Identification of Leafhoppers in Tart Cherry, 2001

Diane G. Alston

Department of Biology, Utah State University

Objectives: To identify the species of leafhopper attacking tart cherry orchards in northern Utah.

Methods: Informal surveys and collections of leafhopper specimens from tart cherry orchards in Utah Co. were made during spring and summer of 2001.

Results: Nymph and adult specimens collected from tart cherry orchards were all white apple leafhopper (Typhlocyba pomaria). The other species that may occur in cherry orchards is the rose leafhopper (Edwardsiana rosae). No rose leafhopper were observed in surveys or identified from collected specimens. The adults of both species appear very similar. The nymphs can be distinguished by the rows of dark spots on the back of the rose leafhopper while the white apple leafhopper has no spots.

White apple leafhopper nymph
Rose leafhopper nymph

The life cycle of the two leafhoppers differs in that the white apple leafhopper spends itís entire life in fruit orchards (apple, cherry, peach, plum, pear), while the rose leafhopper over winters on rose and is not as common or typically reach as high of densities in fruit orchards.

Only minimal direct injury to the fruit or tree has been established for the white apple leafhopper on apple. The piercing-sucking mouthparts pierce the mesophyll layers of leaves removing spots or speckles of contents and color. The feeding injury causes a whitish stippling of leaves. Reduced leaf photosynthesis can affect a treeís ability to set, size and mature fruit; however, Dr. Beers at WSU has found minimal reductions in these parameters even under extremely high leafhopper population pressure. Two other types of injury in apple are tar spots on fruit caused by the insectís excrement and annoyance to fruit pickers by high densities of flying adults. The peak of the second generation of adults coincides with harvest time of many apple varieties. This nuisance factor generally causes growers the most concern about the insect. The fruit spotting is generally easy to remove when fruit are washed. The impact of white apple leafhopper feeding on tart cherry has not been studied. Based on limited 2001 surveys and observations, the extent of leaf and fruit injury did not appear substantial and controls did not seem warranted. However, under high pressure it is possible that tree stress may occur.

 

Tar spots from insect excrement on fruit
Leaf-feeding injury: white stippling

First generation white apple leafhopper monitoring has been established for apple, and monitoring in cherry should utilize a similar approach. Petal-fall monitoring can be done with a beating tray or by inspecting terminal shoots. A threshold of 1 nymph per terminal has been established for apple. If control is warranted, timing should be based on when the majority of the over wintered eggs have hatched, but before many later instar nymphs (4th and 5th instars) are present, because older nymphs and adults are more tolerant of insecticides. Approximately 90% of the nymphs should be 1st-3rd instars and 10% should be 4th and 5th instars. Insecticides that have provided effective control in apples include Thiodan, Provado (not registered on cherry), and Diazinon. Guthion does not seem to provide good control of white apple leafhopper.

Control of leafhoppers in cherry should only be considered if population densities are very high and are causing extensive leaf stippling, injury to fruit or annoyance to cherry harvesters. It appears that leafhopper controls in cherry are not warranted at this time.