Alan L. Knight

A pear-derived kairomone with pheromonal potency that attracts male and female codling moth, Cydia pomonella (L.)

Abstract. Ethyl (2E, 4Z)-2,4-decadienoate, a pear-derived volatile, is a species-specific, durable, and highly potent attractant to the codling moth (CM), Cydia pomonella (L.), a serious pest of walnuts, apples, and pears worldwide. This kairomone attracts both CM males and virgin and mated females. It is highly attractive to CM in both walnut and apple orchard contexts, but has shown limited effectiveness in a pear orchard context. Rubber septa lures loaded with ethyl (2E, 4Z)-2,4-decadienoate remained attractive for several months under field conditions. At the same low microgram load rates on septa, the combined gender capture of CM in kairomone-baited traps was similar to the capture rate of males in traps baited with codlemone, the major sex pheromone component. The particular attribute of attracting CM females renders this kairomone a novel tool for monitoring population flight and mating–ovipositional status, and potentially a major new weapon for directly controlling CM populations.

Attractants from Bartlett pear for codling moth, Cydia pomonella (L.), larvae

Abstract. The alkyl ethyl and methyl esters of (2E,4Z)-2,4-decadienoic acid found in head-space samples of ripe Bartlett pear (Pyrus communis L.) stimulated a response from neonate larvae of the codling moth (CM), Cydia pomonella (L.), in both static-air Petri-plate and in upwind Y-tube and straight-tube olfactometer bioassays. In comparison with the known CM neonate attractant, (E,E)-α-farnesene, ethyl (2E,4Z)-2,4-decadienoate was attractive at 10-fold and 1,000-fold lower threshold dosages in the Petri-plate and in the Y-tube bioassays, respectively. Methyl (2E,4Z)-2,4-decadienoate was attractive to CM neonates in these bioassays at much higher doses than ethyl (2E,4Z)-2,4-decadienoate. Other principal head-space volatiles from ripe pear fruit and pear leaves, including butyl acetate, hexyl acetate, (Z)-3-hexenyl acetate, and (E)-β-ocimene, were not attractive to CM neonates. The potential uses of these pear kairomones for monitoring and control of CM in walnuts and apple are discussed.

Particle Films for Suppression of the Codling Moth (Lepidoptera: Tortricidae) in Apple and Pear Orchards

Abstract Studies were conducted in 1997and 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.

Effects of a Kaolin-Based Particle Film on Obliquebanded Leafroller (Lepidoptera: Tortricidae)

Abstract Studies were conducted in 1997 to evaluate the effects of the kaolin-based particle film formulation M96–018 on adults, eggs, and larvae of the obliquebanded leafroller, Choristoneura rosaceana (Harris). Particle film treatments significantly reduced female longevity, mating success, and number of egg masses oviposited compared with moths on untreated apple leaves in sleeve-cage and screen-cage tests. No differences in mating success or oviposition were caused by the application rates and coverage density of M96–018 on foliage. Females avoided ovipositing on particle film-treated leaves in choice tests. Larval hatch was not affected by topical application or residual exposure to M96–018. Larval weight gain and pupal weight were significantly reduced and larval mortality increased in no-choice feeding tests with M96–018. In choice tests, larvae preferred to feed on untreated leaf surfaces. The negative effects on larval development and survivorship on M96–018-treated foliage did not differ across a fourfold difference in spray application rate. A significant reduction in the number of infested shoots was found in orchard trials when M96–018 was applied before bud break in late March compared with untreated trees. No reductions in larval densities were found compared with an untreated control following prebloom and postbloom applications.

