Insect feeding on cucumber mediated by rhizobacteria-induced plant resistance

Select strains of plant growth-promoting rhizobacteria (PGPR) were evaluated in greenhouse experiments with cucumber for induction of resistance against cucumber beetle (Diabrotica undecimpunctata howardi Barber) feeding and the beetle-transmitted cucurbit wilt disease. When beetles were given a choice between PGPR-treated and nontreated cucumber, their feeding on stems and cotyledons and the severity of wilt symptoms were significantly lower on PGPR-treated plants. HPLC analysis demonstrated that cotyledons from PGPR-treated plants contained significantly lower concentrations of the cucumber beetle feeding stimulant cucurbitacin than nontreated plants. These results suggest that a mechanism for PGPR-induced resistance against cucumber beetle feeding may involve a change in the metabolic pathway for cucurbitacin synthesis.     

Effect of a phloxine B-cucurbitacin bait on diabroticite beetles (Coleoptera: Chrysomelidae)

Cucurbitacin E glycoside, extracted from a bitter mutant of Hawkesbury watermelon [Citrulls lanatus (Thunb.) Matsum. & Nakai (Syn. Citrullus vulgaris Schrad)] is the active ingredient of a feeding stimulant for the corn rootworm complex. It is the primary component of a water-soluble bait that can be combined with toxins for adult diabroticite control. Studies were conducted using phloxine B (D&C Red 28), a xanthene dye, as the toxin. This dye was efficacious against Diabrotica undecimpunctata howardi Barber, spotted cucumber beetle, and Acalymma vittatum (F.), striped cucumber beetle, in cucumber plots and could be recovered from cucumber leaves for 8 d after treatment. The average amount of dye recovered per dead spotted cucumber beetle at 8 d after treatment was 0.173 microg. Concentrated and sugar-free fermented forms of the watermelon extract were developed and compared with the fresh juice in field applications on cucumber plants. There was no significant difference in mortality of beetles from phloxine B-bait prepared with fresh, fermented, or concentrated extract, although in laboratory studies, fermented juice had higher feeding stimulant activity.     

Effects of spinosad, spinosad bait, and chloronicotinyl insecticides on mortality and control of adult and larval western cherry fruit fly (Diptera: Tephritidae)

Effects of spinosad, spinosad bait, and the chloronicotinyl insecticides imidacloprid and thiacloprid on mortality of the adults and larvae of western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), were determined in the laboratory and the field. Spinosad and spinosad bait caused higher adult mortality than imidacloprid, which caused higher mortality than thiacloprid. Only spinosad bait prevented oviposition. All materials were more toxic to adults when ingested than when topically applied. Spinosad bait had the greatest residual toxicity on leaves, killing 100% of adults when aged for 14 d in the field. When materials were sprayed on infested cherries, numbers of live larvae in fruit after 8 d were lower in imidacloprid and thiacloprid than in spinosad and spinosad bait treatments, which did not differ from the control, but all materials reduced larval emergence over 30 d. In the field, spinosad and spinosad bait were as effective in suppressing larval infestations as azinphos-methyl and carbaryl, whereas imidacloprid was effective in most cases and thiacloprid was generally less effective than azinphos-methyl and carbaryl. Overall, results in the laboratory and field show that spinosad and chloronicotinyl insecticides differed significantly in their effectiveness against adults and larvae of R. indifferens but that spinosad, spinosad bait, and imidacloprid seem to be acceptable substitutes for organophosphate and carbamate insecticides for controlling this fruit fly.     

