1 JANUARY/FEBRUARY 2005 GRAPEGROWING

RESEARCH UPDATE Grapevine trunk diseases in California

BY W. D. Gubler, P.E. Rolshausen, F. P. Trouillase, J. R. Urbez, T. Voegel Dept. of , University of California, Davis, CA G. M. Leavitt, University of California Cooperative Extension, Madera, CA E. A. Weber, University of California Cooperative Extension, Napa, CA

rapevine trunk diseases are responsible for significant eco- nomic losses to the wine industry Gworldwide. Symptoms of these diseases include dead spurs, arms, and cordons and eventual vine death due to canker formation in the vascular tis- sue. In dieback, deformed leaves and shoots occur as the pathogen invades spur positions. As cankers develop, yield reductions occur due to the loss of productive wood. The impact of grapevine wood diseases can be significant in older for most canker development in California Figure I: Fruiting bodies (perithecia) of E. vineyards, and usually becomes more vineyards. However, recent findings have lata on a grapevine previously grafted for variety change. The large pruning wound severe as vineyards become older. highlighted the importance of other fungi favored formation of E. lata perithecia on Eutypa dieback, caused by Eutypa lata involved in the death and decline of the dead trunk of the old variety. was originally thought to be responsible grapevines in California. In this regard, species have also been recovered from cankers, and were determined to be the main cause of canker diseases in some California vineyards. Recent research has also indicated the occurrence of several new fungal trunk disease pathogens of grapevine belong- ing to the family Diatrypaceae (the same family as Eutypa). These include Eutypa leptoplaca, Cryptovalsa ampelina, species, and species. We will present current information on the epi- demiology and control strategies of fun- gal organisms responsible for grapevine Figure II: Black stroma bearing perithecia (fruiting bodies) of E. leptoplaca on dead trunk of spur, cordon, and trunk dieback in big leaf maple collected in St. Helena, Napa County, CA. California. JANUARY/FEBRUARY 2005 2 GRAPEGROWING

Eutypa dieback # Ascospores Rain (mm) Eutypa dieback was responsible for 60 4.5 a loss in net income for California wine Temp (…F) grapes estimated to be over $260 mil- 4 50 lion in 1999. Many growers consider 3.5 Eutypa to be the most significant dis- ease of grapevines. 40 Series1 3 Typical symptoms of E. lata include Rain Temp 2.5 formation of a wedge-shaped canker 30 and stunted shoots with cupped, tat- 2 tered, chlorotic, and necrotic leaves that are best seen in spring time. Foliar 20 1.5 symptoms are due to toxins produced 1 by E. lata. Differences in susceptibility 10 of grapevine cultivars to infection have 0.5 been reported, although no cultivars are immune. Cankers develop down- 0 0

