Egg parasitoids (Hymenoptera: Mymaridae and Trichogrammatidae) of Kolla paulula (Walker) (Hemiptera: Cicadellidae) in Taiwan

Pseudoligosita nephotetticum (Mani) (Hymenoptera: Trichogrammatidae) and Gonatocerus (Cosmocomoidea) sp. (Hymenoptera: Mymaridae) have been identified for the first time as egg parasitoids of the sharpshooter leafhopper Kolla paulula (Walker) (Hemiptera: Cicadellidae: Cicadellinae: Cicadellini) in Taiwan. K. paulula has been recently identified as a candidate vector of the phytopathogenic bacterium Xylella fastidiosa, the causative agent of Pierce's disease of grapes and similar diseases of other affected plants in Taiwan, and thus has become of particular economic importance. Also provided is a summary of the known records of egg parasitoids (Mymaridae and Trichogrammatidae) of other leafhoppers from the tribe Cicadellini in the world, as well as taxonomic notes on P. nephotetticum.     

Dispersion of Homalodisca coagulata (Hemiptera: Cicadellidae), a vector of Xylella fastidiosa, into vineyards in southern California

Recent epidemics of Pierce's disease of grapevine in California vectored by Homalodisca coagulata (Say), an invasive vector species, have characteristics that differ from epidemics involving native vectors. Among these differences are the longer distances and greater speed that the disease is spread by H. coagulata. In this investigation, we used yellow sticky traps to study the seasonal dispersion activity of H. coagulata in a southern California grape-growing area in which an epidemic of Pierce's disease has caused large losses. For 21 mo, we monitored adult H. coagulata at the edges of vineyards bordering citrus, an important crop host, natural coastal sage scrub vegetation, and natural riparian vegetation. We also monitored H. coagulata dispersion from 0 to 40 m into vineyards. Finally, we examined the vertical dispersion of H. coagulata adults into grapevines through a season. This investigation showed that H. coagulata is associated with citrus, from where it disperses deep into vineyards, and not just the vineyard edge as with Pierce's disease vectors that are native to California. Peak dispersion into vineyards occurred in the summer. Another period of H. coagulata activity occurred in the winter in vineyards bordering citrus. Through the period of peak flight activity, 97% of all H. coagulata adults trapped between 1 and 7 m were caught at an altitude of 5 m or lower, suggesting the potential of a barrier as a management tactic to keep H. coagulata out of vineyards.     

Seasonal flight activity of two Homalodisca species (Homoptera: Cicadellidae) that spread Xylella fastidiosa in southern California.

Homalodisca coagulata (Say) and Homalodisca lacerta (Fowler) are vectors of a new bacterial disease of oleander in California known as oleander leaf scorch, induced by the bacterium Xylella fastidiosa. H. coagulata also has been implicated in the spread of the strain of X. fastidiosa that induces Pierce's disease of grapevines in California. We monitored the flight activity of H. coagulata and H. lacerta in oleander and citrus by using yellow sticky cards at three southern California locations where outbreaks of oleander leaf scorch have been documented, and where vector compliments are different. Areas sampled included a mesic coastal area (Irvine, CA) that supports predominantly H. coagulata and few H. lacerta, a dry inland location (Palm Desert, CA) that supports predominantly H. lacerta and few H. coagulata, and an intermediate area (Riverside, CA) supporting both Homalodisca species. From November 1996 to October 1999 peak catches of both Homalodisca species occurred during the midsummer at all locations. H. coagulata was trapped in greater numbers in citrus than in oleander at both the Riverside and the Irvine sites. Likewise, H. lacerta in Riverside was more associated with citrus than oleander, yet H. lacerta in Palm Desert was trapped in greater numbers in oleander than citrus.     

Thermal requirements of Fidiobia dominica (Hymenoptera: Platygastridae) and Haeckeliania sperata (Hymenoptera: Trichogrammatidae), two exotic egg parasitoids of Diaprepes abbreviatus (Coleoptera: Curculionidae)

