Peachtree Borer Research Articles

Evaluation of alternative insecticides for peachtree borer management in Georgia peaches, 2022–2023

Evaluation of alternative insecticides for peachtree borer management in Georgia peaches, 2022–2023

Using the Nematode, Steinernema carpocapsae, to Control Peachtree Borer (Synanthedon exitiosa): Optimization of Application Rates and Secondary Benefits in Control of Root-Feeding Weevils

The peachtree borer, Synanthedon exitiosa (Say) (Lepidoptera: Sesiidae), is a major pest of stone fruits including the peach Prunus persica (L.) Batsch. The entomopathogenic nematode, Steinernema carpocapsae, was previously shown to be an effective tool for controlling S. exitiosa. In orchards where irrigation is not available, a sprayable gel (Barricade®) can be used to maintain soil moisture which can facilitate nematode efficacy. However, rates of nematode and Barricade® application had not been optimized for their maximum economic and biocontrol efficiency. Therefore, our objective was to compare rates of S. carpocapsae and Barricade® in field trials. Nematodes were tested at per-tree application rates of 1.5 million, 1 million and 0.5 million infective juveniles. The sprayable gel was used at two rates, 4% and 2%. A reduction in the used nematodes from 1.5 million to 0.5 million per tree showed no difference in efficacy. Similarly, using the gel at half rate also did not impact the efficacy, and treatments containing nematodes controlled the S. exitiosa better than the chlorpyrifos control in several of the tests (p < 0.05). As an added benefit, the nematode treatments were also able to reduce the prevalence of weevil (Coleoptera: Curculionidae) populations as secondary pests of the peach trees. The lower rates of grower inputs will reduce costs, making the nematode biocontrol of the peachtree borer more likely to be adopted by commercial growers of peach.

Comparison of Mating Disruption and Insecticide Application for Control of Peachtree Borer and Lesser Peachtree Borer (Lepidoptera: Sesiidae) in Peach.

Simple SummaryThe peachtree borer and lesser peachtree borer are destructive insect pests of peach and other stone fruit. Damage is caused by larval feeding on the vascular cambium, which reduces tree health and vigor and can lead to tree death. The traditional method to control these pests is with directed trunk sprays of the organophosphate insecticide, chlorpyrifos. However, the ongoing review of pesticide tolerances mandated by the United States Environmental Protection Agency (US-EPA) makes the option of future long-term use of chlorpyrifos uncertain. Mating disruption is an alternative method of control that uses synthetic sex pheromones to disrupt male mate-finding behavior and prevent mating. We conducted field studies to compare the efficacy of mating disruption and application of chlorpyrifos insecticide for control of this pest complex. Although our data indicated that mating disruption can provide growers with an effective non-chemical alternative to chlorpyrifos trunk sprays, several variables may affect its long-term success in West Virginia peach orchards; most notably the presence of high population densities of the pest species, problems with maintaining adequate pheromone coverage in orchards, and the need for area-wide implementation.The peachtree borer, Synanthedon exitiosa, and lesser peachtree borer, S. pictipes, are economically important indirect pests of peach in West Virginia. The purpose of this 3-year study was to compare the efficacy of mating disruption and post-harvest trunk sprays of chlorpyrifos insecticide for control of this pest complex in a commercial peach orchard. Overall, Isomate PTB-Dual disruption dispensers applied at a rate of 371/ha significantly disrupted the male mate-finding behavior of S. exitiosa and S. pictipes. In addition, the infestation of peach trees by S. exitiosa larvae did not vary significantly between mating disruption and insecticide treated plots. Hot-spot maps of S. exitiosa infestation showed significant spatial clusters of infestation predominately near the perimeter of all orchard plots, or where trees were missing within and/or between rows. The generation of standard deviational ellipses revelated that the location of S. exitiosa infestations in orchard plots remained relatively constant between years, and were generally oriented in a north and easterly direction, which coincided with the prevailing wind direction. Although our data indicated that mating disruption can provide growers with an effective non-chemical alternative to chlorpyrifos trunk sprays, several variables may affect its long-term success in West Virginia peach orchards; most notably the presence of high population densities, problems with maintaining adequate pheromone coverage, and the need for area-wide implementation.

