Insect Vectors of Pierce's Disease in Oklahoma Vineyards
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Oklahoma Cooperative Extension Service EPP-7091 Insect Vectors of Pierce’s Disease in Oklahoma Vineyards Eric J. Rebek Extension Entomologist Oklahoma Cooperative Extension Fact Sheets are also available on our website at: Lisa M. Overall http://osufacts.okstate.edu Entomologist Pierce’s disease of grapes (Vitis spp.) is caused by the forewing and extends to the bacterial plant pathogen, Xylella fastidiosa subsp. fastidiosa. front of the head. This blue This disease is a serious concern for grape growers because stripe is bordered on both once vines are infected, there is no cure and vines will eventu- sides by an orange stripe in ally die. Since 2009, Pierce’s disease has been detected in some individuals. The top of several Oklahoma vineyards, and there is concern that Okla- the head is light brown to homa grape producers will experience heavy losses similar to orange and has a light blue California and Texas. Thus, Pierce’s disease poses a threat stripe along the midline. to the vitality of viticulture in Oklahoma, and measures must be implemented to reduce its impact in the state. Pierce’s disease can spread several ways. Sharing cut- tings with other growers may lead to the accidental introduction Overall Photo courtesey L.M. of infected vines to new vineyards. Once Pierce’s disease is Graphocephala coc- established, there is potential for spread among vines via cinea – This species is pruning shears. Also, vine-to-vine transmission is aided by called the candy-striped insect vectors. Key vectors include several species of sharp- leafhopper, red-banded shooters, a group of leafhoppers that feed on xylem tissue leafhopper or red-and- where X. fastidiosa resides. These sucking insects are the blue leafhopper due to most common source of disease transmission. Because they the prominent, alternat- feed on a wide variety of plants that can harbor X. fastidiosa, ing red and blue stripes weed management within the vineyard is an important strat- present on the forewings egy to reduce disease transmission. Effective management and upper thorax (pro- of Pierce’s disease depends on correct identification of key Photo courtesey L.M. Overall Photo courtesey L.M. notum). Adults measure vector species, monitoring their presence in the vineyard, and 3/8 inch (8 mm) long and have a yellow head with a black applying broad-spectrum insecticides when peak numbers stripe running through the eyes along the margin of the head. are detected. The legs and abdomen are bright yellow. The sharpshooters Graphocephala versuta, G. coccinea, and Oncometopia orbona commonly occur in Oklahoma vineyards. Of these, G. versuta is the most prevalent species. Oncometopia orbona – This Graphocephala hieroglyphica, Cuerna costalis and Parauli- species is known as the broad- cizes irrorata also occur in Oklahoma, but are rarely collected headed sharpshooter, presum- in vineyards. In research trials, individuals of G. versuta col- ably for its wide head. Adults lected within vineyards and those nearby, demonstrated the measure 1/2 inch (12 mm) and ability to transmit X. fastidiosa to susceptible plants. However, have an orange head, eyes, legs all of these species are potential vectors of Pierce’s disease and abdomen. The forewings in Oklahoma because they are known carriers of X. fastidiosa. and pronotum have light blue and black speckles. Occasionally, Identification of Sharpshooters females have white patches called Occurring in Oklahoma Vineyards brochosomes on the sides of the forewings. Brochosomes contain Graphocephala versuta – Commonly referred to as the ver- proteins that females smear onto sute sharpshooter, adults measure 3/16 inch (5 mm) long and their eggs to prevent desiccation. have green forewings with several black, tooth-like markings at the wing tips. A light blue stripe runs diagonally along each Photo courtesey L.M. Overall Photo courtesey L.M. Division of Agricultural Sciences and Natural Resources • Oklahoma State University Graphocephala hiero- occurs throughout most of the growing season, inoculative glyphica – Adults of this individuals (i.e., those capable of transmitting X. fastidiosa species measure 3/8 inch to susceptible plants) are not present until mid to late June. (8 mm) long with black and There appears to be one generation per year in Oklahoma. white (or light red) stripes Oncometopia orbona is distributed widely throughout running along the forewings the eastern U.S. from Florida to Maryland, and south from and pronotum. The head is Missouri and Texas to northern Mexico. It is found in Okla- white to light red with black homa vineyards, but less frequently than G. versuta. This markings. sharpshooter prefers feeding on sunflower, hollyhock, okra, lambsquarter, ash, oak, silktree, peach and crapemyrtle. Based on data extrapolated from Oklahoma tree nurseries where O. orbona is more abundant, this species is likely to Photo courtesey L.M. Overall Photo courtesey L.M. be active in Oklahoma vineyards from late May through late Paraulicizes irrorata – This August