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Napa Moth Eradication Cost Near $90 Million

County launches new trapping program for five new pests

by Paul Franson
greg clark napa
Napa County agricultural commissioner Greg Clark announces a program placing sentinel traps for pests known to damage grapevines.

Napa, Calif.—The Agricultural Commissioner’s office in Napa County has launched a sentinel program to gain an early warning if five potential grape pests show up in the county.

Ag commissioner Greg Clark announced that his department is targeting serious pests of wine grapes not known to be established in California. “Placing a base level of traps throughout Napa County provides the opportunity to detect infestations of new pests early, before they become widespread throughout the county.”

The importance of the sentinel trapping is clear. “Prior to 2009, the European grapevine moth (Lobesia botrana) was not known to be established in North America. With its discovery in Napa County in 2009, and 10 additional California counties, a multi-million-dollar federal quarantine program was established.”

He added, “Since 2010, Napa County growers have spent approximately $45 million in treatment and quarantine costs in the EGVM (European grapevine moth) eradication effort. Early detection of serious wine grape pests could potentially save millions of dollars in government and grower resources.”

Humberto Izquierdo, assistant agricultural commissioner for the County of Napa, estimated that local, state and federal governments have spent an additional $45 million to $50 million on trapping and quarantine compliance for EGVM.

The pests selected for the program were identified by reviewing information from the USDA Grape Commodity-based Survey Guidelines, the Cooperative Agricultural Pest Survey (CAPS) for grapes, USDA’s Tortricids of Agricultural Importance and by consulting with CDFA, USDA and international authorities on grape pests.

The pests identified for the trapping program are:

Honeydew moth (Cryptoblabes gnidiella) is distributed throughout Asia, Africa, Europe (including France and Italy), South America (Brazil and Uruguay) and Hawaii. The larvae feed on the stems when fruit is green, causing wilt and berry fall. Feeding in ripe berries can cause juice leakage and secondary rot pathogens.

European grape berry moth (Eupoecilia ambiguella) is distributed throughout Asia, and Europe (including France, Italy and Spain). Larval damage is similar to damage caused by L. botrana. Flower buds, open flowers and young fruitlets can be destroyed as well as developing or mature grapes later in the season. Associated rots can also be an issue. EGVM and European grape berry moth are considered the two most serious wine grape pests in Europe.

Grape berry moth (Paralobesia viteana) is widespread in grapegrowing regions of eastern North America. Recently it has been reported in western Colorado vineyards. Grape berry moth is the primary lepidopteran grape pest in eastern North America. Females lay eggs on individual grapes, blossoms and stems. Larvae of the first generation feed on blossoms or small berries, often webbing together entire clusters. Larvae of subsequent generations tunnel into the berries and feed inside, also webbing together clusters.

Grape tortrix moth (Argyrotaenia ljungiana) is considered a pest of fruit and field crops and ornamentals in southern Europe and the European part of the former USSR. It has been recorded damaging a variety of plants, with most economic losses occurring in apples, grapes and tea. Early instar larvae skeletonize the underside of leaves along the midrib. Later instars roll or fold leaves and may also feed on buds and fruits.

Brown marmorated stink bug (Halyomorpha halys) is a potentially serious pest to wine grapes and wine quality. Brown marmorated stink bug (BMSB) was introduced to the Eastern United States in the mid-1990s and has since spread to various regions of the country. It has been reported in Southern California since 2005. In 2013, a large population was found in central Sacramento, Calif., as well as smaller infestations in Yuba City, Calif., (Sutter County) and Chico, Calif., (Butte County). The pest is known to spread by hitchhiking on household belongings that are moved across the country or around the state.

Approximately 350 traps will be deployed at the rate of one trap per square mile for each of the first four insects. Based on a review of pest life cycles, traps were put up in July and will be removed in October.

Traps for the brown marmorated stink bug will be placed around moving and storage companies, campgrounds and RV parks and larger wineries that receive the most visitors. For this initial BMSB trapping program, 40 traps sites will be selected throughout the county. Data will be shared with researchers from the state working on the infestations in Sacramento, Butte and Sutter counties.

Treatment history and cost
Martin Mochizuki, the EGVM grower liaison, summarized the treatments that have been applied to eradicate the European grapevine moth.

In the first years after discovery of the pests, more than 20,000 acres were treated with pesticides, and mating disruption was extensively used.

As trappings have dropped, however, the treatment areas have been shrinking, and for next year no mating disruption will be employed to avoid compromising the trapping program.

european grape vine moth

The spraying for EGVM in 2014 occurred within 500 meters from places where the bugs were found in 2012 and 2013. This involved approximately 3,000 acres with 80 growers. They sprayed for the first two generations and used isomate pheromones wit hin 500 meters of the 2013 trapping sites.

The conventional vineyards received isomate pheromone for mating disruption by March 15, targeted within 500 meters of the 2013 findings.

One application of Intrepid or Altacor was applied at pre-bloom stage for the first generation of the bugs, then Intrepid or Altacor was used on the second generation using a degree-day model for timing for a total of two or three applications.

Organic vineyards required more sprays—a minimum of four or five sprayings.

As with conventional vineyards, isomate pheromones for mating disruption were set out by March 15 within 500 meters of the 2013 findings.

To fight the first generation, Bt or Entrust treatments were applied at the pre-bloom stage. Based on the residual impact, pest development and timing, two or more applications may be needed.

Bt or Entrust were applied by degree-day model for the second generation but two applications may be necessary.

Olive flowers at bloom, which can host the insects, were sprayed with Bt or Altacor at bloom time only.

Mochizuki summarized the cost of the control measures to growers:

napa vineyard pest program

He added that there was 100% compliance by growers in the treatment areas. Growers within 500 meters of the 2013 finds will need to treat again in 2015, but no isomate pheromones will be used in 2015.

If no EGVMs are found, the restrictions and treatments could end in 2016.


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