Size of orchard trees as a factor affecting behavioural control of apple maggot flies (Dipt., Tephritidae) by traps

Over a 3-year period (1997–1999), we examined the influence of tree size on effectiveness of traps for behaviourally controlling apple maggot flies, Rhagoletis pomonella (Walsh), in small blocks of trees in Massachusetts commercial apple orchards. Traps were red spheres coated with Tangletrap and baited with an attractive synthetic host fruit odour (butyl hexanoate). Traps were placed 6 m apart on perimeter apple trees of each block and were designed to intercept apple maggot flies immigrating into blocks from unmanaged host trees. Based on captures of adults by unbaited red spheres placed near the centre of each block to monitor degree of adult penetration into the interior and on percentages of fruit injured by apple maggot, traps surrounding blocks of small trees (1.5 m canopy diameter) planted at high density were more effective in controlling apple maggot flies (relative to control obtained by insecticide sprays used in comparison blocks) than were traps surrounding blocks of large trees (3.7 m canopy diameter) planted at low density, with traps surrounding blocks of medium-size trees (2.5 m canopy diameter) planted at medium density generally providing an intermediate level of control.     

Evaluation of trap deployment patterns for behavioural control of apple maggot flies (Dipt., Tephritidae)

Abstract: We evaluated three different deployment patterns of sticky red sphere traps, baited with a five-component blend of synthetic attractive fruit odour and placed on perimeter apple trees bordering adjacent habitat (front-row trees), for control of apple maggot flies, Rhagoletis pomonella (Walsh), in small plots of apple trees (about 30 × 30 m) in Massachusetts commercial apple orchards. Degree of fly penetration from front-row to interior apple trees was assessed for R. pomonella of wild origin and for marked adults released in habitats adjacent to front-row trees. Traps placed 10  and 5 m apart on front-row trees or grouped on a single central front-row tree performed as well as grower-applied insecticide sprays in preventing penetration of plots by wild and released flies and in preventing fruit injury . This was equally true for plots whose front-row trees consisted of cultivars comparatively susceptible to apple maggot as for plots whose front-row trees were comprised of comparatively tolerant cultivars. It was also true for each seasonal period during which sampling for treatment performance occurred.     

Comparison of neonicotinoid insecticides for use with biodegradable and wooden spheres for control of key Rhagoletis species (Diptera: Tephritidae).

Field-based studies and laboratory bioassays were conducted with apple maggot, Rhagoletis pomonella (Walsh), and blueberry maggot, Rhgoletis mendax Curran, flies to investigate the performance and duration of activity of insecticide-treated biodegradable and wooden spheres for control of Rhagoletis species. Four neonicotinoid insecticide treatments including imidacloprid, thiamethoxam, and thiocloprid at 2% (AI) were evaluated with biodegradable spheres. In 1999, significantly more apple maggot flies were found killed by imidacloprid-treated spheres compared with thiamethoxam-treated spheres during early and late season. In 2000, spheres treated with either of two formulations of imidacloprid killed significantly more apple maggot flies compared with thiamethoxam, thiocloprid, and untreated spheres. In blueberries, there were no significant differences between the numbers of blueberry maggot flies killed by both imidacloprid-treated or thiamethoxam-treated spheres in 1999. However, during the 2000 blueberry field season, both formulations of imidacloprid were significantly more effective in killing blueberry maggot flies compared with spheres treated with thiamethoxam, thiocloprid and untreated controls. Overall, spheres treated with thiocloprid were ineffective and did not kill significantly more apple maggot or blueberry maggot flies compared with the controls. Laboratory bioassays showed that the effectiveness of field-exposed spheres treated with imidacloprid at 4 and d 8% (AI) and thiamethoxam at 4% (AI) in killing apple maggot flies was not significantly reduced over a 12-wk aging period. Additionally, wooden spheres aged outdoors for 12 wk with and without mold maintained residual activity in laboratory tests, whereas biodegradable spheres of equal aging, with and without mold lost their effectiveness in killing apple maggot flies. In other studies, we confirmed that the addition of an external feeding stimulant (sucrose) significantly increases the effectiveness of both biodegradable and wooden spheres treated with imidacloprid at 2% (AI).     

