Grape berry moth (GBM), Endopiza viteana (Clemens), is a key pest of grape in eastern North America, and can cause severe losses in Virginia vineyards. For some time many growers used methoxychlor for control of GBM, but this compound provides only moderate control and failed when populations reached high densities. Better control is provided by organophosphate insecticides, but the future of this family of pesticides is in doubt because of the Food Quality Protection Act (FQPA); in fact one of the materials most effective against GBM, Penncap, was lost as a result of FQPA at the end of 1999. Another excellent product, azinphosmethyl, was severely restricted in 2000, now largely impractical for grape growers because of the 21-day restricted entry interval.
One alternative to conventional pesticide control is pheromone-based mating disruption. This approach permeates the atmosphere in a vineyard with pheromone, eliminating the ability of male GBM to orient to females. Mating disruption has been used experimentally in Virginia since 1990 (Pfeiffer and Wolf 1990, 1991, 1992, Pfeiffer et al. 1993, 1994, Pfeiffer and Killian 1995). For several years, this approach has been included in the Virginia Tech vineyard pest management recommendations (Pfeiffer et al. 2003). However, commercial adoption has been limited, partly because of cost. Cost of pheromone permeation is high partly because pheromone is released from dispensers all season long, even when males are not flying. It is likely the approach could be made more economical if pheromone were released only during periods of GBM flight. A sprayable formulation has been developed that may accomplish this.
One factor contributing to high populations
is mild winter weather. We have recently had a series of mild
This leads to (a) low winter mortality, and (b) an early spring
GBM more time for population development during the season. In
high levels of GBM injury were reported by many Virginia grape
In mid-July examinations in several vineyards showed high percentages
injured clusters (19, 27, 58, 79, 83, 95% (Pfeiffer
Injury was high in both conventional and pheromone treated blocks.
work is needed on both chemical and pheromone-mediated management of
Mating disruption (MD) involves the use of pheromones, i.e. the chemicals produced by an insect which evoke a specific response in the other individuals of the same species. MD is based on the principle that when a specific pheromone is released in the air in an orchard in sufficiently high quantity, the males are unable to orient to natural sources of pheromone and fail to locate the calling female and the reproduction is prevented.
There are several ways in which MD could work and understanding of these mechanisms is important to the application of MD in the field. The various ways in which MD works are discussed as under:
1-Peripheral and central nervous system effects Olfactory receptors in moths concerned with the detection of pheromones are located on the antennae. When exposed to a constant stimulus, e.g., pheromone, the output from sensory organs declines rapidly; this condition is known as adaptation. The sensory organs recover fairly rapidly (in about 2-3 seconds) once the stimulus is removed. On the other hand a high and uniform concentration of the pheromone could effectively shut down the ability of sensory organs to detect the pheromone.
The exposure to high concentration of pheromone may result in the decline of behavioral response lasting several minutes or few hours. This effect is on the central nervous system and is refereed to as habituation. In this situation nerves do not recover in the normal manner. Thus habituation caused by the exposure of moths to high concentrations of pheromones could play an important role in suppressing normal male responsiveness in the mating disruption.
2 -False trails This phenomenon works when many sources of pheromones are placed in the field and male moths are attracted to false sources, wasting time and energy. Under these conditions, the likelihood of a male finding a calling female would be very low. Under these situations it may be important that all pheromone sources are releasing about the same amount of pheromone as a calling female. Male moths would cease to be attracted to a pheromone source when the concentration of pheromone gets too high i.e. above a response threshold. If this mechanism is important, it would be beneficial to have as many pheromone point sources as possible.
3-Masking In this mechanism the
level of the pheromone is often high enough to mask the odor trail from
a calling female. In this mechanism although, the sensory system of the
male moths is normally functioning but in the high background level of
the pheromone the relatively low concentration trails emitted by
cannot be perceived.
1. Size of disruption block The size of the MD block is one of the most important factors. A disruption block of at least 5-10 acres is considered adequate for the successful MD program for GBM. MD is likely to fail in smaller-sized vineyards.
