Control of Cydia pomonella L. and Cydia molesta (Busck) (Lepidoptera Tortricidae) in pome-fruit orchards with Ecodian sex pheromone dispensers

A mating disruption approach using high densities of pheromone dispensers, has been recently proposed for codling moth, Cydia pomonella (L.), and oriental fruit moth, Cydia molesta (Busck.), (Lepidoptera Tortricidae), control. Ecodian Star dispensers, made of low-cost biodegradable material and easy to apply, were formulated with 10 mg of codlemone (E8,E10-12OH) and 10 mg of grapamone (Z8-12OH) and placed at a rate of 1,400-2,000 dispensers/ha. The pheromone release rates from new and field aged dispensers were evaluated by hexane extraction of the residual attractant (indirectly) and gas-chromatographic analysis. The release rate of field-aged dispensers decreased over time with a good linearity; they released a significant amount of synthetic sex pheromones over the entire season. Dispensers elicited close-range approaches of codling moth males in wind tunnel irrespective of their age. Field trials carried out from 2003 to 2004 confirmed the efficacy of Ecodian Star dispensers for codling moth and oriental fruit moth control, regardless the size of the treated area. Our results demonstrate that Ecodian dispensers achieved a good level of activity and longevity over the season. The potential of this strategy for the control of the moths is discussed.     

Costs of insecticide resistance in Cydia pomonella (Lepidoptera: Tortricidae)

The obvious benefits associated with insecticide resistance for pest species may come at a cost to other life-history traits. In this study, we compared the larval and pupal developmental times, pupal mass wing surface area and wing fluctuating asymmetry (FA) in insecticide resistant and control strains of codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), collected from apple (Malus spp.) orchards in central Canada. Resistant strains had significantly longer larval developmental times and lower pupal masses compared with the susceptible strain. Although the forewings of resistant moths were smaller in resistant than control strain, no difference in wing FA was detected. Longer developmental times could increase exposure time to natural enemies, and reduced adult size could affect longevity and total reproductive output.     

Mating compatibility among populations of codling moth Cydia pomonella Linnaeus (Lepidoptera: Tortricidae) from different geographic origins

The codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) is a serious pest of pome fruit worldwide and the sterile insect technique (SIT) provides an environmentally acceptable approach for its control. As the pest is present in both the southern and northern hemispheres it would be possible for a rearing facility in the northern hemisphere to supply sterile moths to an SIT programme in the southern hemisphere during the northern winter and vice versa. This could greatly improve the economics of moth production and the running costs of rearing facilities. However in order to develop this concept, it is important to assess if populations of codling moth from different geographical regions share mating compatibility. Twelve different laboratory and field populations from both hemispheres were sampled and field cage bisexual mating compatibility tests were carried out between selected combinations. The index of sexual isolation (ISI) and the female and male relative performance index (FRPI and MRPI, respectively) were calculated for each mating combination. In only two of the combinations was there a slight but significant deviation from random mating. There were also some significant differences in mating duration between the homotypic matings and the duration of a particular homotypic mating seemed to depend on the origin of the other population in the cage. It was concluded that there exist no barriers to mating between populations of codling moth from many parts of the world and that it would be feasible for sterile moths to be shipped from one rearing facility to SIT programmes in other parts of the world.     

Genetic analysis of Cydia pomonella (Lepidoptera: Tortricidae) populations with different levels of sensitivity towards the Cydia pomonella granulovirus (CpGV)

Microsatellite (simple sequence repeats, SSR) and mitochondrial DNA markers were used to assess the structure of European codling moth populations showing different levels of susceptibility towards one of the most important biocontrol agents used in apple production, the Cydia pomonella granulovirus CpGV-M. In 638 C. pomonella individuals from 33 different populations a total of 92 different alleles were scored using six SSR loci. The global estimate of genetic differentiation for all 33 populations was not significantly different from zero, thus indicating a lack of genetic differentiation. AMOVA analysis revealed a very weak but significant variance among C. pomonella populations from different geographic regions, however, no significant variation was evident between CpGV-M resistant or susceptible C. pomonella populations. Sequence analysis of a fragment of the cytochrome oxidase subunit 1 in eight C. pomonella populations resulted in 27 haplotypes, which were grouped in two distinct clusters. Again, no genetic differentiation between CpGV-M resistant and susceptible codling moth populations was detectable. In addition, Structure analysis using microsatellites and association tests with mtDNA haplotypes found neither population-level nor individual correlations associated with CpGV-M resistance. Accordingly, this lack of population structure does not allow discriminating between one or several, separate origins of CpGV-M resistance.     