Diaprepes abbreviatus is an exotic root weevil occurring in southern US. It is a highly polyphagous species which can complete its entire life cycle on citrus and several woody ornamental plants. The lack of native egg parasitoids for this weevil in citrus orchards has triggered efforts to evaluate candidate egg parasitoids from the Caribbean Region into Florida. The egg parasitoids Fidiobia dominica and Haeckeliania sperata are two exotic natural enemies of D. abbreviatus recently introduced in the US in a classical biological control program. The thermal requirements of both parasitoids were studied in the laboratory. The upper development threshold (UDT) of F. dominica was 30.0°C, its maximal development rate (MDR) occurred at 27.6°C, its lower development threshold (LDT) was 9.6°C and its thermal constant (K) for development from egg to adult was 293.1 DD. For H. sperata, UDT was 35.0°C, MDR occurred at 31.0°C, LDT was around 15°C and K was 188.1 DD. Based on these results, both species would be able to complete 17 to 18 generations annually in southern Florida. However, host availability during critical periods could severely impair the ability of these egg parasitoids to establish and successfully control D. abbreviatus in areas where winter temperatures fluctuate around 12°C, the LDT for this pest.     

Egg maturation,oosorption, and wing wear in Gonatocerus ashmeadi (Hymenoptera: Mymaridae), an egg parasitoid of the glassy-winged sharpshooter,Homalodisca vitripennis (Hemiptera: Cicadellidae)

Egg maturation and oosorption in Gonatocerus ashmeadi were investigated in the laboratory and the relationship between hind tibia length (HTL) and <12 h egg load, and wing wear and parasitoid age were determined. G. ashmeadi given access to honey-water and hosts, on average, matured 77 eggs in excess of those they were born with. The number of mature eggs in female G. ashmeadi provided honey-water with no hosts significantly declined after 163 degree-days eggs, while the number of ‘dissolved’ eggs (partially disintegrated mature eggs) increased by nine eggs after 163 degree-days. These results are consistent with oosorption. There was a significant positive correlation between HTL and <12 h egg load. The ovigeny index (the number of mature eggs at female emergence divided by potential lifetime fecundity) for G. ashmeadi was calculated as 0.22 indicating that this parasitoid is a syn-ovigenic species when studied under laboratory conditions. There was a significant positive correlation between wing wear (measured as the number of broken setae per wing) and parasitoid age in the laboratory. The practical implications of these results for G. ashmeadi on the biological control of Homalodisca vitripennis are discussed.     

Spatial and temporal dynamics of overwintering Homalodisca coagulata (Hemiptera: Cicadellidae)

A 4-yr landscape-scale study was conducted to investigate spatial and temporal dynamics of overwintering Homalodisca coagulata (Say) (Hemiptera: Cicadellidae) in the lower San Joaquin Valley, California. Spatial structures of H. coagulata distributions were characterized with Moran's I index, and spatial associations between H. coagulata and the surrounding environment were investigated with a geographic information system. H. coagulata was caught consistently with sticky traps throughout the winter, and trap catches formed a distinctive peak in December or January, indicating active flight of H. coagulata during the winter. In 2000-2001, the mean +/-SE trap count was 4.8 +/- 1.21 per trap per wk, and H. coagulata trap catches were spatially autocorrelated within approximately 1.3 km. Approximately 49% of H. coagulata were caught in citrus, 23% in stone fruit, and 11% in grape. After a control program began in spring 2001, the mean trap count was considerably lower (0.041 +/- 0.0004 per trap per wk), and no spatial autocorrelations were detected in 2001-2004. H. coagulata trap catch-crop associations also changed after initiation of the control program. Between 25 and 38% of H. coagulata trap catches were from citrus, between 8 and 20% were from stone fruit, and between 11 and 25% were from grape. Potential for winter-season spread and management of Xylella fastidiosa Wells et al., a pathogen causing Pierce's disease, are discussed.     

Progeny quality of Gonatocerus ashmeadi (Hymenoptera: Mymaridae) reared on stored eggs of Homalodisca coagulata (Hemiptera: Cicadellidae)

This study assessed the effects of refrigerated storage on the suitability of eggs of the glassy-winged sharpshooter, Homalodisca coagulata (Say) (Hemiptera: Cicadellidae), as hosts for propagation of the parasitoid Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae). Development of the host eggs was terminated by chilling at 2 degrees C for 5 d before storage was initiated at 10 degresC for up to 70 d. Parasitism, adult emergence rate, developmental time, and sex ratio were used to gauge the suitability of the eggs as hosts after storage. In addition to these measures, demographic growth parameters also were used to assess the quality of the wasp progeny through the F2 generation. Host eggs stored 20 d remained fully acceptable to the wasps for attack. Although the parasitism rate decreased with storage time, > 80% adult parasitoid emergence was realized from eggs stored 30 d. After 70 d storage, adult emergence rate was decreased by 48%, fecundity decreased by 53%, female production by 19%, developmental time was extended 3 d, and female longevity was shortened 5 d. The emergence pattern of F1 but not F2 adults varied with storage time of the parental and grandparental hosts, respectively. For the F1 generation, emergence rate, development, and sex ratio did not vary with storage time when the F1 parents parasitized fresh host eggs. Demographic parameters for the F, population showed that net reproductive rate was > 20 although it decreased significantly after their parental host eggs were stored for > 30 d. The intrinsic and finite rates of increase, population doubling time, and mean generation time decreased only after storage for 60 d. Our results show that short-term cold storage could be used for maintaining wasp populations in a mass-rearing program and that the detrimental effects of chilling host eggs in storage for over 30 d do not extend to F2 generation.     

