Grape-Thrips, Pacific Northwest Pest Management Handbooks
- 1 Grape-Thrips
- 2 How to Manage Pests
- 3 UC Pest Management Guidelines
- 4 Vineyard Pest Control
- 5 Pest Control is Important
- 6 Grape Vine Disease-Vine vs. Grapes
- 7 Pest Overview
- 8 We are open. And we deliver
- 9 List of discounts
- 10 Our Team, Our Business
Grape thrips (Drepanothrips reuteri)
Western flower thrips (Frankliniella occidentalis)
Pest description and crop damage Thrips commonly found on grapes are approximately 0.04 to 0.6 inch in size. Adult thrips have feather-shaped wings. Nymphs are wingless and usually yellow-orange. They usually appear at bloom as they feed on pollen and tender tissues. However, thrips have been found in early spring in Oregon vineyards, much earlier than bloom. Thrips may scar very young berries as early as fruit set. Later, the scars can restrict berry growth, producing oddly shaped or scarred berries. Occasionally, large populations of thrips may damage shoots and leaves in spring, particularly when cool conditions restrict plant growth. Damage caused by thrips during this period has been reported to be similar to that of rust and bud mites (leaf deformation and shoot scarring). High thrips populations have been observed in western Oregon vineyards and have led to strange growth patterns; however, economic damage was not reported. Damage is usually minor and cosmetic on wine and juice grapes in the Pacific Northwest. These are of cosmetic concern for table grape production. Extremely high populations that cause greater damage are usually found in vineyards located near alternative wild hosts.
Biology and life history Western flower thrips appear to be the most important species on grapes in the Pacific Northwest. This species has up to five or six generations per year. Populations usually peak during spring, which may be a result of migration into vineyards from surrounding host plants that are beginning to senesce. Thrips overwinter as adults or nymphs.
Reproduction may be sexual or asexual. The minute eggs are laid in soft tissue, particularly in flowers. Each female lays about 20 eggs that hatch in about 5 days. Nymphs feed on the host through two nymphal stages lasting 7 to 12 days. Pupation occurs in soil debris. Adult thrips feed on pollen as well as plant tissues. Scarring has been observed on stem, leaf and berry tissue in Oregon.
Grape thrips overwinter as virgin females in the soil; populations usually reach a peak in midsummer. This species may be mostly responsible for young leaf and new growth damage during summer.
Sampling and thresholds Thrips populations can be determined by counting nymphs and adults that have been knocked out of flowers or fruit clusters onto a board or into a container. Reliable thresholds have not been developed, although numbers in the range of 5 to 30 thrips per cluster are unlikely to be damaging. Populations on leaves can be identified using leaf washes in spring and summer using the alcohol wash as described for rust mites.
Little is known about natural control of thrips in vineyards. Some predatory mites, predatory bugs, and spiders are known to feed on them.
Management-chemical control: HOME USE
- azadirachtin (neem oil)-Some formulations are OMRI-listed for organic use.
- insecticidal soap-Some formulations OMRI-listed for organic use.
- kaolin-Applied as a spray to foliage, flowers and fruit, it acts as a repellent to some insect pests. Some formulations are OMRI-listed for organic use.
- plant essential oils (cinnamon, clove, garlic, peppermint, rosemary, thyme)-Some formulations are OMRI-listed for organic use.
- pyrethrins (often as a mix with other ingredients)-Some formulations are OMRI-listed for organic use.
- spinosad-Some formulations are OMRI-listed for organic use.
Management-chemical control: COMMERCIAL USE
- azadirachtin (Aza-Direct, Neemix and other brands)-Rate varies with specific product, consult label for rate. PHI 0 days. Some formulations are OMRI-listed for organic use.
- Chromobacterium subtsugae strain PRAA4 (Grandevo) at 2 to 3 lb product per acre. PHI 0 days. OMRI-listed for organic use.