A survey of molecular diversity and population genetic structure in North American clearwing moths (Lepidoptera: Sesiidae) using cytochrome c oxidase I.

The phylogeographic structure of insect species in North America is poorly understood. The moth family Sesiidae (Lepidoptera) contains many economically important pests of agriculture and forestry, as well as beneficial species used in biological control. Despite their significance, this study constitutes the first broad-ranging population genetic study on North American sesiids. It probes the population structure of eight species of sesiid moths based on sequence variation in cytochrome c oxidase I (N = 191). Haplotype diversity levels were high in seven of the eight species, while nucleotide diversity varied considerably. Patterns ranged from limited structure and a starburst pattern in the raspberry crown borer Pennisetia marginata to highly geographically structured populations in the peachtree borer Synanthedon exitiosa and the maple callus borer Synanthedon acerni. These varied patterns suggest differing evolutionary histories and dispersal abilities. By elucidating population genetic structure and barriers to dispersal we can begin to devise conservation and management plans.

Efficacy of pheromonal control of peachtree borer (Synanthedon exitiosa (Say)) in small‐scale orchards

AbstractThe efficacy of pheromone‐based mating disruption for control of the peachtree borer Synanthedon exitiosa (Say) in small‐scale peach orchards (<0.1 ha) was evaluated in a total of six blocks at two locations in New Mexico, USA, from 2010 to 2015. In treated orchards, commercial pheromone dispensers were deployed at rates of approximately 500 or 600 per ha. Pheromone‐based monitoring traps were installed in each block (treated and untreated), and catches of male moths were recorded throughout each growing season to assess the effectiveness of pheromone treatments and to determine the pest's seasonal flight activity. Levels of larval trunk infestation were assessed twice yearly by inspecting all trees at and below soil level. Infestation levels in an unreplicated block of mature peaches at one site (Los Lunas) declined from 57.5% to 8.4% while under pheromone treatment (2010–2011). Pheromone treatments in this block were discontinued in 2012, and infestation levels subsequently increased to 16.9% by spring 2015. In a replicated study in four other peach blocks at the same site, annual application of pheromones from 2012 to 2014 resulted in a significant difference in larval infestations in treated blocks compared to untreated blocks. In addition, when a single block of infested peaches at a second site (Alcalde) was treated with pheromone dispensers for three consecutive years, trunk infestation levels declined significantly, but were not completely eliminated. These results indicate that mating disruption can help protect even very small orchards from damage by S. exitiosa. However, the technique is likely to be more effective where such orchards are relatively isolated and/or where the surrounding pest pressure is moderate or low.

Curative Control of the Peachtree Borer Using Entomopathogenic Nematodes.

The peachtree borer, Synanthedon exitiosa (Say 1823), is a major pest of stone fruit trees in North America. Current management relies upon preventative control using broad-spectrum chemical insecticides, primarily chlorpyrifos, applied in the late summer or early fall. However, due to missed applications, poor application timing, or other factors, high levels of S. exitiosa infestation may still occur and persist through the following spring. Curative treatments applied in the spring to established infestations would limit damage to the tree and prevent the next generation of S. exitiosa from emerging within the orchard. However, such curative measures for control of S. exitiosa do not exist. Our objective was to measure the efficacy of the entomopathogenic nematode, Steinernema carpocapsae, as a curative control for existing infestations of S. exitiosa. In peach orchards, spring applications of S. carpocapsae (obtained from a commercial source) were made to infested trees and compared with chlorpyrifos and a water-only control in 2014 and 2015. Additionally, types of spray equipment were compared: nematodes were applied via boom sprayer, handgun, or trunk sprayer. To control for effects of application method or nematode source, in vivo laboratory-grown S. carpocapsae, applied using a watering can, was also included. Treatment effects were assessed 39 d (2014) or 19 d (2015) later by measuring percentage of trees still infested, and also number of surviving S. exitiosa larvae per tree. Results indicated that S. carpocapsae provided significant curative control (e.g., >80% corrected control for the handgun application). In contrast, chlorpyrifos failed to reduce S. exitiosa infestations or number of surviving larvae. In most comparisons, no effect of nematode application method was detected; in one assessment, only the handgun and watering can methods reduced infestation. In conclusion, our study indicates that S. carpocapsae may be used as an effective curative measure for S. exitiosa infestations.

