Particle Film, Surround WP, Effects on Glassy-winged Sharpshooter Behavior and Its Utility as a Barrier to Sharpshooter Infestations in Grape (original) (raw)
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A combination of field and laboratory experiments in this study have been designed to advance our understanding of the operative host-plant factors utilized by adult glassy-winged sharpshooters (GWSS) and associated natural enemies as long- range cues to locate feeding and oviposition hosts in a complex agricultural landscape. Specifically, a second year of field studies have been conducted to determine the influence of continuous deficit irrigation regimes implemented in sweet orange cv. 'Valencia' oranges on the population dynamics of GWSS and other associated natural enemies. Dispersal and population dynamics of GWSS were monitored under continuous irrigation treatments receiving 60%, 80%, and 100% of evapo- transpiration (ETc) rates. Similar to the results obtained in our 2005 season, citrus trees irrigated at 60% ETc had warmer leaves, significantly higher xylem matric potential, and fewer adult and immature GWSS than experimental trees irrigated with 80% and 100% ETc. ...
2006
Outlined experiments in this study have only recently begun and are designed to advance our ability to define the operative host-plant factors utilized by adult glassy-winged sharpshooter (GWSS) and associated natural enemies as long-range cues to locate feeding and oviposition hosts in a complex agricultural landscape. Specifically, experiments are underway to determine how continuous deficit irrigation regimes in Valencia oranges influence the population dynamics of GWSS and other associated natural enemies. Populations of GWSS were monitored in a citrus orchard maintained under continuous irrigation schedules receiving 60%, 80%, and 100% of evapo-transpiration (ET c ) rates. Throughout the season, citrus trees irrigated at 60% ET c had warmer leaves and higher water potential than the trees irrigated with 80% and 100% ET c . Mean numbers of adults collected on beat samples, caught on sticky traps, and observed during the visual inspection, and egg masses within foliage were higher in the 80% and 100% ET c treatments than the 60% ET c treatment. Preliminary caged experiments using grape and oleander conducted in Riverside, California, illustrated GWSS population shifts that occurred between plants. Individual plants maintained under a well-watered treatment (ET c =100%) exhibited higher insect counts compared with a continuous deficit-irrigated treatment (ET c =50%). Identifying how the dispersing lifestages of GWSS locate and exploit specific host species will begin to provide the necessary information required to develop strategies for control of this highly mobile insect and further to limit the spread of Xf movement into susceptible crops.
files.piercesdisease.org
Our results indicate that: 1. Glassy-winged sharpshooter (GWSS) populations in untreated groves at University of California, Riverside (UCR) Agricultural Operations have been declining steadily since the beginning of 2002 through mid 2005 when sampling ceased. Current population densities are only 10% as dense as those during 2001-2002. 2. Forecast analysis indicates that, if current trends continue, untreated GWSS populations should decrease to their minimum densities sometime after winter 2008 and prior to summer 2013, depending on the Citrus species on which they are feeding. 3. Forecast analyses indicate that adult GWSS densities are cycling around an equilibrium density of 600 adults per Valencia tree and 950 adults per lemon tree when left untreated. 4. Population analyses indicate that 30% of the first instar nymphs survive to become fifth instar nymphs and less than 15% become adults on the citrus cultivar. Egg mortality is not included. 5. Current estimates of GWSS' impact on citrus production and fruit quality is an overestimate because the GWSS densities under which these measurements were made are 9 to 25 times more dense per tree than those that currently prevail in most untreated commercial orchards.
2009
The glassy-winged sharpshooter (GWSS; Homalodisca vitripennis) was found in several North Carolina counties that were not previously reported between 2006 and 2009. Data from this four-year study showed that GWSS has been expanding to new sites; this movement appeared to start in the south coastal region and move to the northern and western parts of the state. Several GWSS specimens were found in Currituck Co. (in the most northeastern part of the state) in 2006 and none was found in Wake Co. (Piedmont) the same year in a vineyard that was heavily monitored since 2004, but GWSS appeared in this vineyard in 2007 and 2008. In addition, we found that GWSS preferred the mimosa tree, Albizia julibrissin. In areas close to creeks, large numbers of adults and nymphs were recorded in these plants. In the laboratory, this insect laid eggs and completed its life cycle feeding only on this plant. Currently, GWSS appears to have established populations in most of the Coastal Plain and in severa...
Host Plant Influence on Glassy-Winged Sharpshooter and Its Natural Enemies
We followed the abundance of glassy-winged sharpshooter and its natural enemies on different host plants in residential areas near Bakersfield, California. We also used potted plants to provide a replicated array of similarly-conditioned GWSS host species in order to follow GWSS host plant preference. Results show GWSS seasonal-long densities were influenced by host plant species, with oleander, Xylosma, and crape myrtle as some of the preferred host plant species for the spring and summer GWSS populations. GWSS preferred different host plant species for adult and nymph feeding as compared with egg-laying. The most effective natural enemies were mymarid parasitoids, with Gonatocerus ashmeadi and G. triguttatus reared from egg masses collected on most host plants. Predators were present, especially spiders, and often observed feeding on GWSS. However, results did not show any one predator species to be consistently associated with GWSS or with a reduction in GWSS densities.
IDENTIFYING KEY PREDATORS OF THE GLASSY-WINGED SHARPSHOOTER IN A CITRUS ORCHARD Project Leaders
2000
Over 1,500 predators were screened for glassy-winged sharpshooter (GWSS) remains using a GWSS egg-specific monoclonal antibody (MAb) and several GWSS-specific genetic markers. Specimens were collected in 2002 and 2003 from a citrus orchard (Riverside, CA) harboring high densities of GWSS. We found that 6.2% of all specimens examined tested positive for GWSS remains. The most frequent predators to test positive