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Grape Fan Leaf Virus
Infected leaves are often malformed with abnormally gathered primary veins, giving the leaf the appearance of an open fan. Other symptoms may include a yellow mosaic pattern on leaves or bright yellow bands along major veins.The disease is spread by dagger nematodes,
The symptoms generally start appearing in late August through September as irregular blotches onleaf blades on basal portions of shoots. The secondary and tertiary veins turn partly or fully red. Occasionally, the reddening of leaf blade in the interveinal zones between secondary veins resembles those of leafroll diseases, but the leaf margins do not roll downward.
Red colored grape cv.: Red leaves in fall“Rolled under” leavesReduced vigor
White colored grape cv.: Leaf curlingChlorosisReduced vigor
The leafroll virus is spread primarily via mealybugs.
- The bacterium that causes Pierce's disease (Xylella fastidiosa) lives in the water-conducting system of plants (the xylem).
- systemic colonization of the xylem
- Symptoms appear when a significant amount of xylem becomes blocked by the growth of the bacteria. It’s spread from plant to plant by sap-feeding insects that feed on the xylem.
- Symptoms of Pierce's disease first appear as water stress in midsummer, caused by blockage of the water-conducting system by the bacteria
4 symptoms of Pierce's disease
- 1) Dried leaves fall leaving the petiole attached to the shoot
- 2) Leaves become slightly yellow or red along margins in white (top) and red (bottom) varieties.
- 3) fruit clusters shrivel or raisin(4) wood on new canes matures irregularly, producing patches of green, surrounded by mature brown bark
Pierce's Disease Vector
- Glassy Winged Sharpshooter
- This vector is a serious threat to California vineyards because it moves faster and flies greater distances into vineyards than the other species of sharpshooters. The glassy-winged sharpshooter occurs in unusually high numbers in citrus and avocado groves and on some woody ornamentals. Current control measures for PD include insecticide sprays and cultural practices (severe pruning, removal of infected vines and avoid planting vineyards near citrus orchards).
Breeding Resistance to PD
V. arizonica/candicans b43-17 has single dominant gene resistance to PD and it’s homozygous All progeny from crosses to b43-17 are resistant to PDGenetically mapped PD resistance (PdR1), to chromosome 14. Linked markers have been used for marker-assisted selection (MAS)
Types of Pests
- Grapevine pests are organisms that damage or interfere with grapevines.Pests may not cause direct damage, but may transmit disease, which in turn can affect vine health. A pest can be:
- invertebrate (insect, mite)
- nematode vertebrate (bird, rodent, or other mammal)
- a plant (weed)
- Birds are the biggest pest, especially the starling
- type of damage
- small birds (e.g. Finches) will peck at the fruit
- Starlings and larger birds will remove the entire berry
- If the berries are damaged then pathogens can invade and spred throughout the bunches
- 1. Grape leafhoppers
- 2. Sharpshooters
- 3. Western grapeleaf skeletonizer
- 4. Grape leaffolder
- 5. Spider mites
- 1. Mealybug
- 2. Orange Tortrix
- 3. Thrips
Bud or new growing shoot tip pests
- 1. Phylloxera
- 2. Nematodes
- complete metamorphosis
- four life stages: as an embryo or egg, a larva, a pupa and an imago or adult
- grape omnivorous leafrollers
- incomplete metamorphosis
- variegated western grape leafhopper
natural enemy: Predators
- he arthropod predators of insects and mites include beetles, true bugs, lacewings, flies, midges, spiders, wasps, and predatory mites. Insect predators can be found throughout plants, including the parts below ground, as well as in nearby shrubs and trees. Some predators are specialized in their choice of prey, others are generalists. Some are extremely useful natural enemies of insect pests. Unfortunately, some prey on other beneficial insects as well as pests.
- (Spider mite destroyer) lady beetle
natural enemy: Parasitoids
- Insect parasitoids have an immature life stage that develops on or within a single insect host, ultimately killing the host. Adult parasitoids are free-living and may be predaceous. Most beneficial insect parasitoids are wasps or flies.Most insect parasitoids only attack a particular life stage of one or several related species.
- female adult Bracon cushmani laying eggs on the body of leaffolder larvae
European grapevine moth
- ative to Mediterranean Europe, European Grapevine moth was reported for the first time in the United States in Napa Valley in October of 2009.
- Young larvae are creamy white with black heads. Older larvae are tan to yellow-brown, turning dark green or maroon as they mature. They have visible white tubercules at the base of the body hairs. Heads are tan to yellow-brown, with a distinct dark border on the outer edge of first segment behind the head.
