Dispersal and movement of the glassy-winged sharpshooter and associated natural enemies in a continuous, deficit-irrigated agricultural landscape (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. ...
Journal of Economic Entomology, 2009
A 2-yr study was conducted in a citrus orchard (Citrus sinensis L. Osbeck cultivar Valencia) to determine the inßuence of plant water stress on the population dynamics of glassy-winged sharpshooter, Homalodisca vitripennis (Germar). Experimental treatments included irrigation at 100% of the crop evapotranspiration rate (ET c ) and continuous deÞcit-irrigation regimens at 80 and 60% ET c . Microclimate and plant conditions monitored included temperature and humidity in the tree canopy, leaf surface temperature, water potential, and fruit quality and yield. Glassy-winged sharpshooter population densities and activity were monitored weekly by a combination of visual inspections, beat net sampling, and trapping. Glassy-winged sharpshooter populations were negatively affected by severe plant water stress; however, population densities were not linearly related to decreasing water availability in plants. Citrus trees irrigated at 60% ET c had signiÞcantly warmer leaves, lower xylem water potential, and consequently hosted fewer glassy-winged sharpshooter eggs, nymphs, and adults than trees irrigated at 80% ET c . Citrus trees irrigated at 100% ET c hosted similar numbers of glassy-winged sharpshooter stages as trees irrigated at 60% ET c and a lower number of glassy-winged sharpshooter nymphs than the 80% ET c treatment, speciÞcally during the nymphal density peak in mid-April to early July. Irrigation treatments did not affect populations of monitored natural enemies. Although the adult glassy-winged sharpshooter population was reduced, on average, by 50% in trees under severe water stress, the total number of fruit and number of fruit across several fruit grade categories were signiÞcantly lower in the 60% ET c than in the 80 and 100% ET c irrigation treatments.
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
Neotropical Entomology, 2008
Análise Faunística de Cicadelíneos (Hemiptera: Auchenorrhyncha, Cicadellidae) em Pomar de Laranjeira 'Westin' RESUMO -O objetivo deste trabalho foi analisar a fauna de cigarrinhas em pomar de laranjeira 'Westin' enxertada sobre limoeiro 'Cravo', em plantas com cinco anos de idade. Foram instaladas armadilhas adesivas amarelas na borda da mata, na periferia do talhão e no interior do talhão, sendo avaliadas quinzenalmente, por três anos. As cigarrinhas que ocorreram com maior freqüência foram Acrogonia citrina Marucci & Cavichioli, Bucephalogonia xanthophis (Berg) e Oncometopia facialis (Signoret). B. xanthophis ocorreu mais na borda da mata, principalmente na primavera e inverno. A. citrina ocorreu mais na borda da mata, principalmente na primavera. A a maior incidência de O. facialis foi no interior do talhão, e maior na primavera e verão. A ocorrência de outros cicadelíneos foi maior na borda da mata, principalmente no verão. Segundo a análise faunística, A. citrina, B. xanthophis, Dilobopterus costalimai Young e O. facialis foram predominantes em todos os locais estudados; A. citrina, B. xanthophis e O. facialis foram super dominantes, super abundantes, super freqüentes e constantes, exceto no interior do talhão, onde B. xanthophis foi dominante, muito abundante, muito freqüente e constante. D. costalimai e Homalodisca ignorata Melichar foram dominantes, muito abundantes e muito freqüentes na borda da mata e periferia do talhão, sendo que D. costalimai também foi predominante no interior do talhão. Scopogonalia subolivacea (Stål) foi predominante na borda da mata e interior do talhão e Plesiommata corniculata Young, na periferia do talhão (ambas foram dominantes, muito abundantes, muito freqüentes e acessórias).
GLASSY-WINGED SHARPSHOOTER IMPACT ON ORANGE YIELD, FRUIT SIZE, AND QUALITY Project Leader
2000
The California citrus growers needed to know what impact if any the glassy-winged sharpshooter Homalodisca coagulata (GWSS) has on fruit yield, size and quality as well as tree vigor. The goals of this project are to determine the usefulness of the management of GWSS to prevent yield loss, fruit size reduction, and degraded fruit quality. First we have to know what impact GWSS has on citrus, and second we need to know how to use currently available materials against the GWSS in IPM programs to prevent potential losses as well as minimizing negative impact to other citrus pests. This information is paramount before we can even begin to incorporate these into conventional IPM programs. Prior to the initiation of this study, we didn't know what the effects of heavy GWSS feeding has on the vigor of citrus trees or fruit yield, size, sugar/acid ratio, peel thickness etc. GWSS suppression in citrus was done to prevent the movement of GWSS into grape under areawide management programs to limit the spread of Xylella fastidiosa (Xf). Therefore, the focus of this study is to determine the impact of heavy GWSS feeding on citrus yields, fruit size, and quality.
Environmental Entomology, 2008
Host plant water status is thought to inßuence dispersal of the xylophagous leafhopper Homalodisca vitripennis Germar, especially where plants are grown under high evaporative demand. Preference by adult H. vitripennis for plants grown under different water deÞcit and nitrogen form fertilization regimens was studied under laboratory conditions. Leafhopper abundance and ovipositional preference were studied on potted ÔWashington navelÕ orange and ÔHaasÕ avocado in cage choice tests, and feeding rate was estimated using excreta produced by insects conÞned on plants. A similar study compared responses to citrus treated with 1:1 and 26:1 ratios of fertigated nitrate-N to ammonium-N. The insects were more abundant, oviposited, and fed signiÞcantly more on surplus-irrigated plants than on plants under moderate continuous deÞcit irrigation except avocado feeding, which was nearly signiÞcant. Plants exposed to drought became less preferred after 3 and 7 d in avocado and citrus, respectively. Citrus xylem ßuid tension at this point was estimated at 0.93 MPa. A corresponding pattern of decline in feeding rate was observed on citrus, but on avocado, feeding rate was low overall and not statistically different between treatments. No statistical differences in abundance, oviposition, or feeding were detected on citrus fertigated with 26:1 or 1:1 ratios of nitrate-N to ammonium-N. Feeding occurred diurnally on both plant species. Discussion is provided on the potential deployment of regulated deÞcit irrigation to manage H. vitripennis movement as part of a multitactic effort to minimize the risk of disease outbreaks from Xylella fastidiosa Wells et al. in southern California agriculture.