Efficacy of Steinernema carpocapsae plus fire gel applied as a single spray for control of the lesser peachtree borer, Synanthedon pictipes

The efficacy of aboveground applications of entomopathogenic nematodes (Heterorhabditis spp. and Steinernema spp.) can be severely limited by the nematode’s susceptibility to UV radiation and desiccation. The lesser peachtree borer, Synanthedon pictipes, is a major pest of stone fruit; larvae attack trees aboveground by tunneling into the trunk and scaffold limbs. In previous research, Steinernema carpocapsae, caused high levels of S. pictipes mortality when a sprayable fire gel (Barricade®) was applied on top of the nematode application as a protectant. One drawback to the approach is that two applications must be made (first nematodes are applied followed by the fire gel); furthermore, the previous experiments did not compare nematode application to the existing standard chemical insecticide. Therefore, the objectives of this study were to (1) determine if a diluted rate of fire gel can protect nematodes when applied as a single spray, and (2) compare the efficacy of nematode applications with the chemical insecticide, chlorpyrifos. The experiment was conducted in a peach orchard in Quincy, Florida in 2013 and 2014. Treatments included: (1) chlorpyrifos, (2) S. carpocapsae applied in aqueous suspension only or (3) with a full rate (approximately 4% applied separately) or (4) 2% Barricade® (applied with nematodes in a single spray), and (5) a non-treated control. The treatments were applied post-harvest (in the fall) to S. pictipes-infested bark wounds; S. pictipes survival was assessed 8 (2013) or 14 (2014) d post-application. In 2013, chlorpyrifos and nematodes with Barricade® at 2% or the full rate reduced S. pictipes survival relative to the non-treated control and nematodes without Barricade®. In 2014, nematodes applied with 2% Barricade® was the only treatment that reduced S. pictipes survival. We conclude that S. carpocapsae and Barricade® can be applied as a single spray, and in our experiments the treatment was at least as effective as the chemical standard.

Field suppression of the peachtree borer, Synanthedon exitiosa, using Steinernema carpocapsae: Effects of irrigation, a sprayable gel and application method

The peachtree borer, Synanthedon exitiosa, is a major pest of stone fruit trees in North America. In prior studies, the entomopathogenic nematode, Steinernemacarpocapsae, caused substantial reductions in S. exitiosa damage when applied by watering can to peach trees that were irrigated regularly. Here we report two additional studies that assessed S. carpocapsae efficacy in suppressing S. exitiosa damage in peach orchards; one study focused on irrigation requirements and the other on application method. In the first experiment we compared S. carpocapsae applied with and without irrigation, and application of a sprayable gel, Barricade®, as a potential replacement for irrigation. In the second experiment, we compared application methods that growers might use including a boom sprayer, handgun, trunk sprayer and watering can (used as a positive control). In both experiments chlorpyrifos was also included as a positive control, and in the application methods experiment an untreated (negative) control was also included. All treatments were applied in the fall of 2012 and 2013 and S. exitiosa infestation was assessed following the spring of 2013 and 2014, respectively. In the first experiment, nematodes applied without irrigation did not prevent high levels of infestation levels (75% of trees were infested) whereas nematodes applied with the sprayable gel suppressed damage at the same level as chlorpyrifos (<20% infestation). Thus, our results indicate that the sprayable gel applied to soil around the tree base can enhance entomopathogenic nematode efficacy, and the gel may be used as a substitute for irrigation when applying S. carpocapsae for S. exitiosa control; this finding may be applicable to similar pests in various cropping systems. This is the first report of direct application of the sprayable gel to soil (previous reports concerned aboveground applications). Also in the first experiment, intermediate levels of damage (31–38% infestation) were observed in plots that received nematodes with irrigation. We suspect that a higher rate of irrigation would have improved efficacy. In the second experiment, the boom sprayer, trunk sprayer and watering can methods of nematode application resulted in S. exitiosa infestations that were similar to the chemical insecticide standard treatment (chlorpyrifos) and below levels in the non-treated control, whereas the handgun treatment was not different from the untreated control or chemical standard.