Revisiting within-tree trap positioning for apple maggot fly (Dipt., Tephritidae) behavioural control

Abstract:  Aiming to minimize visual competition between large red apples and red sphere traps from influencing effectiveness of traps for apple maggot fly (AMF) control, we compared AMF captures by red spheres in standard recommended position (no fruit within 15 cm), red spheres in similar position but with all fruit removed within a 30-cm radius (fruitless), red spheres with additional visual competition provided by three plastic red spheres hung 15 cm from sphere traps, and yellow panels. Traps were coated with adhesive, baited with synthetic fruit odour, and hung on trees of an apple cultivar bearing red fruit (Akeene) and trees of an apple cultivar bearing pale yellow fruit (Golden Delicious). On Akeene trees, red spheres in recommended position and fruitless red spheres caught more AMF than red spheres surrounded by plastic spheres and than yellow panels. Towards harvest, effectiveness of red spheres in recommended position decreased as reflectance of the surface of Akeene apples approached that of red spheres. By contrast, effectiveness of fruitless spheres increased over time. On Golden Delicious trees, fruitless spheres were the most effective, followed by spheres surrounded by uncoated plastic spheres and red spheres in recommended position. We conclude that removing all fruit within a 30-cm radius around red sphere traps results in similar or increased trap effectiveness relative to red spheres in recommended position.     

An index for assigning distances between odor-baited spheres on perimeter trees of orchards for control of apple maggot flies

Previously, the distances between odor‐baited spheres deployed on perimeter trees of apple orchards for behavioral control of apple maggot flies, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), have been assigned largely arbitrarily. Here, we report a new approach for assigning distances that employs an index incorporating the state of four environmental variables: the size of orchard trees, quality of pruning, cultivar composition, and nature of bordering habitat. The deployment of odor‐baited spheres on the perimeters of 12 plots of apple trees (each ～0.4 ha) in commercial orchards in 2003 resulted in an apple maggot control which was no different from that achieved by insecticide sprays in adjacent plots in 2003, and no different from that achieved by an arbitrary assignment of distances between odor‐baited spheres on perimeter trees in these same plots in 2001 and 2002. However, only 61–67% of spheres were used under the new index approach compared with the previous arbitrary approach, thereby substantially reducing the cost of behavioral control. Our findings are discussed in relation to use of the index for blocks of trees which are large in size and pruned poorly vs. small in size and pruned well, and in relation to the cost‐competitiveness of odor‐baited perimeter spheres vs. insecticidal sprays for the control of apple maggots.     

Evaluation of various deployment strategies of imidacloprid-treated spheres in highbush blueberries for control of Rhagoletis mendax (Diptera: Tephritidae)