The British species of Gonatocerus Nees (Hymenoptera: Mymaridae), egg parasitoids of Homoptera

Abstract. The thirteen British species of Gonatocerus Nees are characterized by means of a key and short diagnostic notes based on the females, with notes on their hosts and distribution. The species-groups proposed by Debauche are discussed; two species, Gonatocerus rogersi and G.minor, are described as new, and eighteen specific synonymies are proposed.     

Identification of egg parasitoids of rice leafhoppers and planthoppers (Hemiptera: Cicadellidae and Delphacidae) of economic importance in Taiwan,part 1: Mymaridae (Hymenoptera)

Fairyfly egg parasitoids (Hymenoptera: Mymaridae) of rice leafhoppers and planthoppers (Hemiptera: Cicadellidae and Delphacidae) known from Taiwan are identified taxonomically, keyed, and illustrated. Their host associations are determined by rearings using sentinel eggs of mainly four key pest species. The previously published records of such egg parasitoids in Taiwan are critically analyzed in the unfortunate absence of almost any voucher specimens. Three species of Mymaridae are shown to be the predominant egg parasitoids of one leafhopper and three planthopper major pests of rice in Taiwan: Anagrus (Anagrus) incarnatus Haliday of the green rice leafhopper Nephotettix cincticeps (Uhler) and the delphacids Laodelphax striatella (Fallén) (small brown planthopper), Nilaparvata lugens (Stål) (brown planthopper), and Sogatella furcifera (Horváth) (whitebacked planthopper), as well as Gonatocerus aegyptiacus Soyka and Mymar taprobanicum Ward of N. cincticeps. The zig-zag leafhopper Maiestas dorsalis (Motschulsky), which is also common in paddy fields, is newly recorded as a host for A. incarnatus, G. aegyptiacus, Lymaenon litoralis (Haliday), and M. taprobanicum. Additional new records of some other Mymaridae in Taiwan, mostly from the rice field agroecosystems, are indicated. Litus assamensis Rehmat and Anis, syn. nov. from India, is synonymized with L. sutil Triapitsyn and Berezovskiy from Thailand, which is also newly recorded from Taiwan.     

Transmission of Xylella fastidiosa to grapevines by Homalodisca coagulata (Hemiptera: Cicadellidae)

Pierce's disease (PD) of grapevines is caused by a xylem-limited bacterium Xylella fastidiosa (Wells, Raju, Hung, Weisburg, Mandelco-Paul, and Brenner) that is transmitted to plants by xylem sap-feeding insects. The introduction of the sharpshooter leafhopper Homalodisca coagulata (Say) into California has initiated new PD epidemics in southern California. In laboratory experiments, the major characteristics of H. coagulata's transmission of X. fastidiosa to grapevines were the same as reported for other vectors: short or absent latent period; nymphs transmitted but lost infectivity after molting and regained infectivity after feeding on infected plants; and infectivity persisted in adults. Adult H. coagulata acquired and inoculated X. fastidiosa in <1 h of access time on a plant. Inoculation rates increased with access time, but acquisition efficiency (20% per individual) did not increase significantly beyond 6-h access. Estimated inoculation efficiency per individual per day was 19.6, 17.9, and 10.3% for experiments where plant access was 1, 2, and 4 d, respectively. Freshly molted adults and nymphs acquired and transmitted X. fastidiosa more efficiently than did older, field-collected insects. H. coagulata transmitted X. fastidiosa to 2-yr-old woody tissues of grapevines as efficiently as to green shoots. H. coagulata transmitted X. fastidiosa 3.5 mo after acquisition, demonstrating persistence of infectivity in adults. About half (14/29) of the H. coagulata from which we failed to culture X. fostidiosa from homogenized heads (with a detection threshold of 265 CFU/head) transmitted the pathogen to grape, and 17 of 24 from which we cultured X. fastidiosa transmitted.     

