Grape Leafhopper Research Articles

Landscape Diversity and Crop Vigor Influence Biological Control of the Western Grape Leafhopper (E. elegantula Osborn) in Vineyards.

This study evaluated how the proportional area of natural habitat surrounding a vineyard (i.e. landscape diversity) worked in conjunction with crop vigor, cultivar and rootstock selection to influence biological control of the western grape leafhopper (Erythroneura elegantula Osborn). The key natural enemies of E. elegantula are Anagrus erythroneurae S. Trjapitzin & Chiappini and A. daanei Triapitsyn, both of which are likely impacted by changes in landscape diversity due to their reliance on non-crop habitat to successfully overwinter. Additionally, E. elegantula is sensitive to changes in host plant quality which may influence densities on specific cultivars, rootstocks and/or vines with increased vigor. From 2010–2013, data were collected on natural enemy and leafhopper densities, pest parasitism rates and vine vigor from multiple vineyards that represented a continuum of landscape diversity. Early in the season, vineyards in more diverse landscapes had higher Anagrus spp. densities and lower E. elegantula densities, which led to increased parasitism of E. elegantula. Although late season densities of E. elegantula tended to be lower in vineyards with higher early season parasitism rates and lower total petiole nitrogen content, they were also affected by rootstock and cultivar. While diverse landscapes can support higher natural enemy populations, which can lead to increased biological control, leafhopper densities also appear to be mediated by cultivar, rootstock and vine vigor.

Vineyard proximity to riparian habitat influences Western grape leafhopper (Erythroneura elegantula Osborn) populations

The purpose of this study was to evaluate the impact of vineyard proximity to riparian habitat on the biological control and population densities of the Western grape leafhopper, Erythroneura elegantula Osborn (Hemiptera: Cicadellidae). Natural enemy and pest populations were monitored over a two-year period at multiple vineyard sites adjacent to riparian habitat in northern California. At each site, natural enemy and pest population data were collected along a transect that extended from the riparian habitat into the vineyard. Additionally, a subset of the original research sites were further evaluated for crop vigor, pest density and parasitism rates between the vineyard edge and interior. Results from this study indicate that lower E. elegantula egg deposition and nymph abundance at the vineyard edge were primarily due to reduced crop vigor at the sampled sites and that the most likely cause for these changes were differences in microclimate and soil fertility that were found to be associated with proximity to the riparian habitat.

Influence of Intensity and Duration of Regulated Deficit Irrigation on <I>Erythroneura elegantula</I> (Hemiptera: Cicadellidae) on Grape

We conducted studies in a Paso Robles, CA, grape (Vitis vinifera L.) vineyard in 2002 and 2003 to estimate the impact of regulated deficit irrigation (RDI) intensity and duration on western grape leafhopper, Erythroneura elegantula Osborn. Treatments were based on deficit intensity, 50 and 25% of standard irrigation (moderate and severe deficits, respectively), and deficit duration, 3 or 6 wk time, initiated at the grape phenological stage of berry set. The standard irrigation served as the control, and was intended to be as close to 100% of evapotranspiration (1.0 ETc) for grape in this area. Each week we took counts ofleafhopper nymphs and estimated stomatal conductance, and at the end of each leafhopper generation we counted live, hatched and parasitized leafhopper eggs. Second generation leafhopper nymphal density was lowered by about 38 and 70% in 2002 and 2003, respectively, but in 2003 only the severe deficit had a negative effect on the third generation. This same pattern was seen in oviposition: second generation egg density was reduced by about 44% in the deficit treatments, but in the third generation only the severe deficit was lower than the control. There was little difference between the 3 vs. 6 wk duration in nymphal or egg density. The differences among treatments in second generation peak nymphal density were greater than the differences in second generation hatched eggs, suggesting that in addition to egg mortality, the deficits also affected nymphal mortality. Management strategies for maintaining leafhopper density low in the second generation and third generations include maintaining a sub-1.0 ETc irrigation strategy after the main RDI period, or reinstating the RDI to correspond to the third generation.

