Robert Holdcraft

Relative Toxicity and Residual Activity of Insecticides Used in Blueberry Pest Management: Mortality of Natural Enemies

ABSTRACT A series of bioassays were conducted to determine the relative toxicities and residual activities of insecticides labeled for use in blueberry (Vaccinium corymbosum L.) on natural enemies, to identify products with low toxicity or short duration effects on biological control agents. In total, 14 insecticides were evaluated using treated petri dishes and four commercially available natural enemies (Aphidius colemani Viereck, Orius insidiosus [Say], Chrysoperla rufilabris [Burmeister], and Hippodamia convergens [Guérin-Menéville]). Dishes were aged under greenhouse conditions for 0, 3, 7, or 14 d before introducing insects to test residual activity. Acute effects (combined mortality and knockdown) varied by insecticide, residue age, and natural enemy species. Broad-spectrum insecticides caused high mortality to all biocontrol agents, whereas products approved for use in organic agriculture had little effect. The reduced-risk insecticide acetamiprid consistently caused significant acute effects, even after aging for 14 d. Methoxyfenozide, novaluron, and chlorantraniliprole, which also are classified as reduced-risk insecticides, had low toxicity, and along with the organic products could be compatible with biological control. This study provides information to guide blueberry growers in their selection of insecticides. Further research will be needed to determine whether adoption of a pest management program based on the use of more selective insecticides will result in higher levels of biological control in blueberry.

Sucrose Improves Insecticide Activity Against Drosophila suzukii (Diptera: Drosophilidae)

ABSTRACT The addition of sucrose to insecticides targeting spotted wing drosophila, Drosophila suzukii (Matsumura), enhanced lethality in laboratory, semifield, and field tests. In the laboratory, 0.1% sucrose added to a spray solution enhanced spotted wing drosophila feeding. Flies died 120 min earlier when exposed to spinosad residues at label rates enhanced with sucrose. Added sucrose reduced the LC50 for dried acetamiprid residues from 82 to 41 ppm in the spray solution. Laboratory bioassays of spotted wing drosophila mortality followed exposure to grape and blueberry foliage and/or fruit sprayed and aged in the field. On grape foliage, the addition of 2.4 g/liter of sugar with insecticide sprays resulted in an 11 and 6% increase of spotted wing drosophila mortality at 1 and 2 d exposures to residues, respectively, averaged over seven insecticides with three concentrations. In a separate experiment, spinetoram and cyantraniliprole reduced by 95–100% the larval infestation of blueberries, relative to the untreated control, 7 d after application at labeled rates when applied with 1.2 g/liter sucrose in a spray mixture, irrespective of rainfall; without sucrose infestation was reduced by 46–91%. Adding sugar to the organically acceptable spinosyn, Entrust, reduced larval infestation of strawberries by >50% relative to without sugar for five of the six sample dates during a season-long field trial. In a small-plot field test with blueberries, weekly applications in alternating sprays of sucrose plus reduced-risk insecticides, spinetoram or acetamiprid, reduced larval infestation relative to the untreated control by 76%; alternating bifenthrin and phosmet (without sucrose) reduced infestation by 65%.

Disruption of Sexual Communication of Oriental Beetles (Coleoptera: Scarabaeidae) in Highbush Blueberries with Retrievable Pheromone Sources

Abstract The feasibility of disrupting sexual communication in oriental beetle, Anomala orientalis (Waterhouse), was evaluated by placing 50–75 ChemTica dispensers/ha (50–75 g active ingredient/ha) that released (Z)-7-tetradecen-2-one, the major sex pheromone component of oriental beetle, or red rubber septa deployed at the same density, but loaded with only 5–7.5 g active ingredient/ha, in 2002 and 2003. In both years, pheromone trap captures in plots treated with dispensers and rubber septa were significantly lower compared with pheromone trap captures in untreated control plots. Significantly fewer grubs were found in 2002 in blueberry plants placed in the two disrupter treatments compared with untreated control plots. In 2003, fewer females recovered from disrupter plots were found mated compared with females placed in untreated control plot. These studies indicate that sexual communication in the oriental beetle can be disrupted by deploying retrievable dispensers releasing high rates of pheromone at lower densities than previously thought.