Rapid assessment of the sex of codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) eggs and larvae

Two different methods were tested to identify the sex of the early developmental stages of the codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) with a WZ/ZZ (female/male) sex chromosome system. First, it was shown that the sex of all larval stages can be easily determined by the presence or absence of sex chromatin, which is formed by the female‐specific W chromosome in interphase nuclei. This trait can also be used to identify the sex of newly hatched larvae but it does require care and accuracy. Secondly, a new sexing technique was developed based on a molecular marker of the codling moth W chromosome. Flanking regions of an earlier described W‐specific sequence (CpW2) were isolated and sequenced and a 2.74 kb sequence (CpW2‐EcoRI), specific for the W chromosome, was obtained. Several PCR tests were conducted, which confirmed that the CpW2‐EcoRI sequence is a reliable marker for the sex identification in codling moth samples of different geographical origin. In addition, a fragment of a codling moth gene, period (Cpper) was isolated and sequenced. Results of southern hybridization of the Cpper probe with female and male genomic DNA suggested that the Cpper gene is located on the Z chromosome. Then a multiplex PCR assay was developed, which co‐amplified the CpW2‐EcoRI sequence to identify the W chromosome and the Z‐linked Cpper sequence, which served as a positive control of accurate processing of tested samples. The multiplex PCR provides an easy and rapid identification of the sex of embryos and early larval instars of the codling moth.     

Responses to sex pheromone and plant odours by olfactory receptor neurons housed in sensilla auricillica of the codling moth, Cydia pomonella (Lepidoptera: Tortricidae)

Antennal olfactory receptor neurons located in a limited number of two types of sensilla auricillica, the rabbit-eared shoehorn and the regular shoehorn, located on the 5-30 flagellomere of the codling moth, Cydia pomonella, antenna were screened for selectivity to 11 plant compounds, the major sex pheromone component, three minor pheromone components and one behavioural antagonist. Both types of sensilla housed at least three neurons characterised by different action potential amplitudes. Neurons in both males and females responded to the plant compounds, ethyl (E,Z)-2,4-decadienoate, (+/-)-linalool, (E)-ss-farnesene, hexanol, (Z)-3-hexenyl acetate, 4,8-dimethyl-1,3,(E)7-nonatriene, nonanol, the major pheromone component codlemone [(E,E)-8,10-dodecadienol] and the minor pheromone component tetradecanol. Additionally, (E,E)-alpha-farnesene and (Z)-3-hexenol elicited responses specifically in female neurons, whereas (E,E)-farnesol elicited a specific response in a male neuron. Neurons responded to 1-3 odorants, with sometimes overlapping response spectra. A scanning electron microscopic study of the antennae of both sexes supported an earlier study, apart from that long s. trichodea were present in a wreath at the proximal margin of the flagellomere and in addition evenly distributed over the remaining surface, and a previously non-described sensillum type with external basiconic features was revealed, distributed on the proximal and medial region of the flagellomeres.     

Insecticidal resistance and cross-resistance in populations of Cydia pomonella (Lepidoptera: Tortricidae) in central Europe

Insecticide bioassays were used to investigate resistance of Cydia pomonella (L.) (Lepidoptera: Tortricidae) to insecticides with various types of active ingredients. The efficacy baselines of selected insect growth regulators (fenoxycarb), insect growth inhibitors (diflubenzuron and teflubenzuron), organophoshorous insecticides (phosalone), and neonicotinoids (thiacloprid) against the eggs and first and fifth instars of sensitive laboratory strains of codling moth were determined. According to concentration-mortality baseline, 50% lethality concentration values and 90% lethality concentration values were determined for all the tested insecticides. The lethal concentration ratio quantified the relation between the efficacy of selected insecticides against fifth instars found by topical application and against first instars found by diet-treated bioassay. No difference was detected when the efficacy of technical grade diflubenzuron diluted in tetrahydrofuran and diflubenzuron in the formulated product Dimilin 48 SC diluted in water was compared. However, just before the application of insecticide, the integument of larvae must be treated with acetone. Two bioassays were used to monitor the resistance of codling moths collected in 2003-2005 in two apple (Malus spp.) orchards with different intensities of chemical control. Resistance ratios (RRs) to the tested insecticides were determined for both field populations of codling moth. For the population of codling moth from a commercial apple orchard in Velké Bílovice, cross-resistance to fenoxycarb, teflubenzuron, and phosalone was detected after the topical application of insecticides to fifth instars. The population of codling moth from Prague-Ruzyne was slightly resistant to phosalone and teflubenzuron. No resistance to diflubenzuron was detected in either tested population.     

