Tomato Spotted Wilt Virus: TSWV in Vegetable Crops: Tospoviruses

Tospoviruses In Solanaceae and Other Crops in The Coastal Plain of Georgia

Epidemiology

Environment
Alex Csinos

In Brazil where growers have dealt with TSWV on tobacco for more than 25 years they have made observations that suggest that rainfall may have an effect on incidence of TSWV. Periods of rainfall at or just before transplanting tended to reduce the incidence of TSWV on tobacco. In Georgia, in years where rainfall amounts were greater than 8 inches in the month of March, TSWV was low, when compared to those years where rainfall was less than 8 inches. The incidence is relative to location only. If the same area is examined over several years, those years with heavy rainfall resulted in lower TSWV, particularly in early season. Heavy rainfall early in the year may have a harmful effect on thrips reproduction, and thus reduces the number of potential vectors visiting the crop. In addition, heavy rainfall during March may keep weeds in surrounding fields green longer. Thrips may be reluctant to leave a succulent viable host for another crop. Thus the crop plants may be out of phase with moving viruliferous thrips and highest susceptibility of the crop to infection.

More recent data has indicated that heavy spring rains may not have a lasting effect on reducing TSWV infection, and thus total incidence and severity of TSWV at the end of the season may still be high. In 2005, heavy rains in the last week of March and cool temperatures in April resulted in no significant infection occurring until mid-May. However, with increased temperatures, both thrips populations and TSWV infection increased dramatically. Thus, infection of the host may be limited at or during rainfall events, but subsequent environmental conditions may be favorable for thrips development and subsequent TSWV infection.

In the event that the window of infection for TSWV is early in the season (transplanting time), the heavy rain at that time would be expected to reduce TSWV infection. However, if the infection window is later (May), then March rains may not have an effect on the level of infection.

top