RESEARCH ARTICLE ▼ -related dieback and control investigated in noncoastal California grapevines

by Lynn Epstein, Sukhwinder Kaur and Jean S. VanderGheynst

Dieback, or “dead arm,” in noncoastal runk and cordon cankers that cause the ribosomal DNA (called ITS), was California grapevines is most com- vine dieback are serious economic routinely isolated from the margins of monly caused by Botryosphaeria spp. problemsT in vines 12 years and older. cankers in woody tissue in all parts of Using Koch’s postulates, we demon- Vines are infected, at least primarily, the vines. B. dothidea, B. stevensii and through pruning wounds. Historically, E. lata were also occasionally isolated. strated that isolates of B. obtusa are dieback in California vineyards was at- Except for a loss of vigor in shoots pathogenic on grapevines. We initi- tributed to the Eutypa lata, but adjacent to cankered regions, the vines ated studies to investigate the life cy- many of the vines, particularly in the were relatively free of foliar symptoms. cle of B. obtusa and ways to control it Sacramento and San Joaquin valleys, Nonetheless, in springtime some vines are actually infected by fungi in the with multiple dead spurs had de- with cultural practices. Fungal spores genus Botryosphaeria (Urbez-Torres et al. formed, chlorotic (yellow) leaves consis- disseminated by rainstorms were 2006); cankers caused by Botryosphaeria tent with symptoms of Eutypa dieback. collected in traps in an Arbuckle vine- spp. are called “Bot canker.” In all 21 vines with foliar symptoms sampled, only B. obtusa was isolated yard from December 2006 through Signs of disease on grapevines from the margins of discolored woody spring 2007. The data suggests that Between fall 2004 and spring 2007, tissue. B. obtusa was rain-disseminated we monitored ‘Zinfandel’ grapevines B. obtusa pycnidia were observed, throughout winter and spring, and in Arbuckle, Calif., in an approximately generally infrequently and at low den- that pycnidia on deadwood in the 18-year-old vineyard with many dead sity, on the surface of completely dead spurs and cordons (arms of a grape- wood on vines. (Pycnidia are fl ask- vines is a major source of inoculum vine). Our sampling included the exten- shaped structures that contain conidia, for new infections. Transmission sive dissection of 36 vines in decline. which are asexual spores.) In contrast, may also be possible via vegetative There were two predominant signs of pycnidia were observed frequently on disease in woody tissue: a brownish, of- propagation, pruning shears and prunings and detached wood on the ten wedge-shaped necrosis (dead tissue) vineyard fl oor. Individual pycnidia are insects. Durable latex paints were in- in cross-sections of cankered regions, black and approximately 0.01 inch (0.25 vestigated for protecting pruning and and dark brown to blackish streaks in millimeter) in diameter. They are gen- surgical wounds; a self-priming latex longitudinal sections of wood adjacent erally aggregated but sometimes sepa- to pruning wounds. B. obtusa, identi- rate. When fi rst formed, the pycnidia paint was shown to be an effective fi ed by a combination of microscopy are submerged in wood, but as they barrier and was nonphytotoxic. and DNA sequencing of a portion of mature they erupt above the trunk sur-

Pycnidia of Botryosphaeria obtusa form on prunings on the vineyard fl oor. Left, B. obtusa pycnidia are primarily clustered in aggregates (white outline) with some separate individual pycnidia (circle). Right, immature pycnidium (IP) are still partially buried in the plant tissue; mature pycnidium (MP) before spore release; and discharged pycnidium (DP). Microscopic examination of spores is required to identify pycnidia as B. obtusa rather than other Botryosphaeria spp.

