Influence of canopy aspect and height on codling moth (Lepidoptera: Tortricidae) larval infestation in apple, and relationship between infestation and fruit size

Monitoring systems based on traps with female attractants are expected to enhance forecasting of insect population size and damage. The optimal placement of such traps should match the small-scale distribution of ovipositing females. In the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), fruit infestation takes place in proximity to the oviposition site. We characterized the within-tree distribution of codling moth infestations and the size of uninfested fruit based on a survey of 40,000 apples (Malus spp.) from trees belonging to 160 different apple genotypes and growing in two different environments. Each tree was subdivided into 12 sectors, considering canopy aspect (north, east, south, and west) and canopy height (bottom, middle, and top). This study revealed that fruit infestation by the first but not by the second generation of larvae correlated significantly with canopy aspect. Similarly, fruit size differed significantly between the north- and the south-facing tree side for the period of infestation by the first but not by the second larval generation. Significantly lower fruit infestation was observed on the north- compared with the south- or east-facing tree side for the first generation. A significant influence of canopy height on larval infestation was observed in three of eight assessments, in which the middle height level showed the highest infestations. Significant differences in within-tree distribution of codling moth infestation suggest that oviposition preference is guided by nonrandom factors including microclimate, fruit phenology, and wind direction. These cultivar-independent findings should be considered in future monitoring systems that focus on female codling moth.     

Cold tolerance of the overwintering larval instars of light brown apple moth Epiphyas postvittana

The light brown apple moth, Epiphyas postvittana, a leafroller native to southeastern Australia was discovered in California in 2006. The highly polyphagous nature of this pest adds to the importance of being able to predict the potential distribution of this invader across the North American continent. The spread of ectothermic species that lack winter diapause, such as E. postvittana, can be limited by their ability to tolerate cold temperature extremes. In this study we examined the cold hardiness of 4th to 6th instar E. postvittana, the only life stages known to overwinter in California, through a combination of supercooling point (SCP) and mortality at low temperatures. Our results showed that the mean SCP for E. postvittana ranged from −14.1 °C for 6th instars to −16.0 °C for 4th instars. Lethal time leading to 50% mortality (LT₅₀) for the three instars combined were 2.5 h at −10.5 °C, 41 h at −6.5 °C and 198 h at −0.9 °C. At 3 °C, the LT₅₀ of 4th instars was significantly lower at 775 h than that for 5th and 6th instars combined at 1029 h. The cold hardiness characteristics of later-instar E. postvittana larvae were comparable to those of pink bollworm, Pectinophora gossypiella, a diapausing invasive with a geographic distribution restricted to southern California. Slightly greater cold hardiness is shown by the indigenous non-diapausing leafroller Argyrotaenia franciscana, which is restricted to the Pacific Coast of North America. We therefore conclude that the moderate cold hardiness of E. postvittana will substantially limit its spread into northern temperate regions of North America.     

Death of Cydia pomonella larvae and damage to apple fruit, after field application of codling moth granulosis virus

In field experiments, larvae of codling moth Cydia pomonella (L.) rarely acquired granulosis virus on hatching from the egg, but picked up most later, on the tree surface. Deposits of virus sprayed in 1.0% w/v skimmed milk did not affect neonate larval behaviour. Larvae died, usually in the first instar, after entering treated fruit, but they frequently entered via the calyx or near the base of the stalk or through cracks in the skin, where little feeding damage by first-and sometimes second-instar larvae was seen.