Naturally occurring egg parasitoids of the genus Trichogramma (Hymenoptera: Trichogrammatidae) in a pomegranate orchard in Tunisia

Four Trichogramma species were found in a pomegranate orchard in Gabès, an arid region of Tunisia, from parasitized eggs of Ectomyelois ceratoniae Zeller (Lepidoptera: Pyralidae), an economically important insect pest. Identification based on assessment of male genitalia and internal transcribed spacer 2 ( ITS 2) sequences showed that they were T. bourarachae Pintureau and Babault, 1988, T. oleae Voegelé and Pointel, 1979, T. cacoeciae Marchal, 1927 and T. evanescens Westwood, 1833. Trichogramma evanescens is reported for the first time in Tunisia. Trichogramma cacoeciae was the largely dominant species in the analyzed samples, whereas T. bourarachae was present in a minor portion of 1.38%. The implications of these results for attempts at controlling E. ceratoniae are discussed.     

Pollen as a source of food for egg parasitoids of the genus Trichogramma (Hymenoptera: Trichogrammatidae)

The value of corn pollen as a food source for Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) was assessed in the laboratory by testing the effect of different pollen diets on the longevity, capacity of parasitism and other life-table parameters. T. brassicae females that fed on corn pollen and water (wet filter paper dusted with pollen) lived significantly longer (4.97 days) than females that fed on water alone (2.67 days), but significantly shorter than those feeding on honey alone (8.37 days) or corn pollen and honey (8.23 days), respectively, in the absence of host eggs. The presence of European corn borer eggs (Ostrinia nubilalis Huebner, Lepidoptera: Pyralidae) significantly increased longevity. With host eggs available, female T. brassicae that fed on corn pollen and water lived significantly longer (4.9 days) than on water alone (2.60 days), but significantly shorter than on honey alone (12.33 days) or corn pollen and honey (12.17 days), respectively. The cumulative lifetime fecundity was 82.53 offspring pupae when fed on pollen and water, which was significantly higher than 61.70 for water alone but lower than feeding on honey alone (95.70) or corn pollen and honey (99.97), respectively. Compared to water alone, corn pollen and water increased the net reproduction rate (R₀), intrinsic rate of increase (r_m), and finite rate of increase (λ), and reduced the doubling time (T₂), but had no effects on the emergence rate, sex ratio, and mean generation time (T_c). In another set of experiments, 13 out of 30 females reduced the number of pollen grains offered to them. The average number of pollen grains utilized per female in this 48-h test 2.46±0.40 (mean±SE). Hence, T. brassicae used corn pollen as food that significantly increased longevity and fecundity of the tested females. Pollen and honey supplied a complete diet for T. brassicae, compared to pollen and water or water alone.     

The effect of temperature and humidity on the bionomics of six African egg parasitoids (Hymenoptera: Trichogrammatidae)

The life table statistics of six native Kenyan species/strains of Trichogramma and Trichogrammatoidea were established using a factitious host Corcyra cephalonica, Stainton (Lepidoptera: Pyralidae), at eight different temperatures (10, 15, 20, 25, 28, 30, 32 and 35 degrees C) and two humidity levels (40-50 and 70-80%). The objective was to select insects with superior attributes for augmentative release against lepidopteran pests in horticultural crops. Both temperature and humidity affected developmental time and life table parameters of the parasitoids but temperature played a more critical role. Developmental time was inversely related to temperature. The intrinsic and finite rates of increase increased with temperature up to 30 degrees C. Both net reproduction rate and intrinsic rate of increase were higher at the lower humidity. Temperature inversely affected generation time of parasitoid strains regardless of the relative humidity. Two strains of Trichogramma sp. nr. mwanzai collected from both low and medium altitudes and Trichogrammatoidea sp. nr. lutea from the mid-altitudes, were better adapted to both low and high temperatures than the other strains, as indicated by the high intrinsic and net reproductive rates, at both humidity levels. These three strains appear to be promising candidates for augmentation biocontrol against the African bollworm Helicoverpa armigera in Kenya.     