Emergence of Root-feeding Weevils (Coleoptera: Curculionidae) in Central Georgia Peach Orchards

Injury to peach, Prunus persicae (L.) Batsch, roots is common by several plant pathogen species and by larvae of the peachtree borer, Synanthedon exitiosa Say (Lepidoptera: Sesiidae). External feeding injury to peach roots was observed that was not consistent with S. exitiosa injury but was suspected to be caused by the larvae of root-feeding weevil species (Coleoptera: Curculionidae). Thus, we used conical emergence traps for 3 yr to sample in unsprayed peach orchards (within the dripline of trees and at missing tree sites) to monitor for root-feeding weevils. Fuller rose beetle, Naupactus cervinus (Boheman), whitefringed beetles, Naupactus spp., and the twobanded Japanese weevil, Callirhopalus bifasciatus (Roelofs), (Coleoptera: Curculionidae) were captured at significantly higher numbers within the dripline of the tree than at missing tree sites. Adult N. cervinus emerged from soil year around; whereas, the other 2 species had seasonal emergence. In commercial peach orchards comprised of cultivars with early, mid, and late-season fruit ripening dates, N. cervinus was more abundant than other species. The later a cultivar ripens, the higher the number of insecticide applications it receives; however, we did not detect a difference in N. cervinus emergence between the cultivars. In another sprayed orchard, N. cervinus was again more common than other curculionid species captured. Damage ratings (0 - 5; none to heavy, respectively) on roots revealed a mean rating of 2.79 ± 0.12. Year-long emergence of N. cervinus is likely why it persisted in sprayed orchards. Modification of existing pest management programs will be needed to manage N. cervinus attacking peach roots.

Lesser Peachtree Borer (Lepidoptera: Sesiidae) Oviposition on Prunus Germplasm

The lesser peachtree borer, Synanthedon pictipes (Grote and Robinson) (Lepidoptera: Sesiidae), is a serious pest of peach, Prunus persica (L.) Batsch, across the southeastern United States. We examined oviposition by S. pictipes on field-grown Prunus scion and rootstock cultivars and two endemic Prunus spp. when sawn limbs, not roots, were assayed in the laboratory. A choice test compared oviposition on the peach scion 'Harvester', peach rootstock 'Guardian', plum×peach hybrid rootstock 'MP-29', and the plum hybrid rootstock 'Sharpe'. A significantly lower percentage of eggs occurred on limbs of Sharpe rootstock than other choices. A choice test using two endemic hosts, black cherry (P. serotina Ehrh.) and Chickasaw plum (P. angustifolia Marsh.), along with Sharpe rootstock, found a lower percentage of eggs on limbs of Sharpe than either endemic host. However, when only limbs of Sharpe and a decoy were used, almost all eggs were laid on Sharpe. Interestingly, when Harvester and Sharpe limbs were paired side by side, a higher percentage of eggs were recovered from the Harvester limb than from the Sharpe limb. An analysis of volatiles from Sharpe may identify why fewer eggs were laid on it. Because S. pictipes attacks host trees above ground and Sharpe rootstock on grafted trees grows below ground, this rootstock might be a management option against the congeneric, root-attacking peachtree borer, S. exitiosa (Say). Our results suggest that high budding a peach scion onto Sharpe rootstock, thus allowing the rootstock to serve as the trunk, warrants further investigation against S. exitiosa under orchard conditions.

