Grandisoic Acid Research Articles

Methyl salicylate improves the effectiveness of the odor-baited trap tree approach for adult plum curculio, Conotrachelus nenuphar (Coleoptera: Curculionidae), monitoring and attract-and-kill.

In commercial apple orchards, the odor-baited trap tree approach involving the synergistic lure composed of benzaldehyde (BEN) and the PC aggregation pheromone grandisoic acid (GA) serves as an effective monitoring tool as well as an attract-and-kill strategy for plum curculio (PC), Conotrachelus nenuphar Herbst. (Coleoptera: Curculionidae), management. However, the relatively high cost of the lure and the degradation of commercial BEN lures by UV light and heat discourage its adoption by growers. Over a 3-yr period, we compared the attractiveness of methyl salicylate (MeSA), either alone or in combination with GA, to plum curculio (PC) with that of the standard combination of BEN + GA. Our main goal was to identify a potential replacement for BEN. Treatment performance was quantified using 2 approaches: (i) unbaited black pyramid traps (2020, 2021) to capture PC adults and (ii) PC oviposition injury (2021, 2022) on apple fruitlets of trap trees and of neighboring trees to assess potential spillover effects. Traps baited with MeSA captured significantly more PCs than unbaited traps. Trap trees baited with a single MeSA lure and 1 GA dispenser attracted a similar number of PCs as trap trees baited with the standard lure composed of 4 BEN lures and 1 GA dispenser based on PC injury. Trap trees baited with MeSA + GA received significantly more PC fruit injury than neighboring trees suggesting no or limited spill-over effects. Our collective findings suggest that MeSA is a replacement for BEN thereby cutting costs of lures by ca. 50% while maintaining trap tree effectiveness.

Profile of Terpenoid Compounds Mediating a Plant-Herbivore Interaction: Screening by Static Headspace Solid-Phase Microextraction-Gas Chromatography/Q-ToF Mass Spectrometry.

Conotrachelus dimidiatus (Coleoptera: Curculionidae) interacts with immature guava fruits (Psidium guajava L.) for feed, sleep, mate and oviposit. Determination of the volatile organic compounds (VOCs) emitted by the insect and immature fruits can help improve understanding of plant-insect and intraspecific insect interactions between females and males of C. dimidiatus. Daytime fruit setting emissions of immature guava consist mainly of limonene, caryophyllene, and aromadendrene. In addition to the host's volatiles, the aim of this study was to assess the VOCs released by the insect. Static headspace-solid phase microextraction (SHS-SPME), combined with gas chromatography/quadrupole time of flight mass spectrometry (GC/Q-ToF-MS), allowed the identification of the C10 terpenoids: grandlure I, II, II, IV, grandisoic acid, papayanol and papayanal bioactive compounds released by female and male C. dimidiatus under laboratory conditions. These chemical compounds are candidates for the preparation of a lure formulation.

Exploring an Odor-Baited "Trap Bush" Approach to Aggregate Plum Curculio (Coleoptera: Curculionidae) Injury in Blueberries.

This 2-year study (2013–2014) assessed the efficacy of an odor-baited “trap bush” approach to aggregate plum curculio, Conotrachelus nenuphar, adult injury, i.e., number of oviposition-scared fruit, in four commercial highbush blueberry farms in New Jersey (USA). In each farm, we compared fruit injury in bushes baited with grandisoic acid and benzaldehyde along the perimeter of trap-bush plots versus unbaited bushes in control plots. We also measured the amount of fruit injury in neighboring bushes (i.e., spillover effect) and in the plots’ interior. In both years, the amount of fruit injury by C. nenuphar adults was greater on and near odor-baited bushes in trap-bush plots compared with those on and near unbaited bushes in control plots, indicative of aggregation. Injury in unbaited bushes neighboring trap bushes was often greater than unbaited bushes in control plots, providing some evidence for a spillover effect. However, no difference in fruit injury was found between interior trap-bush and control plots. Therefore, odor-baited trap bushes can be used in blueberries to manipulate C. nenuphar foraging behavior, i.e., aggregate adults, without compromising injury in field interiors. Under this approach, insecticides could then be targeted at only a few (perimeter-row) bushes within fields rather than entire fields.