Larval development of Empoasca vitis and Edwardsiana rosae (Homoptera: Cicadellidae) at different temperatures on grapevine leaves

AbstractThe grape leafhopper Empoasca vitis (Homoptera: Cicadellidae) is regarded as a major insect pest in many European grapevine growing areas, with an increasing importance realized in recent years maybe as a result of climatic change. Both larvae and adults feed on the phloem vessels of the leaves, causing characteristic symptoms also referred to as hopperburn. Phenology of adult leafhoppers was monitored in one vineyard in three successive years and indicated that immigration of a few hibernated E. vitis individuals into vineyards might take place already quite early in the year depending on winter temperatures and starts to progress in substantial numbers right at grapevine bud burst. In addition, these monitoring studies have shown that there are several other leafhopper species occurring on grapevine plants besides E. vitis, such as the rose leafhopper Edwardsiana rosae (Homoptera: Cicadellidae). Here, we report on the development of larval instars of both leafhopper species, E. vitis and E. rosae on grapevine leaves under different temperature regimes in the laboratory. Shortest larval developmental time was observed at night temperatures of 13–15°C and day temperatures of 23–25°C, which was in agreement with predicted optimal temperatures for both species. At the temperature regime of 20°C night and 30°C day temperature, either no egg hatch was observed or early development of first‐instar larvae was not successful for both species. These results suggest that warm (18°C) nights and moderately warm (28°C) days are representing the upper thermal threshold for development of both E. vitis and E. rosae embryonic stages on grapevine leaves, questioning current assumptions of an increasing importance of E. vitis as a grapevine pest under future climate change.

Autumnal emergence of Anagrus wasps, egg parasitoids of Empoasca vitis, from grapevine leaves and their migration towards brambles

1 The Anagrus‘atomus’ parasitoid group (Hymenoptera: Mymaridae), associated with Empoasca vitis (Gothe) (Homoptera: Cicadellidae), overwinters on vegetation surrounding vineyards. The emergence of parasitoid adults from grapevine leaves in autumn was studied in north-eastern Italy, both in relation to the E. vitis egg-laying period and to the presence of leafhoppers overwintering as eggs on Rubus bushes. 2 Autumnal peaks of Anagrus captured using yellow sticky traps were observed first on grapevines and then on brambles. Parasitoid captures in vineyards were observed for more than 1 month after the last first-instar nymphs of the grape leafhoppers were noticed. Two species belonging to the A. ‘atomus’ group, Anagrus atomus and Anagrus ustulatus, were captured both on grapevines and brambles. 3 Parasitoids of the A.‘atomus’ group can emerge from third-generation grape leafhopper eggs in accordance with two different development time patterns (i.e. normal or delayed). Individuals with delayed emergence required up to 2.2-fold more time to develop from an egg to adult than individuals with normal emergence. This meant that some parasitoid adults emerged in autumn from eggs of grape leafhopper laid in August. 4 A delayed emergence as a result of a slower development ensures that the A.‘atomus’ parasitoid group is synchronized with the egg-laying of leafhoppers that overwinter as eggs on Rubus spp. 5 Consequently, leafhoppers overwintering as eggs on brambles play a key role in the ecology of the relationship between grape leafhoppers and the A.‘atomus’ parasitoid group.

Diversity and invasion within a predator community: impacts on herbivore suppression

Summary 1. Management strategies to enhance ecosystem services in agroecosystems often seek to increase predator biodiversity. Invaders commonly dominate predator communities in agricultural landscapes, however, and the impacts of exotic predators on native predators and ecosystem services are largely unknown. Exotic predators may complement native predator diversity and enhance herbivore suppression, or they may disrupt herbivore suppression through predator interference. 2. We examined the impacts of a dominant exotic predator within the diverse predator community of a California vineyard. Interactions between the exotic wandering spider Cheiracanthium mildei, its closest native ecological homologue (the wandering spider Anyphaena pacifica) and a native spider displaying a different hunting mode (the cobweb‐weaving spider Theridion melanurum) were tested in a manipulative field experiment, with the grape leafhopper Erythroneura elegantula acting as a shared herbivore prey source. 3. We found that the exotic wandering spider suppressed both grape leafhoppers and other unmanipulated leafhopper species that were present in cages. Native spiders had little or no impacts on leafhopper suppression. Thus, C. mildei appears to drive predatory impacts in this system, although evidence also indicated that it is limited by intraspecific interactions. The superior predatory ability displayed by this spider may be shared by other invasive predators that dominate agroecosystems. 4. Despite its effects on leafhoppers, C. mildei negatively impacted a range of spider species, including A. pacifica, T. melanurum, and other unmanipulated native spiders. These impacts are likely to have been mediated through intraguild predation. The wandering hunting mode of C. mildei may have facilitated its role as an intraguild predator. 5. Synthesis and applications. Our results highlight the sometimes conflicting aims of biological control and conservation. Here, a dominant invasive predator increased ecosystem services but also caused declines in numbers of native predators. As disturbed conditions in agroecosystems are likely to put invasive predators at an adaptive advantage, efforts to conserve biodiversity in agricultural landscapes should focus on shifting the outcomes of species interactions to favour native species.

