Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2010
Publication Date: 10/1/2010
Citation: Funderburk, J., Reitz, S.R. 2010. Natural and artificial populations of Frankliniella occidentalis, biotic resistance and pest status. Journal of Insect Science. 10(166):14-15. Interpretive Summary: Over the past 30 years, the western flower thrips has invaded numerous countries to become one of the most important insect pests worldwide. However, scientists with the University of Florida and the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology have observed that in many of these invaded regions the western flower thrips is restricted to intensively managed agricultural settings and is largely rare or absent in areas not subject to intensive insecticide applications. It is proposed that the western flower thrips populations are regulated by natural enemies and competitors. In particular, the western flower thrips appears to be an inferior competitor to many native flower thrips that it encounters, and it is subject to more intense predation than corresponding native thrips. When western flower thrips populations are released from competition and predation by broad spectrum insecticide use, they easily reach economically damaging levels. Therefore, conserving interspecific competitors that are non-pests and naturally-occurring predators can help reduce the risk of western flower thrips outbreaks.
Technical Abstract: In its native southwestern North America with Mediterranean and semi-arid climates, Frankliniella occidentalis employs an opportunistic life history strategy, with population characteristics that include polyphagy, rapid development, high reproductive potential, vagility, and a competitive breeding structure. The species, now considered cosmopolitan, is thought to have successfully invaded regions with many different climates. In central Chile, F. occidentalis has replaced and possibly displaced the native flower thrips as the most common thrips species and it feeds and reproduces on the vast majority of the native and introduced plants in the agroecosystem. Most of the plant species are low-quality hosts where populations either decline or remain stable, but they escape predation and competition from native thrips. On a few high-quality hosts that are abundant in the spring, populations in the absence of predators and competitor species build up to very high populations that later disperse due to crowding and declining plant host quality. In Florida, F. occidentalis is an inferior competitor to the native thrips on both cultivated and uncultivated plant hosts, and this competitive asymmetry, along with a reduced ability to avoid predation compared to the native flower thrips, has resulted in its exclusion (but not repulsion) in the agroecosystem. There are only rare opportunities in space and time for natural population buildup on plant hosts in the absence of predation and competition. However, the species is capable of exploitation of insecticide-treated crop fields where they rapidly increase to damaging pests in the absence of predation and competition. Apparently, F. occidentalis similarly encounters serious biotic resistance, even near complete repulsion, in many geographic regions with different climates. Observations show that populations occur in high numbers in insecticide-treated crop fields; only small populations in the form of stray individuals are encountered on the other available plant hosts.