http://CaliforniaAgriculture.ucop.edu • OctOBER–DEcEMBER 2008 161 Stands were used to collect fungal spores disseminated in rainstorms. Left, each stand had a funnel under the cordon for estimating available inoculum within the vine, and a plate on the ground (2.5 inches high by 20 inches wide) at a 45º angle to collect In a pathogenicity test, Botryosphaeria obtusa splash from debris; right, stands also had two tented plates (8 inches high by 12 caused a wedge-shaped lesion. inches wide), which were designed to collect wind-blown rain. face. After conidia are released during to black streaks in a longitudinal sec- vines and constructed plates to collect rainy weather and disseminated via tion. B. obtusa isolates are pathogenic, wind-blown rain. Four replicate spore wind-blown rain, the empty pycnidial and B. obtusa grows more quickly in collectors were placed in each of two cavities remain on the plant surface. woody tissue than E. lata (table 1). Our fields on Dec. 1, 2006, and removed B. obtusa pycnidia were never observed results are in agreement with other on May 8, 2007. In order to inhibit on grape berries, and no sexual spores reports in which B. obtusa and other germination during collection, the of either Botryosphaeria spp. or E. lata Botryosphaeria spp. are identified as im- receptacle bottles contained sufficient were ever observed. portant grapevine pathogens (Leavitt acetic acid for a final concentration of and Munnecke 1987; Phillips 1998, 2002; 12% or more. Rainwater (figs. 1D-G) Pathogenicity of B. obtusa Savocchia et al. 2007; van Niekerk et al. and prunings on the ground (figs. 1B- When we started our work, the liter- 2004, 2006). C) were collected. After rainwater was ature was unclear on whether B. obtusa filtered through membrane filters with Life cycle of B. obtusa in a vineyard isolates are pathogenic or saprophytic grids, conidia were quantified micro- (living on dead tissue). To test for Spore dissemination. Rain is critical scopically at 100×. Weather data were pathogenicity, own-rooted ‘Cabernet in the life cycle of Botryosphaeria spp. obtained from an on-farm monitoring Sauvignon’ with stems approximately at several stages, including the oozing station and the Nickel’s Soil Laboratory 0.7 inch in diameter were inoculated in of conidia out of the pycnidia and then in Arbuckle (fig. 1A). the greenhouse with a disc of fungal the dissemination of conidia in wind- B. obtusa was observed in all rain- mycelium (a mass of fungal hyphae) blown rain. To monitor spores (the re- water collections; other Botryosphaeria into a wound 5 inches above the soil. productive cells) quantitatively in the spp. and E. lata were occasionally ob- After 1 year the plants were examined, vineyard, we used funnels under the served. The most spores were trapped Koch’s postulates were completed and the experiment was repeated with TABLE 1. Pathogenicity of Botryosphaeria obtusa isolates from Arbuckle, Calif. similar results. (Koch’s postulates are a process that allows one to conclude Inoculation* Mean lesion length ± SEM† Replicate isolates that a particular organism causes a inches no. particular disease.) Botryosphaeria obtusa 20 ± 0.8 a 3 The greenhouse pathogenicity test Eutypa lata 14 ± 0.8 b 2 produced the two major symptoms that Mock-inoculated control 7 ± 0.8 c 2 we had observed in the field in infected * ’Cabernet Sauvignon’ own-rooted cuttings were inoculated on June 2, 2005, and examined 1 year later. wood: a brownish, wedge-shaped ne- † Six determinations per isolate and three determinations for each mock-inoculated control, each on a separate vine. The F-test P value = 0.0009. Means followed by the same letter are not significantly different by Tukey’s HD, α = 0.05. crosis in a cross-section and brownish

162 CALIFORNIA AGRICULTURE • VOLUME 62, NUMBER 4 2 80 Pycnidia/in : A 1 icon/column = < 5, Immature, below surface 70 2 icons/column = 5–30, and Mature, before release 60 3 icons/column = > 30 pycnidia After spore release 50 B (current prunings) 40

Avg. temp. (ºF) Avg. Dec. 15 pruning 30 ▲ Fig. 1. Biological and meteorological data 1.00 * from a vineyard in Arbuckle, Calif., between 0.75 Dec. 2, 2006 (Julian day −30), and May 8, 2007 C (old prunings and dead wood) (Julian day 128) (Julian dates start with 1 on 0.50 Jan. 1 of each year). (A) Daily precipitation and average air temperature. (B, C) Development Rain (inches) 0.25 and abundance of pycnidia on (B) current 0 prunings (* indicates Dec. 15 pruning); and (C) D (vine drip/sanitation) E (vine drip/no sanitation) old prunings and dead wood on the vineyard 30 floor. Prunings were partially submerged in soil and partially exposed; examinations occurred 25 each day that spores were collected. Icons are not shown on examination dates when 20 there were no changes from the previous date. New pycnidia were produced on older 15 prunings and wood in multiple years. (D–G) Means ± SE of rainstorm-disseminated spores 10 retrieved in various collectors in a field trial Conidia (thousands) with (D, F) surgical removal of deadwood in 5 the vines, painting of all surgical and pruning 0 wounds and sanitation of pruning debris on the ground, and (E, G) without these measures. F (wind-blown/sanitation) G (wind-blown/no sanitation) (D, E) Total number of Botryosphaeria obtusa 50 conidia collected in a 7.25-inch-diameter funnel 2 below the vine. (F, G) Wind-blown B. obtusa 40 conidia collected on plates facing north, south, east and west. 30