Regulated Deficit Irrigation and Density of <I>Erythroneura</I> spp. (Hemiptera: Cicadellidae) on Grape

This study looked at regulated deficit irrigation (RDI) on leafhoppers in the genus Erythroneura (Erythroneura elegantula Osborn, or western grape leafhopper, and Erythroneura variabilis Beamer) (Hemiptera: Cicadellidae), which are serious pests of cultivated grape (Vitis vinifera L.) in California. RDI is an irrigation strategy that reduces irrigation during a critical point in the phenology of a cultivated perennial crop, to improve vegetative balance and crop quality. Erythroneura spp. are known to respond negatively to vine water stress, and the second generation ofleafhoppers begins during a potential RDI initiation period, between berry set and veraison (beginning of fruit maturation). In experiments at commercial wine grape vineyards, I imposed deficits of between 25 and 50% of crop full evapotranspiration (ET(c)) between berry set and veraison, with control treatments based on the growers' standard irrigations (typically between 0.8 and 1.0 ET(c)), and then we counted leafhopper nymphs weekly, and leafhopper eggs after the second generation. Results show a consistent reduction of second generation nymphal density with this type of RDI, with average density approximately 50% lower under deficit treatments in all three studies. Deficit irrigation reduced second generation egg density by 54% at one site and by 29.9% at another. These results confirm previous studies regarding the sensitivity of Erythroneura spp. to grapevine water stress, and, in addition, they show that a season-wide irrigation deficit is not necessary for reduction in leafhopper density. Results suggest that lower oviposition at least partly explains the lower nymphal density in the deficit treatments.

ENHANCING PLANT DIVERSITY FOR IMPROVED INSECT PEST MANAGEMENT IN NORTHERN CALIFORNIA ORGANIC VINEYARDS

ENHANCING PLANT DIVERSITY FOR IMPROVED INSECT PEST MANAGEMENT IN NORTHERN CALIFORNIA ORGANIC VINEYARDS

The impact of sulfur on the reproductive success of Anagrus spp. parasitoids in the field

Pesticides targeted at pest species have often been demonstrated to have strong adverse effects on the survival of biological control agents in short-term laboratory bioassays; however, studies examining the influence of pesticides on the actual reproductive success of biological control agents in the field are rare. Because natural enemy reproduction is often directly tied to biological control success, effects of pesticides on reproduction are of central importance. Here we use a new technique to examine the influence of sulfur, a fungicide widely used in grape production, on the reproductive success of Anagrus erythroneurae (Hymenoptera: Mymaridae) and Anagrus daanei (Hymenoptera: Mymaridae), egg parasitoids of the grape leafhopper, Erythroneura elegantula (Homoptera: Cicadellidae). Sulfur has previously been shown to be highly toxic to Anagrus spp. in short-term laboratory and field bioassays, creating the expectation that sulfur should also reduce Anagrus reproductive success in the field. Surprisingly, in two studies, the first comparing the oviposition success of Anagrus collected live in paired sulfur-treated versus untreated vineyards and the second comparing the lifetime reproductive success of Anagrus collected at the end of their lives in unpaired sulfur-treated versus untreated vineyards, we found no effect of sulfur on parasitoid reproductive success. In this system, traditional short-term assays of laboratory toxicity do not appear to predict effects on parasitoid reproductive success, suggesting that demographic approaches to assessing the disruptive effects of pesticides may have an important role in designing IPM programs.

