California Agricultural Research Priorities Pierce's Disease (2004) / Chapter Skim
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1 Pierce's Disease and the Glassy-winged Sharpshooter: Their Biology and the Challenges of Their Management
1 Pierce's Disease and the Glassy-winged Sharpshooter: Their Biology and the Challenges of Their Management
Pages 21-44
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From page 21... ...
The Committee was asked to monitor scientific advances in the areas of economically and environmentally important agricultural diseases and pests, including their vectors; respond to requests; identify emerging issues; provide independent analyses of scientific information and of state, federal, and international activities; and to submit a rigorous and timely evaluation of scientific issues in response to identified areas of concern. The specific charge to the committee was the following: The area of proposed study for the committee will be the current outbreak of agricultural diseases caused by Xylella fastidiosa and the disease vector, the glassy-winged sharpshooter.
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From page 22... ...
. It was observed in the Napa Valley in 1887, in the Livermore area in 1888, in the Sacramento and Santa Clara valleys in 1900, and in the San Joaquin Valley in 1921.
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From page 23... ...
He demonstrated that alfalfa dwarf disease was graft-transmissible (Weimer, 1936) , and he reported that the most consistent microscopic characteristic of alfalfa dwarf was the presence of "bacteria-like bodies" in xylem vessels.
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From page 24... ...
al., 1975; Raju et al., 1982; Wells et al., 1981 Elm (Ulmus americana) Elm leaf scorch disease Hearon et al., 1980; Kostka et al., 1984; 1986a Mulberry (Morus Mulberry leaf scorch Kostka et al., 1986b rubra)
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From page 25... ...
More rain falls each year in Florida, and precipitation follows a different pattern in Florida than in California or Virginia. The Florida growing season is notably longer than is that of the other two states, so favorable conditions for Xf last longer and it more likely to that persistent infection will be established host plants.
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From page 26... ...
The disease thus far, has been confirmed along the Eastern Shore of Virginia (in the Delmarva Peninsula and in Tidewater) , but there is considerable uncertainty about the distribution of insect vectors throughout the state (Pfeiffer, 2002)
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From page 27... ...
It can now can be found in Riverside County, and in areas of San Diego, Orange, San Bernardino, Los Angeles, Ventura, Santa Barbara, and Kern counties. Its range is continuing to spread northward, and recently it has been found in the San Joaquin Valley.
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From page 28... ...
on barrier crops for inhibiting GWSS movement. Drawing particularly on Siebert's work, this section presents information related to grape growers' costs attributable to PD, potential economic effects for citrus and almond production, and statewide costs of managing PD and GWSS.
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From page 29... ...
notes, the estimated income loss to grape growers also could affect other aspects of California's economy, such as employment and regional and state income, although those costs are not likely to have a large statewide effect. Siebert's (2001)
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From page 30... ...
30 2% 2% 5% 4% 2% 5% 2% 5% Vines Replanted $18 $3 $105 $103 $47 $256 $64 $22 Cost Replanting 565 622 622 908 566 871 519 1,089 Vines/Acre ortized t/Acre $621 $381 $834 $736 $585 $378 $1,013 $1,227 Am Cos stoC $7.27 $9.56 $17.22 $14.72 $15.27 $11.01 $10.94 $7.40 ting anl Cost/Vine Repd ant t/Acre enm $4,105 $5,949 $10,173 $13,369 $8,640 $11,985 $9,526 $3,839 Established Cos lish Estab blanc le yarde Variety ne sslede Vin sauvignon se Wi Cabernet Zinfand Chardonnay Sauvignon Chardonnay Cabernet Thompson mated Esti3-1 lleyaV daa lleyaV 2001t, ai Obispo Sieber: Variety Nev Mar ble Joaquin Luis Joaquin Ta Area, San Lodi Sierra Sonoma Lake Santa San San SOURCE
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From page 31... ...
For example it is not known whether GWSS can survive in the cooler Northern California vineyards Potential Economic Effects on Almond and Citrus According to information reported to the committee, almond leaf scorch (a disease caused by Xf) has been identified in almond orchards; although neither BGSS nor GWSS has been identified as the vector.
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From page 32... ...
