|Sandanayaka, W.R. Manoharie - HORT NEW ZEALAND|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 3, 2008
Publication Date: August 1, 2008
Citation: Sandanayaka, W., Backus, E.A. 2008. Quantitative comparison of stylet penetration behaviors of glassy-winged sharpshooter, Homalodisca vitripennis, on four crop plants important in New Zealand and the USA. Journal of Economic Entomology. 98:787-813. Interpretive Summary: The glassy-winged sharpshooter (GWSS) is an important carrier of Xylella fastidiosa, the bacterium that causes Pierce’s Disease in grape and scorch diseases in many other horticultural crops. GWSS spread from Hawaii to Mo’orea Island in 2002 and to Cook Islands (2615 km northeast of New Zealand) in 2007. It is expected to continue its dispersal westward across the Pacific. New Zealand is threatened by the imminent arrival of the glassy-winged sharpshooter. Computer climate models indicate that climatic conditions exist for GWSS to establish throughout much of New Zealand. Therefore, it has become important to understand the feeding behavior and potential for X. fastidiosa to be transmitted to New Zealand crops by GWSS. Feeding behaviors of GWSS were studied on three common horticultural crops grown in New Zealand (apple, grape, citrus), as well as a native plant (pohutukawa), using the Electrical Penetration Graph (EPG) technique. While feeding behaviors varied on host plants, apple and grape were the most preferred host plants, on which GWSS spent most of its time feeding. In contrast, pohutukawa was the least preferred host. Insecticide-treated citrus was intermediate between these extremes, with some acceptance of xylem, but less fluid uptake. Implications for host plant resistance and efficiency of X. fastidiosa transmission also are discussed.
Technical Abstract: New Zealand is threatened by invasion of the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, an important vector of Xylella fastidiosa, a gram-negative bacterium that causes Pierce’s Disease in grape and scorch diseases in many other horticultural crops. Therefore, an understanding of the host range, feeding behavior and potential vector efficiency of GWSS on New Zealand crops is important. We tested host plant acceptance and feeding behaviors of GWSS on three common horticultural crops grown in New Zealand (apple, grape, citrus), and a native plant, pohutukawa, using the Electrical Penetration Graph (EPG) technique. Probing (stylet penetration) behaviors varied on host plants primarily as evidenced by differences in waveform event durations. Apple and grape were the most preferred host plants, on which GWSS spent the majority of its time probing and readily located and accepted a xylem cell; this resulted in long durations of sustained xylem fluid ingestion. In contrast, pohutukawa was the least preferred host, on which GWSS spent much less time probing. GWSS engaged in longer and more frequent testing/searching activities, rejected xylem cells frequently, and spent less time with stylets resting, before accepting a xylem cell and ultimately performing the same amount of sustained ingestion. Insecticide-treated citrus was intermediate between these extremes, with some acceptance of xylem, but less ingestion, probably due to partial paralysis of the cibarial muscles. Implications for transmission of X. fastidiosa and host plant resistance also are discussed.