Conidia per in 20 in collectors designed for within-vine drip under an infected cordon in a “no 10 sanitation,” area; that is, with neither surgical removal of infected wood, –30 –10 10 30 50 70 90 110 130 –30 –10 10 30 50 70 90 110 130 painting of pruning wounds or burial Julian day Julian day of prunings (fig. 1E). Conidial dis- semination occurred throughout the pruning period and into the springtime conidia also were collected in angled trunks in springtime. After surgically (May 8) in 2007, in apparent contrast to plates designed to determine if the cutting vines that had at least one in- winter-only dissemination of E. lata in wind could pick up debris from the soil, fected cordon down to the trunk in California. although the densities were lower than December 2004 and allowing them to Our collection plates for wind-blown shown in figs. 1F-G (data not shown). regenerate for one season, we com- rain in the “no sanitation” field (fig. 1G) The sanitation treatment consisted pletely removed 14 vines in December similarly showed conidial dissemina- of surgically cutting vines to the trunk, 2005. B. obtusa infections were observed tion throughout the December-to-spring painting surgical and pruning wounds, in yanked sucker wounds in 9 of the 14 observation period. We monitored the and burying pruning debris (figs. 1D, (64%) vines. Copes and Hendrix (2004) development of pycnidia on the current 1F). Because there were no pycnidia on reported faster conidiation of B. obtusa season’s prunings from Dec. 15 and on these regenerated vines, both the vine at 64°F and 72°F than at 54°F and 86°F. older prunings and wood debris, partly drip (fig. 1D) and wind-blown (fig. 1F) Given temperatures in California (fig. because pycnidia on deadwood in the are estimates of wind-blown inoculum 1A), spring rains may facilitate the most vine are hard to see and partly because from outside of the sanitation area. important B. obtusa infection events. debris on the ground may provide Inoculum concentration in the wind Wood discoloration, a grapevine re- inoculum. Prunings from December was higher later rather than earlier in sponse to infection, appears to occur ap- 2005 and before, and deadwood on the the season (fig. 1F, slope of linear re- proximately 1 year after fungal invasion. ground (fig. 1C), primarily released gression P = 0.0002). Both the patterns of wood discoloration conidia between March 20 and April Infections through wounds. In ad- and the recovery of B. obtusa — from 14, when it rained on 6 days (fig. 1A). dition to observing conidial release incremental segments of shoots from Pycnidia from the current season’s from pycnidia (fig. 1C) and conidia pruning wounds to the shoot termi- prunings matured during 2007, but in all of our traps in springtime (figs. nus — indicate that B. obtusa primarily conidia were not released; release pre- 1D–G), we also had evidence of infec- infects through pruning wounds. In sumably occurred sometime during the tions introduced into wounds made contrast to E. lata, B. obtusa grows into 2007-2008 rainy season (fig. 1B). B. obtusa when suckers were yanked out of the shoots. In infected vines, we isolated