The effects of wilt symptom development and peroxidase induction on interactions between vascular wilt bacteria and cucumber beetles

Infection of cucumber (Cucumis sativus L.) with the bacterial pathogen Erwinia tracheiphila E. F. Smith causes vascular wilt disease in leaves, which may alter the suitability of the host plant for insects and other pathogens. In this study, densities of spotted (Diabrotica undecimpunctata howardi Barber) and striped (Acalymma vittata (Fab.) cucumber beetles (Coleoptera: Chrysomelidae) were higher on wilted leaves of mature and seedling field plants inoculated with E. tracheiphila. Bacterial infection or feeding by D. undecimpunctata howardii beetles increased total peroxidase enzyme activity in inoculated or infested leaves of greenhouse seedlings, but only beetle feeding induced higher activities in untreated systemic leaves on the same plants. Neither bacterial infection nor beetle infestation led to the development of systemic acquired resistance (SAR) to the fungal pathogen Colletotrichum orbiculare (Berk & Mont.) Arx. Susceptibility to this fungus was greater on E. tracheiphila-infected plants than on controls. The positive association between leaf wilt symptom development and beetle occurrence thus occurs in the presence of an oxidative but not anti-pathogenic response induced by both the insect and the pathogen.     

Field and vegetable crops as hosts of larval western spotted cucumber beetle (Coleoptera: Chrysomelidae)

The western spotted cucumber beetle, Diabrotica undecimpunctata undecimpunctata Mannerheim, is an important pest of melons (Cucurmis melo L.) in northern California. Recent observations indicate that adults are using alfalfa (Medicago sativa L.) as a feeding host and larvae may be developing on the roots. Greenhouse studies were conducted during the winters of 2009 and 2010 in which larval development was compared on the roots of six field and vegetable crops commonly grown in the southern Sacramento Valley. The growth parameters used to evaluate the hosts were larval and pupal head capsule width, body width, and body length as well as total survival percentage and survival percentage to the third instar. According to larval growth and survivorship in 2009, maize (Zea mays L.) was the best host, followed by alfalfa and tomato (Solanum lycopersicum L.) that were roughly equivalent to one another. Melon was a slightly weaker host than alfalfa and tomato; sunflower (Helianthus annuus L.) was a completely incompatible host and thus dropped from the 2010 study. In 2010, melon was the weakest host for larval development. Maize was the superior host again followed closely by alfalfa that performed slightly better than tomato and lima bean (Phaseolus lunatus L.). Data suggest that larval western spotted cucumber beetles may primarily develop outside of melon fields and the adults emigrate to melons.     

Consumptive and non‐consumptive effects of wolf spiders on cucumber beetles and cucumber plant damage

Biological control research often focuses on the ability of predators to reduce pest densities and protect crops through consumption. Less studied is their ability to protect crops by altering pest behaviour (non‐consumptive effects). Lab experiments were conducted to test predation rates of striped cucumber beetles (Acalymma vittatum; Coleoptera: Chrysomelidae) and spotted cucumber beetles (Diabrotica undecimpunctata howardi; Coleoptera: Chrysomelidae) by large (>10 mm) wolf spiders (Araneae: Lycosidae). Field experiments were conducted to examine how the physical presence and/or cues of spiders impact the behaviour and mortality of A. vittatum (specialist) and D. undecimpunctata (generalist) cucumber beetles as well as growth and damage of cucumber plants (Cucumis sativus; Cucurbitaceae). A. vittatum and D. undecimpunctata adults were added to caged cucumber plants without a spider, with spider cues only (spider removed before beetle inclusion), with spider only (spider introduced to plants immediately before beetle inclusion), and with spiders and their cues present (spiders introduced 24 hr in advance of beetle inclusion). A. vittatum responded to spider cues primarily by emigrating from plants. Contrarily, D. undecimpunctata did not display obvious responses, such as reduced feeding or increased emigration, to spider foraging and/or cues. Actively foraging lycosids increased A. vittatum mortality and reduced densities of D. undecimpunctata in the field when cucumber plants were flowering. This study highlights how non‐consumptive and consumptive effects can play a role in modifying pest populations, and how these effects can vary across species and plant growth stages.     