Olfactometer Responses of Plum Curculio Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae) to Host Plant Volatiles, Synthetic Grandisoic Acid, and Live Conspecifics

The plum curculio Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae) is a major pest of pome and stone fruit, but will also attack other fruits. Males produce the aggregation pheromone grandisoic acid; emitting only the (+)-enantiomer which is attractive to both sexes of the univoltine and multivoltine strains, while the synthetic racemic mixture contains optical isomers with equal amounts of (+)- and (−)-enantiomers. Synergy between odours can increase trap captures and improve monitoring techniques, therefore tests were performed in a dual-choice olfactometer with odours attractive to plum curculios according to literature to determine 1) under what physiological conditions (mating status, age, starvation period) these odours are attractive or repulsive, 2) if the (+)-enantiomer or the odour of live males synergizes with host plant volatiles, and 3) if there is a difference in response between plum curculio strains. Females were exposed to: benzaldehyde; trans-2-hexenal; apples; extracts of: plums, apples, blueberries; grandisoic acid; and live males. Plum essence was found to be the most attractive host-plant odour for both immature and mature virgin females, and immature whole apples were attractive to starved females, while trans-2-hexenal, McIntosh apple essence, benzaldehyde along with the combination of benzaldehyde and plume essence was found to be repulsive. Starvation, age, and mated status all influence response to odours. No synergistic or additive affects were observed between any of the odour combinations tested, including the combination of both the natural and synthetic pheromone and plum essence or apples.

Tempo-Spatial Dynamics of Adult Plum Curculio (Coleoptera: Curculionidae) Based on Semiochemical-Baited Trap Captures in Blueberries.

Plum curculio, Conotrachelus nenuphar (Herbst), has become an important pest of highbush blueberries in the northeastern United States. Here, we conducted experiments in 2010-2013 to compare the efficacy of semiochemical-baited traps for C. nenuphar versus conventional (beating cloth) sampling methods in blueberries, and to understand the seasonal abundance and distribution of C. nenuphar adults within and among blueberry fields using these traps. Black pyramid traps baited with the C. nenuphar aggregation pheromone grandisoic acid and the fruit volatile benzaldehyde caught three to four times more adults than unbaited traps without causing an increase in injury to berries in neighboring bushes. Numbers of adult weevils caught in traps correlated with those on bushes (beating cloth samples), indicating that trap counts can predict C. nenuphar abundance in the field. Early in the season, traps placed 20 m from field edges near a forest caught higher C. nenuphar numbers than traps placed at farther distances, suggesting movement of overwintered weevils from outside fields. Using a trapping network across multiple fields in an organic farm, we found evidence of C. nenuphar aggregation in "hotspots"; early in the season, C. nenuphar numbers in traps were higher in the middle of fields, and there was a correlation between these numbers and distance from the forest in 2013 but not in 2012. These results show that semiochemical-baited traps are effective in capturing C. nenuphar adults in blueberries, and that these traps should be placed in the interior of fields preferably, but not exclusively, near wooded habitats to maximize their efficacy.

(1R,6R)-2,2,6-Trimethyl-3-oxabicyclo[4.2.0]octan-4-one, a new monoterpene lactone produced by males of the cocoa borer Conotrachelus humeropictus (Col.: Curculionidae)

The cocoa weevil Conotrachelus humeropictus is an economically most important pest on cocoa (Theobroma cacao) and cupuaçu (Theobroma grandiflorum) cultures. Knowledge on the pheromone system of this insect is prerequisite for the development of an integrated pest management system. GC/MS-analysis of headspace volatiles revealed the presence of three male specific compounds, which were identified to be (1R,2S)-grandisol, (1R,2S)-grandisoic acid, and the new bicyclic terpene lactone (1R,6R)-2,2,6-trimethyl-3-oxabicyclo[4.2.0]octan-4-one, which we term grandisolide.

