Stephen Vasquez, Walt Bentley and Matthew Fidelibus
Over the last four years some growers have noticed an unusual worm in their vineyards. The worms are difficult to see if you are passively walking the vineyard but if you peel the old loose bark away from the head, trunk or cordons until you reach the newest bark, you may find holes with large white larvae (Fig. 1). The insect is a moth and has been identified as a member of the Givira genera, which have been mostly associated with old (>35 years) Thompson Seedless vineyards but have been found in vineyards planted to other cultivars too. Many of the older raisin vineyards located in Fowler/Del Rey and to the east in Sanger/Parlier area have documented this wood boring worm. Whether or not they cause direct economic damage is uncertain; most of the worms we saw seemed to be boring into dead wood. However, some growers have said they have seen these worms feeding on living cambial tissue and on young emerging buds and green shoots. Their burrows also offer refuge to vine mealybug, which is undesirable to growers trying to mange this pest.
Often what first attracts a grower’s eye is the adult cast left behind after emergence. The casts stick half way out of a bored hole in old wood (Fig. 2); resembling planes that crash dove into the wood. Figure 3 shows the cast pulled from the hole.
Currently, little is know about the moth’s biology but there are plans to do some trapping in March. Using black light traps, UC researchers hope to catch adult moths that can then be used to identify the species and give researchers a better idea of what potential management methods could be used to reduce populations. Additionally, surveys will take place to try to identify egg masses associated with this genus.
Stephen Vasquez is the UC Cooperative Extension Viticulture Farm Advisor in Fresno County. Matthew Fidelibus and Walt Bentley are Viticulture Extension Specialist and UC IPM Entomology Advisor, respectively, located at the UC Kearney Agriculture Center.
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Stephen Vasquez and Roger Baldwin
Vertebrate pests live in and around vineyard settings and can cause significant damage. Damage will depend on the vineyard location, surrounding habitat, and population size of the vertebrate pest in question. Gophers, ground squirrels, and rabbits are the primary vertebrate pests in the San Joaquin Valley and will cause long-term damage if left unchecked. Gnawing on grapevine roots and trunks will lead to large patches of dead vines. These pests can also damage irrigation systems and cause erosion by diverting water via their burrows. Although these pests have natural predators, growers should not rely on them solely for controlling large populations of vertebrates. Recently, Roger Baldwin and I held a field day that focused on gopher management in vineyard settings. Following are some of the strategies that were discussed at the field day.
Gopher Habitat
Visual identification of gophers may prove difficult since they rarely venture outside of their burrows. Living underground, gopher activity includes the building of an intricate burrow system that can only be detected by the distinct mounds found at each opening. Openings to the burrow matrix will typically be plugged, but recent activity can be indentified by the moist, friable soil that gophers push out of recently made burrows. Growers should focus their management efforts on these types of mounds and not the ones that are dry.
Injury
Feeding mostly on root systems of herbaceous plants, gophers will sometimes pull entire plants below ground or nibble on above ground plant parts near their tunnel entry. Grapevines are damaged when gophers gnaw on roots or bark below the soil line. Vines damaged by this type of feeding will look water stressed or will die as a result of girdling, a process that removes the cambium and does not allow for natural repair. Vineyards older than ten years of age display little damage from gophers, perhaps due to the larger root system characterized by the corky periderm protecting the inner bark layer and cambium.
Management
Traps
Traps, when set correctly, work well against gophers. Traps, like all control methods, are most effective when populations are low. Several types are available, but the two-pronged pincher types are the most popular (Fig. 1). When populations are high, trappers will need to focus their efforts in localized areas with high activity, setting traps multiple times throughout the season. Once gophers are controlled in those areas, new efforts should expand out from these centralized areas until the whole vineyard has been controlled.
Setting Traps
- Locate main burrow using a pr
European grapevine moth (aka European grape berry moth; (Lobesia botrana) was recently found in Napa County, a first known find for California. The insect has the potential to cause great economic harm to California’s diverse grape industries. The moth was trapped in Napa County’s, famous Oakville grape growing region known for high valued wines. Common to Europe and the Mediterranean, European grapevine moth has been intercepted from across the US where international travelers, cargo or mail disembark from planes originating from overseas. Currently, the Napa County Agriculture Commissioner is working with the CDFA and USDA to survey the area where the moth was first located in an attempt to detect additional European grapevine moths.
