Spring precipitation affects Frankliniella fusca (Thysanoptera: Thripidae) population growth and Tomato spotted wilt virus spread within patches of the winter annual weed Stellaria media
Voss SC, Kennedy GG
North Carolina State University, Research Annex West, Raleigh, North Carolina scvoss@ncsu.edu
In North Carolina, winter annual weeds, including common chickweed, Stellaria media, are the primary source of TSWV inoculum that is spread to susceptible crops in spring by Frankliniella fusca Hinds. To test the hypothesis that rainfall influences population growth of F. fusca and spread of TSWV among winter annual weeds, precipitation levels and timing were manipulated to mimic 2002, a year during which F. fusca populations and TSWV incidence in crops reached exceptionally high levels, and 2003 when F. fusca populations and TSWV incidence were unusually low. Rainfall levels were manipulated weekly using a combination of rain shields and overhead sprinklers. Seven experimental treatments were established over identical patches of common chickweed containing a single source of TSWV and infested with F. fusca. The treatments included: low level of precipitation mimicking rainfall patterns of 2002; high level of precipitation mimicking 2003 rainfall; and ambient rainfall. Other treatments included 2003 patterns of rainfall during only February, March, April, or May, with 2002 rainfall patterns during other months. Regression analysis revealed a strong and significant effect of both rainfall amount and number of days with rain on the increase in F. fusca populations and spread of TSWV within chickweed patches. Knowledge of this relationship may be useful for predicting when susceptible crops are at highest risk of TSWV infection.
Webster KW, P Cooper P, Mound LA
CSIRO Entomology, Canberra, Australia.
Correspondence: Laurence.Mound@csiro.au
Kelly's citrus thrips is a major pest of citrus fruit in southern Australia and several Mediterranean countries. Adults are sexually dimorphic and have been demonstrated to have a peak period of sexual activity at 17.00h. Males produce one or more chemical attractants that induce male aggregation and also attract females to these aggregations for mating.
