Non-pesticidal Control of Summer 

 Codling Moths Through Habitat 

 Management 



Ronald J. Prokopy, Margaret M. Christie, James Gamble, 



David Heckscher, and Jennifer Mason 



Department of Entomology, University of Massachusetts 



Worldwide, codling moth continues to be the 

 most damaging of all pests of apple fruit. One reason 

 for this situation is the essentially universal distri- 

 bution of codling moth. It attacks apples on every 

 continent where apples are grown. In contrast, pests 

 such as apple maggot and plum curculio remain 

 confined to North America. Another reason why 

 codling moth is such a pest on a worldwide basis lies 

 in the multiple number of generations per year that 

 it can undergo. Here in the northeastern USA we are 

 fortunate in that there exist only 2 generations each 

 year. In the western USA, there exist at least 3 

 generations. In some other regions, for example 

 parts of Australia, there may be 4 or more genera- 

 tions per year. If there were 20 larvae in an aban- 

 doned orchard in the first generation, there might be 

 200 in the second generation. But if you had a third 

 generation, there might be 2000. A fourth genera- 

 tion might peak at 20,000. 



Even at only 2 generations per year, codling 

 moth was a devastating insect in many commercial 

 orchards in New England before the advent of syn- 

 thetic pesticides in the late 1940s. Since then, it has 

 acquired the status of a relatively minor pest. It has 

 not, however, lost its ability to injure large amounts 

 of fruit on unsprayed trees. For example, on several 

 unmanaged apple trees 600 to 800 feet from 

 Prokopy's small commercial orchard in Conway, 

 MA, second-generation codling moth larvae infested 

 48% of fruit sampled in September during 1985 

 through 1989 [Fruit Notes 55(4):9-14]. In our opin- 

 ion, highly effective control of codling moth in New 

 England commercial orchards over the past 4 dec- 

 ades has resulted fortuitously from use of organo- 

 phosphate sprays such as Guthion™ and Imidan™ 

 that are directed primarily against plum curculio in 

 late May and early June (thereby controlling first 

 generation codling moth larvae) and against apple 

 maggot from mid-July to mid-August (thereby con- 

 trolling second-generation codling moth larvae). 



With the advent of cultural, biological and be- 

 havioral methods as substitutes for using pesticides 

 after early June to control arthropods in second- 

 stage IPM orchards [Fruit Notes 55(l):4-9], a way is 

 potentially open for second-generation codling moth 

 adults to invade orchards in July and August and lay 

 eggs in an orchard atmosphere free of pesticide. Two 

 non-pesticidal approaches for codling moth control 

 are receiving much attention in regions where cod- 

 ling moth has 3 or more generations per year. One 

 approach involves applying, during summer 

 months, several sprays of a selective virus that kills 

 codling moth larvae but little else. The other ap- 

 proach involves permeating the atmosphere of the 

 orchard with synthetic female sex pheromone to 

 disrupt mating behavior. Both approaches show 

 much promise; however, both are expensive to 

 employ. 



Based on work conducted in the 1950s by Theo- 

 dore Wildbolz, we have been evaluating a non- 

 pesticidal approach to managing second-generation 

 codling moths that involves neither use of virus nor 

 mating disruption pheromone but uses habitat 

 management. By releasing mated codling moth 

 females at varying distances from commercial or- 

 chards, Wildbolz determined it was unlikely under 

 Swiss conditions (similar to New England condi- 

 tions) that individual females would move more than 

 100 yards or so in search of egglaying sites. He 

 postulated, therefore, that removal of principal 

 types of unmanaged host trees of codlingmoth (apple 

 and pear) within 100 yards of the perimeter of 

 commercial orchard blocks might provide sufficient 

 isolation to preclude movement of second-genera- 

 tion females into the block. 



In May of 1987, we removed all abandoned apple 

 and pear trees (average of 7 per orchard) within 100 

 yards of each of 6 commercial apple orchard blocks (2 

 to 3 acres each) that received no insecticide after 

 early June from 1987 through 1989. Of the 5400 



16 



Fruit Notes, Winter, 1991 