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Résumé En verger, la pulvérisation d'oeufs de carpocapse avec du virus de la granulose en suspension dans l'eau (additionnée de lait écrémé dilué à 1%) n'a pas modifié la survie des chenilles avant pénétration dans le fruit; par contre la pulvérisation des arbres a provoqué une forte mortalité. Bien que des chenilles consommant des poils et la surface des feuilles aient été observées avant leur pénétration dans le fruit, ce qui aurait pu provoquer leur contamination par le virus, il semble que la contamination létale provienne des fruits seuls.La présence de produit n'a modifié ni le comportement larvaire, ni le taux de pénétration dans les fruits; la mortalité y a lieu ensuite, généralement au premier stade. Dans 74 à 78% des cas, les chenilles ont pénétré dans le fruit par le calice ou près de la base du pédoncule — aucun dégât provenant de larves du premier stade n'y était visible, de même que dans le calice pour les larves du deuxième stade. Par contre, toute pénétration par la surface du fruit était repérable dès le premier stade. Il est possible que la répartition des lieux de pénétration dans le fruit influe sur la létalité due au virus et explique les variations d'efficacité observées en verger. Un système de classification des dégâts, provoqués lors de la pénétration dans le fruit, de chenilles du premier au troisième stade est proposé pour évaluer l'efficacité des essais en verger.

     

Apple and peach fruit volatiles and the apple constituent butyl hexanoate attract female oriental fruit moth, Cydia molesta, in the laboratory

Volatiles emitted from immature and mature peach and apple fruits were all attractive to mated female oriental fruit moth, Cydia molesta (Busck), in a dual choice arena. Females did not discriminate between odours emitted by these two major host plants. The same natural blends were behaviourally ineffective for virgin females. A major component of apple fruit volatiles, butyl hexanoate, also attracted female C. molesta. Mated females were attracted to two medium dosages, while virgin females responded positively to the lowest of the five dosages tested. The time course of the captures of the moths shows a diurnal activity cycle known from the field. The possible implications of a semiochemical which attracts females are discussed in the context of previous findings that gravid females may immigrate from peaches into apple orchards particularly in the later phase of the season.     

Diapause induction in the codling moth, Cydia pomonella: effect of larval diet

The effect of larval diet on diapause induction in the Israeli strain of the codling moth, Cydia pomonella (L.), was studied in a field trial using intact apple fruits of two varieties: Ana (early-ripening, in the end of June) and Granny Smith (late-ripening, in October). Diapause incidence increased as fruit age (determined as days from fruit-set) progressed. These results corroborate former studies on other strains of the codling moth, where excised fruits were used.The combination of 80-day-old, fully ripe, Ana fruit treatment with the longest days of the year, yielded 38% diapause. This result demonstrates that mature fruit (inducing diapause) cannot completely override the effect of long day (averting diapause), but does confirm that larval diet modifies the photoperiodic induction of diapause in the codling moth.Deceased, October 1988     

Optimizing use of codling moth granulovirus: effects of application rate and spraying frequency on control of codling moth larvae in Pacific Northwest apple orchards

New formulations of the codling moth, Cydia pomonella (L.), granulovirus (CpGV) [family Baculoviridae, genus Granulovirus] are commercially available in North America. In field tests on apple (Malus sp. 'Delicious'), we compared different application strategies for CpGV (Cyd-X, Certis USA, Clovis, CA) used in full-season programs against high pest populations. In replicated single tree plots, three rates (0.073, 0.219, and 0.438 liter ha(-1)) and application intervals (7, 10, and 14 d) killed 81-99% of larvae in fruit and reduced the number of mature larvae recovered in tree bands by 54-98%. Although the proportion of deep entries declined by 77-98%, the amount of fruit injury was not reduced compared with controls. There was a statistical trend between increasing dosage and spray frequency intervals and virus effectiveness, but no interaction between these factors. In a commercial orchard, we assessed a standard (0.219 liter ha(-1)) and two reduced rates of the virus (0.146 and 0.073 liter ha(-1)) applied in a weekly spray program in replicated 0.2-ha blocks. In the first generation, fruit injury was reduced in virus-treated compared with three untreated blocks although the decrease was only significant at the standard rate. Mortality rates of larvae (in fruit) were > or =90%, dose dependent, and comparable with rates observed from individual trees sprayed with equivalent treatments in the previous study. Rates of larval mortality declined at all dosages (81-85%) in the first part of the second generation. Most damage and proportionally less mortality occurred in the upper canopy. High pest pressures and untreated blocks contributed to significant damage and the study was terminated early. These data suggest virus programs can be tailored according to the localized pest pressure, but it may not prevent economic damage in high-pressure situations.     

