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Title: Overwintering squash bugs harbor and transmit the causal agent of cucurbit yellow vine disease

Author
item Pair, Sammy
item Bruton, Benny
item Mitchell, F.
item Fletcher, J.
item Wayandande, A.
item Melcher, U.

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2003
Publication Date: 2/2/2004
Citation: Pair, S.D., Bruton, B.D., Mitchell, F., Fletcher, J., Wayandande, A., Melcher, U. 2004. Overwintering squash bugs harbor and transmit the causal agent of cucurbit yellow vine disease. Journal of Economic Entomology. 97(1):74-78.

Interpretive Summary: Since 1988, cucurbit crops, particularly watermelon, cantaloupe, and squash, grown in Oklahoma and Texas have experienced devastating losses from cucurbit yellow vine disease (CYVD), that is caused by a bacterium, Serratia marcescens. Previous work at SCARL showed conclusively that the squash bug [Anasa tristis (DeGeer)] could transmit the bacterium to healthy plants. It is important to know the relationship between the insect vector and the pathogen. In this case, we wanted to know if the bacterium was retained in the insect during it's winter hibernation. If so, insects emerging from hibernation during the spring could readily infest cucurbit crops and transmit the CYVD bacterium. In 2000-01, overwintering populations of squash bug collected from DeLeon, TX were tested for their ability to harbor and transmit the bacterium. Individual squash bugs collected from hibernation and caged for a 7-d period on a series of at least four squash seedlings. Three studies were conducted, one with insects collected in November placed on 1st leaf-stage seedlings and the second and third with insects from an April, 2001 collection, placed on 3-5 leaf-stage squash. Controls consisted of squash seedlings caged without insects. We found that, overall, 10.5 % of the squash bugs harbored and successfully transmitted the bacterium to squash seedlings. None of the control plants expressed CYVD. This study demonstrated that the squash bug harbors S. marcescens in its overwintering state. The squash bug/S. marcescens overwintering relationship reported here greatly elevates the pest status of squash bug and places more importance on development of control strategies for reducing potential overwintering and emergent squash bug populations.

Technical Abstract: Since 1988, cucurbit crops, particularly watermelon, cantaloupe, and squash, grown in Oklahoma and Texas have experienced devastating losses from cucurbit yellow vine disease (CYVD), caused by the phloem-limited bacterium, Serratia marcescens. Squash bug [Anasa tristis (DeGeer)] is a putative vector of the pathogen. In 2000-01, overwintering populations of squash bug collected from DeLeon, TX were tested for their ability to harbor and transmit the bacterium. Individual squash bugs (n = 76) were caged for a 7-d period on a series of at least four squash seedlings. Three studies were conducted, one with insects collected in November placed on 1st leaf-stage seedlings and the second and third with insects from an April, 2001 collection, placed on 3-5 leaf-stage squash. Controls consisted of squash seedlings caged without insects. Squash bug transmission rates of the pathogen in Studies I-III were, respectively 20, 9.1, and 3.6 %. Overall, 10.5 % of the squash bugs harbored and successfully transmitted the bacterium to squash seedlings. All control plants were negative for CYVD symptoms or presence of S. marcescens. Female squash bugs killed a significantly greater proportion of young 1st leaf-stage seedlings than males. Feeding on 3-5 leaf stage squash resulted in no plant mortality regardless of squash bug gender. This study demonstrated that the squash bug harbors S. marcescens in its overwintering state. The squash bug/S. marcescens overwintering relationship reported here greatly elevates the pest status of squash bug and places more importance on development of integrated strategies for reducing potential overwintering and emergent squash bug populations.