- kaolin clay (Surround WP) at 23.75 to 47.5 lb ai/a (25 to 50 lb/a product). The preferred rate is 25 lb of product in 50 gal/a water. For suppression only; supplemental controls may be needed for complete control. Make one to two applications 7 days apart, starting at budbreak. Product may not adhere well to berries early in development (best adherence at véraison and after). See label for specific instructions on use in table, raisin and wine grapes, including information on how harvest may be altered. OMRI-listed for organic use.
- insecticidal soap (M-Pede and other brands) at rates between 0.25 to 4% (see label). Higher rates are used for stand-alone application but 1-2% is used in tank mixes. This is a contact insecticide, and efficacy is related to the solution concentration and contact with the pest. Some formulations are OMRI-listed for organic use. Do not use on Calmeria or Italia grape varieties. Do not mix with sulfur. PHI 0 days.
- spinetoram (Delegate WG) at 0.047 to 0.078 lb ai/a. PHI 7 days. Retreatment interval 4 days. Do not make more than 5 applications per season or exceed 0.305 lb ai/a. Group 5 insecticide. Do not use Group 5 insecticides more than twice consecutively.
- spinosad (Entrust or Success) at 0.065 to 0.125 lb ai/a. PHI 7 days. Treat when pest first appears. Heavy infestations may require repeat applications. Do not exceed 0.45 lb ai/a of Entrust or Success per season. Do not exceed three applications in any 30-day period. Allow at least 5 days between applications. Entrust is OMRI-listed for organic use; Success is not approved for organic production. Group 5 insecticide. Do not use Group 5 insecticides more than twice consecutively.
How to Manage Pests
UC Pest Management Guidelines
Grape thrips: Drepanothrips reuteri
Western flower thrips: Frankliniella occidentalis and others
(Reviewed 7/15 , corrected 12/16 )
In this Guideline:
DESCRIPTION OF THE PESTS
Thrips are small insects, 0.04 inch long, with distinctive feathery wings. Color varies from yellow to brown in color. Grape thrips and western flower thrips are the most important species causing damage on grapes. Both species may be found in most grape-growing areas. Grape thrips populations usually reach their greatest numbers in July; this coincides with peak vine growth, and as vine growth slows, the numbers of thrips decreases. Western flower thrips populations peak in May, coinciding with grape bloom and the drying up of winter plant hosts.
Table grapes are susceptible to fruit damage caused by the western flower thrips. They create halo-spotting on the fruit when they oviposit in berries during bloom and up to fruit set or shortly thereafter. Both western flower thrips and grape thrips can scar berries with their feeding, which renders certain white varieties used for table grapes unmarketable. Thrips scarring is primarily a problem on Red Globe, Calmeria, Italia, and occasionally on Thompson Seedless. Fruit feeding discontinues in summer when both species feed on new vegetative growth.
In the North Coast, western flower thrips can feed in emerging shoots in early spring and stunt shoots and cause leaves to cup, especially during cool, rainy springs. Grape thrips may attack shoot tips in late spring or early summer although damage does not become apparent until the population has already decreased. While summer damage of leaves by thrips is common, it is not considered a problem for most varieties. However, a heavy grape thrips population can be a problem in Salvadors.
In general, thrips are a minor problem on wine and raisin grapes in California with the exception of large populations on emerging shoots in cool growing regions; however, table grapes are susceptible to thrips damage and may require treatment. For table grapes, make thrips management decisions based on pest population and damage in previous years and varietal susceptibility.
Little is known about natural control of thrips in vineyards but predators such as minute pirate bugs undoubtedly play a role in keeping populations in check.
Avoid mowing cover crops infested with thrips at budbreak or before bloom because thrips may move to vines and cause shoot stunting.
Organically Acceptable Methods
Biological and cultural controls and sprays of the Entrust formulation of spinosad are acceptable in organically managed vineyards.
Monitoring and Treatment Decisions
On cool days after budbreak monitor for thrips. Open shoots or gently tap buds over white paper to check for thrips.