Overwintering of codling moth (Lepidoptera: Tortricidae) larvae in apple harvest bins and subsequent moth emergence.

Codling moths, Cydia pomonella (L.), have long been suspected of emerging from stacks of harvest bins in the spring and causing damage to nearby apple and pear orchards. With increased use of mating disruption for codling moth control, outside sources of infestation have become more of a concern for growers using pheromone based mating disruption systems. Studies were designed to provide information on bins as a source of codling moth and the pattern of codling moth emergence from stacks of bins. In these studies, codling moth larvae colonized wood harvest bins at a much higher frequency than harvest bins made of injection molded plastic (189 moths emerged from wood compared with five from plastic). There was no statistical difference in the number of moths infesting bins that had been filled with infested fruit compared with bins left empty at harvest. This suggests that codling moth enter the bins during the time that the bins are in the orchard before harvest. Emergence of laboratory reared adult codling moth from wood bins placed in stacks was found to be prolonged compared with field populations. Temperature differences within the bin stacks accounted for this attenuated emergence pattern. Covering bin stacks with clear plastic accelerated codling moth development in the upper levels of the stack. Codling moth emergence patterns from plastic-covered stacks more closely coincided with male flight in field populations. This information could be important in developing a technique for neutralizing codling moth-infested bins, and in understanding how infested bins may influence pest management in fruit orchards that are located near bin piles. Implications for control of codling moth in conventional orchards and in those using mating disruption as the principal component of an integrated pest management system include increased numbers of treatments directed at areas affected by infested bins.     

Juvenile hormone and regulation of dichotomous spermatogenesis during the larval diapause of the codling moth

Spermatogenesis ceases during diapause and resumes after diapause. A possible causal relationship between the regulation of these phenomena and the fluctuations of the juvenile hormone titre connected with the diapause was examined in the codling moth. Spermatocyte lysis and spermatogenesis arrest are directly and reversibly related to these fluctuations. They are induced in the last-larval instar by sole application of the juvenoid Altosid to the penultimate-instar larvae predetermined not to enter diapause. Conversely, allatectomy of early last-instar larvae predetermined to diapause induces renewal of spermatogenesis and disruption of diapause. However, the continuation of the arrest of the spermatogenesis during diapause is not directly related to the presence of a high titre of juvenile hormone. The arrest extends throughout diapause which may continue for months, although no juvenile hormone could be detected in the species after 35 days of larval diapause.     

Life stage toxicity and residual activity of insecticides to codling moth and oriental fruit moth (Lepidoptera: Tortricidae)

The codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck), are two key pests of apple (Malus domestica Borkh.) in North Carolina. Growers extensively relied on organophosphate insecticides, primarily azinphosmethyl, for > 40 yr to manage these pests. Because of organophosphate resistance development and regulatory actions, growers are transitioning to management programs that use new, reduced-risk, and OP-replacement insecticides. This study evaluated the toxicity of a diversity of replacement insecticides to eggs, larvae, and adults, as well as an assessment of their residual activity, to codling moth and oriental fruit moth. Laboratory-susceptible strains of both species were used for all bioassays. Fresh field-harvested apples were used as a media for assessing the ovicidal activity of insecticides. For larval studies, insecticides were topically applied to the surface of lima bean-based diet, onto which neonates were placed. Toxicity was based on two measures of mortality; 5-d mortality and development to adult stage. Ovicidal bioassays showed that oriental fruit moth eggs were generally more tolerant than codling moth eggs to insecticides, with novaluron, acetamiprid, and azinphoshmethyl having the highest levels of toxicity to eggs of both species. In contrast, codling moth larvae generally were more tolerant than oriental fruit moth to most insecticides. Methoxyfenozide and pyriproxyfen were the only insecticides with lower LC50 values against codling moth than oriental fruit moth neonates. Moreover, a number of insecticides, particularly the IGRs methoxyfenozide and novaluron, the anthranilic diamide chlorantriliprole, and the spinosyn spinetoram, provided equal or longer residual activity against codling moth compared with azinphosmethyl in field studies. Results are discussed in relation to their use in devising field use patterns of insecticides and for insecticide resistance monitoring programs.     