Mating disruption of codling moth Cydia pomonella with high densities of Ecodian sex pheromone dispensers

A mating disruption approach using high densities of pheromone dispensers, has recently been proposed for controlling codling moth, Cydia pomonella (L.) (Lep., Tortricidae). Ecodian® CP dispensers, made of low‐cost biodegradable material and easy to apply, were formulated with 10 mg of codlemone and placed at a rate of 1400–2000 dispensers/ha. Seasonal dispenser performance was evaluated using different methods. The release rate of new Ecodian dispensers, measured directly by solid‐phase micro‐extraction (SPME), was significantly higher than that of the standard monitoring lure. The release rate of field‐aged dispensers decreased over time; it was comparable with that of the standard monitoring lure after 55–90 days of field exposure and significantly lower beyond. Electroantennographic (EAG) recordings showed that field‐aged dispensers strongly stimulated virgin male moths’ antennae. Dispensers elicited close‐range approaches in wind tunnel irrespective of their age. Traps baited with aged Ecodian CP dispensers captured males throughout the season. Our results demonstrate that Ecodian dispensers achieved a good level of activity and longevity over the season. Field trials carried out from 2002 to 2004 confirmed the efficacy of Ecodian CP dispensers for codling moth control, regardless of the size of the treated area. The potential of this strategy for the control of C. pomonella is discussed.     

Gene flow among Cydia pomonella (Lepidoptera: Tortricidae) geographic and host populations in South Africa

Information on gene flow among geographic and host populations of C. pomonella (L.) (Lepidoptera: Tortricidae) in South Africa is lacking, despite the importance of these measures for the success of control practices such as chemical control and sterile insect release, which are affected by the amount of gene flow among populations. Therefore, populations collected from nine geographically distant regions in South Africa from apples, pears, and stone fruit were compared using amplified fragment length polymorphism with five selective primer pairs. Results showed that although populations from different hosts were not genetically differentiated, significant evidence for population substructure was apparent between geographic populations. Over local scales, it was possible to distinguish between populations collected from orchards situated <1 km apart. These results suggest that although extensive gene flow occurs among populations from different hosts, gene flow among local geographic C. pomonella populations may be limited and is explained in terms of limited moth flight, the relative isolation of pome fruit production areas, and the absence of wild hosts.     

Rapid thermal responses and thermal tolerance in adult codling moth Cydia pomonella (Lepidoptera: Tortricidae)

In order to preserve key activities or improve survival, insects facing variable and unfavourable thermal environments may employ physiological adjustments on a daily basis. Here, we investigate the survival of laboratory-reared adult Cydia pomonella at high or low temperatures and their responses to pre-treatments at sub-lethal temperatures over short time-scales. We also determined critical thermal limits (CTLs) of activity of C. pomonella and the effect of different rates of cooling or heating on CTLs to complement the survival assays. Temperature and duration of exposure significantly affected adult C. pomonella survival with more extreme temperatures and/or longer durations proving to be more lethal. Lethal temperatures, explored between −20 °C to −5 °C and 32 °C to 47 °C over 0.5, 1, 2, 3 and 4 h exposures, for 50% of the population of adult C. pomonella were −12 °C for 2 h and 44 °C for 2 h. Investigation of rapid thermal responses (i.e. hardening) found limited low temperature responses but more pronounced high temperature responses. For example, C. pomonella pre-treated for 2 h at 5 °C improved survival at −9 °C for 2 h from 50% to 90% (p < 0.001). At high temperatures, pre-treatment at 37 °C for 1 h markedly improved survival at 43 °C for 2 h from 20% to 90% (p < 0.0001). We also examined cross-tolerance of thermal stressors. Here, low temperature pre-treatments did not improve high temperature survival, while high temperature pre-treatment (37 °C for 1 h) significantly improved low temperature survival (−9 °C for 2 h). Inducible cross-tolerance implicates a heat shock protein response. Critical thermal minima (CTmin) were not significantly affected by cooling at rates of 0.06, 0.12 and 0.25 °C min⁻¹ (CTmin range: 0.3-1.3 °C). By contrast, critical thermal maxima (CTmax) were significantly affected by heating at these rates and ranged from 42.5 to 44.9 °C. In sum, these results suggest pronounced plasticity of acute high temperature tolerance in adult C. pomonella, but limited acute low temperature responses. We discuss these results in the context of local agroecosystem microclimate recordings. These responses are significant to pest control programmes presently underway and have implications for understanding the evolution of thermal tolerance in these and other insects.     

