CODLING MOTH CONTROL THROUGH MATING DISRUPTION

Transcription

1 CODLING MOTH CONTROL THROUGH MATING DISRUPTION Project Leader: R. A. Van Steenwyk Cooperating Personnel: J. K. Hasey, C. Pickel, W. H. Olson Abstract We successfully demonstrated that codling moth (CM) control in walnuts can be achieved by the application of CM pheromone. Two applications of 1200 CM pheromone dispenserslac nearly eliminated CM at harvest (0.3% infested nuts), while 800 pheromone dispensers produced control (1.5% infested nuts) similar to that of the grower's standard insecticide program (1.7% infested nuts). All three control programs produced significantly lower CM infestation than the untreated control, which had 4.2% infested nuts at harvest. We successfully monitored CM populations in pheromone-permeated orchards by increasing the amount of pheromone in the pheromone traps. We provided CM larvae and pupae from various locations to Dr. Millar at UCR for his analysis of the pheromone gland constituents and the volatiles produced by live virgin females. Objectives The long-range objective of this project is to develop the CM pheromone mating disruption technique in walnuts. This year's objectives were to: 1) determine the number of pheromone dispensers needed per tree to effect mating disruption (an unreplicated trial), 2) develop a CM monitoring technique to evaluate CM populationsin pheromone-permeated orchards, and 3) provide Dr. Millar (VCR) CM larvae and/or pupae from different hosts and locations for analysis of the pheromone gland constituents and the volatiles produced by live virgin females. Procedures Codling Moth Matinp:Disruption. - A study was conducted in a matme commercial Ashley walnut orchard near Marysville, CA. The trees were planted on a 4O-ftsquare with one in the middle and were approximately 35 to 40 ft. tall. Four treatments were established in this orchard. The treatments were: 1) 800 Shin-Etsu CM pheromone dispensers/ac, 2) 1200 Shin-Etsu CM pheromone dispensers/ac, 3) grower standard (insecticide-treated), and 4) untreated control. All pheromone dispensers were placed near the top of the tree canopy (approximately at 30 ft) on March (3-day rain delay) and again on June The pheromone and grower standard treatments were 3.9 ac in size each and the untreated control was 2.4 ac. The pheromone treatments were placed downwind from the grower standard and untreated control treatments. The entire plot was treated (alternate row) with Thiodan on 5(24 for aphid control and the grower standard was treated (alternate row) with Lorsban on 7/2, 7/8 and 819. Adult CM populations were monitored by placing 3 pheromone traps (pherocon/l CP- Trece) baited with 1 mg of Codlemone in the grower standard and untreated control treatments each and 4 pheromone traps in the 800 and 1200pheromone dispenser treatments each at a height of approximately 30 ft. The traps were placed in the orchard on April 2 and monitored weekly through Oct. 1. Pheromone caps were changed every 3 weeks and bottoms changed when necessary. All dropped nuts around 9 interior trees from each plot were collected weekly from May 29 through July 9 and inspected for CM infestation. Corrugated cardboard emergence bands were placed around the trunks of 9 interior trees in each treatment on May 29 and again on Aug. 6. The bands were removed 120

