably due chiefly to the inability of the 

 tree to supply moisture fast enough during the 

 sadden onset of hot weather, it may be aggra- 

 vated by a severe infestation of mites, since 

 they remove large quantities of moisture from 

 the leaves. As the trees manufacture their 

 food supply largely in then leaves, any foliage 

 injury will reduce the vitality of the tree, and 

 consequently the size of the fruit, even if it 

 does not cause the leaves to drop off. 



life history 



There are three species of orchard-infesting 

 red spiders in the Pacific Northwest. These 

 T B e E 4'-""I aduft mit x differ somewhat in their habits, and somewhat 

 64. ' v different methods must be used to control 



Apple foliage usually 