The effect of sulfur on biological control of the grape leafhopper, Erythroneura elegantula, by the egg parasitoid Anagrus erythroneurae

We examined the toxicity of a fungicide, sulfur, to the egg parasitoid Anagrus erythroneurae (Hymenoptera: Mymaridae) Trjapitsyn and Chiapini and the vineyard leafhopper pest Erythroneura elegantula Osborn (Homoptera: Cicadellidae) and tested whether or not the use of sulfur in the field affects biological control of E. elegantula. Using field cage bioassays, we demonstrated that sulfur is toxic to adult A. erythroneurae parasitoids, but not toxic to adult E. elegantula leafhoppers. We nonetheless found in a field experiment that sulfur produced no changes in rates of parasitism or E. elegantula egg density, and generated only a very small increase in the density of E. elegantula nymphs. These results suggest that sulfur, although toxic to A. erythroneurae, is not highly disruptive of E. elegantula biological control in vineyards. Our results suggest that simple bioassays of acute toxicity may not accurately predict the impact of agricultural chemicals on biological control.

Identity, Abundance, and Phenology of <I>Anagrus</I> spp. (Hymenoptera: Mymaridae) and Leafhoppers (Homoptera: Cicadellidae) Associated with Grape, Blackberry, and Wild Rose in Washington State

Abstract In 2001 and 2002, we monitored densities of western grape leafhopper, Erythroneura elegantula Osborn, and Virginia creeper leafhopper, Erythroneura ziczac Walsh (Homoptera: Cicadellidae), eggs from June through September in managed and nonmanaged vineyards in Washington state. Anagrus parasitoids (Hymenoptera: Mymaridae) were reared from sampled parasitized leafhopper eggs. Densities of nonparasitized and parasitized E. elegantula eggs, and nonparasitized E. ziczac eggs, were significantly higher in nonmanaged grapevines, although this pattern was not consistent for the latter two groups. Densities of parasitized E. ziczac eggs were consistently low across management regimes. Anagrus erythroneurae S. Trjapitzin & Chiappini, Anagrus daanei S. Triapitsyn, and Anagrus tretiakovae S. Triapitsyn emerged from parasitized E. elegantula eggs, whereas latter two mymarid species also parasitized E. ziczac eggs. Of these species, A. tretiakovae was the most common parasitoid of Erythroneura leafhopper eggs ...

Modeling Leafhopper Nymphs in Temperate Vineyards for Optimal Sampling

Abstract Cicadellids (Homoptera: Cicadellidae) are occasional pests of vineyards in temperate areas, and unchecked populations can build up to high densities to cause leaf burn followed by defoliation and yield loss. Therefore, an optimal sampling scheme would allow determination of risk at minimal cost. Because the development of leafhopper nymphs and feeding injury is closely tied to temperature, a model driven by the accumulation of degree-days was developed to predict leafhopper cumulative abundance at 5, 50, and 95% levels in vineyards. The model was based on 22 data sets collected over 7 yr in three vineyards in southern Quebec. It was based on the cumulative abundance of nymphs of the eastern grape leafhopper; the grapevine leafhopper; the threebanded leafhopper; the Virginia creeper leafhopper; and Erythroneura vitifex Fitch. The lower threshold temperature for development was 8°C. Paired t-tests and the forecasting efficiency confirmed the validity of the model. The model indicated that monitorin...

Calcium Tartrate Crystals in the Midgut of the Grape Leafhopper

Calcium tartrate crystals were observed in the midgut of grape leafhoppers. This unique compound was found for the first time in insects. The size of the crystals varied strongly between and within individuals with a mean length of 153 +/- 87 microm and a mean width of 71 +/- 46 microm. In addition, the number of crystals per individual showed a broad variation and ranged from 1 to 150 crystals/individual. The occurrence of calcium tartrate crystals as well as the number of crystals per individual followed the same seasonal pattern as seasonal vine leaf concentrations of tartaric acid found in a previous study, indicating that calcium tartrate is formed to neutralize the tartaric acid in the gut system. It further implies that the grape leafhopper, rather than being a pure phloem sucker, employs a mixed feeding strategy to satisfy its demands for calcium uptake.

Biology of Anagrus atomus (Hymenoptera: Mymaridae), an egg parasitoid of the grape leafhopper Arboridia kermanshah (Homoptera: Cicadellidae)

AbstractBiology, morphology and oviposition behavior of Anagrus atomus (Linnaeus), an egg parasitoid of the grape leafhopper Arboridia kermanshah Dlabola in Isfahan, Iran, were investigated. Adults were smaller than those so far reported from other regions. Females continuously drummed on plant surfaces with their antennae to search for host eggs. Parasitoid eggs hatched 2–3 days after oviposition, and A. atomus had two larval instars. First instar larvae were sacciform and immobile. Second instar larvae appeared 4 days after oviposition and were very active, and doubled their body length. The prepupal and pupal stages lasted for 1 and 5–6 days, respectively. Adult emergence began 16 days after oviposition, and peaked on day 17.