2 July 9 and Sept. 9, respectively, and inspected for the presence of CM. A one-hour visual search of each plot for CM-infested nuts was conducted on Aug. 8 and 27. At commercial harvest on Sept 9, 100 nuts/tree were collected from around 10 interior trees and inspected for CM infestation. -In the 800 and 1200 Shin- Etsu pheromone dispenser treatments as described above, five pheromone trap cap loads were replicated 4 times each. The pheromone traps were Pherocon/1CP-Trece and the 5 pheromone cap loads were 1,5, 10, 15, and 25 mg of Codlemone per cap. The traps were placed in the orchard on April 2 at a height of approximately30 ft and monitored once a week through Oct 1. All pheromone caps were replaced every 3 weeks and bottoms changed as necessary. H R n R. n I Difti'n - CM larvae and pupae' were collected from walnut in Tulare, Tracy and Gustine during the first generation and from Woodland, Marysville and Chico throughout the season. Also, CM larvae and pupae were collected from apple from Brentwood throughout the season. These larvae and/or pupae were sent to Dr. Millar at UCR for analysis of the pheromone gland constituents and the volatiles produced by live virgin females. Results and Discussion Codlin~ Moth Marin~Disruption- CM response, as measured by moth catch in pheromone traps baited with 1 mg of Codlemone and placed high in the tree canopy, was completely suppressed by both the 800 and 1200 pheromone dispenser treatments (Fig. 1). Totals of 0.5 and 0.75 moths/trap for the entire season were captured in the 800 and 1200 pheromone dispenser treatments, respectively, while totals of 170 and 222 moths/trap for the entire season were captured in the grower standard and untreated control, respectively. There was a significantreduction in the number of CM-infested dropped nuts in the 800 and 1200pheromone dispenser treatments as compared to the untreated control and grower standard (Table 1). Totals of 0.6 and 1.0 CM-infested dropped nuts per tree were found in the 1200 and 800 pheromone dispenser treatments, respectively; while a total of 4.8 infested dropped nuts per tree was found in the combined untreated control and grower standard treatments. At.thispoint in time, the grower standard had just received an insecticide application (material was applied on July 2 and July 8 to every other row which was considered one application). This application had no effect on the overwintering CM generation and, thus, the grower standard and the untreated control were combined into one untreated control. The results from the first banding evaluation were similar to those from the dropped-nut evaluation (Table 2). With the encouraging results from the dropped-nut evaluation and the first banding evaluation, and with few CM adults found in pheromone traps in either the 800 or 1200 dispenser treatments, a second pheromone application of both 800 and 1200 pheromone dispensers was applied on June 24. Also, the low number of CM-infested dropped nuts and CM in the bands in the control and grower standard indicated a low base level of CM in the orchard from the overwintering population

3 Fig. 1 Mean No. of Codling Moth /Trap/Day in the 1200 and 800 Pheromone Dispensers, Grower and Untreated Plots 6 I -e mg ro " a. ro L- " mg Grower Standard :) 41 Untreated Contro I.- If, l\ I (I)..., 0 I: 2 0 z cro 3 I.. N N... Q) I: o ~w~.. 4/9 4/164/234/30 5/ /215/28 6/4 6/ /25 7/2 7/ / /6 8/138/208/27 9/3 9/ /24 10/1,.;i. Date

4 Table 1. Mean number of codling moth-infested dropped walnuts per tree Treatment Mean* no. infested walnuts/tree 1200 dispensers 800 dispensers Untreatedconttol(untreated grower standard included) O.6a 1.0a 4.8b *Means followed by the same letter are not significantly different (DMRT P<O.05) Table 2. Mean number of codling moth larvae and pupae in coitugatedemergence bands per tree on two dates Mean* no.-ofcm/tree on: Treatment 7/ dispensers Oa Oa 800 dispensers O.2a O.4a Grower standard O.9ab O.9b** Untreated control 1.6b *Means followed by the same letter iri-a-columnare not significantly different (DMRT P<O.05) **Grower standard and untreated control were combined for the 719data since the grower standard was not treated until 7/2 and 7/

5 After the second pheromone application, the treatments were further evaluated by conugated bands, two visual searches and nut infestation at harvest All results from the second banding evaluation (Table 2) and the two visual searches (Table 3) were similar to the final infestation at harvest (Table 4). In general, the results show that the 1200 pheromone dispenser treatment had fewer CM than did the 800 pheromone dispenser or grower standard, which did not differ significantly. And these three treatments (1200 dispensers, 800 dispensers and grower standard) had fewer CM than did the untreated control. The fmal nut infestations in the 800 dispenser (1.5%) and grower standard treatments (1.7%) were similar to the previous year's infestation, as reported by the grower. Table 3. Total number of codling moth-infested walnuts found during a I-hour visual search on two dates Total no. infested walnuts Treattnent 8/8 8/ dispensers dispensers 2 1 Grower standard 1 5 Untreated control Table 4. Mean percent codling moth-infested walnuts per tree at commercial harvest Treatment Mean* Larvae absent** 1200 dispensers O.3a Oa O.3a 800 dispensers O.7a O.8b 1.5ab Grower standard O.9a O.8b 1.7b Untreated control 2.5b 1.7c 4.2c *Means followed by the same letter in a column are not significantly different (DMRTJ P<O.05). **A percentage of these nuts would be removed by air leg. Thus, grower infestation would be lower. 124