Biodegradable, ammonium-baited spheres treated with the neonicotinoid insecticide Provado (imidacloprid) at 2% (AI) were evaluated for controlling blueberry maggot flies, Rhagoletis mendax Curran. Three strategies for sphere deployment in highbush blueberries, Vaccinium corymbosum L., were compared with untreated control plots in 1999 and once again compared against control plots and organophosphate insecticide sprays in 2000. The patterns of sphere deployment were as follows: (1) perimeter deployment in which spheres were hung individually and spaced equally around the perimeter of experimental plots; (2) cluster deployment in which four groups of three spheres were hung in equally spaced perimeter locations of experimental plots; and (3) uniform deployment in which spheres were placed 10 m apart (in a grid-like pattern) within experimental plots. In 1999, there were no significant differences in fruit injury levels based on observed R. mendax oviposition scars and reared larvae among plots containing imidacloprid-treated spheres in perimeter, cluster, and internal-grid patterns. However, all plots containing spheres had significantly lower fruit infestation levels (<2%), compared with unsprayed control plots with no spheres deployed, which had infestation levels (>20%). In 2000, there were no significant differences in fruit injury based on observed R. mendax oviposition scars between plots containing imidacloprid-treated spheres in the three deployment strategies tested and plots that received Guthion (Azinphosmethyl) spray applications. However, significantly fewer R. mendax larvae were reared from berries collected from plots that received two applications of Guthion compared with plots in which imidacloprid-treated spheres were deployed. Irrespective of sphere deployment strategies, all sphere-treated and sprayed plots had significantly lower injury levels (<1.5%), based on numbers of reared larvae compared with berries collected from the control plots (>4.0%). Based on captures of flies on unbaited Pherocon AM boards placed in the center of treatment plots, we observed a suppression of R. mendax in plots containing imidacloprid-treated spheres compared with control plots. The potential of using imidacloprid-treated spheres as a behavioral control integrated pest management tactic for blueberry maggot flies is discussed.     

Post-alighting responses of Mexican fruit flies (Dipt., Tephritidae) to different insecticides in paint on attractive spheres

Abstract: Two new, comparatively safe insecticides (spinosad and imidacloprid) were compared with dimethoate (each at 1.5% active ingredient) for behavioural and mortality effects on Mexican fruit flies, Anastrepha ludens . Insecticide was mixed with sugar (as a feeding stimulant) and yellow latex paint (as an extending agent) applied to the surface of fruit-mimicking biodegradable 7 cm spheres made of sugar, flour and glycerin. Flies feeding on spinosad-treated spheres did not differ from flies feeding on untreated spheres in post-feeding intra-tree flight capability, amount of oviposition or mortality. Flies that fed on imidacloprid- or dimethoate-treated spheres for as little as 30 s experienced both high reduction in oviposition and high mortality compared with flies that fed on untreated spheres, and the flies from imidacloprid-treated spheres also showed a much reduced intra-tree flight capability. If baited with attractive odour, biodegradable yellow spheres treated with a surface coating of imidacloprid in latex paint and sugar could have potential for suppressing Mexican fruit flies on host trees.     

Trap position and fruit presence affect visual responses of apple maggot flies (Dipt., Tephritidae) to different trap types

Abstract:  We compared responses of apple maggot flies, Rhagoletis pomonella (Walsh), in a commercial apple orchard in Massachusetts with three different types of visual traps baited with synthetic fruit volatiles. The traps were red spheres, Ladd traps (a rectangular yellow panel between two red hemispheres) and rectangular yellow panels. Traps were placed either in optimal position (D rummond , F.; G roden , E.; P rokopy , R. J., 1984: Environ. Entomol. 13, 232–235.) or sub-optimal position (not surrounded by foliage and fruit from all sides). The study was performed over 3 years. Early in the fruiting season, when apples were small and green, red spheres followed by Ladd traps attracted more flies than yellow panels. Ladd traps were the most sensitive to trap positioning, losing effectiveness when placed in sub-optimal position. Late in the fruiting season, in years yielding crops of large red apples, red spheres in optimal position (surrounded by growing red fruit) lost some effectiveness relative to Ladd traps in optimal position. Red spheres in sub-optimal position were not similarly affected, perhaps because of the lack of fruit in the background. Red sphere performance relative to Ladd traps was re-established after removal of competing fruit from trees at harvest. Because Ladd traps are more expensive to purchase and more difficult to position, red spheres are a better option for commercial growers in eastern North America. Conceivably, loss of capturing power of red spheres because of visual competition from red apples towards harvest could be mitigated by adjusting trap positioning.     