A simplified method for monitoring eggs of the grape leafhopper (Empoasca vitis) in grapevine leaves

Based on a previously reported method for monitoring eggs of the grape leafhopper (Boll and Herrmann 2001) stated as Leda (Leafhopper Egg Detection by Autofluorescence), a simplified but equally reliable version of this method, Sleda (Simplified Leafhopper Egg Detection by Autofluorescence), is introduced. Both methods are based on the fact that the leafhopper eggs show an intense green autofluorescence under blue light excitation. However, in contrast to Leda, for Sleda a fluorescent light microscope is no longer prerequisite, only an optic light source equipped with a blue exciter and a commercial blue cutter are required.

A long-term study on the population dynamics of the grape leafhopper ( Empoasca vitis ) and antagonistic mymarid species

The population dynamics of the grape leafhopper (Empoasca vitis) and its egg parasitoids (Mymaridae) were studied at five representative sites in the Franconian wine-growing region from 1998 to 2001. In contrast to other German wine-growing areas, only one generation of grape leafhoppers per season was observed. In general, irrespective of the application of insecticides, the peak density of the first generation was much lower than that of immigrating grape leafhoppers. As the observed mymarid:leafhopper ratios (1:0.8–1:4.8) of the first generation were extremely high, egg parasitoids might be effectively controlling the grape leafhopper in Franconian vineyards. Slightly elevated leafhopper densities at the end of the growing season were caused by migrating sister species. Intervention thresholds were rarely reached; however, stress symptoms as discoloured intercostal leaf areas or rolled leaf edges were widespread. Over the whole study period three mymarid species occurred at all monitoring sites: Anagrus atomus, Stethynium triclavatum and a species, not previously reported in the German wine-growing region, Anagrus avalae. The dominance relationships of these species were site-specific, differing more strongly between than within sites; however, differences could not be related to the kind of management or natural surrounding of the vineyards. A hatching experiment confirmed the biological significance of A. avalae as an effective antagonist.

Influence of flowering cover crops on Anagrus parasitoids (Hymenoptera: Mymaridae) and Erythroneura leafhoppers (Homoptera: Cicadellidae) in New York vineyards

Abstract 1 We tested the hypothesis that providing nectar‐producing cover crops will enhance the biological control of grape leafhoppers (Erythroneura spp.) by Anagrus wasps in commercial vineyards in New York, U.S.A.2 We established three cover crops between vine rows in a commercial vineyard: buckwheat (Fagopyrum esculentum (Moench)), clover (Trifolium repens L.) and mowed sod (Dactylis glomerata L.).3 There was no effect of cover crop on adult Anagrus in 1996, whereas in 1997 adults were more abundant within edge vines with buckwheat compared to vines with clover or sod; adults were more abundant at the vineyard edge, especially early in the season.4 Parasitism of ‘sentinel’ leafhopper eggs was higher on vines with buckwheat compared to parasitism on vines with clover or sod in 1996; a similar, non‐significant trend, was observed in 1997.5 Neither the abundance nor the distribution of leafhoppers was influenced by cover crops, although in 1997 there was a trend toward greater numbers of nymphs on edge vines with buckwheat.6 In a cage experiment, parasitism by Anagrus of leafhopper eggs on grapes was greater when adults had access to flowering buckwheat rather than buckwheat without flowers.7 In a laboratory study, longevity of female Anagrus was increased when provided with honey or sugar water compared to water only or nothing.8 Our results suggest that parasitism of grape leafhoppers by Anagrus may be enhanced by providing floral resources within vineyards in New York, although it is unclear whether this will produce meaningful reductions in pest abundance.