Correspondence between rates of host plant consumption and responses to the Acalymma vittatum male-produced aggregation pheromone

Abstract In field studies, wind-directed traps were used to investigate the resource-based properties of the male-produced aggregation pheromone of Acalymma vittatum (F.) (Coleoptera: Chrysomelidae). Responses to early season overwintered field-collected male A. vittatum without food were compared with those feeding on pollen, and in turn these were compared with those feeding on cucurbit seedlings. These comparisons were modelled after transitions as they would occur at the initiation of A. vittatum host plant colonization.
In another experiment, colony-reared male A. vittatum that had been fed only near isogenic lines of potted cucumber ( Cucumis sativus ) seedlings that either lacked or contained cucurbitacin were placed as bait in the traps. Using the inverse relationship, which is understood for A. vittatum , between previous exposure and the phagostimulant response to cucurbitacin, rates of foliage consumption could be manipulated. The interaction between relative rates of host plant consumption of the males used as lures and responses to the pheromone could thus be tested. The use of A. vittatum reared entirely without dietary cucurbitacin as bait also enabled evaluation of the potential role of cucurbitacin in pheromone biosynthesis. Trap responses were closely correlated with the rates of feeding of the beetles in the trap lures, but cucurbitacin was neither a precursor nor a prerequisite for the pheromone. Implications for early season field colonization and the adaptive significance of this pheromone are discussed.     

Consumption of residue containing cucurbitacin feeding stimulant and reduced rates of carbaryl insecticide by western corn rootworm (Coleoptera: Chrysomelidae).

Application of insecticide at a reduced rate with a cucurbitacin-based feeding stimulant is a viable alternative to a broadcast insecticide application for control of adult western corn rootworms, Diabrotica virgifera virgifera, LeConte. Because of the small amount of material applied, it is conceivable that a high density of beetles could consume all of the spray residue before economic control is achieved. A laboratory experiment was conducted to determine the amount of cucurbitacin-based spray residue consumed by beetles. Dried residue of four treatments were exposed to three groups of 10 rootworm beetles for 1 h each. Treatments consisted of a cucurbitacin-based adjuvant (Cidetrak CRW, Trécé, Salinas, CA) with carbaryl insecticide (Sevin XLR Plus, Rhone Poulenc, Research Triangle Park, NC) mixed at 0, 0.12, 1.2, and 12 g (AI)/liter. For the treatment with cucurbitacin adjuvant only (no insecticide), beetles consumed 0.029 mg beetle(-1) h(-1) of exposure. Approximately 54% of the beetles were recorded as feeding at any given time during the 60-min feeding period. However, when the spray residue contained carbaryl, no weight loss of treatment residue was measured, though the beetles were observed to feed from the residue during the first few minutes of exposure. When residue included insecticide, beetles quickly ceased feeding (within 20 min), and toxicity behavior was observed 30 min after initial exposure for up to 75% of the beetles, which were classified as moribund (unable to stand upright). Beetle mortality was recorded 24 h after exposure and demonstrated that male beetles (53% dead for three insecticide treatments) were more susceptible to carbaryl toxicity than female beetles (28% dead for three insecticide treatments). Regression analysis showed a significant positive relationship between mortality of female beetles and ovarian development. Based on the measurements of this experiment, it is unlikely that realistic beetle densities would consume enough spray residue to prevent economic control of the beetle population.     

Effects of pesticide applications and cultural controls on efficacy of control for adult Japanese beetles (Coleoptera: Scarabaeidae) on roses