Female Moth Calling and Flight Behavior Are Altered Hours Following Pheromone Autodetection: Possible Implications for Practical Management with Mating Disruption

Female moths are known to detect their own sex pheromone—a phenomenon called “autodetection”. Autodetection has various effects on female moth behavior, including altering natural circadian rhythm of calling behavior, inducing flight, and in some cases causing aggregations of conspecifics. A proposed hypothesis for the possible evolutionary benefits of autodetection is its possible role as a spacing mechanism to reduce female-female competition. Here, we explore autodetection in two species of tortricids (Grapholita molesta (Busck) and Choristoneura rosaceana (Harris)). We find that females of both species not only “autodetect,” but that learning (change in behavior following experience) occurs, which affects behavior for at least 24 hours after pheromone pre-exposure. Specifically, female calling in both species is advanced at least 24 hours, but not 5 days, following pheromone pre-exposure. Also, the propensity of female moths to initiate flight and the duration of flights, as quantified by a laboratory flight mill, were advanced in pre-exposed females as compared with controls. Pheromone pre-exposure did not affect the proportion of mated moths when they were confined with males in small enclosures over 24 hours in laboratory assays. We discuss the possible implications of these results with respect to management of these known pest species with the use of pheromone-based mating disruption.

Behavioral and Electrophysiological Responses of Listronotus maculicollis (Coleoptera: Curculionidae) to Volatiles from Intact and Mechanically Damaged Annual Bluegrass

ABSTRACT Listronotus maculicollis Kirby is a highly destructive pest of low mown, cool-season turfgrasses in the northeastern United States and Canada. Behavioral and electrophysiological assays were conducted to identify compounds that may be useful in developing novel monitoring techniques. In Y-tube assays, males and females responded differently to volatiles from intact and clipped annual bluegrass (Poa annua L.). Females were significantly attracted to intact P. annua but repelled from clippings; males did not respond significantly to either treatment. Electroantennogram (EAG) recordings from both sexes showed a significant response to volatiles from both treatments. Gas chromatography mass spectrometry (GC-MS) identified 12 volatile compounds from P. annua of which nine were common to both intact plants and clippings. On average, seven-fold higher quantities of volatiles were collected from clippings than from intact plants (24.3 versus 3.4 ng/g of tissue/h). Eight compounds were released in significantly greater quantities from clippings of which 50% were the n-C6 compounds hexanal, (E)-2-hexenal, and (Z)-3-hexenyl acetate, commonly referred to as “green leaf volatiles” (GLVs). Only octanal was emitted in greater amounts from intact plants than clippings. These nine compounds were tested individually against male and female antennae. Both sexes displayed greatest sensitivity to nonanal, octanal, and (E)-2-hexenal, but a significant doseresponse relationship was observed with all compounds tested. These studies indicate that both sexes respond physiologically and that L. maculicollis females exhibit behavioral responses to host-plant volatiles. Future studies will need to assess the effects of individual compounds and component mixtures on L. maculicollis behavior in the field.

Pheromone Autodetection: Evidence and Implications.

Olfactory communication research with insects utilizing sex pheromones has focused on the effects of pheromones on signal receivers. Early pheromone detection studies using the silkworm moth, Bombyx mori L., and Saturniids led to the assumption that emitters, especially females, are unable to detect their own pheromone. Pheromone anosmia, i.e., the inability of females to detect their conspecific sex pheromone, was often assumed, and initially little attention was paid to female behaviors that may result from autodetection, i.e., the ability of females to detect their sex pheromone. Detection of conspecific pheromone plumes from nearby females may provide information to improve chances of mating success and progeny survival. Since the first documented example in 1972, numerous occurrences of autodetection have been observed and verified in field and laboratory studies. We summarize here a significant portion of research relating to autodetection. Electrophysiological and behavioral investigations, as well as expression patterns of proteins involved in pheromone autodetection are included. We discuss problems inherent in defining a boundary between sex and aggregation pheromones considering the occurrence of autodetection, and summarize hypothesized selection pressures favoring autodetection. Importance of including autodetection studies in future work is emphasized by complications arising from a lack of knowledge combined with expanding the use of pheromones in agriculture.

SPLAT-OrB reveals competitive attraction as a mechanism of mating disruption in oriental beetle (Coleoptera: Scarabaeidae).

