Impact of Water Capture on the Dynamics of Plant Virus Vectors
Investigators (most current known information)
This project had the goal of elucidating the effects of natural water catchments on the population and dispersal dynamics of potential vectors of plant viruses, including leafhoppers, aphids, whiteflies, and thrips. The study area was the central Arava Valley near Hazeva. Moshov Hazeva, a populated area 5 km. to the east of the study site, is saturated with high input agriculture. Three closely spaced sites were selected, each with different water capture potentials.
All three sites were at about the same elevation and were within 1 km of one another. Local weather (temperature, humidity, solar radiation, and amount and timing of rainfall) was reasonably similar at all sites. The parameter that differed among them was the their ability to capture water, which resulted in differences in the flora contained in each. One site had considerably more grasses, annual flowers, and Acacia trees, while another contained almost none, and the third site contained an intermediate amount of these three plant types.
The major experimental aspects were conducted during the springs of 1995 and 1996. Prior to the spring of 1995, considerable rainfall was recorded in the catchment basin of the experimental sites, however, prior to the spring of 1996, almost no rainfall accumulated.
Liquid-filled yellow pans and malaise traps were used to sample insects during the two-month visit of PI Irwin in March and April, 1995 and April and May, 1996, and continued afterwards by technical assistance. Because of the color attraction, the yellow pan traps could draw specimens flying in the planetary boundary layer (>10 m above ground level), while malaise traps provided quantification of specimens flying within the surface boundary layer (> 10 m), measuring more local movement of vectors within the specific site habitats.
Trap results at each site suggested the following:
- Aphids and whiteflies tended to be more abundant in the sites that captured less water, while leaf hoppers and thrips were most abundant in the site that captured more water.
- Differences among sites were greatest in 1995, following abundant winter rains; these differences were minimal in 1996, following a winter with almost no rainfall.
- No obvious temporal off-setting of flight activity was detected among sites, suggesting that nearby water capture regimes do not greatly offset the life cycles of vectors.
- Yellow pan traps were more effective than malaise traps for thrips (catches were negligible in malaise traps and are not represented in graphs), less effective for leafhoppers and whiteflies, and just as effective for aphids.
- Malaise traps sieve aphids from the surface boundary layer of the atmosphere whereas yellow pan traps attract aphids that are ready to terminate their "migratory" flight. Thus, we hypothesize that malaise trap catches reflect local dispersal while yellow pan traps reflect more generalized long-distance dispersal.
- Most flight activity was recorded in the spring each year (March through May).
- Flight patterns of aphids and thrips generally peaked slightly earlier than those of leafhoppers and whiteflies.
- Most vectors tended to peak earlier in 1995 and they were more abundant than in 1996, probably because of earlier and more consistent rainfall in 1995.
Articles in Journals
Fereres, A., J. M. Thresh and M. E. Irwin, eds. 2000. "Plant virus epidemiology: Challenges for the twenty-first century." Virus Research 71(1&2):1-267.
Irwin, M. E., W. G. Ruesink, S. A. Isard and G. E. Kampmeier. 2000. "Mitigating epidemics caused by non-persistently transmitted aphid-borne viruses: The role of the pliant environment." Virus Research 71:185-211.
Irwin, M.E. 1998. "Biotic interchanges between agricultural and surrounding landscapes: Refocusing our management paradigms." Presented, Centro de Ciencias Medio ambientales, March. Madrid, Spain.
Irwin, M.E. 1997. "Biotic interchanges between agricultural and surrounding landscapes: Refocusing our management paradigms." Presented at a symposium at The University of Illinois, September. Urbana IL.
Irwin, M.E, B. Raccah and G. Kampmeier. 1996. "The role of natural water catchments on the production of vectors of plant viruses in the Arava Valley, Israel." Presented, International Congress of Entomology symposium, August. Florence, Italy.