Field evaluation of commercial formulations of the codling moth granulovirus: persistence of activity and success of seasonal applications against natural infestations of codling moth in Pacific Northwest apple orchards

Inundative applications of the codling moth (CM), Cydia pomonella L., granulovirus (CpGV), which target neonate larvae before or during initial entry into fruit, offer potential for selective control of this key pest. In field tests on apple we compared the persistence and efficacy of single applications of three CpGV products approved for organic orchards in North America. In addition, the success of repeated (2–14) applications of one product (Cyd-X) as a principal control measure for CM in apple orchards was monitored following operational use by cooperating growers at four separate locations. In the first study, an early season application of all products at label rates remained highly effective for the first 24 h (averaging 94% larval mortality relative to controls) and moderately effective after 72 h (averaging 71% mortality) during dry sunny conditions. Significant activity remained up to 14 days, suggesting prolonged survival of the virus in UV-protected locations, such as the calyx of fruit. A second application later in the season was slightly less effective. Data obtained from commercial sites provide circumstantial evidence for the effectiveness of well-timed CpGV applications against CM outbreaks. In all cases where first generation larvae were targeted beginning at egg hatch (≈250 degree days) and treated areas monitored (0.3–1.6 ha plots), fruit damage during the second larval generation was reduced or eliminated. Based on the number of live larvae recovered throughout the season, mortality rates remained high (80.3–100% across sites). The cumulative number of moths caught in pheromone-baited traps was reduced (66–94%) in the second flight. Data from tree bands placed to catch diapause-destined larvae indicated overwintering generations remained low in treated sites (0.18 larvae/band).     

Particle films for suppression of the codling moth (Lepidoptera: Tortricidae) in apple and pear orchards

Studies were conducted in 1997 and 1998 to evaluate the effects of three particle film formulations consisting of kaolin and adjuvants on neonate larvae, ovipositing adult females, and eggs of the codling moth, Cydia pomonella (L.). Neonate larval walking speed, fruit discovery rate, and fruit penetration rate on apple host plants coated with particle films were significantly lower than on host plants without particle films in laboratory assays. Females oviposited less on host plants covered with a particle film residue than on untreated plants in laboratory choice and no-choice tests. Hatch rate of codling moth neonate larvae was unaffected by particle films sprayed on host plants either before or after oviposition. Fruit infestation rates were significantly reduced on particle film-treated trees compared with untreated trees for both first- and second-generation codling moth in field trials in both apple and pear orchards. Particle films appear to be a promising supplemental control approach for codling moth in orchards where moth density is high, and may represent a stand-alone method where moth densities are lower.     

Adjusting the phenology model of codling moth (lepidoptera: tortricidae) in Washington State apple orchards

Studies were conducted with codling moth, Cydia pomonella L., to fit cumulative curves for the occurrence of injured fruits and male moth catches in sex pheromone-baited traps as a function of accumulated degree-days after the start of moth flight. Twelve data sets were collected from seven apple, Malus domestica Bordhausen, orchards in Washington State from 2003 to 2006. Cumulative data were grouped across years for orchards either treated with sex pheromone dispensers or untreated and fit to logistic equations for both the first and second generation. No significant differences were found for the cumulative curves of moth flight or egg hatch between pheromone-treated and untreated orchards; thus, these data were combined. These new logistic models for moth flight and egg hatch were compared with a widely used distributed-delay model originally developed in Michigan. The cumulative flight curves for the logistic and distributed-delay models were statistically different (slopes) for the first but not the second generation. Cumulative egg hatch in the logistic model was significantly different from the distributed-delay model (intercepts and slopes) for both generations. Most strikingly, the timing of 50% egg hatch during the first generation was delayed 100 DD in the logistic model. The potential impact of this change in the characterization of codling moth's phenology on the effectiveness of insecticide programs targeting eggs and newly eclosed larvae was examined. Possible explanations for this significant difference between the models are discussed.     