http://CaliforniaAgriculture.ucop.edu • October–December 2008 163 Vine surgery tested as and continuing Botryosphaeria vine A management strategy infection. The Epstein group initiated a vineyard sanitation trial (see page for Botryosphaeria 161) to quantify Botryosphaeria spores in vineyards with minimal and recom- mended sanitation. Recommended by Hal Huffsmith, Robert Abercrombie, sanitation includes the removal of dead- Todd Berg and Bernardo Farias wood from the vine and either burial or B removal of prunings from the vineyard he Sutter Home Vineyard in Arbuckle floor. Sanitation appears to be useful (Colusa County) was planted in 1988 for suppressing the initiation of new andT 1989 with a high-yielding selection Botryosphaeria infections. The removal of ‘Zinfandel’ (for white ‘Zinfandel’ pro- of Botryosphaeria-infected wood from duction) on ‘Freedom’ and ‘Harmony’ the vine was approached in a couple of rootstocks at 7-foot-by-12-foot spacing, ways. The first trial consisted of remov- with an 18-inch cross-arm. The vineyard ing the cordon near the first healthy encompasses 1,082 planted acres and has spur on either side of the stake and C historically been pruned sequentially (by switching from spur to cane pruning block) starting with block 1 around mid- (see photo A). This approach involved December and finishing block 6 in early severing the cordons, painting the February. In 2000, we began noticing er- wounds, disconnecting the cordon wire ratic budbreak and stunted spring shoot from the stakes, removing the cordons growth in the blocks that were pruned and cordon wire from the vineyard early. These symptoms were visually iden- (burning is an acceptable vine disposal tified as Eutypa lata infections. When Rus- method in Colusa County) and install- D sell Molyneux with the U.S. Department ing a cane wire. This strategy allows for of Agriculture’s Agricultural Research continuous cropping (see photo B) and Service in Albany was unable to extract may be a good way to deal with a mild Eutypa metabolites via high-pressure liq- Botryosphaeria infection. uid chromatography (HPLC) from cane Severe Botryosphaeria infections samples taken at Arbuckle, we began may require a different approach. We questioning this diagnosis. have successfully left the infected cor- At about that time, the American dons in place and utilized cane prun- In ‘Zinfandel’ vines mildly infected with Botryosphaeria obtusa, (A) infected cordon Vineyard Foundation (AVF) Eutypa ing with the remaining healthy and wood was removed, and cane pruning replaced Research Project released a study by productive wood. However, when the spur pruning and (B) regrowth was treated Epstein and VanderGheynst indicating per-acre yield per block falls below by removing the cordon portion with dead that Botryosphaeria (Bot), not Eutypa, an economically viable level, severe spurs; in severely infected vines, (C) almost all of the scion was removed and new canes was the primary cause of spur dieback vine surgery (as opposed to vineyard were trained and (D) most of the cordon was in some Central Valley vineyards. This replanting) will allow vines to stay removed. work was later confirmed in vineyards in the ground and most of the trellis located throughout California (Urbez- and drip irrigation system to remain Torres et al. 2006). In 2004, the Sutter intact. The cost for cutting vines Time will determine if severe vine Home Vineyard management group above the graft union and about 12 surgery is successful in reestablishing teamed up with Epstein’s UC Davis lab to inches from the ground (see photo C), vineyards infected by Botryosphaeria. identify and evaluate the organisms caus- removing and disposing of the upper RH Phillips vineyard managers initi- ing dieback at Arbuckle and to develop portion of the vine and the cordon ated this approach to vineyard revital- a management strategy to deal with dis- wire, painting the wound, reinstall- ization several years ago at a planting eased vines. ing a new cordon wire, retraining and about 10 miles south of the Arbuckle Epstein, VanderGheynst and Kaur tying the vine, repairing trellises and vineyard with vines apparently suffer- made numerous visits to confirm that conducting standard farming activi- ing from Botryosphaeria infection, and Botryosphaeria was the organism causing ties was about $4.20 per vine or about the retrained vines still seem to be vig- spur dieback, evaluate potential sources $2,200 per acre. This method should orous and productive. of infection, conduct wound treatment yield almost a full crop in the second trials and monitor spore release. They year (see photo D). We are currently observed that deadwood on the cordon evaluating several training practices H. Huffsmith is Senior Vice President of Vineyard and prunings left under the vine (on the with the use of either two trunks to Operations, R. Abercrombie is Vice President of berm and between the vine rows) were reestablish bilateral cordons or quad- Vineyard Operations, T. Berg is Viticulturist and B. covered with Botryosphaeria pycnidia and rilateral cordons, or training the vine Farias is Arbuckle Vineyard Manager, all with Sut- were the likely source of spore release for cane pruning (see photo D). ter Home Vineyards, St. Helena.

164 CALIFORNIA AGRICULTURE • VOLUME 62,, NUMBERNUMBER 4 TABLE 2. Two trials in progress on effect of applying Duration paint on pruning and surgical cuts for disease caused by Botryosphaeria spp.

Trial no.* Extent of Painting of surgical Vines with Vines with dead (start date) sanitation† and pruning cuts? weaker growth‡ shoots or spurs‡ ...... % ...... 1 (2005) Minimal No 15 10 1 (2005) Minimal Yes 15 6 2 (2006) Recommended No 2 0 2 (2006) Recommended Yes 3 0 * Each trial was designed for categorical data analysis with approximately 100 replicates in a randomized complete block design with one replicate per block. No statistical differences (P = 0.05, Fisher’s exact test) between painted and unpainted vines in each trial as of 2007. † Recommended sanitation includes surgical removal of all deadwood within the vine and either burial or removal of prunings. ‡ Symptoms consistent with infections by B. obtusa were evaluated in October 2007.