Laboratory Virulence and Orchard Efficacy of Entomopathogenic Nematodes Against the Lesser Peachtree Borer (Lepidoptera: Sesiidae)

The lesser peachtree borer, Synanthedon pictipes (Grote & Robinson) (Lepidoptera: Sesiidae), is indigenous to eastern North America. It is a pest of commercially grown Prunus spp., especially to southeastern peach orchards where earlier regulatory changes affected pesticide use on peach leading to increased S. pictipes damage. Pest management practices are now having a positive effect toward control of this pest, but cost-competitive biological control solutions that promote environmental stewardship are needed. Here, we tested four Steinernema species and five Heterorhabditis species of entomopathogenic nematodes against larval S. pictipes. Included were four strains of S. carpocapsae (All, DD136, Sal, and Hybrid2) and three strains of S. riobrave (3-8b, 7-12, and 355). Larvae treated with any strain of S. carpocapsae always resulted in <20% survival, whereas larval survival was always >50% when treated with any other Steinernema or Heterorhabditis spp. These differences were always significant for the Hybrid2 strain of S. carpocapsae and similarly for other tested S. carpocapsae strains except for when larvae were treated with the 3-8b strain of S. riobrave. In addition, we determined the susceptibility of different size S. pictipes larvae, because they occur simultaneously in orchards, and we found that larvae rated as "medium" and "large" were significantly more susceptible than "small" larvae. Last, we demonstrated that moisture-retaining covers (placed over S. pictipes-infested wounds on peach limbs) increased efficacy of nematode treatments against larval S. pictipes. Even when using highly virulent nematodes against S. pictipes, it is likely that an aboveground application will require an environmental modification to remain efficacious.

Comparison of mating disruption and mass trapping with Pyralidae and Sesiidae moths

Mating disruption and mass trapping for control of lepidopteran pests use synthetic sex pheromone to prevent males from finding and mating with females. Here, we identify the behavioral mechanism underlying mating disruption and mass trapping of American plum borer, Euzophera semifuneralis (Walker) (Lepidoptera: Pyralidae), peachtree borer, Synanthedon exitiosa Say, and lesser peachtree borer, Synanthedon pictipes (Groeten) (Lepidoptera: Sesiidae). In addition, we derive relative dispenseractivity(RelativeDa)fromthecompetitiveattractionequationtocomparethedisruptiveactivity of the devices used in mating disruption and mass trapping. Dispensers and traps were deployed in replicated 0.14-ha cherry or peach plots with E. semifuneralis or the Synanthedon moths, respectively. Dispenser densities were 0, 10, 20, 59, 185, and 371 per ha, whereas trap densities were 0, 10, 20, 40, 79, and 158 per ha. Moth catch in a centrally placed, pheromone-baited monitoring trap in each plot was used to evaluate the treatments. The profile of moth captures in mating disruption and mass trapping with the three species indicates that competitive attraction is the behavioral mechanism responsible for trap disruption. Relative Da is 0.27, 0.23, and 0.53 with American plum borer, peachtree borer, and lesser peachtree borer, respectively, which indicates that the traps are 1.9‐4.4 times more effective in reducing moth catch than the dispensers. Relative Da can be used to compare devices for pheromone-based behavioral manipulation of these and other species that are competitivelyattractedtoartificialpheromone sources. Whenthesametypeoftrap is employed formonitoringandmasstrapping,RelativeDaisthesameasdispenseractivityDa.

Effect of Pheromone Dispenser Density on Timing and Duration of Approaches by Peachtree Borer

