Pests of Grapes

Omnivorous leafroller

Crop: Grapes, citrus, stone fruit, apples, peppers, kiwi, cotton Scientific name: Platynota stultana Order: Lepidoptera Family: Tortricidae Range: Southern half of US Mouthparts: chewing

Distinguishing Characters: adult bell shaped with blackish grey snout-like mouthparts that protrude forward from the head. Forewings are dark rusty brown with tan tips. Size varies from 9.5 to 13 (0.38 to 0.5”) long

larvae have either a black or brown head capsule

Translucent so dorsal vessel can be seen

Mature larvae range in color from cream to brownish green with two whitish slightly convex and oblong tubercles on the top of body segment. Omnivorous Leaf Roller (OLR) larvae usually drop to the ground on a thread when disturbed

Alternate Hosts: numerous weeds Oviposition Site: on leaves Number of generations/year: 4 to 5 Overwintering Stage: in the larval stage in grape mummies, vineyard weeds, and other trash in the vineyard Damaging stages: larvae

Shingle like egg mass of OLR

Larva overwintering in a grape berry mummy on bark

Typical damage: After about 5 days the eggs hatch, larvae tie two young leaves together to form a nest in which they feed - note they fold leaf, not roll it

grape leaffolder, Desmia funeralis rolls grape leaves

Later nests appear in flowers

In bunches

And on shoot tips

primary damage is that it allows rot organisms to enter fruit at the sites where it feeds

Non Chemical control measures: Biological control – has more than 10 parasitoids, but they don’t cause much mortality (<10%) Cultural control – important – plow and disk to bury overwintering larvae. Early harvest to prevent late season damage. Remove trash, mummies and remaining grape bunches.

Chemical Control Measures: Cryolite, Bt, Methomyl – remove basal leaves to increase coverage Current Pest Status: can be serious pest on North Coast and Central Valley, especially if cultural controls are relaxed

Variegated Leafhopper

Crop: grapes Scientific name: Erythroneura variabilis Order: Hemiptera Family: Cicadellidae Range: Southern CA, Central valley as far north as S.J. Co (grape leafhopper is a major pest north of the Tehachapi Mountains, especially in the San Joaquin, Sacramento, and North Coast valleys) Mouthparts: piercing sucking

Distinguishing Characters: adults are distinctly mottled brown, green, and white with a reddish tinge.

Eggs are laid under leaf surface in epidermal tissue

Egg laid in leaf tissue

First instar nymph - The nymphs are almost transparent when first emerged, becoming orange brown to yellow brown

Third instar nymph

Fifth instar nymph

Alternate Hosts: Virginia creeper, apple Oviposition Site: in epidermal tissue on the underside of the leaves Number of generations/year: 4-5 Overwintering Stage: adults Damaging stages: Adults and nymphs

Typical damage: remove contents of leaf cells causing stippling, and even leaf drop. Reduces photosynthesis.

Can cause honeydew spotting

Late season “burn” – high populations cause problem for field workers at harvest

Non Chemical control measures: Biological control – Anagrus parasite is not as effective as it is on grape leafhopper because egg is laid deeper under leaf tissue Cultural control – Remove weeds in vineyards and surrounding areas before vines start to grow in spring Removing basal leaves during berry set and the 2- week period following (before adult leafhoppers emerge) will normally reduce peak leafhopper populations during the season by 30 to 50%

Chemical Control Measures: Imidacloprid (Admire), Naled (dibrom) Current Pest Status: a major pest of grapes in southern California and in the Central Valley as far north as San Joaquin County – under better control in last 10-15 yrs.

Vine Mealybug

Crop: Grapes Scientific name: Planococcus ficus Order: Hemiptera Family: Pseudococcidae Range: Coachella Valley and Kern and Fresno Co in the San Joaquin Valley Mouthparts: piercing sucking

Adults and crawlers Distinguishing Characters: soft, oval, flat, distinctly segmented, and covered with a white, mealy wax that extends into spines (filaments along the body margin and the posterior end). Has a pinkish body that is visible through the powdery wax

Crawlers on an adult female

Adult female grape mealybug, Pseudococcus maritim Nymph of obscure mealybug, Pseudococcus viburni Adult female longtailed mealybug, Pseudococcus longispinus

Alternate Hosts: fig, date palm, apple, avocado, citrus, and a few ornamentals Oviposition Site: wherever female is (on woody tissue) Number of generations/year: 4-5 Overwintering Stage: mostly mated females under the bark, within developing buds, and on roots Damaging stages: adults and nymphs Typical damage: produce honeydew that drops on the bunches - sooty mold. The mealybug itself will be found infesting bunches. Like the other mealybugs, vine mealybug can transmit grape viruses

Non Chemical control measures: Biological control – Anagyrus pseudococci has been released – up to 90% parasitism in some places on central valley. More effective in later generations (August and September) Cultural control – female mealybug is unable to fly so it must be carried by humans, equipment, birds, or on vines at the time of planting. Do not allow contaminated equipment, vines, or grapes near uncontaminated vineyards Mating disruption?