Cultural and chemical controls were evaluated to determine their ability to deter feeding by Japanese beetles, Popillia japonica Newman (Coleoptera: Scarabaeidae), on floribunda type roses, Rosa 'Acadia Sunrise'. Roses were arranged in field plots and exposed to resident adult beetle populations. Cultural controls were designed to block the feeding-induced aggregation response by manually removing beetles and/ or damaged blooms from rose plants. Azadirachtin, carbaryl, and imidacloprid were evaluated in field and laboratory trials. In no-choice laboratory assays, foliar applications of azadirachtin caused low rates of morbidity to adult beetles and were unable to deter feeding. Foliar-applied carbaryl and soil-applied imidacloprid caused high rates of morbidity and reduced feeding injury. In the field, foliar sprays of azadirachtin and carbaryl, deterred feeding on foliage under low beetle pressure (maximum of 29% defoliation in untreated controls), when applied weekly after first beetle flight or every 2 wk after 5% injury was reached. A single foliar application of these materials at the 5% injury level did not significantly reduce peak defoliation. Soil applications of imidacloprid also deterred foliar feeding in the field. Blooms were more difficult to protect with both foliar- and soil-applied insecticides with only weekly application of foliar insecticides providing significant reductions in bloom injury. Removing beetles and/or blooms provided marginally greater reductions in leaf and flower injury. This suggests that blocking the feeding-induced aggregation response of Japanese beetles can provide only modest levels of control in roses where both flowers and feeding-induced volatiles recruit beetles to plants.     

An alternative sampling technique for cucumber beetles (Coleoptera: Chrysomelidae) and diurnal beetle activity on muskmelon

Field studies were conducted to investigate the effectiveness of yellow sticky traps as an alternative sampling technique for striped, Acalymma vittatum (F.), and spotted, Diabrotica undecimpunctata howardi Barber, cucumber beetles (Coleoptera: Chrysomelidae) and the diurnal beetle activity on muskmelon, Cucumis melo L., near Vincennes, IN, in 2003 and 2004. The experimental design included six replications of seven 20-m-long rows each of muskmelon with 1.5 m between rows. On each sampling date, two yellow sticky traps were placed randomly between rows in each replication. One sticky trap was placed vertically with the lower edge even with the top of the canopy, whereas the other trap was placed horizontally, even with the top of the canopy. After traps were placed in the field, number of beetles on plants was counted in situ from 0800 to 1600 hours at 2-h intervals the next day. After 48 h in the field, the number of cucumber beetles adhering on traps was counted. Analyses of variance and Tukey's multiple comparison procedure were used to compare the densities of beetles among sampling times, and regression analyses were applied to correlate the numbers of beetles on traps and the numbers of in situ counts. Results show that both species of cucumber beetles were most active from 1200 to 1400 hours, and 20 beetles on the vertically positioned sticky trap were equivalent to one beetle per plant in the field. The application of the sampling technique and scouting time for cucumber beetle management are discussed.     

Alternative management tactics for control of Phyllotreta cruciferae and Phyllotreta striolata (Coleoptera: Chrysomelidae) on Brassica rapa in Massachusetts

The flea beetles Phyllotreta cruciferae (Goeze) and Phyllotreta striolata (F.) (Coleoptera: Chrysomelidae: Alticinae) are significant pests of crops in the Brassicaceae family. From 2001 to 2003, the efficacy of both new and commonly used treatments for the control of flea beetles in brassicas, Brassica rapa L., were evaluated in three small plot, randomized complete block design trials. Row cover and carbaryl (applied as a weekly foliar spray) were found to be the most consistent at reducing damage in comparison with untreated controls in all trials. Two new products that may provide adequate flea beetle control are spinosad (in either conventional or organic formulations) and thiamethoxam. The plant-derived compounds azidiractin and pyrethrin did not protect treated plants from flea beetle feeding. Treatment of plants with kaolin, or removal of the beetles with a vacuum, also did not reduce the level of crop damage. The level of damage at harvest was found to be correlated with population size of flea beetles in each plot, as measured by captures on yellow sticky traps and direct visual counts. Removal of the outer two leaves of individual B. rapa plants reduced the total number of holes per plant by 40%, while only removing 15% of the leaf area.     