Biological studies on two neotropical egg parasitoid species: Trichogramma nerudai and Trichogramma sp. (Hymenoptera: Trichogrammatidae)

The main biological attributes of two Neotropical egg parasitoids, the arrhenotokous Trichogramma nerudai and the thelytokous Trichogramma sp., were assessed under controlled laboratory conditions. Developmental time from egg to adult, and parasitoid survival, fecundity and fertility were studied using life tables. Results showed that T. nerudai had a faster developmental time than Trichogramma sp. (13.014±0.4019 and 13.595±0.4931 days, respectively). Both species showed similar life table statistics, r_m was 0.222 and 0.225 for T. nerudai and Trichogramma sp., respectively. Parasitoid survival averaged 95% for both species. The results obtained are discussed in the context of selecting one of these natural enemies as a potential biological control agent for the European pine shoot moth Rhyacionia buoliana (Lepidoptera: Tortricidae) in pine forests and the codling moth Cydia pomonella (Lepidoptera: Tortricidae) in apple orchards in Argentina.     

Description of new species of two genera Dayus Mahmood and Znana Dworakowska from Thailand (Hemiptera: Cicadellidae: Typhlocybinae)

Two genera, Dayus Mahmood, 1967 and Znana Dworakowska, 1994 of the leafhopper tribe Empoascini (Hemiptera: Cicadellidae: Typhlocybinae) are reviewed. One new species of each genus, Dayus furcatus sp. nov. and Znana furca sp. nov., are described from Thailand. A checklist and distribution summary of Dayus Mahmood species is given. Male habitus photos and illustrations of male genitalia of the two new species and notes on allied species are also provided.     

Susceptibility of immature stages of Homalodisca coagulata (Hemiptera: Cicadellidae) to selected insecticides

Susceptibility of immatures of the glassy-winged sharpshooter, Homalodisca coagulata (Say) (Hemiptera: Cicadellidae), to 10 insecticides that included chlorpyrifos, dimethoate, endosulfan, bifenthrin, cyfluthrin, esfenvalerate, fenpropathrin, acetamiprid, imidacloprid, and thiamethoxam was evaluated in the laboratory. All five instars were exposed to different doses of each foliar insecticide by the petri dish technique, whereas a systemic uptake method was used to assess the toxicity to imidacloprid and thiamethoxam. All test insecticides exhibited high toxicity to all immature stages of H. coagulata at concentrations below the field recommended rates of each insecticide. Although all five instars were susceptible to test insecticides, mortality was significantly higher in first instars than in the older immatures based on low LC50 values (ranging from 0.017 to 5.75 ng(AI)/ml) with susceptibility decreasing with each successive stage. Fifth instars were generally the least sensitive (LC50 values ranging from 0.325 to 216.63 ng (AI)/ml). These results show that mortality was directly related to age of the insect and suggest that chemical treatment at early stages is more effective than at late stages. Acetamiprid (neonicotinoid) and bifenthrin (pyrethroid) were the most toxic to all five instars, inducing most mortality within 24 h and showing lower LC50 values ranging from 0.017 to 0.686 ng/ml compared with other insecticides (LC50 values ranging from 0.191 to 216.63 ng(AI)/ml). Our data suggest that a diverse group of very effective insecticides are available to growers for controlling all stages of H. coagulata. Knowledge on toxicity of select insecticides to H. coagulata immatures may contribute to our understanding of resistance management in future for this pest by targeting specific life stages instead of the adult stage alone.     

Effect of pesticides on Colpoclypeus florus (Hymenoptera: Eulophidae) and Trichogramma platneri (Hymenoptera: Trichogrammatidae), parasitoids of leafrollers in Washington.

Pesticides were evaluated for their effect on two parasitoid species, Colpoclypeus flouts and Trichogramma platneri, that are potential biological control agents of leafrollers in apple orchards. Organophosphate and carbamate insecticides were highly toxic to both parasitoids in topical applications, but foliar residues of some products were nontoxic after 7 d. At reduced rates, topically applied pyrethroids were low in toxicity to C. florus were highly toxic to T. platneri, and foliar residues were nontoxic after about 7 d. Imidacloprid and abamectin were highly toxic when applied topically to both parasitoids but were not toxic as 1-d-old residues. Insect growth regulators did not cause mortality either as topical applications or residues; however, diflubenzuron caused severe sublethal effects, completely blocking the production of C. florus offspring. Biorational pesticides, such as soap, oil, and B. thuringiensis products, caused no toxicity to C. florus but had a direct impact on T. platneri as topical applications through physical immobilization. The potential to integrate different pesticides with biological control of leafrollers and the need for a step-wise approach to evaluate the impact of pesticides against natural enemies is discussed.     