ward at a faster rate than toward the 10:0012:0014:0016:0018:0020:0022:00 0:00 2:00 4:00 6:00 8:0010:0012:0014:0016:0018:0020:0022:00 0:00 2:00 4:00 6:00 8:0010:00 end of cordons and also increase in diameter over time. Extended infection Figure III: Ascospore release curve of E. lata during a period of rainfall recorded in December of grapevines by E. lata leads to vine 2001 in Davis using a Burkard spore trap placed around dead grapevine trunk bearing perithecia. death. Eutypa lata spreads to new pruning xylem vessels, weaken the plant by pro- ods of rainfall, starting a few hours wounds by wind-driven and water- ducing toxins and cause wood decay by after the onset of a rain (Figure IX). splashed ascospores released during excreting cell wall degrading enzymes. Over 80 plant species around the rain events. Ascospores develop Eutypa lata also produces asexual world have been reported to be poten- inside perithecia (fungal fruiting bod- spores called conidia. These are formed tial hosts for E. lata. In California, ies) that form when the enters inside pycnidia (another type of fruiting many of these species were found to its sexual stage. The sexual stage body) that develop on wood, but these be infected with Eutypa lata and bore develops on dead wood, where conidial spores do not play a role in dis- perithecia producing ascospores in masses of perithecia are produced in a ease epidemiology. the vicinity of vineyards. We now black substrate referred to as stroma In California, ascospore discharge know that these species serve as nat- (Figure II). The sexual stage develops of E. lata occurs from the first rain of ural reservoirs of E. lata inoculum. in regions that receive over 16 inches the early fall until the last rains of the In the 1970s, grapevine, apricot, of rain. It is common to find stroma and spring (Figure III). Ascospore dis- and Ceanothus were found to be nat- perithecia on old grapevines and other charge decreases significantly in late ural hosts of E. lata. More recently we types of wood in the North Coast and February and remains low to nil by have identified kiwifruit, blueberry, Delta production areas. early March (Figure IX). and cherry to be hosts in California Ascospores infect grapevines through However, ascospore release may and they were shown to bear the fruit- fresh pruning wounds during the dor- occur during rains in March and April ing bodies (perithecia) of E. lata. mant season. They germinate, invade if they are preceded by several weeks Additionally, a recent survey iden- of no rain and sunny, warm weather. tified almond, crab , and pear Such releases may occur because trees as new fruit crop hosts for E. perithecia are able to recover in pro- lata, and showed the presence of ductivity during the dry period, or because spores that would have been released in the winter months are released in the spring simply because they were not released in the winter. This scenario more often occurs in years when there is little rainfall dur- ing the winter months. Ascospore release from individual Figure IV: Typical wedge shape canker perithecia may occur continuously for formed by Botryosphaeria in the cordon of Figure V: Mature Botryosphaeria obtusa grapevine. approximately 24 hours during peri- conidia. 3 JANUARY/FEBRUARY 2005 GRAPEGROWING

Figure VII: Botryosphaeria obtusa pycnidia Figure VI: Mature Botryosphaeria found under the bark on the arm of an infected grapevine. theobromae conidia. Figure VIII: Botryodiplodia theobromae pycnidia found on old grapevine pruning perithecia of E. lata on several other Large amounts of viable inoculum wood left on the vineyard. new hosts in California including were found in several old vineyards near It is our opinion after this study California buckeye, big leaf maple, Healdsburg, Sonoma County. Perithecia that even though E. lata and E. lepto- willows, and oleander (Figure X). were particularly well-developed on placa ascospores can travel over con- Perithecia of E. lata were found to vines that had been previously top- siderable distances and cause dis- be particularly well established on worked for variety change. Stroma on ease, Eutypa dieback is primarily a dead branches of various willow those vines had developed on old wood disease of local origin, developing in species occurring along natural creeks below the grafting wound down to the the vicinity where the ascospores are union with the rootstock (Figure I). and irrigation waterways. released. While E. lata appears to be the pri- It appears likely that the flora sur- mary Eutypa species involved in dieback rounding vineyards is potentially a Control in California, we have identified a second Disease management should include key factor in disease epidemiology Eutypa species that can also cause removal of the dead parts of grapevines and surely acts as an inoculum reser- dieback in grapevines (Figure XIII). This and other host plants because of the poten- voir. Sanitation of the dead wood of species is E. leptoplaca, a slower growing tial risk of increased inoculum. We cur- potential hosts of E. lata in areas sur- fungus in culture but with the capability rently have no proof that sanitation will rounding vineyards is advised in to do the same kind of damage as E. lata. reduce the disease level in vineyards, but it order to decrease the inoculum level. This new fungus occurs in the North seems appropriate if local production of Sanitation can be accomplished by Coast but seems to be more limited in inoculum is considered to be a key to removing the infected tissues on its distribution. disease development. plants that show disease. Generally speaking, this disease can be identi- fied on other hosts by the black # Ascospores Rain (mm) stroma that is produced (Figure II). By 160 6 removing the stroma-infected wood Temp (…F) and burning it, the number of spores 140 5 released in winter can be reduced. Surveys inside vineyards and apri- 120 cot and cherry orchards have revealed 4 100 Spores an abundance of inoculum in planti- Rain Temp ngs of approximately 20 years and 80 3 older. Only a few perithecia have been found in almond orchards. 60 Perithecia of E. lata were found to 2 be prevalent in vineyards or sur- 40 rounds in the counties of Napa, 1 Sonoma, Yolo, Sacramento, Contra 20 Costa, San Benito, El Dorado, 0 0 Mendocino, San Joaquin, Stanislaus, and Merced. Perithecia of E. lata were 14:0016:0018:0020:0022:00 0:00 2:00 4:00 6:00 8:0010:0012:0014:0016:0018:0020:0022:00 0:00 2:00 4:00 6:00 8:0010:0012:00 not found in Madera, Fresno, Kings, Figure IX: Ascospore release of E. lata recorded on the 12th, 13th and 14th of April 2000 in a Tulare, and Kern counties. vineyard in Healdsburg, Sonoma County, CA, with rainfall and temperature data. Ascospore release occurred for 24 hours during the rainfall period. JANUARY/FEBRUARY 2005 4 GRAPEGROWING