Behavioral Response of Plum Curculio,Conotrachelus nenuphar, to Synthetic Fruit Volatile Lures and the Male-Produced Aggregation Pheromone

Plum curculio,Conotrachelus nenupharHerbst (Coleoptera: Curculionidae), is a key pest of stone and pome fruits in North America. The behavioral response of adults of different physiological states (sex, age, diet, and mating status) to three commercially available synthetic lures, benzaldehyde (BZ) and plum essence (PE), the male-produced aggregation pheromone, grandisoic acid (GA), or their combinations, was studied in the laboratory. Four choice olfactometer bioassays demonstrated significant attraction of both sexes to PE lure. Both BZ and GA lures were not attractive to plum curculio when tested as commercially formulated. PE had higher release rate (1.51 mg/hr) than BZ (0.36 mg/hr) and GA (ca. 0.04 mg/hr), suggesting that the higher attractiveness of PE may be due to its relatively higher release rates. Tests with combined lures showed a neutral effect of combining GA with PE and an inhibitory effect of combining BZ with PE. The physiological conditions of the weevils had no significant effect on their response to the lures. Olfactometer tests with pure 1,2,4-trichlorobenzene (TCB) confirmed that this compound was inhibitory to plum curculio. These results are discussed in relation to the contrasting field reports which implicated BZ + GA as an effective attractant for plum curculio.

Evaluating Electrophysiological and Behavioral Responses to Volatiles for Improvement of Odor-Baited Trap Tree Management ofConotrachelus nenuphar(Coleoptera: Curculionidae)

Plum curculio, Conotrachelus nenuphar (Herbst), one of the most important pests of apple in eastern and central North America, is usually managed in New England apple orchards by multiple full-block insecticide applications. Efforts to reduce insecticide inputs against plum curculio include using an "attract and kill" approach: odor-baited trap trees deployed in the perimeter row of apple orchards. The standard approach is based on baiting apple trees with two olfactory stimuli, the fruit volatile benzaldehyde and the aggregation pheromone of plum curculio, grandisoic acid. We attempted to improve attraction, aggregation, and retention of adult plum curculios within specific baited trap tree canopies within apple orchards using an additional host plant volatile found to be highly stimulating in electroantennogram studies, trans-2-hexenal. We also attempted to increase aggregation using increased release rates of grandisoic acid. We found that trans-2-hexenal did not provide increased aggregation when deployed as an additional attractant within trap trees or when conversely deployed as a "push" component or repellent in perimeter trees lateral to the baited trap tree. Although increasing the release rate of grandisoic acid 5× actually appeared to increase overall aggregation within trap trees, it was not significantly different than that obtained using the standard dose. Therefore, we believe that the standard olfactory stimuli are sufficient to provide aggregation within trap trees, but that other means should be used to manage them after their arrival.

Establishing abiotic and biotic factors necessary for reliable male pheromone production and attraction to pheromones by female plum curculiosConotrachelus nenuphar(Coleoptera: Curculionidae)

AbstractThe plum curculio (PC),Conotrachelus nenupharHerbst (Coleoptera: Curculionidae), is a key pest of stone and pome fruit in North America. Though grandisoic acid (GA) was identified as a male-produced aggregation pheromone for this species, other components likely exist, as have been identified for various curculionids. To better determine these components, an understanding of the conditions necessary for optimum pheromone production and attraction is needed, this is essential for the improvement of monitoring techniques and to achieve better biological control. The goal of this study was to determine the biotic and abiotic factors influencing both the response to pheromones and pheromone production. Tests were conducted in a dual-choice still-air vertical olfactometer using live male PCs as odour sources and live females as responders, to determine which physiological factors (age, number of males, mating status) influenced female response to males. Head-space collections of GA production under various conditions (airflow rate and frequency, collection zone strata, variation of humidity, temperature, and presence of a harbourage) were also done, as were electroantennograms (EAG) using synthetic pheromone mixtures. Results revealed that for both strains, the odour of two virgin mature males elicited significantly greater and more consistent attraction from mature virgin females than other ages and numbers of males when compared with the control. Head-space collections indicate that male PC have increased production of GA under high humidity in the presence of fruit, indicating that these conditions are necessary for optimal pheromone production and collection. EAG studies revealed significant responses to GrandLures I, II, III/IV and to the positive enantiomer of GA, and the amplitude of the signal varied with concentration. Our data identify the optimal physiological state and conditions at which pheromone collections should be performed, and what physiological life stages respond to these stimuli. These results have implications for optimising monitoring tools for this serious crop pest. This species has a northern univoltine strain and a southern multivoltine strain, both of which were examined in this study.