Comparative analysis of peach and pear fruit volatiles attractive to the oriental fruit moth,Cydia molesta

Cydia molesta is an important pest of peach and pear fruits late in growing season. We identified and quantified volatiles from immature and mature fruits of peach and pear using gas chromatography-mass spectrometry. Antennally, active compounds were identified by gas chromatography-electroantennogram detection and were further tested in the field. Consistent electroantennographic activity was obtained for nine compounds from headspace collections of the mature fruits of two peach and two pear varieties. Esters were the major components, but qualitative and quantitative differences were found among four odor profiles. Blends mimicking pear fruit volatiles were more attractive to both sexes than blends mimicking peach fruit volatiles in both orchards. Our finding indicated that mixtures mimicking peach and pear fruit volatiles attracted both females and males of C. molesta, and these host volatiles may also be involved in the host switch behavior from peach to pear in mid-late season.     

The influence of citrus fruit condition on egg laying by the false codling moth, Cryptophlebia leucotreta

The oviposition response of Cryptophlebia leucotreta (Meyrick) (Lepidoptera: Tortricidae) to healthy navel and Valencia orange, Citrus sinensis (L.), fruit was measured in experimental orchards at Nelspruit, eastern Transvaal, South Africa, and was compared with the response to prematurely ripened fruit and injured fruit. Both premature ripening and injury increased the number of eggs laid on these fruit. Damaged fruit was almost twice as attractive as ripe fruit if the number of eggs laid can be used as a measure of attraction. Large wounds were no more stimulating than small lesions. The quantity of stimulus was not statistically significant, yet five or ten treated fruit in a cluster led to more egg-laying per fruit than a single treated fruit. More eggs were observed on healthy fruit within 50 cm of clusters of treated fruit than on healthy fruit on different trees, but this effect was not statistically significant.

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Résumé La ponte de c. leucotreta Meyrick (Lep.; Tortricidae) sur oranges (Navel et Valencia) saines a été évaluée dans des vergers expérimentaux de Nelspruit à l'est du Transvaal, en Afrique du Sud. Elle a été comparée à la ponte observée sur des fruits prématurés ou endommagés. Ces deux dernières situations ont augmenté l'effectif d'ufs pondus sur les fruits; si le nombre d'ufs pondus est utilisé comme critère d'attraction, les fruits endommagés étaient presque deux fois plus attractifs que les autres. La taille des blessures est sans effet. Des fruits ont été artificiellement endommagés ou conduits prématurément à maturité avec un badigeon d'acide 2-chloréthylphos-phorique. Ces stimului n'ont pas eu d'effet cumulatif significatif; pourtant la ponte était plus importante sur des paquets de 5 ou 10 fruits artificiellement modifiés, que sur des fruits modifiés isolés. Une ponte plus importante a été observée sur des fruits sains à moins de 50 cm d'un groupe de fruits modifiés. Il est probable que des signaux visuels et olfactifs orientent la découverte du fruit par la tordeuse. Ces résultats suggèrent que les substances volatiles ont plus d'influence que la couleur ou la taille du fruit.La protection contre cet insecte devrait comprendre l'élimination des fruits mûris prématurément ou abîmés, mais il faudrait préciser si les fruits endommagés sont ou non découverts par hasard. La concentration des pontes sur et autour de ces fruits peut aussi réduire les pontes dans le reste du verger.

     

Multiple mating of male and female codling moth (Lepidoptera: Tortricidae) in apple orchards treated with sex pheromone

Studies were conducted with codling moth, Cydia pomonella L., to evaluate the mating status of male and female moths in apple, Malus domestica (Borkhausen), orchards treated with and without sex pheromone dispensers. Laboratory studies first examined the effect of multiple mating of male and female moths on female fecundity and egg fertility. Females that had mated three times had a significantly higher fecundity than singly mated moths. Sequential mating by male moths had no effect on the fecundity of female moths or egg fertility. However, male moth age did impact female fecundity, with significantly fewer eggs laid after mating with virgin 1- versus 3-d-old males. The mean size of the first spermatophore transferred by males was significantly larger than all subsequent spermatophores. Classifying spermatophores based on size was used in field sampling to categorize the mating status of the female's partner. The proportion of mated females with small spermatophores (partner had previously mated) was significantly higher in treated versus untreated orchards. The proportion of female moths caught in traps baited with pear ester that were virgin was low (相似文献   

