NONCHEMICALPOSTHARVEST TREATMENTS/TECHNIQUES FOR CODLING MOTH ON INSHELL WALNUTS: DISRUPTION OF MATING AND MONITORING OF ACTIVITY USING SEX PHEROMONE

Transcription

1 NONCHEMCALPOSTHARVEST TREATMENTS/TECHNQUES FOR CODLNG MOTH ON NSHELL WALNUTS: DSRUPTON OF MATNG AND MONTORNG OF ACTVTY USNG SEX PHEROMONE Charles E. Curtis, Patrick V. Vail, JimmyD. Clark, Shirley Ann May ABSTRACT Mating disruption of codling moth, a field pest, is being tested in a storedproduct situation by placing pheromone dispensers in bagged walnuts (25 kg or 50 lb) in storage at 18 C in continuous darkness. The temperature of 18 C is representative for transoceanic shipments to Japan and Europe. Tests at 18 C using a new colony started with diapausing larvae collected from a Merced County (Delhi) walnut orchard (February 1990) have resulted in 100% control with single pairs and with four pairs of moths per bag. Mating. potential was 0% for single pairs and 1.3% for four pairs of the Delhi strain in untreated bags. Tests with a laboratory strain (started September 1984) resulted in 100% control with single pairs and 57.8% control with four pairs of moth per bag. Mating potential was 2.5% and 7.6%, respectively; for the laboratory strain. Two pheromone dispensers were placed in each bag of walnuts in all tests. Trapping in two walnut packing plants (April l8-0ctober 17) resulted in 223 codling moths being trapped in the outside receiving area of a plant which was adjacent to a walnut orchard and no moths being trapped in the outside receiving area of a plant some distance from any orchards. No moths were trapped in any of the handling and holding areas in either plant. This type of information should be valuable in demonstrating how unlikely it would be for walnuts to become reinfested during storage and handling. OBJECTVES PROCEDURE (1) Determine the mating potential of codling moth in bagged walnuts stored in normal and pheromone permeated atmospheres. (2) Develop existing sex pheromone as a useful tool for controlling the codling moth by disruption of mating in postharvest walnuts. (3) Develop the existing sex pheromone as a useful tool for monitoring codling moth activity in packing and storage areas. (4) Develop alternative postharvest/quarantine detection and control strategies,based on findings in Objectives, 2 and 3, for codling moth causing losses on inshell walnuts. Problems that were evidently related to our codling moth colony evolving into a laboratory adapted strain have been solved by collecting fresh material from

2 a Merced County (Delhi) walnut orchard in February Ye used the collected diapausing larvae to establish a new strain that better represents the real world situation of walnuts coming into handling and storage facilities. Ye plan to use a new strain each year. Our hypothesis is that the pheromone has a greater effect on the mating success of field collected moths and their progeny which have been in colony for no more than one year. Pheromone treatment tests at laoe in metal containers Bags (25 kg or 50 lb) of inshell Persian walnuts were held in 3' x 3' X 3' (27 cubic feet) metal containers placed on a wooden platform in 11'2 x 7'4 x 7'6 high (614 cubic feet) rooms. Two containers, each with a bags, were held as controls in one room free of pheromone. Another room had 2 containers, each having a bags treated with pheromone contained in Shin-Etsu dispensers. All tests had 2 dispensers per bag. All tests had one container in each room infested with the 'Delhi' strain and a second container infested with the laboratory strain. Newly emerged virgin codling moth adults were released into the bags of walnuts. Single pairs and four pairs per bag were used to determine mating potential in untreated and pheromone [(E,E)-8,10-dodecadien- 1-01] treated bags. Pheromone formulated in Shin-Etsu dispensers were provided by Biocontrol Ltd., Australia. Two dispensers containing 75 mg of pheromone per dispenser were placed in each bag. All studies were. made at 18 C in continuous darkness. Pheromone release rates Pheromone release rates over the 4-month useful life of the Shin-Etsu dispensers were determined by 2 methods. First, the column length (cm) of pheromone in each dispenser was measured at the termination of each test (3-4 week intervals). The percentage of pheromone evolved for any test period could then be calculated. Second, the weight (mg) of each dispenser was measured at the termination of each test. The amount of pheromone evolved for any given time period. could be calculated by a subtraction procedure. Pheromone concentrations in air Pheromone concentrations in the air s~ace inside the bags and 27-cubic-foot storage containers were sampled and analyzed by gas chromatographic procedures. Teflon tubes were mounted in each container so air samples could be taken from several areas within the bags of walnuts and from the air space in the container without disturbing the test setup. Samples from within the bags represented air from an area near the pheromone dispenser and areas some distance from the dispensers. An air pump was used to pull 3 liters of air over a 30-min. period from a given sample site through hexane contained in reaction tubes. The hexane/pheromone samples were evaporated to dryness using nitrogen. Hexane (0.5 ml) was added to resusp the pheromone, and one 1 was injected on a capillary column (30 m x 0.32 rom D) and analyzed on a flame ionization detector