During the period of rapid shoot growth, inspect flowers or fruit clusters for adults or larvae, as well as the predatory minute pirate bug, by striking clusters three times over a white piece of cardboard. Normal population levels of western flower thrips range from 5 to 25 adults and 10-50 larvae per cluster. High levels exceed 150 adults and 300 larvae per cluster, but damaging population levels for grape thrips in clusters has not been determined. Bloom sprays may be necessary to prevent berry scarring in table grape vineyards.
At harvest look for damage caused by thrips to assess this year’s management program and to plan for next year.
From dormancy through budbreak, monitor for thrips along with other pests in wine/raisin grapes as outlined in DORMANT/DELAYED DORMANT AND BUDBREAK MONITORING. Inspect new shoots in spring, especially in cool regions, for shoot scarring and distorted leaves. In these areas treatment may be necessary if damage increases and cool temperatures persist. Record observations on a monitoring form (example form— (PDF) ).
|Common name||Amount per acre**||R.E.I.‡||P.H.I.‡|
|(Example trade name)||(hours)||(days)|
UC IPM Pest Management Guidelines: Grape
Insects and Mites
L. G. Varela, UC IPM Program and UC Cooperative Extension, Sonoma County
Acknowledgment for contributions to Insects and Mites:
PDF: To display a PDF document, you may need to use a PDF reader.
Statewide IPM Program, Agriculture and Natural Resources, University of California
For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.
Agriculture and Natural Resources, University of California
Vineyard Pest Control
Grapevine Pests and Diseases
Pest Control is Important
Planting vineyard grapes can be quite a challenge. Aside from thinking about the types of soil, proper spacing of trellises, and even pruning regularly, all vineyard owners need to know how to deal with pests. It seems that insects and animals love grapes as much as humans do.
Grape Vine Disease-Vine vs. Grapes
Vine Diseases & Pests
There are numerous grapevine leaf problems. As a note I will say that in al the years I have had very little problems with my vines. The following is a list of some of the most common.
Grape Diseases & Pests
1. Mycoplasma Organisms: Caused by cicadas. Yellowing of sprouts causing sensitivity to frost. 2. Two Spotted Spider Mite: Insect will colonize on the interior part of the leaf. They sap the fluids of the plant and the leaves fall off. 3. Thrips Bug: Attack grapevine leaves and flowers. 4. Scarab Beetle: Attack sprouts and in some cases the grapes themselves. 5. Vine Moth: Attacks flower buds and grape pulp .
When you see holes on the berries or on the leaves of the vineyard grapes, your vines might be suffering from insect infestation. Some of the most popular insects that love to feed on grape plants include rose chafers and grape berry moths (which eat the berries), grape leafhoppers (which eat the leaves), and Japanese beetles (which inhibits berry production). The best way to deal with these pests is to spray insecticides
Some of the pests that affect grapevines include animals, insects, and even diseases. Birds and deer are the most common animals that love to eat the berries, while the usual diseases that affect the plant include phomopsis cane, mildew, fungus, black rot and leaf spot. You will know that your vineyard grapes are suffering from some kind of disease when you see leaf lesions and discoloration. If you see a thin film-like coating on the leaves of your plant, you should be concerned. This can all cause the berries to decay. The first line of defense that can defeat major diseases of grapes, is a fungicide. After spraying this remedy, you will surely see an improvement within a few days or weeks. However, if this does not help improve the condition of your plant, then you might want to look deeper and study the particular type of disease that hit your grapes.
As mentioned earlier, birds and deer are the most common animals that raid vineyard grapes. One of the most effective ways to shoo away flocks of birds is to use nets. You can literally put a net over your trellis system. However, it is important to remove the nets at least a month before winter comes. Leaving the nets on the trellises during the cold season might damage the plant’s productivity and growth. If you are dealing with a deer, however, nets might not help. What you can do to drive away deer or birds is to use physical repellants or loud noises that scare them away. However, if your vineyard is just in your backyard, you might need to look for other ways. For instance, since coyotes are predators of deer, you might want to use the scent of coyotes as repellant. There are metal silhouettes of wolves that rotate with the wind and they have been effective.
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