Citrus Insect Interactions: Implications for Pest Management
We observed that insect interactions lead to damaged fruits, leaves, stems, and exposed fruits and tree trunks to pathogenic infection, however, some citrus trees were protected by these interactions. Our study shows that Oecophylla longinoda and Crematogaster spp. protect citrus aphids and citrus scale insects from their natural enemies leading to their outbreak and further damage to the citrus plant. Citrus trees with more Oecophylla and Crematogaster had fewer pests such as fruit flies, termites and the variegated grasshopper, Zonocerus variegatus. Our study shows that “chain” formation by weaver ants, Oecophylla enables them to reach the same colony in different citrus trees. We identified wild passion plant, Passiflora sp. as an alternate host for Leptoglossus spp. We recommend Oecophylla and Crematogaster as biological control agents against fruit flies, termites and the variegated grasshopper; however, they could lead to an outbreak of citrus aphids and citrus scale insects. Phasmomyrmex aberrans is antagonistic to Oecophylla and so in an attempt to utilize Oecophylla as a biological control agent, we recommed that care must be taken to ensure that they do not come together. As biological control agents in orchards that do not have closed canopies, we recommend that sticks or ropes be connected to adjacent trees to facilitate movement of the ants to enhance their dispersal in orchards. Care must be taken to clear all Passiflora sp. from citrus orchards.
Brazilian Journal of Biology, 2008
Many species of microhymenopterous parasitoids have been registered on Phyllocnistis citrella, the citrus leafminer. The present study aimed to identify the spatial distribution pattern of the native and introduced parasitoids of P. citrella in two citrus orchards in Montenegro, RS. The new shoots from 24 randomly selected trees in each orchard were inspected at the bottom (0-1.5 m) and top (1.5-2.5 m) stratum and had their position relative to the quadrants (North, South, East and West) registered at every 15 days from July/2002 to June/2003. The leaves with pupae were collected and kept isolated until the emergence of parasitoids or of the leaf miner; so, the sampling was biased towards parasitoids that emerge in the host pupal phase. The horizontal spatial distribution was evaluated testing the fitness of data to the Poisson and negative binomial distributions. In Montenegrina, there was no significant difference in the number of parasitoids and in the mean number of pupae found in the top and bottom strata (χ 2 = 0.66; df = 1; P > 0.05) (χ 2 = 0.27; df =1; P > 0.05), respectively. In relation to the quadrants, the highest average numbers of the leafminer pupae and of parasitoids were registered at the East quadrant (χ 2 = 11.81; df = 3; P < 0.05), (χ 2 = 10.36; df = 3; P < 0.05). In the Murcott orchard, a higher number of parasitoids was found at the top stratum (63.5%) (χ 2 = 7.24; df =1 P < 0.05), the same occurring with the average number of P. citrella pupae (62.9%) (χ 2 = 6.66; df = 1; P < 0.05). The highest number of parasitoids and of miners was registered at the North quadrant (χ 2 = 19. 29; df = 3; P < 0.05), (χ 2 = 4.39; df = 3; P < 0.05). In both orchards, there was no difference between the numbers of shoots either relative to the strata as well as to the quadrants. As the number of shoots did not varied much relative to the quadrants, it is possible that the higher number of miners and parasitoids in the East and West quadrants would be influenced by the higher solar exposure of these quadrants. The data of the horizontal spatial distribution of the parasitism fit to the negative binomial distribution in all sampling occasions, indicating an aggregated pattern.
Agronomy for Sustainable Development, 2016
Predatory insects are key natural enemies that can highly reduce crops pest damage. However, there is a lack of knowledge about the movements of flying predatory insects in agroecosystems throughout the year. In particular, it is still unclear how these predators move from crop to non-crop habitats, which are the preferred habitats to overwinter and to spread during the spring and if these predators leave or stay after chemical treatments. Here, the Neuroptera, a generalist, highly mobile, flying predator order of insects, was selected as model. We studied the effects of farming management and the efficiency of edge shelterbelts, ground cover vegetation, and fruit trees canopy on holding flying predatory insects in Mediterranean traditional agroecosystems. Seasonal movements and winter effects were also assessed. We evaluated monthly nine fruit agroecosystems, six organic, and three pesticides sprayed, of 0.5-1 ha in eastern Spain during 3 years using two complementary methods, yellow sticky traps and aspirator. Results show surprisingly that the insect abundance was highest in pesticide sprayed systems, with 3.40 insects/ sample versus 2.32 insects/sample in organic systems. The biodiversity indices were highest in agroecosystems conducted under organic management, with S of 4.68 and D of 2.34. Shelterbelts showed highest biodiversity indices, S of 3.27 and D of 1.93, among insect habitats. Insect species whose adults were active during the winter preferred fruit trees to spend all year round. However, numerous species moved from fruit trees to shelterbelts to overwinter and dispersed into the orchard during the following spring. The ground cover vegetation showed statistically much lower attractiveness for flying predatory insects than other habitats. Shelterbelts should therefore be the first option in terms of investment in ecological infrastructures enhancing flying predators.