Monitoring cucumber beetles in sweetpotato and cucurbits with kairomone-baited traps

Seven kairomone formulations (Trécé, Inc., Salinas, CA) were evaluated for their effectiveness as attractants for luring three species of cucumber beetles into Pherocon CRW traps (Trécé, Inc.) in cucurbit and sweetpotato fields. The spotted cucumber beetle, Diabrotica undecimpunctata howardi Barber; the banded cucumber beetle, Diabrotica balteata LeConte; and the striped cucumber beetle, Acalymma vittatum (F.), were captured in this study. TRE8276 (TIC mixture: 500 mg of 1,2,4-trimethoxybenzene, 500 mg of indole, and 500 mg of trans-cinnamaldeyde) and TRE8336 (500 mg of 1,2,4-trimethoxybenzene, 500 mg of trans-cinnamaldeyde, 500 mg of 4-methoxyphenethanol) were the most effective lures for spotted and striped cucumber beetles. None of the kairomone lures was very effective for attracting banded cucumber beetles. Three population peaks of spotted cucumber beetles were observed in cucurbit and sweetpotato fields at the U.S. Vegetable Laboratory (Charleston, SC). The efficacy of TRE8276 declined rapidly after 2 wk in the field. An improved design of the Pherocon CRW trap, with a yellow bottom and more-tapered top section, was more effective for capturing cucumber beetles than the original trap design made entirely of clear plastic. Banded cucumber beetles were not captured in sweetpotato fields at inland locations in North Carolina or South Carolina.     

Nontarget arthropod abundance in areawide-managed corn habitats treated with semiochemical-based bait insecticide for corn rootworm (Coleoptera: Chrysomelidae) control

Impacts of semiochemical-based insecticidal bait applications on beneficial arthropod groups common to field corn, Zea mays L., habitats were assessed in areawide-managed field sites in South Dakota and Iowa during 1997 and 1998. Slam, a commercial bait formulation comprised of 87% cucurbitacin and 13% carbaryl insecticide, was used for management of adult rootworm, Diabrotica spp., and controls consisted of cornfield habitats without bait applications. Effects on beneficial organisms were variable, and negative impacts were infrequent. Coccinellidae, Staphylinidae, and Anthocoridae were usually more abundant in bait-treated plots than in controls that received at-plant soil insecticides, especially by 4 wk postapplication. Carabid beetle activity also had increased in bait-treated corn by proportionally greater rates than in control plots at 4 wk postapplication in two of the four site by year combinations in this study. Impacts of semiochemical-based adulticide applications on Formicidae were not consistently negative or positive. The relative lack of consistent negative impacts on nontarget arthropods suggests that other biotic and abiotic factors leading to natural population fluxes may have more influence on these groups of beneficial organisms than applications of semiochemical-based bait containing carbaryl. Overall, it seems that areawide applications of these baits for managing rootworm populations in corn are not likely to impose deleterious effects on the nontarget faunal groups we surveyed, especially in comparison with the at-plant applications of soil insecticides used as experimental controls in this study.     

Resistance of sweetpotato genotypes to adult Diabrotica beetles

Production of sweetpotatoes, Ipomoea batatas (L.) Lam. (Convolvulaceae), is limited by several insect pests, including Diabrotica spp. (Coleoptera: Chrysomelidae), and new integrated pest management (IPM) techniques for this crop are needed. Host plant resistance is one attractive approach that fits well into IPM programs. A host plant resistance research program typically depends on reliable bioassay procedures to streamline evaluation of germplasm. Thus, a bioassay technique was developed for evaluating sweetpotato germplasm by using adults of the banded cucumber beetle, Diabrotica balteata LeConte, and spotted cucumber beetle, Diabrotica undecimpunctata howardi Barber. A single beetle was placed on a piece of sweetpotato peel (periderm and cortex with stele removed) that was embedded periderm-side up in plaster in a petri dish. Feeding and longevity of insects on 30 sweetpotato genotypes were evaluated in two experiments by using this procedure. Adult longevity ranged from 7 to 11 d for starved individuals to 211 d for beetles fed a dry artificial diet. Longevity of banded cucumber beetles that fed on sweetpotato peels ranged from 12 d for the most-resistant genotype to 123 d for SC1149-19, a susceptible control cultivar. Longevity of spotted cucumber beetles was slightly shorter than longevity of banded cucumber beetles. For the most resistant sweetpotato genotypes, both Diabrotica species exhibited a significant delay in initiation of feeding, and more beetles died on these genotypes before they had fed. Both antibiosis and nonpreference (antixenosis) are important mechanisms of resistance in sweetpotato genotypes. This bioassay was consistent with field results, indicating that this technique could be useful for evaluating resistance to Diabrotica spp. in sweetpotato genotypes.     