Wound healing and colonization by epiphytic fungi and bacteria have been shown to occur more readily in the warmer spring months. Ascospore release, germination, and infection are also decreased during this time. Therefore, significant wound protection can be readily achieved simply by late pruning of vineyards. Our work, and other research (Moller and Kasimatis), has shown that pruning wounds made in March heal more rapidly when compared to mid- winter. In our trials, late season prun- ing wounds that were artificially inoc- ulated showed only approximately 10% of the infection rate of pruning wounds inoculated in mid-winter. However, the large acreage of indi- vidual vineyards in California makes late pruning impractical for many growers who need to schedule their labor force throughout the winter months. One way to allow for more efficient late season pruning is to dou- ble-prune a vineyard. This involves going through the vineyard twice dur- ing the pruning season. The first “pre-pruning” pass is made early in the season at which time

Figure X: Geographical area and new hosts of the pathogen E. lata in California. Survey was the canes are simply trimmed back to a conducted in 2002. Areas represented in gray correspond to the areas that were surveyed. set length, usually 12 to 18 inches. This step can be performed mechanically or Grapevine pruning wounds can be In a previous study, more than 1300 by a hand crew. “Final” pruning to susceptible to infection by E. lata for as species of fungi and bacteria were found spurs would take place late in the sea- long as seven weeks, but the length of to colonize grapevine wounds in spring son (March) when the chances for this period varies with the time of prun- conditions. infection are reduced. ing, size of the wound, and age of the wood pruned. Wound susceptibility to E. lata declined faster under higher (70º Table I. Field trials in evaluating control of E. lata in San Joaquin to 90ºF) temperatures. and Yolo Counties in 2001 to 2002 and in Napa and San Joaquin Counties Wound healing occurs by deposition in 2002 to 2003. Pruning wounds were inoculated with 1000 ascopores of polymerized phenolic compounds in of E. lata one and 10 days after application of test material. the opened wood vessels, and concomi- First timing of inoculation Second timing of inoculation tantly, natural establishment of a micro- Mean percent Mean percent Mean percent Mean percent bial population on the wound surface Treatments infection disease control infection disease control provide a natural “bio-barrier” to infec- tion. These natural organisms (epi- Non-inoculated control 3 — 3 — phytes), including Cladosporium Inoculated control 64 — 32 — Boron-free paste 61 4.7 19 40.6 herbarum and Fusarium lateritium, grow C. herbarum 32 50 17 46.9 over the surface of a pruning wound and Boric acid 2 96.9 9 71.9 prevent infection by E. lata spores. Bioshield 4 93.8 7 78.1 Biopaste 1 98.4 2 93.8 5 JANUARY/FEBRUARY 2005 GRAPEGROWING

