Development and Demonstration of a Farm-Wide System for Control of the Principal Lepidopterous Pests of Tomatoes Based on Disruption of Premating Pheromone Communication Between Female and Male Moths

Development and Demonstration of a Farm-Wide System for Control of the Principal Lepidopterous Pests of Tomatoes Based on Disruption of Premating Pheromone Communication Between Female and Male Moths

Summary

Objectives
1.Demonstrate the efficacy of a novel system for distributing synthetic pheromone components into the air over large acreages of whole tomato ranches, for disruption of pre-mating pheromone communication of each of the principal lepidopterous pests of this crop.
2.Determine the minimum size acreage of tomatoes (and adjoining crops) that must be treated by the use of this system, in order to prevent significant numbers of already-mated female moths from entering the pheromone-treated areas from neighboring untreated areas and avoiding the pheromone communication disruption.
3.Calculate the benefits derived from controlling the major lepidopterous pests of tomatoes by this pheromone-communication-disruption system, including reductions in the use of conventional pesticides, preservation of natural enemies in pheromone-treated fields, and reduction in outbreaks of secondary pests of tomatoes.
4.Organize outreach activities that will ensure that this emerging technology is understood by and available to tomato growers, as well as PCAs, regulatory personnel, farm advisors, and other affected personnel.

Abstract
Puffers are novel devices for dispensing pheromones into the air of agricultural fields to disrupt communication and thus eliminate mating of pest moth species. These machines release repeated puffs of pheromone from pressurized aerosol cans, with individual puffs often containing pheromone equivalent to millions of female moths. They have a number of advantages, in comparison to traditional, hand-applied, pheromone-release devices. Because the pheromone is protected from light and oxygen until the moment of release, chemical breakdown is minimized. Two or more pheromones can be mixed and emitted together, giving the opportunity for simultaneous control of more than one species.

The amount of pheromone released is the same for the last puff as it was for the first puff released from a can, giving a predictable amount of pheromone delivered per unit of time. Labor costs for installing puffers are apt to be considerably lower than they are for hand-applied devices. In a number of season-long trials in tomatoes, puffers showed high potential for controlling multiple pest species beet armyworms, tomato fruitworms, and tomato pinworms on a wide area, farm-wide basis. The work indicates that for each species about 20 g of the respective pheromone per acre per 100-day season will be needed to provide economic control of the pests.

The beet armyworm, tomato fruitworm and tomato pinworm are major pests of both fresh-market and processing tomatoes in California. A weak point in the life cycle of all three species is the necessity for the two sexes to come together, with the male being guided to the vicinity of the female by the pheromone odor that she emits when she is ready for mating. We have determined for a number of moth species that if the male can not sense and use the pheromone odor for guidance, he can not locate female moths, which will remain unmated. A method for mating control, which we and other investigators have been researching for various lepidopterous pests, is based on permeation of the atmosphere with the pheromone odor (the pheromones for each of the three pests addressed here have been identified and are purchased through chemical specialty companies). With the odor of receptive females now being everywhere, the males can not find the real females, and they remain unmated.

The tomato pinworm pheromone has already been developed for commercial use in California tomato fields. The tomato pinworm is a very small, weak-flying moth. We think that the early success of communication-disruption programs for this species was aided by the fact that most of the male and female moths probably reside and find each other in the same 40-acre block of tomatoes in which they grew up as larvae. A very restricted movement of mated female moths probably prevents much re-infestation from surrounding tomato fields that are outside pheromone-treated areas. In contrast, the beet armyworm and tomato fruitworm moths are large, robust fliers, and it is obvious that the area through which mated female moths of these species range may well be over a radius of a half mile. This fact indicates that for these species a pheromone-treated area may have to be as large as 160 to 640 acres, or even more, in order to effectively prevent re-infestation by females that mate outside of pheromone-treated areas and then invade the treated areas.

Until recently, application technology has been a limitation to our ability to treat very large areas efficiently and economically. The problems were compounded because the beet armyworm and tomato fruitworm pheromones are quite unstable, breaking down to inactive compounds when exposed to air in conventional pheromone-release devices. Also, application of conventional pheromone-release devices may be very costly. These are machines for the dispensing of puffs of moth pheromones at predetermined time intervals from pressurized aerosol cans. In our earlier research, we found that deployment of only one puffer for every two to ten acres may be adequate for control of mating of the beet armyworm.

Because of early scheduling and quality-control problems that we encountered in contracting with the aerosol-can-filling industry to custom-fill small numbers of cans with experimental pheromone and propellant blends, we developed our own filling facility at the UC Kearney Agricultural Center in Parlier. This facility, which has state-of-the-art commercial-scale equipment, is, to our knowledge, the only such facility in a university laboratory in the United States.

Experiment with Shinetsu Ropes, 1996, One of the most successful conventional (hand-applied) pheromone formulations utilizes the Shinetsu Rope, a length of hollow polyethyene tubing filled with pheromone. The rope is wrapped around a plant stem or leaf petiole in the same manner as a twist’em tie. Shinetsu ropes loaded with beet and armyworm pheromone were received from the manufacturer and hand attached to the foliage of tomato plants in a rectangular 150-acre field in late August 1996. This gave an application rate of about 100 ropes per acre. The Shinetsu rope formulation gave essentially complete disruption of beet armyworm moth pheromone communication for up to two months after application, but the strong flight behavior of the moths probably brought enough mated female moths into a single protected field that the method may not give adequate worm control unless larger areas can be treated.
Out-reach activities have been emphasized during this research. During the 1995 and 1996 seasons, the project has been demonstrated and discussed at eight meetings for growers, pest control advisors, scientists, and regulatory personnel, with a total audience of over 400 persons.

Economic Analysis
This research has not proceeded to the level that permits the calculation of cost-benefits. With the continued support of the California tomato industry, a series of culminating experiments is planned for 1997, including analysis of the economic benefits derived from bringing the major pests of tomatoes under suppression through disruption of their pheromone communication.
Reported in 1997