Fruit IPM Fact Sheet Fruit IPM Fact Sheet White Apple Leafhopper
Reference: Common Tree Fruit Pests
by Angus Howitt
Michigan State University NCR 63
Life History:
This leafhopper has two generations in
the north central states and overwinters as an egg. Eggs hatch from pink stage to petal
fall. Early instar nymphs migrate to the lower surfaces of the older leaves and begin
feeding. These nymphs remain on the same leaves until they reach the adult stage. The
mobility of the nymphs is limited to running-only the adults can hop and fly.
First-generation adults are active during June and early July. About 10 days after first emergence, egg laying begins. These second-generation eggs are placed on the lower surfaces of the leaves, the leaf petioles, and near the midvein and larger veins. No first-generation adults are alive after mid-to-late July. The second-generation eggs begin to hatch in late July, and hatching may continue into September if cool temperatures prevail. The emergence of second-generation adults may begin anytime in late August or early September. These adults lay the overwintering eggs in the bark of the apple twigs.
At times, the potato leafhopper
can be mistaken for the nymphs and adults of the white apple leafhopper. To tell the
difference, note the color and movement of the insects. Nymphs and adults of the potato
leafhopper are pale green and can move backward, forward and sideways. The white apple
leafhopper can only move backward and forward but NOT sideways. So if the leafhopper can
move sideways it is a potato leafhopper. Also, unlike the white
apple leafhopper, the potato leafhopper feeds near leaf edges. These feedings show up as
triangular, chlorotic areas that extend from the feeding sites to the leaf edge. A number
of feedings sites on a leaf will cause the leaf to curve downward. If several leaves on a
shoot are affected, shoot growth may be stunted. I have posted pictures of the
damage on a Leafhopper Burn page.
Life Stages:
Egg: The
eggs are white, elongated and cylindrical. One end is slightly tapered. Dimensions are 0.8
by 0.3 mm. 
The
first-generation or overwintering eggs are laid beneath the bark of the apple twigs in the
cortex. They are laid singly and look like small blisters on the twig. Second-generation
eggs are laid on the leaves, primarily on the lower surface along the main veins. They are
not visible to the naked eye.
Larva: There are five
instars in nymph development. Size varies from 1 to 2.5mm, depending on the stage of
development. The first two instars are pale white with dull red or pink eyes. The last
three instars are white to yellow with white eyes.
Adult: The entire body in a faint yellow with an
orange to red tinge on the thorax and head. The head is redder than
the thorax. Length varies from 3 to 3.5 mm. The female is paler than the male, with little
or no red tinge on the face. The tip of the ovipositor sheath is black.
Host Range:
The primary host is apple, but this leafhopper is also found on hawthorn peach, plum; and sour, sweet and wild cherry. Greening, Baldwin, Duchess and Jonathan are the most susceptible apple varieties. This pest is found in the midwestern and eastern United States and eastern Canada.
Injury or Damage:
First-generation nymphs remove chlorophyll. Feeding sites appear as
whitish spots or stippling on the upper leaf surfaces. When feeding is heavy, the entire
tree may appear whitish or silvery. The loss of chlorophyll may indirectly affect both
fruit quality and bud formation, especially if it occurs early in the season. 
The second generation
is responsible for spotting and streaking on the fruit caused by accumulation of
leafhopper excrement. Once dried, it is difficult to remove. This problem is most serious
in dry seasons.
Factors Affecting Abundance:
The advent of synthetic organic phosphates caused this pest to change from a minor to a major pest under certain conditions. It becomes a problem when it develops resistance to commonly used pesticides.
Monitoring:
From bloom through petal fall, examine 50 leaves selected from leaf clusters in the inside of the tree. Treatment is recommended if there is an average of 0.5 nymphs or more per leaf. For the second generation, examine 50 leaves per tree from 10 trees per orchard for nymphs from late July through August. Treatment is recommended if there is an average of one or more nymphs per leaf. An additional spray may be needed because of extended egg hatching period.
Using 48 degrees F as a base, degree-days (DD) for white apple leafhopper activity:
100 DD first nymph emergence. 550 DD first adult emergence. 1,100 DD peak adult emergence. 1,750 DD peak egg laying
Control:
The white apple leafhopper has a great propensity for quickly developing resistance to pesticides. The insects are present on the undersides of the leaves, and thorough coverage by effective chemicals is essential for control. The first generation is best controlled at petal fall. The second generation usually requires control in early August. Second generation control is generally more difficult than that for first generation leafhoppers. Hatching is more uniform in the first generation, and young leafhoppers are much easier to control than adults. In addition, thorough spray coverage of upper and lower leaves is essential for leafhopper control. Because less foliage is present during first-generation emergence, growers may find it easier to cover leaves and achieve pest control at this stage.