worked well when they were applied 70 67.7 two to three weeks before infection 60 occurred. 52.3 50 Boron was tested as an alternative 47.7 46.7 46.2 40 40.6 control method because this element 34.8 32.2 was proven to be effective at control- 30 24.3 24.7 25.6 ling other wood decay fungi. It is also 20 19.5 20 17.5 used by growers as a fertilizer spray to 12 14.6 12 12 10 9.6 10 improve fruit set. The application of 6.1 boron as a fungicide may not yet be 1 0 0 0 legal to control Eutypa dieback of Mendocino Sonoma Napa San Joaquin Stanislaus Madera Fresno Tulare Monterey San Luis Riverside Kern Obispo grapevines, however, boron can be applied to correct nutritional problems. % of Botryosphaeria recovered from cankers We evaluated boric acid solutions % of Eutypa recovered from cankers and two boric acid-based products as pruning wound treatments. These Figure XI: Relative occurrence of Eutypa spp. and Botryosphaeria spp. in California grapevine included biopaste (5% boric acid production regions. [wt/wt] in a polyvinyl paste) and By eliminating most of the brush wounds was not achievable because bioshield (5% liquid boric acid early in the winter, final pruning should the product did not persist in woody [wt/vol] plus a spore suspension of go more quickly, thereby allowing the tissue for a sufficient time period. Cladosporium herbarum). final cuts to be made late in the season. Therefore, multiple applications of Boric acid reduced ascospore germi- Double-pruning is not appropriate for Benlate would have been required to nation and mycelial growth of E. lata cane-pruned vineyards where long provide protection until pruning under controlled conditions in the lab- canes are retained each year. wounds were completely healed. oratory, and the boron-based products Double-pruning creates an opportu- Benlate was withdrawn from the yielded excellent disease control on nity for wood pathogens such as E. lata market in 2001 leaving growers with- artificially inoculated grapevines in to colonize wounds made early in the out an efficacious chemical treatment both field trials and lab studies in com- dormant season during pre-pruning. to control E. lata. Topsin M was regis- parison to C. herbarum and boron-free However, these infections will be elimi- tered in 2003 under section 18 (emer- paste treatments (Table I). nated during the final pruning step. We gency exemption) in California, but However, in one observation, the bud inoculated pre-pruning cuts throughout this product also belongs to the same located at the first node below the prun- the winter months and showed that by class of fungicides as Benlate, a benz- ing wound failed to push following treat- March, E. lata had not grown downward imidazole, and therefore has the same ment with liquid boric acid. This effect more than four to five cm, which was drawback (short-term protection) as was also reported in peach and nec- well above the point where final prun- Benlate. tarine orchards sprayed with toxic ing cuts were made. Biocontrol agents have been tested amounts of boron-based fertilizers. Late pruning, either in a single step as an alternative method for control of or as the final pass in double-pruned E. lata. Bacillus subtilis, Fusarium lateri- vineyards, is not a guarantee that tium, and Cladosporium herbarum all Eutypa infections will not occur. Late showed some potential activity in lim- spring rains can trigger ascospore iting the establishment of the releases and increase the risk of infec- pathogen. tion of newly pruned vineyards. How- However, unlike chemical applica- ever, late pruning certainly reduces the tions, which have an immediate pro- overall chances for infection and is a tective effect, maximum protection standard recommendation for disease from biocontrol agents requires colo- control. nization of the surface of the wound. Disease management was histori- Thus, there is a window of suscepti- cally achieved by treating pruning bility after treatment, until the biocon- wounds with fungicides. Benlate® trol agent is established well enough (DuPont de Nemours & Co., U.S.) was to prevent development of E. lata in registered for E. lata for 30 years, and the wounded tissue. Figure XII: Comparison between field trials showed good efficacy in Biocontrols tested as alternatives to percentages of cankers infected by Botryosphaeria spp. and other fungi in preventing Eutypa dieback. However, fungicides showed mixed success, but relation with grapevine dieback in long-term protection of pruning both F. lateritium and C. herbarum California grapevines. JANUARY/FEBRUARY 2005 6 GRAPEGROWING