ORGANIC FRUIT PRODUCTION NEEDS AND PEST MANAGEMENT PRACTICES IN THE SOUTHEASTERN UNITED STATES

In 2001, only 14% of the certified organic acreage in the United States occurred in the 12 southeastern (SE) states. Eight of the 12 Land Grant Universities in the SE region had a total of 329 acres certified organic for use in research and extension. In 2004, client-based focus groups identified needs for organic fruit production in the SE: go-to personnel to increase interaction between the University and organic producers; more science-based research on soil, pest and nutrient management; information to be summarized in printed guides on organic production budgets and organic production practices; and local market development. Recently, we demonstrated that several science-based, ecologically low-risk conventional practices could be adapted for organic fruit production. Demonstration blocks in Arkansas showed that first and late season generations of codling moth (CM) and Oriental fruit moth (OFM) could be controlled with CM granulosis virus and Spinosad against CM and Spinosad and Bt against OFM when integrated with mating disruption against the mid-season generations of CM and OFM. The result was less than 1% fruit damage at harvest. Plum curculio adults disperse into the perimeter of fruit orchards in the spring. When plum curculio adults were attracted to perimeter apple trees baited with dispensers releasing volatiles of grandisoic acid (aggregation pheromone) and one or two kairomone compounds, benzaldehyde and plum essence, they caused significantly more fruit feeding damage in baited trees than adjacent unbaited trees. There is potential for using Japanese plum trees or bait trees in apples to focus plum curculio damage. A further advantage occurs with the application of a nematode soil drench to reduce plum curculio larva survival in soil under baited trees. Green June beetle adults feed on ripening fruit. Multiple yellow funnel traps baited with a lure of five-component volatile blend = TRE#8607 or 91% isopropanol were very attractive to green June beetles and may have potential for use in mass trapping this pest.

Field Evaluation of Traps and Lures for Monitoring Plum Curculio (Coleoptera: Curculionidae) in Alabama Peaches

The plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), is a key pest of peaches, Prunus persica (L.) Batsch, in North America. We evaluated the effectiveness of two widely used trap types (pyramid versus Circle traps) and commercially available synthetic lures for monitoring the pest in two peach orchards in Alabama during 2008 and 2009. The lures evaluated alone or in combinations included benzaldehyde (BZ) (a component of fruit odor), plum essence (PE) (a mixture of fruit odor extracted from food grade plum), and grandisoic acid (GA) (a male-produced aggregation pheromone of plum curculio). In general, pyramid traps captured more plum curculio adults than Circle traps, particularly during the first generation. Trap performance was improved numerically by the addition of BZ, PE, or GA alone (single lures) and was significantly enhanced by the addition of the combined BZ + PE lure. In both first and second generations, the combined BZ + PE lure increased plum curculio captures (significant in some trials) over unbaited traps and traps baited with single lures by approximately 1.5-21-fold and had the highest response indices (RIs), which is indicative of high attractiveness. The combined BZ + GA lure and the three-component BZ + PE + GA lure also captured numerically more plum curculio adults than unbaited traps or traps baited with single lures but the differences were rarely significant. Analysis of ratios of interaction suggests the possibility of synergistic interactions between BZ and PE and between BZ and GA; however, additive effects were concluded due to high sample errors. These results are discussed in relation to the physicochemical properties of the lures and the potential of using baited monitoring traps to aid plum curculio management decisions in peach orchards.

DETECTION STRATEGIES FOR ADULTS OF THE GUAVA WEEVIL CONOTRACHELUS SPP.

The guava weevil (Conotrachelus dimidiatus) is one of the most important pests of the guava crop and can cause severe fruit losses if it is not controlled. In general, guava producers use from three to ten pesticide treatments, starting with the beginning of the raining season and regardless whether the guava weevil is present or not. Currently, only the limb jarring method is used to detect the presence of guava weevil adults. However, this method, although very effective, is laborious and unpractical. The objective of the present study was to search for alternative strategies to monitor guava weevil adults. Different kinds of traps were evaluated, including traps with and without grandisoic acid (aggregation pheromone of C. nenuphar males); mesh traps placed around the guava trunk, and the limb jarring method. To obtain possible alarm pheromones, guava weevil adults were collected for extraction by different water: alcohol mixtures. The solutions were concentrated by dynamic aeration and the compounds analyzed in a gas chromatograph. The potential of the volatile products to attract guava weevil males and females was evaluated using Tedders traps. The results showed that both traps captured adults; however, the optimum number of traps still needs to be evaluated. The use of grandisoic acid did not increase captures, whereas the limb jarring method had more and constant captures. Alarm volatile graphs of concentration 20:80 showed three initial peaks and others that appear later at 10.83 to 13.26 min, which are more defined. Volatile differences between healthy and damaged fruits were present among the fastest eluting compounds (2.225, 2.54 and 2.09 min.). Under dynamic aeration two pronounced peaks were observed (7.06 and 9.34 min.) and in-between these two peaks could be some possible sexual pheromones. Finally, traps with male adults captured more guava weevil than those with females. Thus, guava weevil males responded better, a phenomenon which has also been reported for C. nenuphar.