- L. botrana overwinters as pupa under the bark
L botrana generational feeding
In May and June, first-generation larvae web and feed on the flower clusters. Second-generation larvae (July-August) feed on green berries. Young larvae penetrate the berry and hollow them out, leaving the skin and seeds. Third-generation larvae (August-September) cause the greatest damage by webbing and feeding inside berries and within bunches, which become contaminated with frass (excrement).Additionally, feeding damage to berries after veraison exposes them to molds and secondary pests such as raisin moth and fruit flies.Unlike other moths, it does not cause damage to leaves and shoots.
Generally considered a pest of grapes in the coastal areas and valleys where there is a marine influenceOrange tortrix causes the same kind of damage as the omnivorous leafroller in inland areas.Overwintering larvae feed on any soft, exposed vine tissue, weeds, and in grape mummies on the vine. Spring feeding is on buds, and leaves. Larvae then enter the bunches as early as bloom time and make nests of webbing among the berries. Besides injury to leaves and berry stems, their feeding on berries allows entry of bunch rot disease organisms.If orange tortrix is a problem, encourage biological control by the judicious use of insecticides. As for leafroller there are endemic parasitoids that can keep OT population below economic impact thresholds.
- Larva of the omnivorous leafroller folding a leaf by tying edges together with silk threads.
- oastal vineyards. It feeds on leaves, flowers, and berries pre- and after-veraison. The most significant damage occurs after veraison when feeding allows rot organisms to enter fruit at the damage sites.Omnivorous leafroller overwinters in the larval stage in grape mummies, vineyard weeds, and other trash in the vineyard. During the dormant season remove mummy clusters and control vineyard weeds. French plow and disc clusters and weeds to bury overwintering larvae living on weeds in ground duff and dried berries. During dormancy, prune out old fruit mummies and destroy by flailing or shredding.
larvae roll the leaf edges and feed from the inside on the leaf edge.
Parasites play an important role in keeping grape leaffolder below a level that will cause damage.Several parasites attack grape leaffolder. Among the most common is the larval parasite Bracon cushmani. Grape leafroller can reduce leaf surface by constructing leaf rolls and by leaf feeding.Twenty percent leaf reduction can be tolerated 1 month after fruit set in the San Joaquin Valley. Even more leaf damage can be tolerated later. However, if damage is severe enough to cause complete defoliation, it leads to sunburned berries, soft fruit, and direct berry feeding by leaffolder larvae.
- Adult western flower thrips, Frankliniella occidentalis.
- Halo spots on mature grapes around thrips oviposition punctures, visible as small scars
- Starfish pattern of berry scarring caused by thrips feeding on young grape berries
- Thrips are small insects, 0.04 inch long, with distinctive feathery wings. Color varies from yellow to brown in color. They have rasping-sucking mouthparts.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. 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. In general, thrips, are a minor problem on wine and raisin grapes in CA; however, table grapes are susceptible to thrip damage and may require treatment. For table grapes, make thrips management decisions based on pest population and damage in previous years and varietal susceptibility (e.g. Red Globe and Italia).
Western grapeleaf skeletonizer
First through the early fourth instar larvae feed on the lower leaf surface, leaving only the veins and upper cuticle. This gives leaves a whitish paperlike appearance; eventually the entire leaf turns brown.The late fourth and all fifth stage larvae skeletonize the leaves, leaving only the larger veins. When abundant, larvae can defoliate vines by July. Western grape leaf skeletonizer does not occur in all grape-production areas because the moths are not long-distance fliers and this pest has been slow to spread in California since its first appearance in the 1940s. In areas where it does occur, granulosis virus (endemic to Southern CA and introduced in other counties) usually keeps populations below economically damaging levels. When the virus is insufficient, western grapeleaf skeletonizer is easily controlled with insecticides that are also effective on other caterpillars, leafhoppers, ..
The western grape leafhopper is a pest of grapes especially in the San Joaquin, Sacramento, and North Coast valleys. It is also a problem in warmer, interior Central Coastal valleys. The variegated leafhopper is the major pest of grapes in southern California and in the Central Valley as far north as San Joaquin County.Nymphs and adults of both species remove the contents of leaf cells. Loss of leaf efficiency and leaf drop can occur when leafhopper densities are extremely high. This can result in fruit sunburn. Many natural enemies help to provide control of leafhopper. Although leafhoppers infest most vineyards in California, they may not require chemical treatment because vines can tolerate fairly high populations without harm, and predators and parasites may be able to maintain leafhopper populations below tolerance levels.