Attraction of adult Rhagoletis indifferens (Diptera: Tephritidae) to unbaited and odor-baited red spheres and yellow rectangles

Five sizes of red spheres (4, 6, 8, 10, and 12 cm diameter) and 2 orientations of yellow rectangles (vertical and V) were evaluated as unbaited sticky-coated traps for western cherry fruit flies, Rhagoletis indifferens Curran, in unmanaged cherry trees in Washington and Oregon. Red spheres that were 10 cm in diameter attracted more flies than red spheres that were 8 or 12 cm in diameter and significantly more flies than 4- or 6-cm spheres and yellow rectangles of either orientation. In a 2nd test, red spheres (10 cm diameter) baited with ammonium carbonate alone or ammonium carbonate plus putrescine attracted significantly more R. indifferens than similar spheres baited with ammonium acetate alone, putrescine alone, 3-methyl-1-butanol alone, or combinations of these substances. In a 3rd test, vertical yellow rectangles baited with ammonium carbonate alone attracted numerically more R. indifferens than any of the aforementioned substances alone or in combination. We discuss the potential value of 10-cm red spheres baited with ammonium carbonate for monitoring and direct control of R. indifferens.     

Effectiveness of odor-baited trap trees for plum curculio (Coleoptera: Curculionidae) monitoring in commercial apple orchards in the northeast

The plum curculio, Conotrachelus nenuphar (Herbst), is a key pest of pome and stone fruit in eastern and central North America. For effective management of this insect pest in commercial apple (Malus spp.) orchards in the northeastern United States and Canada, one of the greatest challenges has been to determine the need for and timing of insecticide applications that will protect apple fruit from injury by adults. In a 2004-2005 study, we assessed the efficacy and economic viability of a reduced-risk integrated pest management strategy involving an odor-baited trap tree approach to determine need for and timing of insecticide use against plum curculio based on appearance of fresh egg-laying scars. Evaluations took place in commercial apple orchards in seven northeastern U.S. states. More specifically, we compared the trap-tree approach with three calendar-driven whole-block sprays and with heat-unit accumulation models that predict how long insecticide should be applied to orchard trees to prevent injury by plum curculio late in the season. Trap tree plots received a whole-plot insecticide spray by the time of petal fall, and succeeding sprays (if needed) were applied to peripheral-row trees only, depending on a threshold of one fresh plum curculio egg-laying scar out of 25 fruit sampled from a single trap tree. In both years, level of plum curculio injury to fruit sampled from perimeter-row, the most interior-row trees and whole-plot injury in trap tree plots did not differ significantly from that recorded in plots subject to conventional management or in plots managed using the heat-unit accumulation approach. The amount of insecticide used in trap tree plots was reduced at least by 43% compared with plots managed with the conventional approach. Advantages and potential pitfalls of the bio-based trap tree approach to plum curculio monitoring in apple orchards are discussed.     

Effects of pH on feeding responses in the apple maggot fly,Rhagoletis pomonella (Diptera: Tephritidae)

Phagostimulatory effects of pH values of sucrose on Rhagoletis pomonella adults were studied in the laboratory. Flies were standardized for age, diet and food deprivation. Two presentation schemes were employed. The first varied pH value (3.0-10.0) with sucrose concentration kept constant at 40%. The second varied both sucrose concentration (8%, 24% and 40%) and pH value (5.0-8.0). Fly feeding propensity was evaluated by observation of fly acceptance or rejection of sucrose and duration of feeding. When tested on red wooden spheres treated with 40% sucrose, fly feeding acceptance was significantly greater when pH ranged from 5.0 to 8.0, and duration of feeding was significantly longer at pH 6.0-7.0. At pH /=8.0, feeding propensity was significantly reduced. Decrease in sucrose concentration significantly increased fly sensitivity to pH. Males were more responsive to varying pH than females. The sucrose pH shown to stimulate maximal feeding response was 6.4. Such information is relevant to formulation improvement of a coating mixture of sucrose and insecticide applied to red spheres as part of apple maggot fly control programs.     

