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



(40 percent nicotine) should be added to the delayed-dormant and 

 pink-petal applications of lime-sulfur at the rate of 1 pint to 100 gallons 

 of spray material. 



Apple Leafhoppers 



The leafhoppers injure apple trees in much the same manner as do 

 red spiders. They are sucking insects feeding exclusively on the foli- 

 age, and they withdraw the chlorophyll and other cell contents, 

 leaving the foliage with a whitened or mottled appearance. Leaf- 

 hoppers are much larger than red spiders, and it does not require 

 many of them to cause serious injury; a half dozen are able to remove 

 most of the chlorophyll from a single leaf. Slight foliage injury by 

 leafhoppers and red spiders is of no consequence, but as soon as this 

 injury reaches the point where the foliage is reduced below the amount 

 required for the crop, the fruit and buds are directly affected, the fruit 

 failing to reach normal size and the buds being weakened so that they 

 may not set fruit the next season. It is therefore important to guard 

 against extensive injury. 



LIFE HISTORY 



Two species of leafhoppers are prevalent in the Pacific Northwest, 

 both native to the United States. The more common and important 

 of these is the white apple leafhopper (Typhlocyba pomaria McAtee), 

 a slender, active, whitish insect about one-eighth of an inch long. It 

 passes the winter in the egg stage in the bark of the trees. The eggs 

 hatch in April and early in May, and the small white hoppers com- 

 mence to feed at once on the new foliage, remaining among the 

 pubescence of the underside of the leaves. Growth is attained in 3 

 to 6 weeks, and the adults live for 2 months or more. Eggs are laid 

 in the tissue of the leaves from June to August, and hatch in about a 

 month. The second brood of young thus appears late in July and 

 August, and adults are present again from August to November. 

 These lay wintering eggs in the bark, where they appear as small 

 raised blisters. 



The apple leafhopper or green apple leafhopper (Empoasca maligna 

 (Walsh)) has only one generation a year, beginning with the wintering 

 eggs, which are usually laid in the bark of wood 2 or 3 years old. The 

 eggs hatch in April or May; and the yoimg, which are light green in- 

 stead of white, feed in the same manner as do the white apple leaf- 

 hoppers. The green adults appear in May and June and some are 

 still present in July. Most of the eggs are deposited in June and 

 July, and these remain in the bark until the following April. Since 

 it has only a single generation annually, this leafhopper does not 

 become so numerous as the white species. 



CONTROL 



The most effective means of controlling leafhoppers is the use of a 

 spray of nicotine sulfate (40 percent nicotine) in the proportion of 

 one-half pint to 100 gallons, used with an oil emulsion, or with 2 or 3 

 pounds of soap dissolved in water, or with 1 pound of casein spreader. 

 This must be used when the young are on the trees, as the adults are 

 too active to be reached with a contact spray. The application 

 should therefore be made in May for the green leafhopper or the first 