3 Pheromone residues Pheromone residues on the walnut shells, walnut meats and woven-plastic-bag material were sampled and analyzed by gas chromatographic and mass spectrophotometric procedures. Samples containing 40 nuts from each of several sites were taken to represent nuts next to the pheromone dispensers and nuts some distance from the dispensers. A 7.5 x 7.5 cm (56 cm2) piece of bag material was taken to represent material next to the pheromone dispensers and material some distance from the dispensers. For each of the 2 containers, 3 replicates of nuts and bag material were taken from an area next to the pheromone dispensers and 4 replicates of nuts and bag material were taken from the s of the bags representing the 4 compass directions and areas as far away as possible from the dispensers. Trappin~ at packin~houses Pheromone formulated in Consep membranes and placed in sticky traps was used for surveillance of codling moth in 2 packing plants beginning April 18 and ing October 17. One plant was adjacent to a walnut orchard. Two traps were located outside in the receiving area which bordered walnut trees. One trap was located in each of the following areas within the plant: cracking, handling and storage, shipping and storage, and holding. The other plant was at least one mile removed from any outside sources of codling moth. One trap was located outside in the receiving area and in each of the following plant locations: first floor cracking, second floor cracking, bulk handling, and packaging.. Shipping temperatures We gathered the first data which accurately show the temperature of walnuts being shipped across the Pacific and Atlantic oceans. We recorded temperatures and humidities within the walnut cargo in van containers located both above and below decks beginning September 27, 1990 and ing June 18, We used Ryan Export temperature recorders, Omnidata temperature/ humidity recorders and Omnidata day-degree recorders. Four shipments (7 containers) to Tokyo and four shipments (8 containers) to Rotterdam/Hamburg were monitored. Some shipments were 800 bags of inshe11 walnuts (50 lb. or 25 kg per bag) per 40 foot van container and some shipments were other types of packaged inshe11 walnuts or walnut products. Ryan Export temperature recorders were placed in four location (Fig. 1) per container. One Omnidata temperature/humidity recorder or one Omnidata day-degree recorder was placed in the center position in some containers. Sticky traps baited with insect pheromones were placed inside slotted cardboard boxes that were then placed in two locations (Fig. 1) per container for detection of codling moth and ndianmea1 moth. Tom Hinsch at our research station and two scientists at the ARS Rotterdam, Netherlands European laboratory, have vast experience in transportation of agricultural products and are cooperating in these studies. RESULTS AND CONCLUSONS As a part of a national objective to increase export markets and to reduce deficits in trading with Japan, the USDA has increased research efforts to 162

4 counter Japanese fears of unwanted pest introductions resulting from importation of inshell walnuts. Our laboratory has developed a fumigation treatment to meet the plant quarantine requirements of Japan which had prohibited importation of inshell walnuts due to potential codling moth infestation. ~e are obtaining data to determine the mating potential of codling moth in untreated and pheromone-treated bags of inshell walnuts as they relate to developing protocols relying on methods alternative to chemical control. These studies could provide data needed by walnut handlers and shippers who could apply the pheromone to shipments going into export markets as one method of certifying that codling moth would not be introduced into the importing country. Alternative strategies to meet quarantine security requirements could also be developed to reduce the severity or eliminate the need of a methyl. bromide treatment of inshell walnuts. Pheromone treatment tests at 18 C in metal containers ~en using the 'Delhi' strain, in tests having 2 pheromone dispensers in each bag of walnuts, 100% control resulted with one pair and with four pairs per bag (Table 1). Percent mating was 0 in treated and 0 in controls for bags with one pair and it was 0 in treated and 1.3 in controls for bags with four pairs per bag. Percent mating for moths in empty-plastic-bag controls was 46.7 for one pair and 45.0 for four pairs in a 16:8 (L:D) photoperiod and 0 for one pair and 3.3 for fours pairs in continuous darkness. ~en using the laboratory strain in tests having 2 pheromone dispensers in each bag of walnuts, 100% control resulted with one pair per bag and 57.8% control resulted with four pairs of moths per bag (Table 1). Percent mating was 0 in treated and 2.5 in controls for bags with one pair and it was 3.2 in treated and 7.6 in controls for bags with four pairs per bag. Percent mating for moths in empty-plastic-bag controls was 90.0 for one pair and 74.2 for four pairs in a 16:8 (L:D) photoperiod and 36.7 for one pair and 33.3 for four pairs in continuous darkness. Pheromone release rates Release rates of the pheromone from Shin-Etsu dispensers held at 18 C are shown in Fig. 2. About 22% of the pheromone material was released by the of four-months use. Release rate measurements at 25 C have shown that about 73% of the pheromone material is released by the of a four-month period. Mating was effectively controlled over the entire four-month period. The dispensers were effective over this long time period due to lack of exposure to sunlight and high temperatures. Pheromone concentrations in air Pheromone concentrations for the three component peaks were only a trace or nondetectable in the air space within a container (Table 2). They were picograms (10-12 grams) inside the bags near the pheromone dispensers, but they were usually much lower ( picograms in three out of four cases) in areas of the bags away from the pheromone dispensers. 163