Flower nitrogen status and populations of Frankliniella occidentalis feeding on Lycopersicon esculentum

Alighting and capture of wild olive fruit flies, Bactrocera oleae (Rossi) (Diptera, Tephritidae), on spheres of seven different colours was studied on Chios island, Greece. The 70-mm-diam plastic spheres, coated with adhesive, were suspended on olive trees. Yellow and orange spheres trapped the greatest number of males while red and black spheres trapped the greatest number of females. White and blue spheres were the least effective for both sexes. Peak captures occurred in the late afternoon and especially around sunset. Since mating takes place in the last hours of the photophase, the increased captures during that period may be related to the sexual behaviour of the fly. When red spheres were assessed against glass McPhail traps baited with 2% ammonium sulphate, which consist a standard tool for monitoring the olive fruit fly in Greece, there were no significant differences in male captures. However, spheres trapped almost three times as many females as McPhail traps. The possible mechanisms underlying colour discrimination, the motivation of alighting flies and the possible use of red spheres for monitoring and controlling B. oleae are discussed.     

Effectiveness of thiamethoxam-coated spheres against blueberry maggot flies (Diptera: Tephritidae)

Studies were conducted to evaluate the mortality of blueberry maggot, Rhagoletis mendax Curran, flies exposed to thiamethoxam- and imidacloprid-coated biodegradable (8-cm-diameter) red spheres, under both laboratory and field conditions. Laboratory studies with spheres coated with 0.1-2.0% (AI) of thiamethoxam indicated that they are effective against R. mendax; however, no dose-dependent response was observed. Studies on the effect of visitation time on thiamethoxam-coated spheres showed a decrease in R. mendax mortality as the duration of visitation time decreased from 60 to 10 s. Under field conditions, significantly more flies were captured on Plexiglas panes below the 2% (AI) thiamethoxam-coated spheres when compared with similar panes below untreated spheres. In field evaluations of thiamethoxam- and imidacloprid-coated spheres, imidacloprid-coated spheres (2.0% [AI]) were found to be significantly more effective than thiamethoxam-coated spheres (0.5-4.0% [AI]). Field trials to characterize the levels of mortality associated with aging pesticide-coated spheres revealed that the effectiveness of treated spheres decreased with increasing age of sphere, and this reduction in effectiveness is greater in thiamethoxam-coated spheres than in imidacloprid-coated spheres. These results provide comparative data on the effectiveness of thiamethoxam- and imidacloprid-coated spheres and support the potential of using pesticide-treated spheres for control of blueberry maggot flies.     

Apple maggot fly response to red sphere traps in relation to fly age and experience

Responses of the apple maggot fly,Rhagoletis pomonella (Walsh), to 8 cm red sticky sphere traps, baited with the synthetic fruit odor butyl hexanoate, were investigated in field-caged apple trees containing green or red Gravenstein apples. Trap capture rate and the probability of oviposition in apples before capture generally increased with female age and number of mature eggs in ovaries. Two days of pre-test exposure of mature females to red hawthorns, green Red Delicious apples or green Gravenstein apples had no significant effect on the likelihood of a fly finding a red sphere. However, before capture on a sphere or departing a tree, hawthorn-exposed females found significantly fewer apples and laid significantly fewer eggs than females exposed to Gravenstein apples. Variation in duration of pre-test exposure (1–4 days) of flies to Gravenstein apples had no detectable influence on female response to apples or to a red sphere in a test tree. The relevance of these findings to effectiveness of sphere traps, forR. pomonella control in commercial orchards is discussed.     

