Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2005
Publication Date: 4/1/2006
Citation: Ugine, T.A., Sanderson, J.P., Wraight, S.P. 2006. Within-plant and temporal distribution of western flower thrips frankliniella occidentalis on flowers and foliage of impatiens wallerana and implications for pest population sampling and management. Environmental Entomology. 35:507-515.
Interpretive Summary: Western flower thrips is a key pest of greenhouse floriculture. Current management systems rely almost exclusively on sprays of synthetic and biorational chemical insecticides; however, the thrips-control potentials of a number of natural enemies, including microbial biocontrol agents, are under investigation. Efficacy of biocontrol agents is generally dependent upon pest population densities, and effective monitoring of population levels requires efficient and accurate sampling protocols. Garden impatiens is one of the most valuable bedding crops in the United States, and this paper reports results of investigations designed to identify those parts of impatiens plants most suitable as sampling units for monitoring levels of thrips infestation. Time of day was also investigated as a factor potentially affecting sampling efficiency. Results showed that thrips reside in significantly greater numbers in young flowers with pollen compared to vegetative plant parts or older flowers that have shed their pollen-producing structures and that time of day had little effect on the number of thrips collected per sample unit. Thrips can be easily seen and counted in impatiens flowers, and these findings have thus resulted in identification of an impatiens sample unit that can form the basis of an efficient, accurate sampling protocol for both agricultural researchers and commercial growers.
Technical Abstract: The development of cost effective management and sampling techniques for western flower thrips, Frankliniella occidentalis (Pergande), on garden impatiens, Impatiens wallerana (Hook.f.), necessitates that the within-plant distribution and diurnal patterns of thrips abundance be known. Impatiens flower bud development was divided into five arbitrary stages, designated A-E, with stage A representing tightly closed buds and stage E representing fully-opened flowers. Numbers of thrips immatures and adults associated with these flower stages were determined at six times daily (00:00, 02:00, 06:00, 08:00, 14:00 and 20:00 h). In addition, thrips distribution was determined among flowers with pollen, flowers with pollen removed, and on budless foliage, at two times daily (08:00 and 00:00 h). Thrips were also enumerated on terminal 7-cm sections of stems with foliage from impatiens plants with and without flowers. Each successive stage of flower from A to D contained significantly more adult female and immature thrips than the previous stage. Stage E buds contained significantly fewer adult female and immature thrips than stage D buds. There was little effect of sampling time on thrips density across all sample units. Flowers with pollen had significantly more adult females and males than flowers without pollen, but numbers of immature thrips were not affected by presence of pollen. Flowers with and without pollen contained significantly more immatures than foliage.