Mechanisms involved in bud failure are not understood, and the economic impact has not been assessed. However, we do not recommend liquid boric acid for Eutypa dieback control. Treatment of pruning wounds with boron-based products offers an effec- tive, economical, and environmentally- safe management strategy to control Eutypa dieback in vineyards. However, formulations have to be optimized in order to increase control over longer time periods on the surface of pruning wounds, and to limit possible effects on bud failure of grapevines. We believe strongly that if boron is used, it should be put in a paste so that it stays where it is placed. In earlier studies, soaps also pro- vided good protection of pruning wounds against E. lata. However, most soaps, including dishwashing deter- gents, were phytotoxic. One laundry detergent, Dreft, not only provided excellent control of E. lata, but has never shown any phytotoxicity. This detergent, when used at 30% aqueous suspension (wt/vol), provided excel- lent disease control. Further fungicide testing is under- way, and we are trying to convince the chemical industry that Eutypa control products are worth registering for California viticulture.

BOTRYOSPHAERIA canker diseases “Botryosphaeria canker disease” of grapevine is a wood disease caused by Figure XIII: Fungal colonies of Eutypa lata (a) and E. leptoplaca (b) growing on PDA-tet dishes as many as four different Botryosphaeria incubated at 24ºC under intermittent fluorescent lighting (12 h) for 22 d. Scanning electron species in California. Although it is well microscope images of perithecial ostiola showing the roundish ostiole of E. lata (c) and the 3 to 4 sulcate ostioles of E. leptoplaca (d) (Bars = 100µm). Compound microscope images of accepted that some Botryosphaeria the ascospores of E. lata (e) and smaller ascopores of E. leptoplaca (f) at same magnification species have been shown to be the (Bars = 10 µm). causal agent of canker diseases of vari- ous crops and woody plants in and Brazil. In California, wedge- ease it causes was referred to as “Bot California, the importance of these shaped cankers caused by Botryo- canker.” fungi as pathogens of grapevines has sphaeria can be found on vines 10 Fungi often produce both an asex- been largely ignored throughout the years old and older, especially where ual (imperfect) stage and a sexual (per- state. large pruning wounds have been fect) stage, and they may have different Various species of Botryosphaeria, made in retraining vines. names. Botrysphaeria rhodina is the causing different symptoms, have been For several years, Botryosphaeria rho- name for the sexual stage of this fun- reported in the last decade as dina has been known to cause wedge- gus; Botryodiplodia theobromae is the pathogens on grapevines in the U.S., shaped canker symptoms in California. name of the asexual stage. South Africa, Australia, France, Italy, This species was previously known as We prefer to use the name Botryo- Portugal, Egypt, India, Mexico, Chile, Botryodiplodia theobromae, and the dis- sphaeria instead of Botryodiplodia. The disease is still known as Bot Canker. 7 JANUARY/FEBRUARY 2005 GRAPEGROWING

on grapevines infected by different 70 species of Botryosphaeria (B. stevensii, B. 60 63.6 obtusa and B. dothidea). 50 54.5 The wedge-shape cankers caused by Botryosphaeria are visually indistinguish- 40 able from those formed by Eutypa lata or 36.5 30 E. leptoplaca. All three fungi can cause 26 26 cankers and can be detected in the vine Botryosphaeria 20 at the same time. The best distinguishing 16

% of cankers infected by 10 12.2 characteristic is the presence of cankers and the absence of the stunted or 0 Sauvignon Chardonnay Cabernet French Flame Perlette Thompson chlorotic spring growth which is typical Blanc Sauvignon Colombard Seedless of infections by Eutypa lata. Figure XIV: % of cankers infected by Botryosphaeria in wine and table grape varieties in Botryosphaeria spp. are wound California. pathogens entering the vine through fresh pruning wounds. Large numbers The fungus is now considered to be an and cordons (Figure IV) and dead spur of Botryosphaeria conidia are exuded endemic species in many vineyards in positions. No foliar symptoms associ- from black fruiting bodies (pycnidia) warm and hot climate areas in ated with Botryosphaeria-induced found on diseased vine parts, under California. canker diseases have been observed in the bark of cordons, trunks, and spurs Typical symptoms caused by Botryo- California grapevines. This is in con- (Figure VII) or on the residual pruning sphaeria on grapevines in California are trast to other areas in the world where wood left in the vineyards. wedge-shaped cankers in the trunk foliar symptoms have been observed In addition, we also know that many of these species cause disease on different hosts around the vineyards. The formation of numerous fruiting bodies provides an excellent source of spores for further infections in the vineyard. Conidia may be easily dis- tributed over the vineyard due to wind, or they may be waterborne in splashed drops from rain or sprinkler irrigation, but very little information is available concerning the Botryosphaeria disease cycle. Like Eutypa lata and E. leptoplaca, the canker formed by Botryosphaeria spp. grows more rapidly basipetaly (or toward the root from the point of infec- tion). The canker develops for several years in the trunks and cordons depend- ing on where the infection was located. Death of the infected vine part occurs when the last live wedge of tissue is killed by the growth of the fungus. Eutypa dieback and “Bot canker disease” decrease the life of the vine- yard, reduce yields and increase pro- duction costs due to the application of control treatments, cultural prac- tices to prevent infections, pruning out