5 Pheromone residues Pheromone residues ranged from 2.4 to 5.4 ~g/inz on bag material near the pheromone dispensers (Table 3). They ranged from 0.4 to 2.9 ~g/in2 on bag material at the s of the bag away from the dispensers. Residues were much higher on shells than on meats. They ranged from 1.7 to 10.3 ~g/g on shells and from undetectable to 0.5 ~g/g on meats in samples of nuts taken from around the pheromone source. They were generally lower on nuts from other parts of the bags. Trapping at packinghouses Trapping in two (2) walnut packing plants began on April 18 in the receiving, processing and holding areas. There were 223 codling moths trapped in the receiving area of one plant which was adjacent to a walnut orchard. No codling moth was trapped within either plant or in the receiving area of the plant far removed from any walnut orchards. Shipping temperatures Four different shipments (7 containers) of walnuts destined for Tokyo have been fitted with temperature and humidity recorders (Table 4). A~so, four shipments (8 containers) of walnuts destined for Rotterdam/Hamburg have been fitted with temperature and humidity recorders and insect traps. One ndianmeal moth and DQ codling moths were trapped within the containers shipped to Rotterdam/Hamburg. nsect traps were not placed in containers destined for Tokyo. Temperatures were as high as 27 e and as low as ooe within walnuts shipped to Tokyo and as high as 28 e and as low as 2 e within walnuts shipped to Rotterdam/Hamburg (Table 4). SUMMARY The data obtained in this in-progress study indicate that the mating incidence of field collected codling moth adults in bagged walnuts is very low and that mating can be eliminated in bags treated with sex pheromone. The pheromone treatment could be an effective adjunct to quarantine treatments such as fumigation or cold storage in the prevention of pest introductions via bags of inshell walnuts. The results from these tests can be used as the basis for developing a surveillance and control strategy for inshell walnuts being shipped in van containers for export

6 Table 1. Codling moth (CK) mating in 50 lb bags of inshell walnuts treated with two (2) 75-mg Shin-Etsu pheromone dispensers per bag and untreated controls held at l8ec in 27-cubic-feet metal containers. Tests were made between July, 1990 and Kay 2, Bagged inshell walnuts in continuous darkness Plastic bags (no walnuts) Untreated Treated with CM sex, reduction Continuous darkness 16:8 (L:D) photoperiod pheromone in mating No. mated/, mated No.mated/, mated No. mated/, mated No. mated/, mated no. observed no. observed no observed no. observed Delhi strain 0/39 0 0/ / / Laboratory strain 1/ / / / Delhi strain 2/ /15, / / Laboratory strain 12/ / / / ) \D...

7 Table 2. Concentration of pheromone (picograms/liter of ~) in treated (2 Shin-Etsu 7S-mg dispensers/bag) and control SO-lb bags of inshell walnuts contained in 27-cubic-foot metal chambers held at 18 C. Air samples were taken on March 19, Peak 1 Peak 2 Peak 3 Control -* Room air Container #1 Air - Trace Nuts High 6.2 Trace Center** Low 6.2 Trace Container #2 Air Nuts High 9.3 Trace Center** Low *No detectable peak. **Near pheromone source/dispenser

8 Table 3. Residues of pheromone in shells, meats and bag material from treated (2 Shin-Etsu 75-mg dispensers/bag) and control 50-lb bags of inshell walnuts contained in 27-cubic-foot metal chambers held at l8 e. Samples were taken on ~pril 4, Residue level (Total for 3 peaks) Position in bag Position in stack Bag material (Jjg/in2) Shell (Jjg/ g) Meat (Jjg/g) Control Center Top -* Middle Bottom Container #1 Center** Top 5.3 Middle 5.4 Bottom East West Top 1.3 Middle 1.0 North. Middle 0.4 South Bottom 0.6 Container #2 Center** Top 2.4 Middle 3.6 Bottom West Top East Middle 2.9 North South Middle Bottom 0.8 *No detectable peak. **Near pheromone source/dispenser

9 Table 4. Transoceanic shipping temperature (OC) for walnuts in van containers. Date Temperature (high/low)* Cargo Loaded Unloaded High Middle Low A!1.: Tokyo /6 15/4 16/4 30/ /0 12/6 15/4 35/ /15 18/13 38/ /15 22/17 24/14 40/9 Rotterdam /16 27/17 28/12 37/ /7 27/10 27/5 32/ /4 20/2 23/4 30/ /13 23/13 27/13 31/9 *See Fig. 1 for locations of temperature recorders

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