Electroantennogram Technique forConotrachelus nenuphar(Coleoptera: Curculionidae)

Reliable electroantennogram (EAG) responses were obtained from the plum curculio, Conotrachelus nenuphar (Herbst), by using a whole body mount with glass electrodes filled with KCl-saturated AgCl solution that penetrated the antennal club (recording electrode) and the membrane attached to the cervical sclerite between the thorax and the head (indifferent electrode). Known attractive odor sources including extracts of headspace collections of 'Stanley' plum and 'Empire' apple tissues and a synthetic source of racemic grandisoic acid were used to verify the sensitivity of the technique. The amplitude of responses was significantly greater for females than males among all candidate stimuli evaluated. The recorded amplitudes for all odor stimuli evaluated were significantly greater than the methylene chloride solvent control. The development of this EAG technique will facilitate use of a coupled gas chromatographic-electroantennographic detection system to aid in detection of novel, biologically and behaviorally active volatile sources that can be subsequently evaluated in behavioral trials and ultimately lead to more powerful attractants for use in monitoring and management programs for plum curculios in commercial fruit orchards.

Impact of Temperature on Plum Curculio (Coleoptera: Curculionidae) Responses to Odor-Baited Traps

In 2005, captures of overwintered adult plum curculios, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), in standard black masonite pyramid traps deployed in apple (Malus spp.) orchards from half-inch green until fruit reached 7 mm and baited with known attractants did not result in significant captures compared with unbaited traps as they had in 2003 and 2004. These baits included the synthetic aggregation pheromone, grandisoic acid (GA) alone, a six-component synthetic host plant volatile combination (6-Tree) identified from foliar and woody tissues of a Stanley plum tree in combination with GA (6-Tree+GA), and the synthetic fruit volatile benzaldehyde (BEN) in combination with GA (BEN+GA). In 2005, the average daily temperature was below 13 degrees C, much cooler than in 2003 and 2004. We hypothesized that plum curculio could not discriminate between baited and unbaited traps because of reduced release rates of odor-bait stimuli due to their temperature-driven release system. From data collected from 2003 to 2005, we found that plum curculio captures in traps baited with GA alone, 6-Tree+GA, and BEN+GA were significantly related to temperature. We created a predictive model to determine the level of activity, i.e., trap captures in baited traps compared with unbaited traps, we would expect to observe at a particular temperature for these same odor stimuli. Our models predicts that at temperatures between approximately 11 to 13 degrees C we would expect to see no difference between captures in baited and unbaited traps. For captures in odor-baited traps to reach twice those in unbaited traps, our model predicts that temperatures must reach 19.2 degrees C for GA alone, 18.5 degrees C for 6-Tree+GA, and 15.8 degrees C for BEN+GA.

Impact of Temperature on Plum Curculio (Coleoptera: Curculionidae) Responses to Odor-Baited Traps

In 2005, captures of overwintered adult plum curculios, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), in standard black masonite pyramid traps deployed in apple (Malus spp.) orchards from half-inch green until fruit reached 7 mm and baited with known attractants did not result in significant captures compared with unbaited traps as they had in 2003 and 2004. These baits included the synthetic aggregation pheromone, grandisoic acid (GA) alone, a six-component synthetic host plant volatile combination (6-Tree) identified from foliar and woody tissues of a Stanley plum tree in combination with GA (6-Tree+GA), and the synthetic fruit volatile benzaldehyde (BEN) in combination with GA (BEN+GA). In 2005, the average daily temperature was below 13°C, much cooler than in 2003 and 2004. We hypothesized that plum curculio could not discriminate between baited and unbaited traps because of reduced release rates of odor-bait stimuli due to their temperature-driven release system. From data collected from 2003 to 2005, we found that plum curculio captures in traps baited with GA alone, 6-Tree+GA, and BEN+GA were significantly related to temperature. We created a predictive model to determine the level of activity, i.e., trap captures in baited traps compared with unbaited traps, we would expect to observe at a particular temperature for these same odor stimuli. Our models predicts that at temperatures between ≈ 11 to 13°C we would expect to see no difference between captures in baited and unbaited traps. For captures in odor-baited traps to reach twice those in unbaited traps, our model predicts that temperatures must reach 19.2°C for GA alone, 18.5°C for 6-Tree+GA, and 15.8°C for BEN+GA.