6 This is the first trial to successfullydemonstrate that CM can be controlled in walnuts using the pheromone mating disruption strategy. The success of this trial can be attributed to a number of factors. First, the initial overwintering CM population was low and we did not have to overcome an explosive situation. In earlier trials, infestation rates from the previous year were between 3 and 5%. Second, all pheromones were placed high in the tree canopy as compared to 213high and 1/3 low in previous trials. Preliminary studies on the movement of the pheromone in the tree canopy indicate that the pheromone moves downward, with very little upward movement. Since CM populations are concentrated high in the tree canopy, the pheromone must be placed high to gain the greatest benefit from the treatment. Third, the number of pheromone dispensers was increased from 400/ac (amount recommended in pear) to 800 and 1200/acto compensate for the greater row-tree volume in walnut. The 1200/acrate, which is cost-prohibitive at this time, may be reduced when whole orchards are treated and when CM populations have been reduced to very low levels. The 1200dispenser treatment in this study nearly eliminated CM from the plot. ~. This was an unreplicated study and replicates were obtained by using subsamples. Thus, results must be viewed as preliminary. Validation of these results will have to wait until replicated trials can be completed... C()(ilin~Moth Monitorin~in a Pheromone-permeatedOrchard - The number of CM caught in pheromone traps loaded with different amounts of Codlemone which were placed in the 1200 and 800 dispenser/ac treatments increased with increasing amounts of Codlemone in the pheromone traps (Table 5). The response decreased at 25 mg Codlemone in the 1200 pheromone dispenser plot. Thus, it is possible to monitor CM populations in pheromonepermeated orchards by increasing the amount of pheromone in the pheromone traps. Table 5. Codling moth catch in traps baited with various amounts of Codlemone in orchards with pheromone dispensers Mean* no. CMltrap Codlemone bait 800 dispensers 1200 dispensers 1 mg O.5abc O.8b 5mg O.Oc 1.5ab lomg O.8abc 3.3ab 15mg 1.0ab 4.5a 25mg 1.3a 3.0ab *Means followed by the same-letterin acolumn are not significantly different (DMRT P<O.20). Although more moths were captured in the higher pheromone loaded traps than in the standard pheromone loaded (1 mg Codlemone) traps, the moth catch did not occur earlier in the season in the higher pheromone loaded traps than in the standard pheromone loaded traps. For example, in the 800 dispenser/ac treatment, the first moth was captured on May 14 in a I-mg trap, the second moth on June 11in a 15-mg trap and the third moth on July

7 16 in a lo-mgtrap. All other moths were caught between Aug. 8 and 27. In the'1200 dispenser/ac treatment, the first 4 moths were captured on July 16 (1 moth in a 1-mg trap, 1 moth in a lo-mgtrap and 2 moths in a 25-mg trap). The majority of moths in the 1200 dispenser treatment were captured between July 16 and Aug. 13. If increasing amounts of pheromone in the trap were to indicate a breakdown in pheromone concentrationin the orchard, we would expect to see the traps with the highest pheromone load catch moths earlier in the season than those with the lower pheromone loads. Since we maintained the pheromone concentration at a level high enough to demonstrate control (see section on CM mating disruption) and did not have breakdown in the pheromone concentration, these results are to be expected. It is also interesting to note that more moths were captured in the 1200 pheromone dispenser plot (52 total moths for all traps combined) as compared to the 800 dispenser plot (14 total moths). The cause of this increased trap catch is not known. It is possible that the 1200 dispenser plot was located in an area of the orchard with a high resident CM population. However, despite the higher pheromone trap catch, the 1200 dispenser plot had very little CM infestation throughout the study. Host Race and RelPonal Differences in Codlin~ Moth Pheromone -See J. Millar report for host race and regional differences in CM pheromone production. Acknowled~ent - We greatly acknowledge Mr. Ren Fairbanks of Deseret Farms for his cooperation and willing assistance in various aspects of this study