2. Distance from sources of immigration The disruption blocks ideally should be adequately isolated from wild grapevines. This is to reduce the chances of flight of mated females from the abandoned blocks to the mating disruption blocks.
3. Application rate and dispenser release In order to have a continuously high concentration of pheromone in the orchard, two factors play an important role i.e. the application rate and the dispenser release rate. The rate of pheromone applied in the disruption block may be expressed in terms of pheromone released per area a function of release rate per dispenser and the density of dispensers in the orchard. A dispenser application rate of 1000 per ha or 400 per acre at a release rate of about 37 mg/ ha / h has been found to be effective for CM and LR. The application rate will however vary with the size of the disruption block and with the type of the dispenser. Release rate per dispenser is beyond the control of the grower; however, the grower can pay careful attention to pheromone rate per acre by basing dispenser placement on the number of trees per acre.
4. Placement of dispensers Placement of dispensers in an apple orchard at different heights has been found to have a variable effect on reducing damage to acceptable levels. It has been reported that lower pheromone heights do not give an effective control against a variety of apple orchard pests particularly against tortricids. This is less likely to be a factor in grape berry moth mating disruption since the vineyard architecture is more restricted.
5. Vineyard edges The edges of vineyards
diverse habitats. These habitats are the source of alternate hosts
wild grapevines) which migrate to the vineyards. Also these vineyard
plants give shelter to many beneficial organisms which play an
role in the biological control that is compatible with MD. Thus orchard
edges contribute both positive and negative forces in a MD program. It
is generally recommended to spray the edge rows of the orchard to
immigration of gravid females and other potential pests (e.g. grape
beetle). This is less of a concern in vineyards in open settings
corn field, etc.).
Monitoring is crucial to the successful use of MD in an IPM program. The number of moths captured not only gives an indication of how well MD is working, but it also gives information about the emergence times which may be used for timing the spray schedule in an orchard against a pest. It is helpful to place traps in the treated vineyard aswell as untreated areas; this gives an idea of the suppression of the ability of males moths to orient to pheromone point sources. Furthermore, the sprayable phreomone peoduct should be applied at 2-3 week intervals during flight. Trapping lets the grower know when flight periods occur. Another type of monitoring would be the assessment of fruit damage. Weekly sampling is recommended; more frequent examination may be needed at times of anticipated population activity.
The importance of monitoring cannot be overestimated; it is more important than in a more conventional management program.
[An isolation distance of 50-100 m is suggested for GBM. Where this is unrealistic (often the case in Virginia vineyards), the upper end of the application rate should be used, and growers should spray edge rows of the vineyard.
Mating Disruption for Grape Berry Moth
Mating disruption has been carried in our vineyard IPM research program from 1990 through the present. Most treated vineyards used a two-component blend dispenser from Pacific Biocontrol (Isomate-GBM), containing 69 mg of Z-9-dodecen-1-yl acetate (90%)/ Z-11-tetradecen-1-yl acetate (10%). Limited use was also made of a single-component dispenser from AgriSense, containing only the main component of GBM pheromone, Z-9-dodecen-1-yl acetate. Both single and two component dispensers provided effective control of GBM. In most situations, damage was higher in the edge of both pheromone-treated and conventionally managed blocks. The edge effect was minimized by providing greater pesticide coverage in edge rows.
A sprayable mating disruption preparation is produced for GBM, by 3M Canada, London, Ontario. Preliminary results were reported by Trimble et al. (1998). They compared sprayable formulations of Z-9-dodecen-1-yl acetate with Isomate dispensers as well as organophosphate insecticide. The pheromone release rate in the sprayable setting was double that in the Isomate blocks. The incidence of cluster infestation was similar among the sprayable, Isomate and organophosphate blocks. This material has performed well in Virginia trials as well.
The following links provide label information for GBM mating disruption products:
Chugai Boyeki Co.