Nonfruiting Host Tree Volatile Blends: Novel Attractants for the Plum Curculio (Coleoptera: Curculionidae)

Abstract We evaluated the attractiveness of novel synthetic host plant volatiles alone and in combination with the synthetic aggregation pheromone, grandisoic acid (GA), to overwintered adult plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae) in association with black masonite pyramid traps deployed in an unsprayed apple orchard in 2003 and 2004. Synthetic host plant volatiles evaluated included (1) those identified from foliar and woody tissues of a nonfruiting Stanley plum tree (6-Tree) or the two major components (2-Tree); (2) those identified from Stanley plum fruit (7-Plum) or two components eliciting positive GC-EAD response from plum curculios (2-Plum); and (3) benzaldehyde formulated into rubber septa and replaced weekly [Ben(s)] or dispensed into polyethylene vials and replaced weekly [Ben(r)], not replaced [Ben(nr)], and formulated with 10% 1,2,4-trichlorobenzene and not replaced [Ben(TCB)]. In 2003, the greatest numbers of plum curculios were captured in traps baited wit...

Using Odor-Baited Trap Trees as Sentinels to Monitor Plum Curculio (Coleoptera: Curculionidae) in Apple Orchards

In commercial orchards in Massachusetts in 2003, we conducted experiments aimed at developing guidelines for use of perimeter-row trap trees baited with grandisoic acid plus benzaldehyde as sentinels in a practical approach to determining need and timing of insecticide applications against overwintered plum curculios, Conotrachelus nenuphar (Herbst). Evaluations were based on percentages of sampled fruit injured by plum curculio. Trap trees baited with grandisoic acid released at ≈1 mg/d plus benzaldehyde released at ≈40 mg/d performed as well as or better than trap trees baited with greater or lesser amounts of these attractants in combination. The distance over which a trap tree baited with such odor was effective in aggregating damage to fruit extended to at least 31–33 m (maximum evaluated) along a perimeter row. Trap trees at corners of orchard blocks were as effective as perimeter-row trap trees midway between corner trees. Within the canopy of a trap tree, damage did not tend significantly to be localized in the vicinity of the odor source but tended to be rather evenly distributed among various sectors of the canopy. Finally, among three candidate thresholds evaluated as a trigger for insecticide application, a threshold of one freshly injured fruit proved better than thresholds of two or four freshly injured fruit out of 50 fruit sampled on a trap tree in assuring that orchard-wide damage would remain below a preset economic injury level of 1%. Our findings lead us to suggest that after a whole-orchard application of insecticide to apple trees in Massachusetts orchards shortly after petal fall, subsequent applications of insecticide against plum curculio can be confined to peripheral-row trees and be driven by a provisional threshold of one freshly injured fruit out of 50 fruit sampled on a perimeter-row trap tree baited with the above-mentioned odor.

3 using odor-baited trap trees as sentinels to monitor plum curculio (Coleoptera: Curculionidae) in apple orchards.