Male traits under cryptic female choice in the spotted cucumber beetle (Coleoptera: Chrysomelidae)

Males of the spotted cucumber beetle (Diabrotica undecimpunctata howardi) rhythmically stroke females with their antennae during copulation. Males that stroke quickly have a higher probabilityof being accepted as a mate. We determined (1) the mechanismby which females prevent unattractive males from passing spermatophores,(2) whether antennal stroking signals to females the likelihoodof receiving a nuptial gift, and (3) if other male traits inaddition to stroking are subjected to sexual selection fromfemale preference. Dissections of pairs flash-frozen in copuladuring and after antennal stroking showed musculature that,when contracted, folded the vaginal duct leading to the female'sbursa copulatrix in a way that prevented complete penetrationby the aedeagus. These muscles were always contracted whilemales were stroking and always relaxed after stroking had ceased.Males accepted as mates did not differ from males that failedto pass a spermatophore in either absolute or relative bodyweight, aedeagus length, or the amount of cucurbitacins (potentialnuptial gifts) sequestered in their spermatophores. Although99% of the beetles that came to cucurbitacin-rich Cucurbitafruits in the field were males, males that had sequestered cucurbitacins did not stroke females faster than males withno cucurbitacins, and fast-stroking males were not more likelyto find and sequester cucurbitacins than were males that strokedmore slowly. Males with a cucurbitacin slurry painted on theirantennae had no mating advantage over controls. We concludethat females discriminate among males after copulation hasbegun on the basis of antennal stroking displays (or some traitcorrelated with stroking speed) that males perform to enticefemales to relax their bursal sphincter.     

Feeding and foraging of wild and sterile Mediterranean fruit flies (Diptera: Tephritidae) in the presence of spinosad bait

The sterile insect technique (SIT) is used to control wild Mediterranean fruit fly introductions in California and Florida in the U.S. In the past, bait sprays containing malathion proved invaluable in treating new outbreaks or large populations before the use of SIT. Recently, a spinosad protein bait spray, GF-120, has been developed as a possible alternative to malathion, the standard insecticide in protein bait sprays. In this study, protein-deficient and protein-fed Vienna-7 (sterile, mass-reared, "male-only" strain) flies and wild males and females were evaluated to determine the effectiveness of the GF-120 protein bait containing spinosad with respect to bait attraction, feeding, and toxicology. There were no effects of diet or fly type on feeding duration in small laboratory cages. Wild flies, however, registered more feeding events than Vienna-7 males. Flies that fed longer on fresh bait died faster. Protein-deficient flies were more active and found the bait more often than protein-fed flies. Data suggest that adding protein to the diet of SIT flies may decrease their response to baits, therefore, reduce mortality, and thus, allow the concurrent use of SIT and bait sprays in a management or eradication program.     

