Dispersal, patch Leaving, and distribution of Homalodisca vitripennis (Hemiptera: Cicadellidae)

Authors: NORTHFIELD, T - UNIVERSITY OF FLORIDA; MIZELL, R - UNIVERSITY OF FLORIDA; PAINI, D - UNIVERSITY OF FLORIDA; ANDERSEN, P - UNIVERSITY OF FLORIDA; BRODBECK, B - UNIVERSITY OF FLORIDA; RIDDLE, T - UNIVERSITY OF FLORIDA; Hunter, Wayne

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2008
Publication Date: 10/20/2008
Citation: Northfield, T.D., Mizell, R.F., Paini, D.R., Andersen, P.C., Brodbeck, B.V., Riddle, T.C., Hunter, W.B. 2008. Dispersal, patch-leaving, and distribution of Homalodisca vitripennis. Enviromental Entomology. 38(1):183-191.

Interpretive Summary: We identified the impact of plant diversity, and quality which were found to influence leafhopper tendencies to either disperse, or to remain, within a patch of plants. Understanding the underlying influences for leafhopper movement provides the information needed to create better management strategies aimed at reducing the spread of Pierce’s disease of grapes by leafhoppers, like the glassy-winged sharpshooter, GWSS. Pierce’s disease has caused millions of dollars in damage to southern California vineyards in recent years, where spatial patterns of the disease are highly correlated with the invasive insect, Homalodisca vitripennis, the GWSS. However, the relationship between the dispersal and aggregation of GWSS and the surrounding vegetation is not well understood. Therefore, the relationship between dispersal rates and patch quality were tested, as well as the basic predictions of the Marginal Value Theorem- where an animal exploiting a resource must decide when to move to the next patch. Additional experiments were conducted to compare GWSS aggregation in an isolated host patch of crape myrtle and in a crape myrtle host patch bordering two alternative host plant patches. In the dispersal tests, GWSS adults dispersed farther from the central release point in a patch of less preferred host plants, peach than in a patch of preferred host plants, crape myrtle. The amount of time that GWSS resided in the two different host plants correlated with the plants nutritional qualities needed by the leafhoppers. GWSS movements were influenced by the known changes in plant physiology, suggesting that leafhoppers follow the basic predictions of the marginal value theorem. In the aggregation tests, GWSS was not aggregated in the isolated crape myrtle patch, but in a patch bordering cottonwood and peach. Where a mixed host plant environment was available GWSS was aggregated, as along the edges shared with other plant species. These data suggest that alternate plant hosts bordering cropping systems are important to the spatial dynamics of the GWSS, and may affect the spread of plant diseases.

Technical Abstract: We identified the impact of plant diversity, and quality which were found to influence leafhopper tendencies to either disperse, or to remain, within a patch of plants. Understanding the underlying influences for leafhopper movement provides the information needed to create better management strategies aimed at reducing the spread of Pierce’s disease, PD, of grapes by leafhoppers, like the glassy-winged sharpshooter, GWSS, Homalodisca vitripennis, Germar. Pierce’s disease has caused millions of dollars in damage to southern California vineyards in recent years, where spatial patterns of the disease are highly correlated with an invasive vector, H. vitripennis. The relationships between the dispersal and aggregation of H. vitripennis and the surrounding vegetation are not well understood. We evaluated the relationship between H. vitripennis dispersal rates and plant patch quality, as well as the basic predictions of the marginal value theorem, which considers optimal foraging. Additional experiments were conducted to compare H. vitripennis aggregation in an isolated host patch of crape myrtle (Lagerstroemia indica) and a L. indica host patch bordering two alternative host plant patches. In the dispersal tests, H. vitripennis adults dispersed farther from the central release point in a patch of less preferred host plants (P. persica) than in a patch of preferred host plants (L. indica). H. vitripennis also resided in L. indica patches longer than in P. persica and adjusted patch residence times in P. persica to correlate with known changes in plant physiology, suggesting that H. vitripennis follows the basic predictions of the marginal value theorem. In the aggregation tests, H. vitripennis was not aggregated in the isolated L. indica patch, but in a patch bordering cottonwood (Populus sp.) and peach (P. persica) H. vitripennis was aggregated along the edges shared with each plant species. Females dispersed farther than males on all release dates, suggesting that females are likely more sensitive to host quality than males. Females are not only foraging for food, but for quality oviposition sites as well, and because L. indica and P. persica are not good hosts for nymphs, females may travel farther in search of an adequate oviposition host. H. vitripennis nymphs exhibited high dispersal rates and moved to new hosts quite readily. Both edge effects due to plant diversity, and dispersal from a host patch, due to host quality, strongly influence leafhopper movement. Therefore, special attention should be paid to plants in field margins when managing X. fastidiosa-related diseases based on their propensity to host X. fastidiosa. These findings also suggest that development and use of trap crops in proximity to X. fastidiosa-infected crops may be a viable management strategy for H. vitripennis and should be researched along with the associated underlying behavioral mechanisms which influence leafhopper movement. These data suggest that alternate hosts bordering cropping systems may be important to the spatial dynamics of H. vitripennis, and other leafhoppers. The implications of these behavioral characteristics on the biology and behavior of H. vitripennis will influence potential control methods.