Attract and kill for codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) control in Syria

The possibility of controlling the codling moth Cydia pomonella (Linnaeus) using an attract and kill approach as an alternative to chemical sprays with contact insecticides was investigated in widely separated orchards. The results of a 4‐year study have shown that, using an attract and kill approach, three applications/season kept infestation rates in treated orchards below the economic injury level except in one with a too high codling moth population density. The mean number of male codling moths/trap/week in attract and kill‐treated orchards was much lower in comparison with control orchards which were treated with the usual cover sprays of insecticides. The results also showed that the efficacy of attract and kill under orchard conditions decreased with time and the relationship between time effect and codling moth death rate was very strong. These data indicate that the attract and kill technique applied at a rate of three application per season resulted in good control of codling moth in well managed orchards in Syria.     

Fruit Bins Washed with Steinernema carpocapsae (Rhabditida: Steinernematidae) to Control Cydia pomonella (Lepidoptera: Tortricidae)

A bin washing apparatus (drencher) was used to treat late-instar codling moth, Cydia pomonella Linnaeus-infested wooden fruit bins with the entomopathogenic nematode Steinernema carpocapsae . Sentinel late-instar codling moth larvae were placed in strips of wood, made from dismantled bins, that were subsequently screwed into the corners of real bins before treatment. Pre-soaking the bins with water prior to treatment and covering the bins with a plastic tarp post-treatment, to maintain a high humidity, significantly increased sentinel codling moth mortality. Treatment for 1 min with 50 S. carpocapsae infective juveniles mL -1 water resulted in more than 80% mortality over 6 h in which the nematodes were continuously pumped through the drencher. The temperature of the water in the bin washer was ≤15°C and the chlorine in the city water was too low to harm the nematodes. The key disadvantage of washing the bins was the labour involved. It may be possible to reduce post-treatment holding time and increase codling moth mortality by holding the bins at a higher temperature post-treatment, however this parameter was not included in the study. The presence of the codling moth granulosis virus within the larvae did not influence the nematode-induced codling moth mortality over a range of concentrations and two temperatures in laboratory trials.     

Long flights in Cydia pomonella L. (Lepidoptera: Tortricidae) measured by a flight mill: influence of sex, mated status and age

Abstract. The flight capacity of Cydia pomonella L. (Lepidoptera: Tortricidae) was measured in the laboratory by using computer-linked flight mills. Codling moths showed a large variation in flight capacity between individuals. We defined arbitrarily a longest single flight (LSF) of more than 5 km as an index for long-flyers. About 16.7% of virgin and 10.0% of mated males and 20.0% of virgin and 7.4% of mated females undertook such flights. Based on the LSF and the total distance flown (TDF^we concluded that males and females have little or no difference in flight capacity and that both the within-and between-habitat flights are similar in number and magnitude for both sexes. In the field, females are therefore potentially able to undertake flights of up to 11 km, as reported for males by other authors. This ability was highest at ages of 2–7 days after emergence, i.e. the first third of their lifetime, for virgin and mated male moths and for virgin female moths. Mated females showed peak flight capacity between 1 and 3 days after eclosion, which corresponded with the major egg-laying period. Few long flights were undertaken before oviposition. These findings do not agree with the oogenesis flight syndrome described by other authors, and this theory is believed not to apply to C.pomonella. Our laboratory results are discussed in relation to field experiments in general and hypotheses are developed about the significance of long-flyers for this species.     