Behavioral responses of Homalodisca vitripennis (Hemiptera: Auchenorrhyncha: Cicadellidae) on four Vitis genotypes

Pierce's disease is a major threat to the California grape industry. The disease-causing bacterium Xylella fastidiosa is vectored by a number of leafhoppers including Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae). Experiments were conducted to study H. vitripennis preference, feeding, and survivorship in response to four Vitis genotypes. Plants of V. vinifera ('Chardonnay'), V. girdiana, V. candicans, and a V. rupestris x V. arizonica/candicans hybrid (D8909-17) were grown in pots in the greenhouse and transferred to laboratory conditions for experiments with field-collected H. vitripennis. A choice test without prior insect acclimation on grapes revealed that H. vitripennis selected Chardonnay over V. candicans throughout the duration of the experiment, whereas a shift in preference between D8909-17 and V. girdiana was observed over time. In a second set of choice tests, which were preceded by an acclimation on one of the four grape genotypes, significant genotype, time, and acclimation x genotype effects were observed. Chardonnay was preferred over V. candicans independent of acclimation genotype. Although H. vitripennis confined on D8909-17 excreted 1.8-fold (dry-weight corrected) the amount of insects feeding on V. candicans, differences in the rate of excreta production per insect or insect dry weight were not significant among grape genotypes. Adult mortality was greatest on V. candicans when H. vitripennis were confined in parafilm sachets for excreta collection as well as in a no-choice test. Grape genotype affected the behavior of adult H. vitripennis under controlled conditions, which may influence Pierce's disease epidemiology under field conditions.     

Preference-performance linkage of the xylem feeding leafhopper, Homalodisca vitripennis (Hemiptera Cicadellidae)

Insect species exhibiting a weak linkage between adult preference and immature performance have frequently been shown to be prone to outbreaks. We used choice and no-choice tests to examine the preference-performance linkage of the xylem fluid-feeding leafhopper, Homalodisca vitripennis Germar. Leafhoppers were offered a choice of hosts common to their native range and also a choice from hosts where they have been recently introduced. Behavior (residence preference, oviposition preference, and consumption rates) was quantified in choice tests. Performance (development of immature leafhoppers, fecundity, body weights, and survivorship) was quantified in no-choice tests. Virtually all aspects of leafhopper behavior and performance varied with host species, yet there were no linkages between adult preference and immature performance. Lagerstroemia indica and Citrus sinensis were the preferred hosts, but both species supported <30% of neonate development until the second stadia. Glycine max was the superior developmental host with development to the adult stage exceeding 40%, but this host was seldom used by adult leafhoppers. Adult preference reflected aspects of adult performance including increases in fecundity, body weights, and survivorship. These preference-performance linkages were impacted by environmental context, insect reproductive status, and insect feeding history. Essential amino acids were consistently correlated with performance of both adult and developing insects; relationships between nutrients and preference were less consistent. The weak linkage of adult preference and immature leafhopper performance are discussed in terms of outbreaks of H. vitripennis.     

Impact of a screen barrier on dispersion behavior of Homalodisca coagulata (Hemiptera: Cicadellidae)

The recent incursion of the sharpshooter Homalodisca coagulata (Say) (Hemiptera: Cicadellidae), a vector of the plant pathogenic bacterium Xylellafastidiosa, into southern California has caused new epidemics of plant diseases. The potential of H. coagulata to spread throughout the state and disseminate disease has encouraged the development of techniques to limit further spread of the vector and to manage disease epidemics where the insect already exists. We evaluated a unique tactic to curtail the immigration of H. coagulata into high-value crops, including nursery stock, where they can be spread via commercial transportation throughout the state and into disease-susceptible vineyards. This tactic consists of a 5-m-high screen barrier surrounding the crop that is impenetrable to H. coagulata. We examined H. coagulata orientation and flight direction when placed near or on the screen barrier, and determined the proportion of insects that flew over it. When released midway between a barrier and adjacent vegetation 71.5% of H. coagulata flew away from the barrier and in the direction of the vegetation; whereas 29.5% flew in the direction of the barrier. Of the total number of H. coagulata released, 7.5% flew over the barrier. When placed on the barrier, H. coagulata generally climbed up an average of 1.16 m before flying away from the structure. Of the total number of H. coagulata placed on the barrier, 6% flew over it. These results suggest that a screen barrier can be a part of a management strategy to reduce number of H. coagulata in high-value crops.