Figure XV: Geographical distribution of Botryosphaeria species found in the grapevine production areas in California during 2003 and 2004. JANUARY/FEBRUARY 2005 8 GRAPEGROWING

of diseased tissue, and training new cordons and spur positions to replace 40 those killed by the disease. 35 36.5 Field survey of Botryosphaeria 30 33.4 isolated In a recent field survey (2003–2004), 25 over 1,100 samples showing the typi- 20 cal wedge-shaped cankers were col- lected from 110 vineyards in 12 coun- 15 18.5 ties (Mendocino, Napa, Sonoma, from cankers 15

Botryosphaeria 10 Monterey, San Luis Obispo, Madera, Stanislaus, San Joaquin, Fresno, Kern, 5 % of Tulare, and Riverside County). 0 Botryosphaeria species were found in 10–20 years old 21–30 years old 31– 40 years old > 41 years old every grape growing area surveyed (Figure XV), showing that Botryo- Grapevine age intervals sphaeria species are prevalent in cankered cordons and spurs in Figure XVI: Effect of vineyard age on the occurrence and incidence of Botryosphaeria spp. grapevines in California. Botryosphaeria was the main fungus sphaeria obtusa, B. rhodina (Botryodiplodia Botryosphaeria was found in vine- recovered from cankers in five coun- theobromae), Botryosphaeria dothidea and yards of all ages sampled (Figure XVI), ties: Mendocino, Sonoma, Monterey, an as yet unidentified Botryosphaeria but was isolated most frequently from San Luis Obispo, and Riverside. species called Botryosphaeria sp1 (Figure cankers in 21 to 30-year-old Botryosphaeria was also isolated in a XV). grapevines (36.5%), followed by those higher percentage than Eutypa in It is also important to emphasize grapevines that were 10 to 20 years old Madera, Fresno, and Tulare counties that only Botryosphaeria rhodina (33.4%). (Figure XI). Eutypa lata was the main (Botryodiplodia theobromea) was recov- The main fungi isolated from all fungus isolated from cankers in Napa, ered from cankers in the desert area of wedge-shaped cankers collected in San Joaquin, and Stanislaus County. In Coachella Valley. No other California have been Botryosphaeria Mendocino, Sonoma, Napa, Monterey, Botryosphaeria species or other wood (25.5%), followed by Eutypa (20%), San Luis Obispo, Stanislaus, and San invading, canker-causing fungi were Phomopsis viticola (8.7%), Phaeomoniella Joaquin counties both fungi were occa- isolated from the wedge shape cankers chlamydospora (5.2%) and Phaeoacre- sionally isolated from the same canker. in this region. Only Botryosphaeria rho- monium aleophilum (4.3%) (Figure XII). It is important to note that dina has been proven to cause a However, the latter two pathogens do dieback disease causing a wedge- Phomopsis viticola was the principal not cause cankers and were picked up shape canker. The precise role of the fungus found in cankers from Fresno in these studies as hitchhikers on other species isolated from cankers is and Tulare counties. We have yet to wood showing symptoms of other still not clearly understood. initiate a project there to evaluate the cankers. In a parallel study, Eutypa lep- In the 2003–2004 survey, (Figure significance of this finding but plan to toplaca was also isolated from vines in XIV), Botryosphaeria was isolated most do so. often from Sauvignon Blanc (63.6% the North Coast but was not part of The fungi that cause Esca or black recovery from cankers tested) fol- this survey. measles (Phaeomoniella chlamydospora lowed by Chardonnay (54.5%). and Phaeoacremonium aleophilum) were Cabernet Sauvignon had the most Other wood decay fungi also isolated in a low percentage in cankers with Eutypa (57.7%). Besides Eutypa lata and Botryo- this study. These pathogens produce Botryosphaeria was isolated in the sphaeria species, several other fungi different types of internal symptoms same percentage from cankers of were recovered from cankers of grape- and were not a target of this work, but Perlette and Flame seedless (26%). vines. These include Phomopsis viticola, they reside in the same vascular tissue Fewer cankers with Botryosphaeria Phaeomoniella chlamydospora, and as the canker pathogens and thus will were found in Thompson seedless Phaeoacremonium aleophilum. Others, be isolated from time to time. (12.2%). Thompson Seedless appears such as Diatrypella sp., Diatrype sp., Four different Botryosphaeria species highly susceptible to Phomopsis viticola Crytovalsa ampelina and E. leptoplaca are associated with the wedge-shape and the pathogen was isolated from were also isolated from the margins of canker symptom in California; Botryo- 29% of Thompson Seedless cankers infected tissue. tested. 9 JANUARY/FEBRUARY 2005 GRAPEGROWING