In commercial orchards in Massachusetts in 2003, we conducted experiments aimed at developing guidelines for use of perimeter-row trap trees baited with grandisoic acid plus benzaldehyde as sentinels in a practical approach to determining need and timing of insecticide applications against overwintered plum curculios, Conotrachelus nenuphar (Herbst). Evaluations were based on percentages of sampled fruit injured by plum curculio. Trap trees baited with grandisoic acid released at approximately 1 mg/d plus benzaldehyde released at approximately 40 mg/d performed as well as or better than trap trees baited with greater or lesser amounts of these attractants in combination. The distance over which a trap tree baited with such odor was effective in aggregating damage to fruit extended to at least 31-33 m (maximum evaluated) along a perimeter row. Trap trees at corners of orchard blocks were as effective as perimeter-row trap trees midway between corner trees. Within the canopy of a trap tree, damage did not tend significantly to be localized in the vicinity of the odor source but tended to be rather evenly distributed among various sectors of the canopy. Finally, among three candidate thresholds evaluated as a trigger for insecticide application, a threshold of one freshly injured fruit proved better than thresholds of two or four freshly injured fruit out of 50 fruit sampled on a trap tree in assuring that orchard-wide damage would remain below a preset economic injury level of 1%. Our findings lead us to suggest that after a whole-orchard application of insecticide to apple trees in Massachusetts orchards shortly after petal fall, subsequent applications of insecticide against plum curculio can be confined to peripheral-row trees and be driven by a provisional threshold of one freshly injured fruit out of 50 fruit sampled on a perimeter-row trap tree baited with the above-mentioned odor.

Monitoring Plum Curculio, Conotrachelus nenuphar (Coleoptera: Curculionidae), Populations in Apple and Peach Orchards in the Mid-Atlantic

We evaluated responses of plum curculio, Conotrachelus nenuphar (Herbst), to four trap types in commercial and unsprayed apple and peach orchards. Trap types included black pyramid and clear Plexiglas panel traps deployed outside the orchard 2 m from the border row, and branch-mimicking cylinder and trunk-mounted screen traps attached to trees in the border row. Bait treatments evaluated in conjunction with each trap type included the synthetic fruit volatile benzaldehyde, the aggregation pheromone grandisoic acid (GA), benzaldehyde in combination with GA, and an unbaited control treatment. In commercial apple orchards, significantly more plum curculio were captured in traps baited with benzaldehyde + GA compared with traps baited with other treatments. Furthermore, significantly more plum curculio were captured by screen traps baited with benzaldehyde + GA compared with unbaited control traps. Significantly more plum curculio were captured by screen traps compared with other trap types in an unsprayed apple orchard. Very few captures were recorded in commercial peach orchards. Dissections of trapped females indicate that bivoltine populations are present in the mid-Atlantic. In general, correlations between timing and amount of trap captures and timing and amount of fruit injury inflicted concurrently or 1 wk after trap captures were very weak for all trap types and bait combinations. Our results agree with previous studies in the northeastern United States in which trap captures are increased by presence of semiochemical baits but fail to serve as reliable tools to determine need for and timing of insecticide application against plum curculio.

Field evaluation of plant odor and pheromonal combinations for attracting plum curculios.

The attractiveness of different synthetic host odors and a synthetic aggregation pheromone (grandisoic acid [GA]) to overwintered adult plum curculios (PCs), Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), was examined using two types of traps (sticky panels and black pyramids) placed in border areas surrounding an unsprayed section of an apple orchard in Massachusetts. In 2001, we evaluated the response of PCs to three synthetic fruit volatiles (benzaldehyde [BEN], ethyl isovalerate [EIV], and limonene [LIM]) assessed alone and in combination with GA, as well as the response to GA alone and a no-odor (control) treatment. BEN was the only host volatile that synergized the response of PCs to GA for both trap types. For both trap types, GA was as attractive to PCs as a single component as when in combination with either EIV or LIM. In 2002, four release rates of BEN (0, 2.5, 10, and 40 mg/day) and two release rates of GA (1 and 2 mg/day) were evaluated for attractiveness to PCs using panel and pyramid traps. For panel traps, an increase in amount of GA released (from 1 to 2 mg/day) was associated with a 35% increase in captures. However, PC captures by pyramid traps were similar regardless of the amount of GA released. For panel traps, 10 and 40 mg/day of BEN were the most attractive release rates regardless of the amount of GA released. For pyramid traps baited with GA. PC captures were enhanced by the presence of BEN, regardless of release rate. In 2003, GA at 1 mg/day + BEN at 80 mg/day of release did not enhance PC captures by panel traps relative to lower release rates of BEN. Pyramid traps releasing GA at 1 mg/day performed best when baited with BEN at 10 mg/day of release; a release rate of 80 mg/day of BEN decreased the attractiveness of the binary combination of BEN + GA. Combined results suggest that BEN at 10 mg/day + GA at 1 mg/day of release constitutes an attractive lure that may improve the effectiveness of monitoring traps for PCs.