Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
email: Office@practicalwinery.com
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Spring 2011
GRAPEGROWING
Far Left: First generation larva feeding in pre-bloom flower cluster.
Left: Second generation larva feeding inside a post-veraison berry. Note webbing and feeding holes in berry.
the most effective and least disruptive insecticide application at the best timing.
In particular, we need to avoid exacerbating natural enemies of grape mealybug. This could create a more severe problem, such as the increased spread of viruses causing grapevine leafroll disease. Finally, the highest risk pathways in which these insects spread were investigated, to help regulatory agencies develop effective containment programs.
What was learned about EGVM in Napa County vineyards in 2010?
European grapevine moth (EGVM) completes three generations per year in the majority of the grape growing regions of California. Models predict the possibility of a partial fourth generation in the Central San Joaquin Valley, although populations in that region are too low to be able to verify this in the field.
Eggs are laid by females on or near flowers or fruit. Larvae develop through five stages before pupating. Adults emerge from pupae. One generation is defined as the development from egg to adult. The spring (first) generation develops from bud break through berry set. The summer (second) generation develops from berry set through post-veraison. The late summer/fall (third) generation develops from post-veraison through post-harvest.
This insect spends the winter as pupae under the bark, in a resting state of reduced metabolism (diapause) to survive cold temperatures. We are currently verifying a degreeday model that will be useful in predicting the occurrence of events in the EGVM life cycle.
The main host of consequence identified so far in California is grape (Vitis vinifera). Moth larvae feed preferentially on grape flowers and fruit. Untreated populations can cause extensive damage to clusters, mainly as a result of secondary fungal infections.
Olive flowers were a minor host in Napa County during the first generation of 2010. The number of eggs and larvae found on olive flowers was 0.3 to 3.0% of what was found in vineyards during regular sampling. Olive fruit did not host either the second or third generations.
BY
Monica L. Cooper,
Lucia G. Varela, Rhonda J. Smith,
University of California Cooperative Extension
I
nvasive species are an increasing threat to agricultural sustainability in our global economy. Detection of an invasive species triggers the development of regulatory programs, and a need for research and educational programs.
Regulatory programs encompass pest detection and containment efforts such as trapping, quarantines, and treatment recommendations. Such programs are coordinated locally by Agricultural Commissioners, statewide by the California Department of Food and Agriculture (CDFA), and nationally and internationally by the U.S. Department of Agriculture (USDA).
The regulatory program for the European grapevine moth (EGVM), Lobesia botrana, was developed in response to the pest’s first detection in North America, in Napa County in September 2009.
A 2010 detection program deployed pheromone-baited delta traps in all vineyard regions of California, at densities of 16 to 25 traps per square mile. Male moths were found in traps in 10 California counties: Fresno, Mendocino, Merced, Monterey, Napa, San Joaquin, Santa Clara, Santa Cruz, Solano, and Sonoma.
To date, populations of this insect have not been found in North America outside California. Napa County populations were the largest: more than 100,000 males were trapped, compared with 128 males in all other counties combined (Table I).
During an aggressive treatment program, populations in Napa County decreased from 99,236 moths caught during the first flight to 1,278 and 279 in the second and third flights respectively.
A quarantine program is established if two or more moths or any other life stage is detected in a generation. Of the 10 counties, only eight counties have areas under quarantine. Single moth detections in Monterey and Santa Cruz counties did not trigger quarantines.
In four counties, very few moths were trapped and treatments were applied in 2010. If no moth is caught in these areas during the 2011 growing season — at a density of 100 traps per square mile and without mating disruption — these areas may qualify to be removed from quarantine. In the remaining counties, quarantine restrictions will remain in 2011.
Research and educational programs are addressing the need for reliable scientific information on pest identification, biology, and management. Researchers evaluate the effectiveness of tools such as traps, lures, and pesticides.
When EGVM was detected, growers, researchers, and regulatory agencies were confronted with many unknowns, including a lack of experience with the life cycle under California conditions, and the role that alternate hosts have on development and mechanisms of pest spread. There was a need to develop pest management strategies aimed at eradication.
This is very unlike the situation in Europe, where the objective is to obtain clean fruit at harvest, not to completely reduce populations. Studies were needed to identify