Effects of carbaryl and cyhexatin on survival and reproductive behaviour of Cydia pomonella (Lepidoptera: Tortricidae)

The effects of carbaryl, an insecticide and an abscission agent, and cyhexatin, an acaricide, on the survival, reproductive behaviour and subsequent egg hatch and larval migration of the codling moth, Cydia pomonella L., were investigated under laboratory conditions. Dilution series starting with the concentration recommended for high volume application in the field were evenly sprayed in plastic cups. Depending on the concentration used, both pesticides resulted in high adult mortality, males being more susceptible. Although the total number of the eggs laid by C. pomonella females was significantly reduced in most treatments, the females exposed to different residues of carbaryl laid significantly more eggs during the first 24 h of exposure. This was not the case for cyhexatin. While in all treatments almost 50% of the eggs were laid on the side of the cups, the spatial distribution of the eggs laid under the lid and on the floor was concentration dependent. With one exception, continuous exposure of the moths to carbaryl significantly reduced the number of spermatophores per female. Less than one spermatophore per female was transferred at the highest four concentrations of carbaryl and the highest three concentrations of cyhexatin; whereas, the number of spermatophores per female amounted to about four per female for the other treatments. In contrast to carbaryl, which exhibited a high ovicidal effect at all concentrations, the ovicidal activity of cyhexatin was low. This was manifested in a high rate of egg hatch and the extent of embryonic development in most of the treatments. Furthermore, while carbaryl killed the newly-hatched larvae at all concentrations, cyhexatin acted as a larvicide at the highest two concentrations only.     

Control of Lobesia botrana (Lepidoptera: Tortricidae) by biodegradable ecodian sex pheromone dispensers

Mating disruption with a high density of sex pheromone dispensers is a new strategy recently developed for the control of the moth Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae). Ecodian LB dispensers, made of low-cost biodegradable material, were formulated with 10 mg of (E,Z) -7,9-dodecadienyl acetate and placed at a rate of 1,600 dispensers per ha. Seasonal dispenser performances were studied using different methods. The female attractiveness disruption and the efficacy of the method were evaluated in the field. The release rates of field-aged Ecodian LB dispensers, measured directly by solid phase microextraction, was comparable with that of the standard monitoring lure after 50-60 d of field exposure and significantly lower beyond 60 d; however, at the end of the season, it was approximately 46 times higher than that of a calling L. botrana female. Electroantennographic recordings showed that dispensers of different field age strongly stimulated male antennae. In a wind tunnel test, dispensers elicited close-range approaches and direct source contacts irrespective of their age. In fields treated with Ecodian dispensers the attractiveness of traps lured with calling females and monitoring baits was significantly reduced. Our data suggest that Ecodian dispensers are active sources of pheromone throughout the season. The efficacy of Ecodian strategy for L. botrana control was comparable with standard mating disruption and curative insecticides.     

Thermal conditioning of fifth-instar Cydia pomonella (Lepidoptera: Tortricidae) affects HSP70 accumulation and insect mortality

Abstract.  Levels of HSP70 protein of fifth-instar codling moth [ Cydia pomonella (L.) (Lepidoptera: Tortricidae)] are determined after conditioning at 35 °C for different times and also after recovery at 22 °C. Protein samples from larvae conditioned for different times are separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis electrophoresis. Sub-lethal thermal conditioning at 35 °C for 40 min, 2, 6 and 18 h induces new protein bands in the extracts from treated codling moth larvae. Immunodetection with an antibody to a heat-inducible HSP70 indicates a stronger reaction after 35 °C for 2, 6 and 18 h than after 35 °C for 40 min or control and, during the recovery period at 22 °C, the level of heat shock protein decreases. Conditioning of fifth-instar codling moths at 35 °C also induces thermotolerance in the insects and necessitates longer times at a lethal temperature to ensure mortality. Thermotolerance is correlated with the accumulation of heat inducible HSP70 protein.     

Identification of a four-component sex pheromone blend in Bonagota cranaodes (Lepidoptera: Tortricidae)

Analysis of sex pheromone glands of the apple leafroller Bonagota cranaodes Meyrick by gas chromatography coupled with mass spectrometry or electroantennographic detection showed the presence of 14 structurally related acetates and alcohols of the chain length 10-18, including the main pheromone component (E,Z)-3,5-dodecadienyl acetate (E3,Z5-12Ac). Male antennae responded to the main compound, its Z,Z isomer, (E,Z) -3,5-tetradecadienyl acetate (E3,Z5-14Ac), and the monoenes (Z)-5-dodecenyl acetate (Z5-12Ac) and (Z)-9-hexadecenyl acetate (Z9-16Ac). Traps baited with a four-component blend of E3,Z5-12Ac, Z5-12Ac, E3,Z5-14Ac, and Z9-16Ac in a 100:5:5:100 ratio were significantly more attractive than the main compound alone. This improved trap lure is more suitable for monitoring population densities of B. cranaodes, and for detection of the onset of the seasonal flight period. A more complete pheromone blend is of importance also with respect to current attempts to develop mating disruption for control of this major pest of apple in Brazil.     

