Monday, December 11, 2006

Spring precipitation affects Frankliniella fusca (Thysanoptera: Thripidae) population growth and tomato spotted wilt virus spread within patches of the winter annual weed Stellaria media

Shannon Voss, and George G. Kennedy, North Carolina State University, Entomology, 3210 Ligon St, Raleigh, NC

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, types and timing were manipulated using a combination of rain shields and overhead sprinklers. Experimental treatments were established in each of 2 years over identical patches of common chickweed containing a single source of TSWV and infested with F. fusca. Year 1 treatments included: low levels of precipitation all season; high levels of precipitation all season; and ambient rainfall. Other treatments included periods high of rainfall during only March, April, or May, with low rainfall patterns during other months. Year 2 treatments included: ambient rainfall; ambient rainfall with early and late periods of hard rain; ambient rainfall with early and late periods of light rain showers and ambient rainfall with early and late periods of constant drizzle. Regression analyses revealed a strong and significant effect of rainfall for the amount, type and number of days with rain on the increase in F. fusca populations and the spread of TSWV within chickweed patches. These relationships are useful for predicting when susceptible crops are at highest risk of TSWV infection.

Species 1: Thysanoptera Thripidae Frankliniella fusca (tobacco thrips)