Antagonist effects of non-host fruit volatiles on discrimination of host fruit by Rhagoletis flies infesting apple (Malus pumila), hawthorn (Crataegus spp.), and flowering dogwood (Cornus florida)

In previous flight‐tunnel tests Rhagoletis pomonella (Walsh) (Diptera: Tephritidae) flies originating from domestic apple (Malus pumila), hawthorn (Crataegus spp.), and flowering dogwood (Cornus florida), displayed greater numbers of upwind flights to blends of volatiles identified from their natal fruit compared to non‐natal fruit. Here, we show that when certain non‐host volatiles were added to the host blend, significantly fewer apple, hawthorn, and dogwood flies exhibited sustained upwind flight to the source. Specifically, the upwind flight of apple flies to the apple blend was significantly antagonized by the addition of the hawthorn or dogwood blends, the addition of 3‐methylbutan‐1‐ol alone (a key volatile for hawthorn and dogwood flies), or the combination of 3‐methylbutan‐1‐ol and another key dogwood volatile, 1‐octen‐3‐ol. Similarly, the upwind flight of dogwood and hawthorn flies to their respective natal blends was antagonized by the addition of the apple blend or the key apple volatile butyl hexanoate. Experiments were also conducted to determine whether non‐natal fruit volatiles could disrupt the close‐range flight response of flies to the visual stimulus of fruit alone, represented by an odorless red sphere. Tests with apple‐origin flies showed that when the hawthorn blend, the dogwood blend, or the key antagonist volatiles from each (3‐methylbutan‐1‐ol and 1‐octen‐3‐ol) were added to a red sphere fruit mimic, significantly lower proportions of flies were captured, compared with captures when no odor was present. Our results support the hypothesis that agonist and antagonist properties of fruit volatiles can play an important role in host recognition/discrimination by Rhagoletis flies.     

Foliar application of aminoethoxyvinylglycine (AVG) delays fruit ripening and reduces pre-harvest fruit drop and ethylene production of bagged “Kogetsu” apples

Covering apple fruits with double layer waterproof bags to enhance fruit quality and evenness of blush colour is typical on many cultivars in Korea and Japan. Aminoethoxyvinylglycine (AVG) applied to unbagged apple fruits at 3–4 weeks before commercial harvest reduces ethylene production in the fruit, delays fruit ripening and reduces pre-harvest fruit drop. Spray application of AVG to trees of bagged apples should have no effect on apple ripening as there is␣no direct contact with the fruit and the translocation of AVG in apple trees is regarded as negligible. However, preliminary experiments suggested that AVG applied to trees of bagged apples reduced pre-harvest fruit drop in “Kotgetsu” apples. This study investigated the effect of spray treatments of 125 ppm of AVG on fruit drop, fruit ripening (firmness, starch conversion and soluble solids) and ethylene production to whole trees with bagged or unbagged “Kogetsu” fruit, as well as sprays of only the bagged or unbagged fruit on trees on two orchards. AVG applied to whole trees with unbagged apples reduced fruit drop from an average of 58.9% to 10.4%, delayed starch conversion and decreased ethylene production. AVG applied to whole trees with bagged fruit was equally effective in reducing pre-harvest drop, delaying fruit ripening and reducing ethylene production. Application of AVG to unbagged fruit only was nearly as effective as application to whole trees with unbagged fruit but application to bagged fruit only had no effect on fruit ripening or ethylene production. Application of AVG to bagged fruit only did reduce fruit drop to an average of 42.5% but this was not as effective as spraying unbagged fruit only or whole trees with bagged fruit. Possible mechanisms for this effect are discussed.     

Attraction of apple maggot flies, Rhagoletis pomonella (Diptera: tephritidae) of different physiological states to odour-baited traps in the presence and absence of food

Adults of apple maggot fly Rhagoletis pomonella (Walsh) of differing physiological states were marked and released in blocks of apple trees ringed by sticky red spheres. Spheres were either unbaited, baited with butyl hexanoate (synthetic host fruit odour) or baited with both butyl hexanoate and ammonium carbonate (synthetic food odour). All trap and lure treatments were compared in the presence or absence of food (bird faeces) in the blocks. Simultaneously, the response of wild immigrant flies to treatments was measured and wild females were dissected to determine state of ovary development. Large proportions (25-40%) of released mature male and female R. pomonella were recovered in blocks having traps baited with butyl hexanoate. Ammonium carbonate did not enhance trap captures and presence of food had little effect on response to synthetic odours by mature R. pomonella. Immature flies of each sex responded weakly to traps and to both types of synthetic lures and may have been arrested in blocks having food. Wild flies of both sexes exhibited a response pattern very similar to mature released flies, regardless of eggload (in the case of wild females). Results indicate that wild R. pomonella immigrating into apple orchards are primarily mature, and not hungry for protein. Behavioural control strategies are discussed in that context.     