Seasonal susceptibility of 'Bartlett' pears to codling moth (Lepidoptera: Tortricidae) infestation and notes on diapause induction

Seasonal susceptibility of 'Bartlett' pear, Pyrus communis L., to codling moth, Cydia pomonella (L.), infestation, successful completion of larval development after infestation, and the induction of C. pomonella diapause was studied from 1992 through 1995. The seasonal variation in C. pomonella infestation and larval survival were effected by changes in fruit maturity. In late May through mid-June, pears were hard and were not as successfully infested by C. pomonella and produced less larvae compared with fruit later in the season. In late June to mid-July, pears became more suitable for infestation and a greater percentage of the larvae completed their development. In late July through mid-August, pears were susceptible to infestation, but the larvae were less likely to successfully complete development than in the late June to mid-July period due to pear tissue breakdown. From mid-August through September, pears are unsuitable for infestation, and few larvae were produced. When fruit were infested with neonate larvae in late May and mature larvae emerged from the fruit in July, a low percentage of the larvae entered diapause. However, when fruit were infested with neonate larvae in early July and mature larvae emerged from the fruit in early August, the majority of the larvae entered diapause. When fruit were infested with neonate larvae in late July through September and mature larvae emerged from the fruit after mid-August, nearly all C. pomonella larvae had entered diapause.     

Evaluation of border sprays for managing the codling moth (Tortricidae: Lepidoptera) and the apple maggot (Tephritidae: Diptera) in Ontario apple orchards

The efficacy of two insecticide control programs for managing the codling moth, Cydia pomonella (L.), and the apple maggot, Rhagoletis pomonella (Walsh), were compared in the Georgian Bay, London, Niagara, and Quinte apple production areas of Ontario during 1995, 1996, and 1997. In the border spray program, an initial cover spray of organophosphorus insecticide was applied to eradicate codling moths that may have colonized a test plot during the previous growing season. Subsequent sprays were applied only to a four-tree-wide zone (approximately 20 wide) around the perimeter of the plot to control immigrating codling moths or apple maggots. In the cover spray program, all sprays of organophosphorus insecticide were applied to the entire plot. Apple maggot injury was significantly greater in border spray program plots than in cover spray program plots only during 1995 in the London production area. There was no significant difference in codling moth injury between border spray and cover spray plots in the four production areas during the three-year study. The elimination of cover sprays from border spray plots during July and August may have left the apple crop more susceptible to damage by second generation larvae of the obliquebanded leafroller, Choristoneura rosaceana (Harris), in the London production area during 1995. There was a trend of increasing codling moth injury from 1995 to 1997 in two border spray plots, and apple maggot injury was detected in these plots during the third year of the study.     

Direct sampling of resting codling moth (Lepidoptera: Tortricidae) adults in apple tree canopies and surrounding habitats

Field investigations were conducted to determine the resting locations of codling moth (Cydia pomonella [L.]) (Lepidoptera: Tortricidae) males and females in mating disrupted and nondisrupted apple (Malus domestica Borkh.) orchard plots. A custom-made sampling device, consisting of a leaf blower converted into a powerful vacuum, yielded 20-24% success in recovering marked moths, released in the tree canopy in orchards. Four collections each were made between 0900 and 1800 hours and 1800 and 2200 hours in 2005. Ninety-four moths were collected during the 1800-2200 hours samples. In mating disruption plots, 42% of females and 22% of males were found in the top third of the tree canopy (3.0-4.5m), 46% females and 43% males in the middle third (1.5-3.0m), and 12% female and 35% male in the lower third (0-1.5m). In nondisrupted plots 36.4% of females and 40% of males were in the top third of the canopy, 36.4% females and 52% males in the middle third, and 27.2% females and 8% males in the lower third of the tree canopy. Daylight vacuum sampling recovered only one female and two male moths from the top, four males from the middle and one male from the lower third of the tree canopy. Release-recapture studies of marked adult codling moths were conducted in 2006-2007 in screened tents to determine within orchard habitats for adult moths during 0900-1800 hours. Of moths recaptured, 14.6% of females and 13.5% of males were from the ground (herbicide strip and drive-row grass) and 32.9% of females and 24.6% of males were captured in the tree canopy 16-h post release, 17.4% of females and 3.4% of males from the ground and 26.5% of females and 38.2% of males in the tree 40-h post release, and 15.1% of females and 18.6% of males from the ground and 15.7 of females and 25.5% of males in the tree 64-h post release. Application of pyrethrum + PBO by using an orchard blast sprayer in 2007 resulted in the recapture of 28% and 37% of laboratory reared male and female moths, respectively, from trees during 0900-1800 h. Our results suggest that distributing pheromone dispensers throughout the tree canopy may be more effective than placing them in one location, such as near the tree crown.     