The timing and duration of approaches by male peachtree borer Synanthedon exitiosa Say (Lepidoptera: Sesiidae) to commercial pheromone dispensers placed singly or at high density in peach orchards was determined by using field-deployed video cameras and digital video recorders. Cameras were trained on one dispenser, and one standard lure was placed in a peach orchard, and on 12 dispensers in a separate orchard where dispensers for mating disruption had been placed at 371 per hectare. Male moth approaches were video recorded at the peak of peachtree borer annual flight, from 13 to 18 August 2009. The mean approach timing (h:min:sec±SD) during the study period was 11:33:12 ± 00:46:43, 11:43:52 ± 00:45:58, and 11:41:21 ± 00:45:54 AM with the single dispenser, high-density dispensers, and lure, respectively. Day-to-day variability in approach timings suggested that there were no biologically significant differences among treatments. The frequency distribution of approach durations varied among treatments, as the high-density dispensers had mostly short approaches, while the distribution of approaches to the single dispenser and lure was wider. The median (interquartile range) approach duration was 3 (2-4), 1 (1-2), and 4 (2-6) seconds with the single dispenser, high-density dispensers, and lure, respectively. The relative rank of median approach durations was constant throughout the period, indicating differences among treatments. This study showed that the presence of pheromone dispensers for mating disruption did not cause an advancement of peachtree borer diel rhythm of response. Shorter approaches to dispensers placed at high density than singly suggest that dispenser retentiveness is not constant with peachtree borer, which may bias estimates of disruption activity as a function of dispenser density.

Tree Height Influences Flight of Lesser Peachtree Borer and Peachtree Borer (Lepidoptera: Sesiidae) Males

Capture of male lesser peachtree borer, Synanthedon pictipes (Grote & Robinson), and peachtree borer, S. exitiosa (Say) (Lepidoptera: Sesiidae), in pheromone traps positioned from 0 m to 6 m above ground was affected by surrounding tree height. In a peach orchard with a 3 m canopy height, more S. pictipes were captured within the canopy zone at 1.8 m than above at 5.5 m. Trap capture was similar for S. pictipes in a mating disruption orchard with more caught at 2 m than at 4 m or 6 m. Capture at 1.8-5.5 m in mixed deciduous woods, with an average canopy height of 22 m, was not significantly different. In orchards, more S. exitiosa were captured at 1.8 m rather than at 5.5 m but no difference was detected in numbers captured from 0 m to 5.5 m in mixed deciduous woods. In a peach-pecan interplanted orchard, where pecan trees were three times taller but only one-ninth the density of peach, capture of both species was similar to capture in peach orchards when traps were entirely surrounded by peach. However, when traps were adjacent to a single, taller non-host pecan tree, capture was similar to mixed deciduous woods. These data suggest that habitat structure supersedes presence/absence of host plants affecting vertical flight activity of male S. pictipes and S. exitiosa.

Efficacy of Steinernema carpocapsae for control of the lesser peachtree borer, Synanthedon pictipes: Improved aboveground suppression with a novel gel application

Safe and effective tactics are needed for control of the lesser peachtree borer, Synanthedon pictipes (Grote & Robinson), which is a major pest of stone fruits ( Prunus spp) in eastern North America. Virulence of the entomopathogenic nematode, Steinernema carpocapsae (Weiser) , to S. pictipes has been demonstrated in the laboratory. However, achieving field efficacy has been difficult because S. pictipes attacks the tree aboveground where nematodes are subjected to damaging environmental conditions, e.g., UV radiation and desiccation. We investigated the potential of various formulations to improve the efficacy of aboveground applications. First, we screened five potential adjuvants at 2%, 20%, and 40% concentrations in water for toxicity to S. carpocapsae in the laboratory: Anti-Stress, Moisturin®, Nu-Film®, Shatter-Proof, and Transfilm®. In general, the adjuvants did not adversely affect nematode survival except at the highest rate. Subsequently, Shatter-Proof was tested in field trials in 2008 and 2009. S. carpocapsae was applied alone or with Shatter-Proof to peach limbs pre-infested with S. pictipes larvae. Furthermore, the experiments included the following treatments: S. carpocapsae followed by a post-application covering of latex paint, moistened diaper, or a gel spray (Barricade®). Controls of water-only, or water plus Shatter-Proof, Barricade®, or paint (without nematodes) were also included. The nematodes-only treatment failed to reduce S. pictipes survival relative to the water-only control in either year. Additionally, the nematode treatments with Shatter-Proof or paint did not differ from nematodes-only, water-only or their respective control treatments without nematodes. The diaper treatment with nematodes showed some potential as an efficacy enhancer (e.g., insect survival was reduced relative to nematodes-only in one year). In contrast, in both years, nematodes plus Barricade® reduced S. pictipes relative to the controls and the nematodes-only treatment; survival in the Barricade® treatment was 30% and 0% in 2008 and 2009, respectively. We conclude that nematode treatments followed by application of a sprayable gel such as Barricade® can enhance control of S. pictipes and possibly other aboveground pests as well.