32 RESEARCH PRIORITIES: PIERCE'S DISEASE Table 1-4 Grape Acreage by End Use, Citrus Acreage, Almond Acreage in California Counties, 2001 Raisins Table Wine Grapes Citrus Almond County Grapes Alameda 0 0 1,627 0 0 Amador 0 0 2,728 0 0 Butte 1 18 159 130 37,613 Calaveras 0 0 491 0 25 Colusa 0 0 1,350 0 22,138 Contra Costa 3 0 1,550 0 10 El Dorado 0 0 1,238 0 Fresno 173,271 11,826 47,241 31,126 65,994 Glenn 0 0 1,748 570 29,390 Humboldt 0 0 10 0 0 Imperial 0 273 0 3,179 0 Kern 25,316 33,003 31,845 44,987 92,989 Kings 1,391 832 2,408 0 2,967 Lake 0 14 7,147 0 1 Los Angeles 0 0 75 0 0 Madera 44,248 3,017 47,787 4,745 51,153 Marin 0 0 87 0 0 Mariposa 0 0 57 0 0 Mendocino 0 2 16,008 0 0 Merced 1,339 149 13,962 0 85,734 Monterey 0 1 41,154 1,022 0 Napa 0 1 42,929 0 0 Nevada 0 1 350 0 0 Placer 0 1 91 0 40 Riverside 2,695 10,872 1,894 23,200 7 Sacramento 0 0 16,808 0 124 San Benito 0 0 3,440 0 1 San Bernardino 179 563 1,114 4,772 50 continues
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From page 33... ...
. Almond pruning is done to promote tree balance for wind tolerance, to stiffen main limbs, to manage light for increased productivity, and to limit alternate bearing -- the tendency of some perennial crops, such as almonds, to exhibit intrinsic yield variability.
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From page 34... ...
Research on PD is coordinated broadly through the Pierce's Disease Control Program [Figure 1-2] -- an alliance consisting of CDFA, the agricultural commissioners of the various counties involved, researchers in the UC system and USDA, various state and local agencies, and several California agricultural organizations (CDFA, 2002a)
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From page 35... ...
Because those investigators are familiar with the California agricultural landscape and because of their proximity to active PDGWSS infestations and 1AB 1394 was amended by AB 2890 in September 2002.
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From page 36... ...
ARS-the internal biological-research unit of USDA -- is distributed among various facilities throughout the United States. Its San Joaquin Valley Agricultural Sciences facility in Parlier, California is considered USDA's headquarters for PD research.
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From page 37... ...
In its consultation with various representatives of industry, the committee learned of potentially growing frustrations among representatives of various industries, such as growers and nursery operators. The frustrations have emerged from questions about who should be held accountable and who should be responsible for implementing strategies for managing GWSS populations.
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From page 38... ...
In 2000, the Northern California River Watch threatened to sue growers who used aerial sprays to control GWSS (CAWG, 2000) , and in 2003, a coalition of NGOs filed suit in California Superior Court in defense of greater measures for protecting the environment and against the use of pesticides for managing GWSS (CATS, 2003)
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From page 39... ...
Surveys entail setting traps at retail and wholesale nurseries and treatment commonly involves the application of ovicides or other chemical compounds to kill sharpshooter egg masses. Although chemical pesticides do not provide a comprehensive approach to treating sharpshooters that have infested nursery stock, it is suspected that older insects are more vulnerable to them (Akey et al., 2001)
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From page 40... ...
Vegetation Management Removing plants that serve as sharpshooter hosts outside of vineyards could help disrupt GWSS populations and thereby reduce the number of insects feeding on vines. However, when those plants are removed, many growers have replanted them, thereby introducing new host plants because many of those plants also are habitat for beneficial insect species and other wildlife.
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From page 41... ...
Scientists are exploring the possibility of transferring the genes that confer resistance in muscadine grapes to wine grapes. This is a goal of long-term research that targets PD (Cavanaugh, 1999)
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From page 42... ...
Given the diversity and distribution of fruit, vegetable, tree nut, and grain production in California, any decision to pursue research that leads to new management strategies must account for those potential influences to ensure that practical management strategies result. For example, a PDGWSS management strategy emerging from research that calls for chemical control of GWSS in citrus groves could conflict with current IPM practices for citrus, and citrus growers who are not involved in grape production might be reluctant to change their IPM practices for the sake of PDGWSS management in grapes.
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From page 43... ...
Regulatory Factors Because crop production practices can be influenced by PD management strategies, those that are consistent with a variety of research priorities research priorities considered in subsequent chapters of this report could require additional regulatory control. For example, orchard sanitation in citrus could be required to reduce GWSS populations to protect neighboring vineyards.
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From page 44... ...
. Clearly, the scale of the recent investment into PDGWSS research indicates the potential economic consequences for California's agriculture and economy.
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