ESTIMATING THE CONSEQUENCES OF APPARENT COMPETITION:A METHOD FOR HOST–PARASITOID INTERACTIONS

To evaluate the role of natural enemies for the coexistence of competing species, it is necessary to estimate quantitatively the way in which the selectivity of the natural enemies changes the strength of competition between the competitors. This paper presents one method for doing this in host–parasitoid systems with discrete generations. The method is illustrated by analyzing the interaction between variegated leafhoppers (Erythroneura variabilis) and grape leafhoppers (E. elegantula) feeding on domestic grapes. The analysis confirms earlier observations that the recent replacement of grape leafhoppers with variegated leafhoppers is likely to be a consequence of the shared egg parasitoid Anagrus epos. Finally, we argue that the method can provide a tool to evaluate the potential of biological control measures involving alternative prey, e.g., in intercropping systems.

The effects of a vegetational corridor on the abundance and dispersal of insect biodiversity within a northern California organic vineyard

During 1996 and 1997, two adjacent 2.5 has organic vineyard blocks (A and B) were monitored to assess the distributional and abundance patterns of the Western grape leafhopper Erythroneura elegantulaOsborn (Homoptera: Cicadellidae) and its parasitoid Anagrus eposGirault (Hymenoptera: Mymaridae), Western flower thrips Frankliniella occidentalis (Pergande) and generalist predators. The main difference between blocks was that block A was cut across by a corridor composed of 65 flowering plant species which was connected to the surrounding riparian habitat, whereas block B had no plant corridor. In both years, leafhopper adults and nymphs and thrips tended to be more numerous in the middle rows of block A and less abundant in border rows close to the forest and corridor where predators were more abundant. The complex of predators circulating through the corridor moved to the adjacent vine rows and exerted a regulatory impact on herbivores present in such rows. In block B all insects were evenly distributed over the field, no obvious density gradient was detected from the edges into the center of the field. Although it is suspected that A. epos depended on food resources of the corridor, it did not display a gradient from this rich flowering area into the middle of the field. Likewise no differences in rates of egg parasitism of leafhoppers could be detected in vines near the corridor or in the vineyard center. The presence of riparian habitats enhanced predator colonization and abundance on adjacent vineyards, although this influence was limited by the distance to which natural enemies dispersed into the vineyard. However, the corridor amplified this influence by enhancing timely circulation and dispersal movement of predators into the center of the field.

Colonization of New York Vineyards by Anagrus spp. (Hymenoptera: Mymaridae): Overwintering Biology, Within-Vineyard Distribution of Wasps, and Parasitism of Grape Leafhopper, Erythroneura spp. (Homoptera: Cicadellidae), Eggs

A study was conducted in New York to identify the Anagrus species present in vineyards, to determine the plants in which Anagrus species overwinter, and to characterize the dispersal of wasps and level of parasitism of grape leafhopper eggs in vineyards. Anagrus daanei S. Triapitsyn and Anagrus erythroneurae S. Trjapitzin and Chiappini were the most abundant species reared from Vitis labrusca Bailey and Vitis vinifera L. cultivars, respectively. V. labrusca cultivars are infested predominantly by Erythroneura comes (Say), whereas V. vinifera cultivars are infested primarily by the Erythroneura vitifex Fitch–Erythroneura bistrata McAtee complex. Anagrus tretiakovae S. Triapitsyn was reared from seven grape cultivars in approximately equal proportions. Thus, A. daanei and A. erythroneurae appear to possess greater degrees of host specificity than A. tretiakovae. These results support the belief that, although Anagrus species have relatively broad host associations, host preferences do exist. These preferences may be mediated by the plant associations of particular leafhopper species. Anagrus species use alternate hosts that infest several plant species. In particular, diapausing insect eggs in Acer saccharum Marshall, Robinia pseudo-acacia L., Rosa multiflora Thunberg, Salix nigra L., Vitis riparia Michaux, and Zanthoxylum americanum Miller may play important roles in the overwintering biology of the Anagrus species that are most abundant in vineyards. Following emergence from overwintering hosts, Anagrus adults are aggregated at the vineyard edge early in the season (May and June). By midseason or later (August and September), the pattern of wasp colonization and parasitism indicates that parasitoids are more widely dispersed in the vineyards. This pattern is consistent with colonization from vineyard edges, followed by relatively slow dispersal into the vineyard interior. Further investigations are necessary to identify the alternate host(s) that Anagrus exploits during the winter and spring and to delineate the phenology of such alternate hosts, as well as that of the grape leafhoppers and Anagrus species in the spring. Habitat management studies could then be conducted to identify strategies that would accelerate population growth of Anagrus in the spring and increase the rate of dispersal into vineyards.