Monitoring codling moth (Lepidoptera: Tortricidae) in apple with blends of ethyl (E, Z) -2,4-decadienoate and codlemone

Abstract Studies evaluated blends of the pear-derived kairomone ethyl (E, Z)-2,4-decadienoate and codlemone, loaded in gray halobutyl septa, as attractants for adult codling moth, Cydia pomonella L. Studies were conducted in apple orchards, Malus domestica Borkhausen, treated with or without sex pheromone dispensers for mating disruption (MD). Septa were loaded with either one or both compounds at rates of 0.0, 0.3, and 3.0 mg pear ester and 0.0 and 3.0 mg codlemone in the first series of tests. Traps baited with a 3.0/3.0-mg blend caught significantly more males and total number of codling moths than traps baited with either compound alone in both types of orchards. Traps baited with two lures loaded individually with pear ester (3.0 mg) and codlemone (3.0 mg) caught significantly fewer males and total moths than traps baited with the dual lure (3.0/3.0 mg). The addition of 3.0 mg codlemone to pear ester did not significantly affect the capture of female moths. However, increasing the loading of pear ester from 0.3 to 3.0 mg in the dual lure significantly increased female moth catch in the untreated orchard but not in the sex pheromone MD orchard. Increasing the loading of pear ester to 20.0 mg in a dual lure with 3.0 mg codlemone significantly increased total codling moth catch compared with a 3.0 mg codlemone lure, but female catch was significantly lower compared with traps baited with a 3.0 mg pear ester lure. Adding a 3.0 mg pear ester lure to traps baited with a 42.0 mg sex pheromone lure significantly reduced male moth catch compared with the sex pheromone lure alone but did not reduce the catch of female moths compared with traps baited with a 3.0 mg pear ester lure alone.

This is not an Apple-Yeast Mutualism in Codling Moth

The larva of codling moth Cydia pomonella (Tortricidae, Lepidoptera) is known as the worm in the apple, mining the fruit for food. We here show that codling moth larvae are closely associated with yeasts of the genus Metschnikowia. Yeast is an essential part of the larval diet and further promotes larval survival by reducing the incidence of fungal infestations in the apple. Larval feeding, on the other hand, enables yeast proliferation on unripe fruit. Chemical, physiological and behavioral analyses demonstrate that codling moth senses and responds to yeast aroma. Female moths are attracted to fermenting yeast and lay more eggs on yeast-inoculated than on yeast-free apples. An olfactory response to yeast volatiles strongly suggests a contributing role of yeast in host finding, in addition to plant volatiles. Codling moth is a widely studied insect of worldwide economic importance, and it is noteworthy that its association with yeasts has gone unnoticed. Tripartite relationships between moths, plants, and microorganisms may, accordingly, be more widespread than previously thought. It, therefore, is important to study the impact of microorganisms on host plant ecology and their contribution to the signals that mediate host plant finding and recognition. A better comprehension of host volatile signatures also will facilitate further development of semiochemicals for sustainable insect control.

Tebufenozide Targeted Against Codling Moth (Lepidoptera: Tortricidae) Adults, Eggs, and Larvae

Abstract The effectiveness of tebufenozide applied against the adult, egg,and larvae of codling moth, Cydia pomonella (L.), wasevaluated. Significant reductions in fecundity and egg hatch occurredafter 1-h and 24-h exposures of females and 24-h exposures ofmales-only to residues in plastic plates. A significant reduction inegg hatch was also found after a 1-h exposure of males. The ovicidaleffects of tebufenozide in field trials did not significantly differfor eggs laid on residues or treated topically. Corrected egg mortalityexceeded 95% for cohorts laid <130 degree-days after sprays wereapplied. Fecundity and egg hatch were measured after either a 24-hexposure of moths or a 10-d exposure of moths and eggs on apple trees.Significant reductions in both fecundity and fertility occurredcompared with an untreated control up to 7 d in the 24-h assaysand accounted for 60–70% fewer larvae produced per mated female. Themean numbers of larvae produced per mated female after the 10-dexposure were reduced 100–75% in assays started on day 0–21 afterthe spray application compared with the untreated control. Fecunditywas significantly reduced for 7 d and egg hatch was reduced forthe entire 21-d test period in these trials. Residues had a 14-dhalf-life on apple foliage. Residues applied to foliage or to foliageand fruit did not significantly increase the proportion of uninjuredfruit compared with the untreated control in bioassays where neonateswere placed on foliage 10 cm from fruit. However, the proportion ofinjured fruits with shallow stings versus deep entries was higher onthe treated versus the untreated plants. Field applications oftebufenozide reduced fruit injury >90% when applied early duringemergence. Plots treated after the beginning of egg hatch had a largerproportion of injured fruits with shallow larval feeding.