ABSTRACT This study compared the efficacy of SPLAT-OrB, a new pheromone formulation for oriental beetle mating disruption that can be mechanically applied, with hand-applied plastic dispensers in commercial blueberry fields. Both formulations were tested at 2.5 and 5 g of the major sex pheromone component (Z)-7-tetradecen-2-one per hectare, and evaluated by measuring trap shutdown, mating success of caged females, and the number of grubs in sentinel blueberry pots baited with tethered females. All pheromone-treated plots had fewer male captures in traps and lower mating success of caged females compared with untreated plots. SPLAT-OrB, and plastic dispensers at the higher rate, also reduced the number of grubs in sentinel pots. To understand the mechanism of mating disruption in oriental beetle, males were observed approaching the pheromone sources in disrupted plots. In addition, male oriental beetle captures were quantified in plots treated with varying SPLAT-OrB dollop densities per ha. Consistent with predictions for competitive attraction, field observations revealed males approaching the pheromone source and male captures decreasing concavely with increasing dollop density. In a mark-release-recapture study, male oriental beetles responded to SPLAT-OrB dollops and plastic dispensers at least 60 m from the source. Additionally, SPLAT-OrB emitted pheromone that was attractive to male oriental beetles for >5 wk; however, emission rates and attraction dropped rapidly during the first 3–4 wk. This study demonstrates the feasibility of using SPLAT-OrB for oriental beetle mating disruption as an alternative to hand-applied plastic dispensers, and conclusively reveals that a principal mechanism is the competitive attraction of males.

Sex Pheromone of the Scarab Beetle Phyllophaga (Phytalus) georgiana (Horn)

The sex pheromone of Phyllophaga (Phytalus) georgiana was characterized as valine methyl ester, tentatively the l-enantiomer. This is the first sex pheromone identified from the Phyllophaga subgenus Phytalus. The pheromone was extracted from female glands, the active component isolated by coupled gas chromatography–electroantennogram detection analysis, characterized by mass spectrometry, and shown to be active in field tests. The seasonal flight pattern was determined for P. georgiana as well as for three other species, P. anxia (both northern and southern genitalic forms), P. gracilis, and P. postrema. The latter three species were captured in traps baited with l-isoleucine methyl ester.

Entomopathogenic nematodes for control of Phyllophaga georgiana (Coleoptera: Scarabaeidae) in cranberries

Abstract A series of laboratory and greenhouse experiments evaluated the entomopathogenic nematodes Steinernema scarabaei Stock & Koppenhöfer, Heterorhabditis bacteriophora Poinar, and H. zealandica Poinar for control of second- and third-instar cranberry white grub, Phyllophaga georgiana Horn (Coleoptera: Scarabaeidae), in cranberries. Steinernema scarabaei was the most effective species with 76–100% control at a rate of 2.5×109 IJ/ha in the greenhouse experiments. H. zealandica and especially H. bacteriophora were generally less effective and required rates of 5×109 IJ/ha for acceptable control. Larval stage had no effect on H. zealandica and H. bacteriophora performance, whereas S. scarabaei was more effective against third instars than second instars in the laboratory but not in the greenhouse experiments. Steinernema scarabaei, should it become commercially available, could be an effective alternative to chemical insecticides for P. georgiana management.

Toxicity of Insecticides on Various Life Stages of Two Tortricid Pests of Cranberries and on a Non-Target Predator

Laboratory and extended laboratory bioassays were conducted to determine the residual toxicities of various insecticides against two key pests of cranberries, Sparganothis sulfureana and Choristoneura parallela (Lepidoptera: Tortricidae), and their non-target effects on the predatory Orius insidiosus (Hemiptera: Anthocoridae). The effects of nine insecticides with different modes of action on S. sulfureana and Ch. parallela eggs, larvae, and adults were tested in the laboratory, while the efficacy of a post-bloom application on larval mortality and mass of these pests and on adult O. insidiosus was evaluated in extended laboratory experiments. The organophosphate chlorpyrifos and the spinosyn spinetoram provided long-lasting (seven-day) control against all stages of both pests. The growth regulator methoxyfenozide and the diamides chlorantraniliprole and cyantraniliprole had strong (1–7 days) larvicidal, particularly on young larvae, and growth inhibitory activity, but only the diamides were adulticidal. Among neonicotinoids, acetamiprid had stronger ovicidal and adulticidal activity than thiamethoxam, showing within-insecticide class differences in toxicities; however, both were weak on larvae. Lethality of novaluron and indoxacarb was inconsistent, varying depending on species and stage. Chlorpyrifos was most toxic to O. insidiosus. These results show species- and stage-specific toxicities, and greater compatibility with biological control, of the newer reduced-risk classes of insecticides than older chemistries.