Pacific spider mite is the primary pest mite species in the San Joaquin Valley and may also be the primary pest mite in certain North Coast grape-growing areas. Pacific spider mite prefers the warmer upper canopy of the vine. Although it can cause damage early in the season, Pacific spider mite generally prefers the hotter, dryer part of the season.
Willamette spider mite is pale yellow. It is often considered an early-season mite. It prefers the cooler parts of the plant and is found mostly in the shady parts of the vine. In certain areas (e.g., North Coast) and during certain years, populations can persist throughout the growing season. Willamette spider mite is primarily a problem in the Salinas Valley and Sierra foothill production areas where it can cause economic damage to varieties such as Zinfandel. In the North Coast it can cause damage in early spring when shoot growth is delayed or later in the season in vines with small canopies. Willamette spider mite is seldom a pest in the San Joaquin Valley, especially on Thompson Seedless.
Twospotted spider mite, Tetranychus urticae, is almost identical in appearance to the Pacific spider mite except it rarely has spots on the rear of the body. It is only occasionally found on grapes in California and rarely causes damage.
- Dust contributes to spider mite populations
- Many natural enemies help to control pest mite populations (important: when monitoring mites, note the presence of mite predators).
- Sixspotted thrip
- Spider mite destroyer
- Western predatory mite
Three species of mealybugs in the genus Pseudococcus may infest vineyards: the grape, obscure, and longtailed mealybugs. The grape mealybug and the obscure mealybug closely resemble each other. One method of distinguishing them in the field is to poke a female with a sharp point (without puncturing the body) to elicit the release of a defensive excretion. If the color of the fluid excreted is reddish orange, then it is most likely grape mealybug; if it is clear, it is most likely obscure mealybug. Longtailed mealybug is similar in appearance to the other two species but has much longer waxy filaments on the posterior end (they are as long or longer than the body of the adult female). Longtailed mealybugs are only a problem in Central Coast vineyards. Mealybugs damage grapes by contaminating clusters with cottony egg sacs, larvae, adults, and honeydew. Often the honeydew is covered with a black sooty mold. All three species can transmit grape viruses.Parasites and predators can help keep mealybug populations down.Honeydew-seeking ants must be controlled in order to allow natural enemies of mealybugs to aid in mealybug control. Controlling ants may sufficiently allow parasites and predators to control mealybugs.
- Grape phylloxera is a tiny aphid like insect that feeds on Vitis vinifera grape roots, stunting growth of vines or killing them.Grape phylloxera damages the root systems of grapevines by feeding on the root, either on growing rootlets, which then swell and turn yellowish, or on mature hardened roots where the swellings are often hard to see.
- Galls formed on woody, mature storage roots are termed tuberosities, while galls on feeder root tips and roots that have not suberized are termed nodosities.
- High numbers of tuberosities limit root function, resulting in aboveground symptoms of reduced vine growth and fruit production, possibly correlated with water stress and nutrient deficiencies. Ultimately, soil fungi decay aging tuberosities, leading to death of the grapevine.
Phylloxera is native to the eastern and shouthern United States, where native American grape species coevolved with the insect.The American grape species V. rupestris, V. berlandieri, and V. riparia are resistant to phylloxera. European grapevines, V. vinifera, are the most susceptible. It was introduced into Europe on specimens imported to museums in 1863. By 1900, 75% of vineyards in France were destroyed.It spread rapidly throughout France and then to other locations in Europe and N. Africa.Spread to California in 1870 – 1873.European grapes grafted onto American root stock are tolerant to the root gall form of the insect.
Nematodes, the most abundant multi-cellular animals on the planet, are unsegmented roundworms that inhabit soil, freshwater and marine environments.80% of multicellular animals are nematodes.Species that are parasites of plants may feed externally or internally in roots or other tissues.
Root knot nematode
- (Meloidogyne spp.)
- Root knot nematodes produce small galls on the roots (about 0.125 inch in diameter), but they can be larger when multiple infections cause galls to coalesce.
- Xiphinema index
- he dagger nematode feeds on root tips causing them to swell in a manner similar to the nodosities caused by phylloxera. Virus (grapevine fanleaf virus) transmission by dagger nematode produces symptoms on leaves such as yellowing of veins, mosaic, and malformation with symptom expression less apparent among white varieties and in warmer regions.
- Compete for water, nutrients, and light with grapevines - Interference is especially problematic during establishment years - Can affect crop management, irrigation, and harvest operations - Impacts on other pest problems - Crop quality concernsDifficult weeds are species that withstand, tolerate, or are resistant to the control measures used in a particular system and have an economic impact
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