Recently, another Eutypa species (E. nia vineyards. More studies should be References leptoplaca) and Cryptovalsa ampelina conducted to elucidate the impact of Irelan, Nancy, W.D. Gubler, and were found to be pathogenic on the different species of Botryosphaeria, Richard de Granzo. “Efficacy listing of Eutypa chemical and biocontrol candi- Dia- and other fungi detected in cankers. grapevines as were species of dates with DNA-based diagnostics.” The virulence of many of these species trypella and Diatrype. These fungal Practical Winery & Vineyard Jan/Feb 1999 species all belong to the same family as remains to be determined. 47–56. E. lata and closely resemble E. lata in These recent discoveries have led to Rolshausen, P.E., F. Trouillas, and W.D. their spore shape, size, and by their the conclusion that grapevine trunk Gubler. “Identification of Eutypa lata by appearance in culture (Figure XIII). diseases are more complicated than PCR-RFLP.” Plant Disease 88: 925-929. Rolshausen, P.E. and W.D. Gubler. These fungi also have been found initially thought, and that a complex of “Use of boron for the control of Eutypa commonly on various host plants in fungi may be involved. Development of information regarding the biology, dieback in grapevines.” Plant Disease 88: the vicinity of vineyards. In Press. epidemiology and control of each of Eutypa lata and the other diatrypa- Siebert, J. “Eutypa, the economic toll these fungi and diseases is underway. ceous fungi have the same morpholog- on vineyards.” Wines & Vines April 2001 Nevertheless, we know that vineyard ical characteristics in culture including 50–56. sanitation through the removal of spore shape and color. It is apparent Trouillas, F. and W.D. Gubler. “Identifi- infected parts of vines is highly that over the last several years, E. lata cation and characterization of Eutypa lepto- advised, and where possible, sanita- placa, a new pathogen of grapevine in was not the only pathogen being iso- tion of surrounding areas where other northern California.” Mycological Research lated from cankers. Not until this potential hosts of these pathogenic 108: 1195-1204. study did we realize that more than fungi reside. ■ Urbez, J. R., G. M. Leavitt and W.D. one pathogen was capable of causing Gubler. “Identification of Botryosphaeria the same type of disease. spp. causing grapevine disease in Califor- Given these results, it is evident Acknowledgements: We wish to nia.” In Preparation. that Eutypa lata is not the only cause of thank the American Vineyard Foundation grapevine canker diseases in Califor- and the USDA Viticulture Consortium for partial funding of this work.

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