Chemical Control Measures: bloom time application of imidacloprid. The following year, treat with chlorpyrifos and oil in the delayed dormant period Current Pest Status: limited distribution, expected to become a major pest

Western Grapeleaf Skeletonizer

Crop: grapes Scientific name: Harrisina brillians Order: Lepidoptera Family: Zygaenidae Range: Central CA to Mexico Mouthparts: chewing

Distinguishing Characters: adults are metallic bluish or greenish black and fly during the day. Body length is about 15 mm (0.6 inch) and the wing span is 25 33 mm (1 to 1.3 inches)

Whitish capsule shaped eggs

Eggs are laid in clusters on underside of leaves

There are five larval stages There are five larval stages. The first two stages are cream colored, the third stage is brownish

Fourth and fifth stages are yellow with two purple and several blackish bands

Larvae have conspicuous tufts of long black poisonous spines that cause skin welts on field workers

Alternate Hosts: Boston ivy, Virginia creeper Oviposition Site: in clusters on underside of leaves Number of generations/year: three generations per year in the Central Valley and two generations in the cooler coastal regions Overwintering Stage: pupae under bark Damaging stages: larvae Typical damage: defoliate vines. When defoliated, larvae will then feed on bunches causing rot. Defoliation can cause sunburn of fruit and reduces quality

Damage from early instar larvae

Damage from early instar larvae

Damage from fourth instar larvae

Severe defoliation

Non Chemical control measures: Biological control – two parasitoids have been introduced – one is common in San Joaquin Valley A granulosis virus has also been introduced in some areas with excellent success A Tachinid fly parasitoid

Symptoms of granulosis infected WGLS: Eggs scattered and # reduced, many don’t hatch Larvae feed in patches Larvae shrink and die

Chemical Control Measures: Bt, Cryolite, Methomyl (Lannate), Carbaryl (Sevin) – good under leaf coverage is required Current Pest Status: occasional flare-ups in isolated vineyards, but much less of a problem that it was (increasing lately?)

Grape Phylloxera

Crop: grapes Scientific name: Daktulosphaira vitifoliae Order: Hemiptera Family: Phylloxeridae Range: wherever Vitis vinifera rootstock is grown. Prefers heavy clay soils that are found in the cooler grape-growing regions of the state such as Napa, Sonoma, Lake, Mendocino, and Monterey counties, as well as the Sacramento Delta and the foothills. Although grape phylloxera is present in the heavier soils of the San Joaquin Valley, damage may not be as severe. It is not a pest on sandy soils.

Mouthparts: piercing sucking Distinguishing Characters: majority of grape phylloxera adults are wingless females. They are generally oval shaped, but egg layers are pear shaped. They are small 1 mm long. .5 mm wide (0.04 x 0.02 “) and vary in color from yellow, yellowish green, olive green, to light brown, brown, or orange. Newly deposited eggs are yellow, oval, and about twice as long as wide.

Alternate Hosts: none Oviposition Site: deposited on roots Number of generations/year: 3-5 Overwintering Stage: small nymphs on roots Damaging stages: adults and nymphs Typical damage: damage the root systems causing swelling of the root – can kill sections of root. May also cause leaf galls. Causes vines to become stunted and produce less fruit.

Root heavily infested with grape phylloxera

Leaf galls caused by Phylloxera

Non Chemical control measures: Biological control – very little known Cultural control – use of resistant rootstocks is the key - Avoid rootstocks that have V. vinifera parentage. In the hot Central Valley, phylloxera damage may be reduced by good water management, fertilization, and other cultural practices that help limit plant stress

Chemical Control Measures: Carbofuran through drip irrigation, Imidacloprid - pesticide treatment will not eradicate phylloxera populations; the chemical cannot easily penetrate the heavy soils that this pest prefers. Current Pest Status: becoming more of a problem in central valley because of V. vinifera rootstock planted

Glassy Winged Sharp Shooter

Crop: Grapes, Citrus, Ornamentals Scientific name: Homalodisca vitripennis Order: Hemiptera Family: Cicadellidae (same as leafhoppers) Range: SO Cal, and half way up San Joaquin Valley (native to SE US – introduced to CA in late 80’s) Mouthparts: piercing sucking

GWSS and blue-green sharpshooter Distinguishing Characters: large head, bulging eyes, shiny (glassy) wings, adult approx. 12 mm (½ inch) long (big for a sharpshooter), abdomen is whitish or yellow,

Whitish abdomen

Head has numerous ivory to yellowish spots

Identification

Alternate Hosts: numerous ornamentals Oviposition Site: in mass of 10-12 under epidermis of leaf, usually on underside Number of generations/year: 2 Overwintering Stage: adult Damaging stages: nymph and adult Typical damage: suck large amount of plant sap, lower vigor of plant. Main problem is it vectors bacteria that causes Pierce’s Disease – on grapes, oleander leaf scorch on oleander, almond leaf scorch

Pierce’s disease on grapes

Xylella fastidiosa in the xylem of Chardonnay

Chalky, white sharpshooter rain (excrement) residue on lemon

Non Chemical control measures: Biological control – egg parasitoids, one native, one being introduced Cultural control – quarantine on movement of materials from south to north CA

Chemical Control Measures: Imidacloprid (admire) is main method of control now – eradication strategy in Fresno Co – mainly for reducing chance of vectoring Pierce’s disease Current Pest Status: a serious concern if it spreads to Napa and Sonoma