Mating disruption of Lobesia botrana (Lepidoptera: Tortricidae): effect of pheromone formulations and concentrations

The reluctance of Israeli vine growers to adopt the mating disruption technique to control the moth Lobesia botrana Den. & Schiff. has been attributed to the high cost of this method compared with that of traditional insecticide control. In this study, we tested the possibility of reducing the cost, first by testing different pheromone formulations (and thus open the market for competition) and second by reducing the pheromone concentration used in vineyards. Comparisons were made between two pheromone formulations--Shin-Etsu (Tokyo, Japan) at 165 g/ha and Concep (Sutera, Bend, OR) at 150 g/ha--and between two concentrations of Shin-Etsu, 165 and 110 g/ha. Pheromone dispensers were placed at the onset of the second moth generation. Comparison of the numbers of clusters infested with eggs and larvae of L. botrana showed no significant differences in the performance, either between the two formulations, or between the two tested concentrations. The results suggest that 1) the two formulations are equally effective, and 2) a low pheromone concentration is sufficient to maintain good control of small populations of L. botrana. However, when the population is high, pest control efficacy is not improved by increasing the pheromone concentration. Therefore, in the interest of reducing the relatively high cost of mating disruption, we emphasize that increasing the pheromone concentration does not provide improved control of high populations of L. botrana. The cost of mating disruption can be diminished by reducing the applied pheromone concentration and by using the least expensive pheromone formulations     

Comparison of fatty acid composition in total lipid of diapause and non-diapause larvae of Cydia pomonella （Lepidoptera： Tortricidae）

Seasonal changes in the fatty acid composition of the total lipid extracted from the whole body of Cydia pomonella L. larvae were determined by gas chromatography. The six most abundant fatty acids in both non-diapause and diapause larvae of codling moth were oleic （35%-39%）, palmitic （23%-33%）, linoleic （16%-30%）, palmitoleic （5%-10%）, stearic （1.5%-3.0%） and linolenic acids （1.0%-2.5%）. This represents a typical complement of Lepidopteran fatty acids. The fatty acid composition of total lipid of C. pomonella larvae was related to diapause. In similarity to most other reports, the proportion of unsaturated fatty acids increased in diapause initiation state. The total lipid of diapause larvae contained more linoleic acid （25.8% vs. 16.1%） and less palmitic acid （24.7% vs. 33.4%）, than that of non-diapause larvae. The weight percentage of linoleic acid （C 18：2） increased from 16% to 26% from early-August through early-September during transition to diapause, while palmitic acid （C16：0） decreased from 33% to 25% at the same time. These changes resulted in an increase in the ratio of unsaturated to saturated fatty acids （UFA/SFA） from 1.72 in non-diapause larvae to 2.63 in diapause larvae.     

Rainfastness of a microencapsulated sex pheromone formulation for codling moth (Lepidoptera: Tortricidae)

The rainfastness of a microencapsulated sex pheromone formulation for codling moth, Cydia pomonella (L.), was evaluated in a series of laboratory experiments with detached apple, pear, and walnut leaves. Increasing the intensity and duration of simulated rainfall significantly increased the removal of microcapsules from both the top and bottom of apple leaves. The removal of microcapsules was significantly higher from the top versus the bottom of leaves at all rates tested. Leaf angle was a significant factor affecting the removal of microcapsules from the top surface of apple leaves with fewer microcapsules removed, because leaves were oriented with a steeper downward angle. Both leaf surfaces of apple and pear retained a higher proportion of microcapsules than walnut leaves, and the bottom surface of apple leaves retained significantly more than pear leaves. Three spray adjuvants were evaluated as stickers for microcapsules. No difference was found in the number of microcapsules deposited on apple leaves among three stickers tested at rates from 0.06 to 0.25%. However, in a second test a latex sticker significantly increased the deposition of microcapsules on apple leaves compared with a polyvinyl polymer and a pine resin sticker at a rate of 0.06%. Significantly more microcapsules were retained on the bottom versus the top of apple leaves with all stickers. The latex and polyvinyl stickers significantly increased the retention of microcapsules versus the pine resin sticker and the control on apple leaves. In another test, the addition of 0.06% latex sticker did not increase the deposition of microcapsules on any of the three leaf types. However, the addition of the latex sticker significantly increased the retention of microcapsules on the top of apple and pear leaves and the bottom of apple leaves. The addition of a latex sticker did not affect the retention of microcapsules on walnut leaves.