Elsevier

Biological Control

Volume 37, Issue 2, May 2006, Pages 214-223
Biological Control

Entomopathogenic nematodes for control of codling moth (Lepidoptera: Tortricidae) in apple and pear orchards: Effect of nematode species and seasonal temperatures, adjuvants, application equipment, and post-application irrigation

https://doi.org/10.1016/j.biocontrol.2005.09.015Get rights and content

Abstract

Codling moth (CM), a serious pest of apple and pear in most countries where these fruits are grown, overwinters in cryptic habitats as cocooned diapausing larvae. Control of diapausing CM larvae would reduce or eliminate damage to fruit early in the following growing season. Entomopathogenic nematodes (EPNs) have shown promise as biological control agents of cocooned CM larvae in the Pacific Northwest and elsewhere, but several factors, such as choice of EPN species and other operational factors warrant investigation to provide growers with practical control options. Field trials with Steinernema carpocapsae and S. feltiae were conducted in apple and pear orchards to determine the effects of seasonal temperatures, adjuvants, post-application irrigation, and method of application on control of cocooned CM larvae. In studies conducted in late summer, fall and early spring (1999–2000), EPNs were applied to apple trees (Golden Delicious) with a backpack sprayer at a rate of 106 infective juveniles (IJs)/tree plus supplemental wetting to aid survival of IJs. Good control by both EPN species was observed in September (94–95% mortality in sentinel CM larvae). In October, control by S. feltiae was also effective (90% mortality), but S. carpocapsae was less effective (58% mortality), ostensibly due to the cooler conditions. In identical applications the following spring, the efficacy of S. carpocapsae and S. feltiae was reduced during cool windy conditions in March 30 tests, providing 26 and 65% control of sentinel larvae, respectively, but improved during warmer conditions in April 12 tests (71 and 86% control, respectively). In further tests in the same location in mid-October 2001, S. feltiae (106 IJs/tree) were most effective for control of sentinel CM larvae cocooned in cardboard strips (≈ 80% mortality) and logs (34–47%) when combined with a wetting agent (Silwet L77) or a humectant (Stockosorb) and the trees were misted for 4 h post-treatment. In the absence of post-application wetting, the addition of either adjuvant (Silwet and Stockosorb) to IJs also increased larval mortality in strips, although it did not significantly improve nematode efficacy on logs. In another test in late summer 1999, the use of a lance applicator (applying 2.0 × 106 IJs/tree) did not significantly improve control of cocooned larvae for either EPN species, when compared with a tractor-mounted airblast sprayer. Two further tests in the fall of 2003 with S. carpocapsae and S. feltiae compared post-application wetting with existing and modified irrigation in 4-year-old trellised apple (Gala) and established Bartlett pear orchards. No significant improvements in sentinel larval mortality were observed following application of both EPN species with an airblast sprayer (1–2.5 × 109 IJs/ha) when conventional overhead rotator sprinklers were replaced with lower volume microsprinklers.

Introduction

Codling moth (CM), Cydia pomonella (L.), is a global pest of apple, pear, and walnut (Barnes, 1991), and the principal pest of apple in the Pacific Northwest of the United States (Beers et al., 1993). In late spring, adults emerge and begin laying eggs when fruit is available. Neonate larvae enter the fruit and feed until full grown, then exit as fifth instars in search of cryptic habitats in which to spin their cocoons and pupate. In the Pacific Northwest there may be two to three generations per growing season depending upon weather (Beers et al., 1993).

A variety of broad spectrum insecticides are employed for CM control in conventional orchards during the growing season (Beers et al., 1993). Softer approaches that include the use of mating disruption (Calkins ans Faust, 2003) and the CM granulovirus (Arthurs and Lacey, 2004) are also employed. In temperate climates, CM overwinters in cryptic habitats as cocooned diapausing larvae. Thus, overwintering larvae represent the entire CM population in the fall, winter, and early spring. Their elimination or significant reduction at this stage would provide complete or substantial protection to fruit early in the following growing season. However, few interventions are employed for control of overwintering larvae. Cryptic habitats, such as those used by CM for their overwintering sites (under loose bark, in litter at the base of trees, in nearby woodpiles, fruit bins and the like) may also provide favorable environmental conditions for entomopathogenic nematodes (EPNs) (Begley, 1990, Koppenhöfer, 2000). Used under optimal conditions of warm temperatures and available free water, EPNs can be effective control agents of cocooned CM larvae in orchards (Kaya et al., 1984, Lacey et al., 2000, Nachtigall and Dickler, 1992, Sledzevskaya, 1987, Unruh and Lacey, 2001) and fruit bins (Cossentine et al., 2002, Lacey and Chauvin, 1999, Lacey et al., 2005). Studies by Kaya et al., 1984, Unruh and Lacey, 2001 elucidated the importance of moisture for control of CM by Steinernema carpocapsae in California and Washington, respectively. The habitat of overwintering CM and environmental conditions may vary from orchard to orchard and within orchards depending on the season and other factors. Further improvements of application methods and how irrigation systems and adjuvants can be used to enhance persistence and activity of EPNs will be necessary to provide growers with practical control options. Other factors such as the choice of nematode species that could influence the success or failure of EPNs in orchards have yet to be studied in detail. It was the objective of our research to investigate the effects of EPN species and seasonal temperature, addition of adjuvants, application method, and type of post-application irrigation on the efficacy of EPNs for control of cocooned CM larvae. Field trials were conducted over a 4-year period in orchards in eastern Washington State to elucidate the effect of these factors.