Predator interference limits fly egg biological control by a guild of ground-active beetles

We examined whether predator interference could prevent effective conservation biological control of Delia spp. flies, important pests of cole crops, by an assemblage of carabid and staphylinid beetles. In laboratory feeding trials we found that the smaller (<1 cm) beetle species common at our site readily ate dipteran eggs, while the most common large carabid species, Pterostichus melanarius, rarely did. However, P. melanarius did eat several of the smaller beetle species. We conducted two field experiments where we manipulated immigration rates of the ground predator guild and then measured predation on fly eggs. Predation rates were consistently higher in cages where predators were added at ambient densities, compared to cages where ground predators were removed. However, in the second field experiment, when we quadrupled predator immigration rates neither beetle activity-density nor predation rate increased. High immigration rate plots had a higher proportion of P. melanarius in the predator community, compared to plots with beetles added at ambient densities, suggesting that P. melanarius was reducing activity-densities of the smaller beetles, perhaps through intraguild predation. Thus, tactics to improve the biological control of Delia spp. by conserving generalist predators, such as providing in- or extra-field refuges, could be thwarted if the primary predators of fly eggs, small carabids and staphylinids, are the targets of intraguild predation by also-conserved larger predators.     

Dispersal of Steinernema glaseri (Nematoda: Steinernematidae) in adult Japanese beetles, Popillia japonica (Coleoptera: Scarabaeidae)

Japanese beetle adults, Popillia japonica, can become infected with and disperse the entomopathogenic nematode, Steinernema glaseri, under laboratory and field conditions. After a 24-h exposure to 10 000 infective juveniles/20 adult beetles, 45% of the beetles died within 4 days post-treatment, but only 59% of these were infected with the nematode. Corresponding control mortality was 6.5%. An average of 238 infective juveniles were produced/beetle. Beetles exposed to 4000 and 10 000 infectives/10 adults carried with them an average of 17 and 59 infectives/adult on external body surfaces respectively. When beetles that had been exposed to 4000 infectives/20 adults were transferred to, and held in, cages containing soil for 2 weeks, up to 89% of the adults died, as did 74% of the P. japonica larvae that were subsequently placed in the cages. When adults that had been exposed to 50 000 infectives/250 beetles in moist sand for 16 h were released into screened cages in the field at soil temperatures of over 25 C, the soil beneath 83% of the cages tested positive for the nematode, using Galleria mellonella larvae as bait, 2 weeks after releasing the beetles. No nematodes were detected in control plots. The potential of infected adult P. japonica for dispersing S. glaseri by flight was investigated by exposing adults to 50 000 infectives/250 beetles, marking and releasing them in the field and recapturing them in lure-baited Japanese beetle traps. Less than 1% of the treated beetles were recaptured, but 33% of these had one or more nematodes in their hemocoels. Accordingly, this approach does not appear to be feasible for large-scale augmentation and dispersal of the nematode using currently developed methods of infection. If improvements in mass-inoculation methods can be made that enable a rapid high percentage of infection while still permitting flight, this concept could be employed to establish new foci of infection or for the introduction of other species of nematodes.     

Behavioral responses of Rhagoletis cingulata (Diptera: Tephritidae) to GF-120 insecticidal bait enhanced with ammonium acetate

GF-120 is a baited formulation of the insecticide spinosad containing 1% ammonium acetate, developed for control of economically important fruit flies. The response of feral cherry fruit flies, Rhagoletis cingulata Loew, to GF-120 augmented with 0, 5, or 10% ammonium acetate was evaluated under orchard conditions. Significantly more flies were observed within 30 cm of bait droplets with 10% ammonium acetate added compared with standard bait or to a water control. These fly visits to GF-120 enhanced with 10 or 5% ammonium acetate lasted an average of 263.2 +/- 85.2 and 337.6 +/- 72.6 s, respectively, compared with 50.3 +/- 36.4 s for standard GF-120. Droplets containing additional ammonium acetate also were contacted by more flies, and more flies fed upon these droplets than on GF-120 or the water control. Furthermore, the duration of feeding on GF-120 bait enhanced with either level of additional ammonium acetate was significantly greater compared with standard GF-120 or water. Feeding events lasted between 61.5 +/- 30.7 and 73.4 +/- 21.0 s on enhanced GF-120 compared with 6.8 +/- 5.7 s on standard GF-120. Collectively, these results indicate that the interaction of feral R. cingulata with GF-120 droplets and the toxicant spinosad can be increased by addition of ammonium acetate.