Reduced-Risk Pest Management Programs for Eastern U.S. Apple and Peach Orchards: A 4-Year Regional Project

Studies were conducted from 2002 to 2005 to determine the effectiveness of reduced-risk (RR) tactics for managing key pests in 50 commercial apple orchards (114 ha) in Michigan, North Carolina, New York, Pennsylvania, Virginia, and West Virginia; and 20 peach orchards (190 ha) in Michigan, New Jersey, Pennsylvania, and West Virginia. At each apple site, a block of up to 5 ha received a seasonal program of selective RR and organophosphate-replacement insecticides, with or without pheromones for mating disruption of key lepidopteran pests of apple (codling moth, oriental fruit moth, and obliquebanded leafroller) and peach (oriental fruit moth, lesser peachtree borer, and peachtree borer). A comparison block at each site with the same varieties and tree training was managed using each grower's standard program of conventional insecticides (STD). Pheromone traps for lepidopteran species were hung in all plots and monitored weekly. Foliar samples were taken during the season to estimate phytophagous and predator mite densities. Red sphere traps baited with fruit volatiles were used to monitor apple maggot adults in apple orchards. Fruits were inspected for insect damage at harvest, and graded according to USDA standards. Partial budget analysis was used to assess the net profitability of RR programs to produce apples and peaches for their intended market in each state. Fruit damage at harvest caused by direct fruit pests was generally low across all blocks and treatments. There were no statistically significant differences in fruit damage or mite populations between the RR blocks, with or without pheromones, and the growers' standards. Insecticide use patterns in the RR plots represented up to 88 and 78% reduction in the amount of active ingredient applied per hectare, and an 85 and 77% decrease in their Environmental Impact Quotient for apples and peaches, respectively. However, RR programs were more expensive and generally less profitable compared with growers' standard programs. Regression analysis estimated that RR apple programs with and without mating disruption were on average &dollar;465 and &dollar;144/ha more expensive, and &dollar;544 and &dollar;159/ha less profitable, respectively, compared with standard programs. RR+MD programs for peaches cost an average &dollar;314/ha more and returned about &dollar;284/ha less than STD peach programs.

Influence of &lt;I&gt;Prunus&lt;/I&gt; spp., Peach Cultivars, and Bark Damage on Oviposition Choices by the Lesser Peachtree Borer (Lepidoptera: Sesiidae)

An examination of oviposition choices by the lesser peachtree borer, Synanthedon pictipes (Grote and Robinson) (Lepidoptera: Sesiidae), showed that wounded peach, Prunus persica (L.) Batsch, bark was attractive to females for oviposition. Females responded to bark that was injured mechanically (e.g., hammer blows, knife cuts, pruning wounds), infested by lesser peachtree borer larvae or injured by disease. In fact, there was no difference in female oviposition response to knife cut wounds and knife cut wounds infested with lesser peachtree borer larvae. Oviposition on wounded bark from three different high chill peach cultivars was similar and strongly suggests that the narrow genetic base of high chill peach cultivars grown in the southeastern United States has little inherent resistance to the lesser peachtree borer. In stark contrast, when provided different Prunus spp., i.e., exotic peach and the native species P. angustifolia and P. serotina, the exotic peach was highly preferred for oviposition by the native lesser peachtree borer.