with a distinct peak in abundance in late July. There species is among the largest appears to be one generation per year in Oklahoma. encountered in vineyards, with Graphocephala coccinea is distributed throughout North adults measuring 9/16 inch America, occurring from Ontario, Canada south to Florida (14 mm) long. The common and west to California and Mexico. This species is even less name, speckled sharpshooter, common than O. orbona in Oklahoma vineyards as it prefers refers to the mottled appear- to feed on blackberry, forsythia, pittosporum, rose, milkweed, ance of the forewings and goldenrod and other plants. Recent sampling efforts in Okla- pronotum. The body and head homa vineyards yielded too few specimens to determine peaks are dark, with white to pale yel- in the abundance of this species; however, it was collected low markings scattered along from late May through August, with most individuals captured the lateral margins. The front in June. of the head may have parallel orange markings. Managing Insect Vectors of Pierce’s Disease Successful management of Pierce’s disease depends on effective control of potential insect vectors and eliminating Photo courtesey L.M. Overall Photo courtesey L.M. weeds that may serve as sources of future infections. While all of the sharpshooter species described in this publication have potential to carry and transmit X. fastidiosa to grapevines, Cuerna costalis – This colorful monitoring efforts should focus on the versute sharpshooter species measures 5/16 inch because of its high prevalence in Oklahoma vineyards and (10 mm) long. The forewings demonstrated ability to transmit X. fastidiosa to susceptible have narrow, alternating black plants. Based on several years of sampling data from Oklahoma and red stripes with a thicker vineyards, monitoring for the versute sharpshooter should oc- red stripe along the wing mar- cur from early June through late August. The best monitoring gins. The head and pronotum tools for jumping and flying insects like sharpshooters are sticky are black with white markings cards. Sticky cards can be purchased online from garden and and a white stripe extends from greenhouse supply companies. Purchase yellow sticky cards the front of the head, through that measure approximately 3 inches by 5 inches and have the eyes, to the end of the adhesive on both sides. Sticky cards should be attached to abdomen. The legs are red the upper vine support cable using a clip or clothespin and and black. spaced evenly around the perimeter of the vineyard and on diagonals through the vineyard center. For most Oklahoma vineyards, which are two acres or less, 12 to 16 sticky cards Photo courtesey L.M. Overall Photo courtesey L.M. should be sufficient for monitoring versute sharpshooters. Distribution, Host Plants and Life History Sticky cards should be checked at least twice per week, and changed every two weeks. Due to the small size of these of Major Insect Vectors insects, use a hand lens with at least 15X magnification to Graphocephala versuta is common in the southern U.S., identify specimens caught on sticky cards. If identification is ranging from as far west as Texas, north to Illinois. It is active in doubt, check with the local county Extension office for as- in Oklahoma vineyards from early June through late August sistance. with a distinct peak in abundance from late June through Treatment thresholds are not established for the versute mid-July. Adults overwinter in woody habitats and move to sharpshooter, so insecticides should be applied as soon as herbaceous perennials in March. Females lay eggs on the these insects are observed in the vineyard. Remember, it lower leaf surface of ragweed, sunflower, okra and other only takes one infective individual to spread X. fastidiosa species. This insect feeds on blackberry, grape, honeysuckle, throughout the vineyard. Table 1 lists products labeled for privet, cherry and other deciduous trees. While this species control of sharpshooters and other sucking pests in Oklahoma EPP-7091-2 CB vineyards. Contact insecticides in Group 3A (i.e., pyrethroids) ers are applied as a foliar spray and absorbed across the leaf provide quick knockdown of target pests and can be used to membrane (i.e., translaminar and systemic activity). However, control a broad spectrum of vineyard pests. However, these neonicotinoids should not be applied prophylactically because products should be used judiciously because they also kill it is difficult to predict the severity of pest populations from year beneficial arthropods such as lady beetles, lacewings and to year. A recommended approach is to use a combination of parasitic wasps. Pyrethroids also have short residual activity, curative and preventative insecticides applied as a tank mix so it may be necessary to reapply every 14 days to control or in succession. Thus, the contact insecticide provides rapid severe infestations. Preventative insecticides in Group 4A (i.e., knockdown of the pest population, followed by season-long neonicotinoids) provide long-term control of sucking pests protection provided by the systemic insecticide.