Second-stage integrated management of apple arthropod pests

To date, integrated pest management (IPM) of arthropods in commercial apple orchards has been comprised almost exclusively of a suite of what we term first-stage IPM practices focused upon pest monitoring. These practices predict first appearance, rate of development, and abundance of pest and beneficial arthropods, which leads to recommendation of selective properly-timed pesticides as the sole tactic of controlling pests not effectively suppressed by beneficials. Here, we evaluated in Massachusetts the effectiveness of what we term second-stage IPM practices. These involved integration of pesticidal control of early season apple arthropod pests and behavioral, cultural and biological control of mid and late season apple arthropod pests in the absence of insecticide and acaricide application after mid June. The behavioral approach consisted of ringing the perimeter of several apple orchard blocks (each ca. 1 ha) with sticky-coated red spheres baited with synthetic apple odor to intercept immigrating Rhagoletis pomonella (Walsh) flies. The cultural approach focused on removing unmanaged host trees in a ring around the orchard block perimeter to prevent entry of Cydia pomonella (L.) and Argyrotaenia velutinana (Walker) females. The biological approach emphasized buildup of natural enemies of foliar pests in an orchard environment free of insecticide and acaricide use after mid June.During the second year (1988) of second-stage IPM implementation, test blocks in which baited red spheres were placed 5 m apart on perimeter apple trees and in which all unmanaged host trees within 100 m of the block perimeter had been removed received only 0.6% combined fruit injury by the above and all other pests active after mid June. Nearby blocks treated under first-stage IPM practices received 0.4% combined injury from such pests. As revealed by unbaited within-block monitoring traps, comparatively few R. pomonella flies penetrated the ring of interception traps, despite the large numbers caught on the latter. Beneficial predators of pest mites and aphids were nearly twice as common in second-stage as first-stage IPM blocks. Total cost was essentially the same for second-stage as first-stage IPM practices. But we propose a potentially much less costly, labor-saving method as a substitute for using a sticky substance to control R. pomonella flies alighting on perimeter-tree spheres.

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Résumé A ce jour, la lutte intégrée (IPM) contre les arthropodes des vergers commerciaux de pommiers, —que nous nommons IPM de première génération —, est conçue presque exclusivement comme une suite de pratiques focalisées sur l'interception des insectes nuisibles. Ces pratiques calculent d'abord la date d'apparition, la vitesse de développement et l'abondance des phytophages et des entomophages, conduisant à l'épandage à des dates appropriées d'insecticides sélectifs, comme seule tactique de protection contre les phytophages qui ne sont pas supprimés efficacement par des entomophages.Nous avons examiné au Massachusetts l'efficacité de ce que nous avons appelé le seconde génération d'IPM. Elle implique l'intégration de la lutte chimique contre des insectes consommateurs précoces, et de la lutte comportementale, culturale et biologique contre les insectes de pleine saison et tardifs, sans traitements insecticides ou acaricides des pommiers à partir de la mi-juin.L'approche comportementale consiste à encercler plusieurs massifs de pommiers (chacun de 1 ha) avec des sphères rouges engluées d'odeur synthétique de pommier pour intercepter les vols de Rhagoletis pomonella Walsh. L'approche culturale est concentrée sur l'élimination autour du verger des pommiers non inclus dans le programme de protection pour empêcher la pénétration de femelles de Cydia pomonella L. et Argyrotaenia velutinana Walker. L'approche biologique insiste sur la mise en place après la mi-juin des entomophages des ennemis du feuillage dans un verger sans insecticide ni acaricide.Pendant la seconde année (1988) de l'application du programme, les fruits attaqués par tous les phytophages après la mi-juin n'ont été que de 0,6% pour les parcelles d'arbres témoins dans lesquels les pièges rouges avaient été placés tous les 5 mètres sur les arbres du pourtour et dont les arbres non inclus dans l'expérience, avaient été enlevés sur une bande de 100 m autour de la parcelle. Des parcelles proches, traitées avec IPM première génération, avaient un taux d'attaque de 0,4% par les mêmes espèces d'arthropodes. Par rapport aux parcelles sans sphères rouges, relativement peu de R. pomonella ont pénétré au-delà de la rangée de pièges, malgré le grand nombre de mouches capturées dans ceux-ci. Les prédateurs d'acariens et de pucerons nuisibles étaient 2 fois plus abondants dans les parcelles protégées par IPM de deuxième génération, que dans celles protégées par IPM de première génération. Les coûts totaux sont à peu près les mêmes, mais nous proposons une méthode potentiellement beaucoup moins coûteuse, demandant moins de maind'uvre, par remplacement l'utilisation de la glue sur les sphères comme protection contre la pénétration de R. pomonella dans la parcelle.