A novel approach to biological control with entomopathogenic nematodes: Prophylactic control of the peachtree borer, Synanthedon exitiosa

Generally, microbial control agents such as entomopathogenic nematodes are applied in a curative manner for achieving pest suppression; prophylactic applications are rare. In this study, we determined the ability of two Steinernema carpocapsae strains (All and Hybrid) to prophylactically protect peach trees from damage caused by the peachtree borer, Synanthedon exitiosa, which is a major pest of stone fruit trees in North America. In prior studies, the entomopathogenic nematodes S. carpocapsae and Heterorhabditis bacteriophora caused field suppression when applied in a curative manner to established S. exitiosa populations. In our current study, nematodes were applied three times (at 150,000–300,000 infective juveniles/tree) during September and October of 2005, 2006, and 2007. A control (water only) and a single application of chlorpyrifos (at the labeled rate) were also made each year. The presence of S. exitiosa damage was assessed each year in the spring following the treatment applications. Following applications in 2006, we did not detect any differences among treatments or the control (possibly due to a low and variable S. exitiosa infestation of that orchard). Following applications in 2005 and 2007, however, the nematode and chemical treatments caused significant damage suppression. The percentage of trees with S. exitiosa damage in treated plots ranged from 0% damage in 2005 to 16% in plots treated with S. carpocapsae (Hybrid) in 2007. In control plots damage ranged from 25% (2005) to 41% (2007). Our results indicate that nematodes applied in a preventative manner during S. exitios’s oviposition period can reduce insect damage to levels similar to what is achieved with recommended chemical insecticide treatments.

Genetic Variation of the Lesser Peach Tree Borer, Synanthedon pictipes (Lepidoptera: Sesiidae) in Arkansas

The lesser peach tree borer, Synanthedon pictipes (LPTB), belongs to the economically important Lepidopteran family Sesiidae. No studies on genetic variation or population structure on the genus Snyanthedon have been previously published. We examined DNA sequence variation in a 603 bp region of the mitochondrial cytochrome oxidase I gene (COI), tRNA-leu and cytochrome oxidase II gene (COII) from three LPTB populations in Arkansas. From 114 LPTB collected from three populations, a total of 53 nucleotide positions were polymorphic, and 12 distinct haplotypes were observed. The most frequent haplotype occurred in 88% of the sampled LPTB's and in all three populations. Sequence divergence among haplotypes ranged from 0.2% to 8.8%. According to the standard molecular clock proposed for lepidopteran mtDNA, the haplotypes have been diverging for up to 2.5 million years. The greatest amount of haplotype diversity was observed in the Fayetteville population where borer management is not maintained. High levels of gene flow were observed among the Clarksville, Springdale and Fayetteville populations suggesting the LPTB has a broad dispersal range. Examination of the genealogical relationships and phylogenetic analysis of the 12 haplotypes supports the existence of three genetically distinct but morphologically indistinguishable subspecies.

Semiochemical‐mediated oviposition behavior by female peachtree borer, Synanthedon exitiosa

AbstractThe peachtree borer, Synanthedon exitiosa (Say) (Lepidoptera: Sesiidae), is an important pest of commercial cultivations of peach trees, Prunus persicae (L.) (Rosaceae). Identification of semiochemicals that mediate host selection by adult S. exitiosa may lead to the development of a new earth‐friendly tactic within integrated programs for control of S. exitiosa. Larvae develop in the phloem of peach trees where their feeding stimulates the production of gum frass, a mixture of tree phloem particles, tree sap (gum), and larval feces (frass). We tested the hypothesis that gum‐frass semiochemicals signal a potential host tree, and induce oviposition by female S. exitiosa. In coupled gas chromatographic‐electroantennographic detection analyses of Porapak Q‐collected gum frass volatiles, 21 compounds elicited responses from male or female S. exitiosa antennae. These compounds included four acids, four hydrocarbons, four ketones, three acetates, two aldehydes, γ‐decalactone, conophthorin, 2‐phenylethanol, and 2‐isopropyl‐3‐methoxypyrazine. In dual‐choice laboratory experiments, all groups of compounds, except the acetates, were needed to induce significantly more egg laying by female S. exitiosa on treatment than on unbaited control oviposition sites. By responding to gum frass semiochemicals, female S. exitiosa seem to exploit signals that are complex, detectable, and that reliably indicate a potential host tree for larval development.