Toxicity and residual activity of methoxyfenozide and tebufenozide to codling moth (Lepidoptera: Tortricidae) and oriental fruit moth (Lepidoptera: Tortricidae)

A series of studies were conducted to examine the residual activity and toxicity of the ecdysone agonists tebufenozide and methoxyfenozide to codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck), in North Carolina apple systems. Methoxyfenozide exhibited greater activity than tebufenozide against codling moth eggs in dose-response bioassays, with a 4.5- and 5.3-fold lower LC50 value to eggs laid on fruit treated before or after oviposition, respectively. Oriental fruit moth eggs were 57- and 12-fold less sensitive to methoxyfenozide than were codling moth eggs on fruit treated before and after oviposition, respectively. Methoxyfenozide was effective in reducing larval entries of both codling moth and oriental fruit moth in field residual activity bioassays, exhibiting activity for at least 28 d after application. Residue breakdown on fruit was approximately 80% at 28 d after treatment for both methoxyfenozide and tebufenozide, with the most rapid residue decline (60%) occurring during the first 14 d after application. Two applications of methoxyfenozide applied at 14-d intervals provided better canopy coverage and higher residue levels than one application. Spray volume (683 versus 2,057 liters/ha) did not affect the efficacy of methoxyfenozide. Leaf and fruit expansion during the season was measured to determine potential plant-growth dilution effects on residual activity. There was very little increase in leaf area after mid May, but increase in fruit surface area over the season was described by a second order polynomial regression. Implications for codling moth and oriental fruit moth management programs are discussed.     

Comparative activity of baculoviruses against the codling moth Cydia pomonella and three other tortricid pests of tree fruit

The granulovirus of Cydia pomonella (L.) (CpGV) offers potential for selective control of codling moth. Two major limitations of CpGV are its narrow host range and lack of persistence in the orchard agroecosystem. The nucleopolyhedroviruses of the alfalfa looper Autographa californica (Speyer) (AcMNPV) and those of the celery looper Anagrapha falcifera (Kirby) (AfMNPV) have broad host ranges. Comparative assays of CpGV, AcMNPV, and AfMNPV against codling moth neonate larvae revealed a 54-93-fold greater susceptibility of codling moth to the granulovirus than to the two nucleopolyhedroviruses based on the LC(50) values for each virus. The LC(50)s for CpGV, AfMNPV, and AcMNPV were 32.7 capsules/mm(2), 1.77 x 10(3) occlusion bodies (OBs)/mm(2), and 3.05 x 10(3)OBs/mm(2), respectively. The LT(50) determined for AfMNPV using an approximate LC(95) of the virus against neonate larvae was 3.6 days. Histological examination of tissues in moribund codling moth larvae that had been treated with AfMNPV revealed the presence of nonoccluded and unenveloped virus rods in midgut tissue. Neither OBs nor signs of infection were detected in other tissues. The activity of AfMNPV was also evaluated in three other tortricid apple pests (obliquebanded leafroller, Choristoneura rosaceana (Harris); Pandemis leafroller, Pandemis pyrusana Kearfott; and the oriental fruit moth, Grapholitha molesta (Busck)). Codling and Oriental fruit moths were significantly more susceptible to AfMNPV than were the two leafroller species.