Vertical distribution of codling moth adults in pheromone‐treated and untreated plots

The vertical distribution of codling moth, Cydia pomonella (L.) within pheromone‐treated and untreated apple and pear orchard canopies was determined using tethered virgin females, unbaited sticky traps, and blacklight observation of released moths. Mating of virgin females tethered at various heights in untreated orchard canopies increased with placement height from 1–4 m. Application of pheromone dispensers for mating disruption at 2 and 4 m above the ground greatly decreased mating. Greatest capture of males and females on unbaited sticky traps occurred at mid‐ and upper‐canopy heights. Total capture of males and females in pheromone‐treated plots was not statistically different than in untreated plots. The percentage of mated females captured on sticky traps did not vary with trap height or pheromone treatment. Released moths marked with fluorescent powder and observed at dark with a blacklight indicated that moths are primarily distributed high in the canopy. However, males shifted to a position lower in the canopy when pheromone dispensers were placed 2.1 m above the ground. Results suggest that pheromone dispensers be placed in the upper canopy for optimal disruption of codling moth mating.

Neural coding merges sex and habitat chemosensory signals in an insect herbivore.

Understanding the processing of odour mixtures is a focus in olfaction research. Through a neuroethological approach, we demonstrate that different odour types, sex and habitat cues are coded together in an insect herbivore. Stronger flight attraction of codling moth males, Cydia pomonella, to blends of female sex pheromone and plant odour, compared with single compounds, was corroborated by functional imaging of the olfactory centres in the insect brain, the antennal lobes (ALs). The macroglomerular complex (MGC) in the AL, which is dedicated to pheromone perception, showed an enhanced response to blends of pheromone and plant signals, whereas the response in glomeruli surrounding the MGC was suppressed. Intracellular recordings from AL projection neurons that transmit odour information to higher brain centres, confirmed this synergistic interaction in the MGC. These findings underscore that, in nature, sex pheromone and plant odours are perceived as an ensemble. That mating and habitat cues are coded as blends in the MGC of the AL highlights the dual role of plant signals in habitat selection and in premating sexual communication. It suggests that the MGC is a common target for sexual and natural selection in moths, facilitating ecological speciation.

Factors Affecting the Differential Capture of Male and Female Codling Moth (Lepidoptera: Tortricidae) in Traps Baited with Ethyl (E, Z)-2,4-Decadienoate

Abstract Studies were conducted in apple to evaluate factors that differentially affect the catch of male and female codling moth, Cydia pomonella L., in traps baited with ethyl (E, Z)-2,4-decadienoate (pear ester). We examined the time of moth capture in the diel cycle and the recapture rates of marked moths in sex pheromone mating disruption (MD) and untreated orchards. The attractiveness of pear ester–baited traps was compared among five apple cultivars. Experiments also assessed the influence of trap height, the distance of the trap from sex pheromone dispensers, proximity of foliage surrounding the trap, trap size, and proximity of adjacent clean and codling moth–injured fruit on moth captures. The responses of male and female moths significantly differed in response to many of these factors. For example, the time of peak female capture occurred earlier than for males. A higher proportion of recaptured, marked moths were females in MD versus untreated orchard plots. Significantly more male but not female moths were caught in traps placed high versus low in the tree canopy. Traps placed on the perimeter of the canopy caught significantly more female moths than traps placed within the canopy and surrounded by foliage. Smaller trap surfaces caught significantly more males than females. Traps placed adjacent to uninjured fruit caught significantly more females than traps placed away from fruit. No differences occurred between sexes in response to other factors: significantly higher counts of both sexes occurred in blocks of ‘Granny Smith’ versus four other apple cultivars; recapture rates of marked moths were not different at release points ranging from 10 to 50 m for either sex; and trap placement relative to MD dispensers or injured versus uninjured fruits was not a significant factor affecting moth catches or their sex ratio. Effective monitoring for either or both sexes of codling moth should consider standardizing these factors. Lure and kill strategies should include factors that optimize the captures of female moths.