Utah State University

Logan, Utah

Based on results from five small, rural pome orchards during two years of study, codling moth fruit injury can be maintained below 5% (acceptable upper tolerance for rural orchardists) when border effects are minimized. Prominent border effects were found in orchards with upwind, adjacent open areas that likely served as "mating sites" for moths. A "mega" (10 mg codlemone lure trap did detect higher numbers of male moths than a standard 1 mg lure trap in mating disruption sites, but its usefulness to predict expected fruit injury is limited in small (1-3 acre) orchards with prominent border effects.

Major Objective

To determine if sex pheromone-based mating disruption (MD) for codling moth (CM) can provide "satisfactory" control in small (1-3 acre), isolated pome fruit orchards in rural Utah.

The MD approach for CM control is generally not appropriate for most commercial pome fruit acreage in Utah because of high CM pressure (50-200 moths/trap/season in insecticide-treated orchards) and close proximity to untreated hosts (e.g., backyard trees, abandoned orchards). However, strong interest by small, rural orchardists in soft to organic programs for CM prompted interest in this study.

Methods

MD experiments were conducted in 5 small, rural orchards in 1992 and 1993 (Table 1). All orchards were isolated by at least 180 m from outside CM sources. In 1992, NM was tried in small urban orchard that was not isolated from immigrating CM (Kaysville site).

All MD orchards received a first cover spray of Guthion or Imidan timed at approximately 250 Degree-days (DD) after biofix. Shin-etsu pheromone dispensers supplied by Pacific Biocontrol Corp. were applied at 400 dispensers/acre on interior trees and at 800 dispensers/acre on border trees. Capitol Reef sites received two applications of dispensers/season and Draper and Kaysville sites received a single application per season.

Pherocon 1C traps were baited with either a red septa loaded with 1 mg or 10 mg codlemone dose. Because of small orchard size, only one trap of each dose was placed in each trial block.

Traps were hung at 2-2.5 m high on the north side of tree canopies. Lures were replaced every 3 weeks. Percent fruit injury was determined at harvest by cutting open 2,000-4,0000 fruit per site.

Results

1). Can fruit injury be maintained below approximately 5%?

At harvest fruit injury ranged from 0.2-29.2% (Table 2). Injury was maintained at 5.5% or below in all rural orchards except one in 1992 (Capitol Reef C). Injury in the non-isolated, urban orchard (Kaysville) was 11.1% in 1992.

2). How strong are the border effects?

Border effects were strong in the Capitol Reef C orchard, the Draper B orchard, and the Kaysville orchard in both years. Strong border effects caused overall fruit injury to be the greatest in these orchards (Table 2).

Direction of the prevailing wind and presence of an adjacent open area may have caused greater border effects in 2 of the 5 orchards. The presence of trees and shrubs and nonhost orchard tree on the upwind side of the other 3 orchards may have reduced border effects. No moths were caught in pheromone traps

(1 mg lure) placed in adjacent vegetation during 1992 and 1993.

3). Can fruit injury be predicted from moth catch in a 10 mg lure trap?

Cumulative moth catch in traps baited with 10 mg lures was greater than in 1 mg traps in MD orchards. Moth catch in nearby insecticide-treated orchards was less or the same in 10 mg trap as compared to 1 mg traps. Regression of percent fruit injury at harvest on total moth catch for the season in 10 mg traps showed no relationship when all sites were included.

Table 1. Orchard site descriptions.

Orchard                      Crop                            Size                                            CM Biofix Date

Capitol Reef A         Apple                         1.5 acres                                                 April 29

B                                                                 1.2 acres

C                                                                 1.0 acres

Draper A                Apple                                 1.5 acres                                                 April 15

B                        Asian pear                         3.0 acres

Kaysville                Apple                                 2.0 acres                                                 April 13

Table 2. CM trap catch with I mg lure and % fruit injury at harvest.

                       # moths/trap/season*

Orchard                  Insecticide              MD                            % fruit injury at harvest

1992

Capitol Reef A                 12                         4                                   0.2

B                                                                 12                                   4.4

C                                                                 14                                   29.2

Draper A                         168                         2                                   1.1

B                                                                 10                                   5.5

Kaysville                         63                          2                                   11.1

1993

Capitol Reef A                 21                          0                                    1.0

B                                                                  0                                    0.8

C                                                                  0                                    5.3

Draper A                         177                         0                                    0.3

B                                                                  3                                    5.4

*Trap catch in nearby insecticide treated orchard and in MD orchards.

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