European grapevine moth identification
European grapevine moth can be confused with American grape berry moth (Endopiza viteana) native to the eastern United States or European grape berry moth (Eupoecilia ambiguella). Wings of the invasive European grapevine moth, L. botrana, have a mosaic shaped pattern with black-brown, cream, and gray-blue ornamentation (Fig. 1). Larvae tend to develop a purple cast after feeding and will often be found inside the berry. Samples should be taken to a trained university or state entomologist for proper identification and documentation. It is important to note that samples should be enclosed in a sealed container, jar, or vial if found prior to moving the insect (all stages) from an infested site.
Damage
Damage can be seen to both grape flowers and developing fruit. Larvae feed on flowers prior to bloom and continue through bloom. As bloom peaks, larvae protect themselves by producing webbing around the damaged flowers and feeding on neighboring flowers and parts. Second and third generation larvae feed on berries hollowing and contaminating them with excrements (Fig. 2). Cultivars that naturally have tight clusters—like Chardonnay, Pinot noir and Zinfandel—will suffer the most damage. Much like infestations from other worm pests, feeding damage will lead to infections by bunch rot fungi. Raisin and table grape cultivars will also experience damage, especially when bloom is prolonged due to weather, making flowers less responsive to applications of gibberellic acid used for bloom thinning. Table grape cultivars with tight clusters have the least tolerance for the moth due to fruit feeding damage and contamination with webbing, excrements and rot. All life stages can be found in vineyards infested with European grapevine moth but larvae from the second and third generations have been found to be the most damaging when fruit is maturing.
Host range
The host range for European grapevine moth is diverse. In addition to Vitis vinifera (cultivated grape), they also feed on other important agri
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University of California (UC) researchers have extended information at Grape Days for 58 years. Here is a brief history, as remembered by Amand (Kas) Kasimatis and L. Peter Christensen, Extension Specialist Emeriti, Dept. of Viticulture and Enology, UC Davis.
Commodity days were quite popular on the Davis campus in the early fifties; the first Grape Day was held there in Aug., 1951. H. B. Richardson, Ext. Specialist, and A.J. Winkler, Chair of the Dept. of Viticulture and Enology, organized the first program. At the time, there was a lot of field research being done in the University vineyard, so most of the Department faculty put on a demonstration. It included lunch on a lawn with shade trees around the Viticulture fieldhouse and had a luncheon speaker. L. Peter Christensen remembers attending one of campus Grape Days in the mid 1950s. “Nick Dokoozlian Sr. drove the van. It was very popular and awe inspiring for a farm boy.” Amand Kasimatis took over in 1956 and chaired the campus programs yearly until the early 1980’s. In January 1976, Kasimatis, in collaboration with California Association of Wine Growers, developed Wine Grape Day. Additional Wine Grape Days were held every February through 1985, on the Davis campus, with the exception of one that was organized by Vince Petrucci (Professor of Viticulture, CSU Fresno), and held in Fresno. No Grape Days have been held on campus since 1985, but the Department presents RAVE (Recent Advances in Viticulture and Enology) in March.
In the 1960s, Kas established several regional Grape Days at off campus facilities. The first of these was the Coast Grape Day, at the Oakville Station, Napa Valley. Grape Day at Oakville continued for some time, eventually under the direction of Jim Wolpert. The first Grape Day at the Kearney Agricultural Center (KAC), also initiated by Kasimatis, was held in 1967, two years after the center was opened. Kasimatis directed Kearney Grape Days until 1973, when Fred Jensen (Extension Specialist Emeritus, UC Davis) assumed those responsibilities. In the mid 1980s, L. Peter Christensen became an Extension Specialist, and then was responsible for the Grape Day at Kearney until Nick Dokoozlian (former Specialist, Dept. of Viticulture and Enology, UC Davis) took over in the early 1990s. Since 2005, Matthew Fidelibus has organized Grape Day at the KAC. We hope you find this year’s program to be interesting and enjoyable, and that you will join us again in 2011.
Erineum mite populations seem to be exploding this season. In the past two weeks, a half-dozen samples have been dropped off at my office for inspection. Normally, a few samples are brought in from backyard vineyards, which I expect. However, the most recent samples and calls have been from commercial wine grape vineyards with concerns that it is downy mildew. First, let me assure you that it is not downy mildew. The Valley has not experienced an outbreak of downy mildew since the mid-90’s when a few table grape vineyards were identified with the disease after optimal weather; rain and warm temperatures. The recent erineum mite outbreaks in commercial vineyards are easily explained by a reduction in sulfur use for powdery mildew. Winegrape vineyards tend to experience more frequent outbreaks when wineries request a reduction in sulfur dust so it does not interfere with fermentation. Below is a summary of erineum mite life cycle.
