|WESTERN FLOWER THRIPS|
|Biology and Management of
Arthropods in Peppermint
Report - 1991
We surveyed peppermint fields in 1991 in western and central Oregon to determine the incidence of thrips in peppermint. Two yellow sticky traps were placed in each of nine fields in western and central Oregon (18 total traps in each production area). In central Oregon, the thrips survey was conducted in cooperation with Mr. Steve James, Central Oregon Agricultural Research Center in Madras. Traps were placed in peppermint fields in mid-June and removed before harvest in mid-August.
Results of this survey indicated that thrips (western flower thrips) were very abundant in peppermint fields during the growing season, which suggests that the potential for spread of TSWV is high. However, we did not determine whether or not the thrips collected on the traps were infected with TSWV and cannot say for certain that the incidence of TSWV increases in peppermint fields during the summer. A detailed study of the vector/virus relationships in peppermint must be conducted before the economic impact of TSWV on commerical peppermint is known.
Diane Sether, a graduate student in Entomology, confirmed that western flower thrips can successfully transmit TSWV to peppermint. She fould that TSWV is ingested by nymps but is transmitted to peppermint only by adult thrips, greater than two days old. She described the general symptomology of TSWV infection of peppermint as follows: stunting and downword curling of leaves occasinally accompanied by tip necrosis, older leaves occasionally with sunken, brownish-gray lesions and a bronzy appearance, yellow mottling on leaves which may become more evident under cool temperature conditions. ELISA (enzyme-linked immunosorbent assay) detection of virus throught the plant indicates the infection is systemic.