Section snippets

Materials and methods

Table 1 summarizes experimental information for studies conducted from September 1999 through October 2003 including application rates, type of orchard, EPN strains, and factors addressed in each experiment. Two procedures that are common in the experiments reported below are method of assessment of mortality using sentinel CM larvae and quality control bioassays of the EPNs tested.

Experiment 1. Nematode species and seasonal temperature

The efficacy of nematode applications (106 IJs/tree applied with a back pack sprayer) varied between species on two of the four treatment dates (P < 0.0001 in each case) (Fig. 1). In all cases control mortality remained ⩽5.3%. Late summer applications (September) were the most effective, resulting in 94.4% (S. carpocapsae) and 94.7% (S. feltiae) mortality in CM larvae (Fig. 1B). S. feltiae was also effective in the mid-October application, although there was a significant reduction of control for

Discussion

The main obstacles for successful CM control with EPNs are low temperatures and desiccation of IJs before they have penetrated the host’s cocoon. Applications that are made too late in the fall or too early in the spring when prevailing temperatures remain below the threshold of activity of the EPN species will be ineffective. CM pupae are also less susceptible to infection by EPNs than CM larvae (Lacey et al., 2005) emphasizing the need to target spring applications before larvae pupate. The

Conclusions

EPNs can provide effective control of overwintering CM when temperatures are 10–15 °C and higher (depending on nematode species) and moisture is maintained for several hours post-application. The use of a cold-active species, such as S. feltiae, will provide more flexibility on when orchards can be treated relative to less cold-active species such as S. carpocapsae. In our studies, moisture was adequately maintained by wetting trees before and after application of IJs using existing irrigation

Acknowledgments

We thank Jeff Upton, Ivan Campos, Richard Chauvin, Leon Ganuelos, Martha Marquez, and Laura Willett for technical support. We are grateful to our grower cooperators, Ron Wilcox in Wapato, Wade Smith in Quincy and Bill Pershall and Jim Nelson in Monitor and to Don Hostetter and Lisa Neven for review of the manuscript and their constructive comments and suggestions. We also thank Gerry Gefre and John Harvey for their help with field trials at the USDA-ARS-YARL experimental farm. We are grateful

References (42)

  • S. Arthurs et al.

    An analysis of using entomopathogenic nematodes against above-ground pests

    Bull. Entomol. Res.

    (2004)
  • M.M. Barnes

    Tortricids in pome and stone fruits, codling moth occurrence, host race formation, and damage

  • M.E. Baur et al.

    Effects of adjuvants on entomopathogenic nematode persistence and efficacy against Plutella xylostella

    Biocontrol Sci. Technol.

    (1997)
  • Beers, E.H., Brunner, J.F., Willett, M.J., Warner, G.M., 1993. Orchard Pest Management: A Resource Book for the Pacific...
  • J.W. Begley

    Efficacy against insects in habitats other than soil

  • A.B. Broadbent et al.

    Foliar application of Steinernema carpocapsae (Rhabditida: Steinernematidae) to control Liriomyza trifolii (Diptera: Agromyzidae) larvae in chrysanthemums

    Environ. Entomol.

    (1995)
  • C.O. Calkins et al.

    Overview of areawide programs and the program for suppression of codling moth in the western USA directed by the United States Department of Agriculture-Agricultural Research Service

    Pest Manag. Sci.

    (2003)
  • J.F. Campbell et al.

    Inter-specific variation in entomopathogenic nematode foraging strategy: dichotomy or variation along a continuum?

    Fund. Appl. Nematol.

    (1997)
  • J.E. Cossentine et al.

    Fruit bins washed with Steinernema carpocapsae (Rhabditida: Steinernematidae) to control Cydia pomonella (Lepidoptera: Tortricidae)

    Biocontrol Sci. Technol.

    (2002)
  • S.R. Dutky et al.

    Note on parasitic nematode from codling moth larvae, Carpocapsa pomonella

    Proc. Entomol. Soc. Wash.

    (1955)
  • I. Glazer

    Survival and efficacy of Steinernema carpocapsae in an exposed environment

    Biocontrol Sci. Technol.

    (1992)
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