     

Effect of trap position, habitat, and height on the capture of pepper maggot flies (Diptera: Tephritidae)

Trapping results indicate that pepper maggot, Zonosemata electa (Say), flies occupy tree canopies adjacent to fields when not on host plants. Several in- and near-field trap positions were used to find a reliable monitoring system for adult pepper maggots. Traps baited with liquid ammonium hydroxide (Stills-style trap), hung in the canopy of trees on the edges of pepper fields, caught significantly more Z. electa flies than when positioned lower along the treeline or in the field. In a second experiment, significantly more pepper maggot flies were captured in sugar maples compared with choke cherry trees, which indicates a pest preference for certain nonhost habitats. The lowest trap height tested (2.1 m) failed to capture Z. electa flies in either tree species when the pest population level was low. These studies demonstrated that pepper maggot flies can be reliably detected with Stills-style traps positioned at approximately 6.4 m height within the canopy of sugar maple trees adjacent to pepper fields. Fruit oviposition scars also are useful site-specific indicators of pepper maggot presence/absence and may aid in determining if insecticide applications are necessary and in timing sprays.     

Mortality and oviposition of western cherry fruit fly (Diptera: Tephritidae) exposed to different insecticide baits for varying periods in the presence and absence of food

Spinosad bait is used to control western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), by killing flies before they oviposit. However, effects of different insecticide baits on management of reproductively mature flies are largely unknown. Objectives here were to determine mortality and oviposition of reproductively mature R. indifferens exposed to different insecticide baits for varying periods in the presence and absence of dried yeast extract and sucrose food. Spinosad bait (spinosad in a mix of protein, sugar, and other ingredients) was compared with acetamiprid, thiamethoxam, and imidacloprid in sucrose or Nu-Lure + sucrose bait. When flies were exposed to treatments and then offered cherries, Prunus avium (L.) L., for oviposition or when they were exposed to treatments and cherries simultaneously, both thiamethoxam bait and imidacloprid bait resulted in higher mortality and lower oviposition than spinosad bait and acetamiprid bait. Exposures to thiamethoxam bait and imidacloprid bait for six and 24 h were similarly effective, but 6-h exposures to spinosad bait and acetamiprid bait were less effective than 24-h exposures. There was little difference between sucrose and Nu-Lure + sucrose baits. When food was present, thiamethoxam bait and imidacloprid bait caused greater mortality and lower oviposition than spinosad bait and acetamiprid bait, but when food was absent, patterns were less consistent. Because of its ability to kill flies sooner after it is exposed to flies when food is present or absent, thiamethoxam or imidacloprid in sucrose or Nu-Lure bait may reduce infestations in cherries more than spinosad bait when mature R. indifferens are present in orchards.