In preliminary experiments, in which yanked out or when the mechanical duct tape covered with the sticky prod- harvester injured the trunk. Moreover, uct Tanglefoot was placed over prun- sampling of the wood just above the sur- ing wounds, we recovered rove beetles gical cut indicated that 10 of the 36 vines (Staphilinidae) infested with B. obtusa. (28%) had infections of B. obtusa at the We also detected B. obtusa in material surgical cut, of which only three had any that could have been used for vegeta- indication of discoloration. Although in tive propagation. As indicated above, some cases the mechanical harvester ap- we isolated B. obtusa from asymptomatic peared to have damaged the vines, we shoots. B. obtusa also was isolated from never had evidence that B. obtusa in the Top, Duration paint is being tested as a the internal tissue of buds that were trunk per se caused vine debilitation. treatment for surgical cuts on grapevine surface-disinfected, in 13% of the buds Based on patterns of discoloration in the trunks; lower, an untreated vine. (n = 60) of symptomatic shoots and 9% trunk, infections of B. obtusa appear to of the buds (n = 57) from asymptomatic grow primarily toward the base of the B. obtusa in 28% of asymptomatic shoots shoots on infected vines. stem. While we observed infections in and 90% of symptomatic 1-year-old the rootstock, we never observed infec- Strategies for cultural control shoots (n = 54) 3 inches from the cordon. tions in the roots. A long-term study is Symptomatic shoots that were surface- Surgical removal. Several options are needed to determine whether over time, disinfected and incubated in a humid available for surgical treatment: (1) the B. obtusa in the trunk leads to a reduc- chamber at 74°F for 3 weeks produced terminus of the affected cordon(s) can tion in yield. B. obtusa pycnidia. Overall, our data are be removed, or (2) most of the scion can Protection with durable paint. We consistent with a life cycle in which B. be removed, retaining only sufficient are investigating two strategies for obtusa grows asymptomatically within wood for the regeneration of new canes integrated pest management of Bot grapevine shoots and woody tissue. We (see sidebar). In either case, the reten- canker: (1) the protection of surgical postulate that damage to the vine occurs tion of a mature root system allows wounds and new pruning wounds with primarily by the grapevine’s release of rapid regeneration of the scion. The a durable paint and (2) the reduction of self-defense compounds that kill its own best location for the surgical cut is not inoculum sources. Two field trials are in cambium. always clear. Certainly, cuts should be progress to test wound protection (table Other means of spread. Although made below all necrotic and symptom- 2). In 2005, we surveyed paints for use we postulate that pruning wounds are atic tissue. We have isolated B. obtusa as protectants and selected candidates primarily infected by B. obtusa conidia in wood up to 4 inches in front of the with the following properties: high disseminated in wind-blown rain, some discolored margin. Although dieback elasticity (reduced likelihood for crack- inoculum may also be disseminated symptoms often appear to be most ing); breathability (presumably less by other mechanisms. Pruning cuts severe at the ends of the cordons, mul- likely to mold under the painted sur- through mature pycnidia can release tiple infection foci can be distributed face); durability to exposure to ultravio- conidia onto shear blades. Even in cases across the length of asymptomatic por- let light and rain; and fungal resistance. with only mycelium and no spores, tions of the cordon (data not shown). After preliminary trials, we selected transmission is possible via pruning Consequently, we favor cutting down to Duration (Sherwin Williams K34T154) shears. We made pruning cuts on 25 the trunk. paint, a self-priming exterior latex with shoots that we knew, retrospectively, However, trunks can be infected too. an ultradeep base that was stained with were infected. After making the cuts, Of the 36 sampled vines, 28 (78%) had 6 ounces of N1 Raw Umber per gallon. we wiped the blades onto sterile paper infections on the trunk that emanated Duration paint forms an impen- and then cultured the paper; B. obtusa from wounds on the trunk; wounds etrable and stable physical barrier on was recovered on 24% of the wipes. were made either when suckers were grapevine surgical cuts and pruning

http://CaliforniaAgriculture.ucop.edu • October–December 2008 165 wounds. Experimental treatments in or removal of prunings. Further re- knowledge. Answers to the following which the paint was applied onto prun- search is required to determine the questions will be useful: How long are ing wounds and over buds indicated no contribution of this inoculum to vine pruning wounds susceptible to infec- phytotoxic or inhibitory effects on foli- infections. tion by Botryosphaeria spp.? What train- age or bud out-growth (data not shown). B. obtusa may be transmitted by ing and pruning strategies minimize The California Department of Pesticide pruning shears. In a study on the the area of susceptible wounds? How Regulation stated that Duration paint potential transmission of grapevine does the timing of conidial release can be used as a physical barrier on pathogens in infected propagation vary in different weather conditions? grapevines without fungicide registra- material, Aroca et al. (2006) detected In different vineyards, how impor- tion. Possible advantages of paint over Botryosphaeria spp. and Phomopsis along tant are various modes of pathogen fungicide include that the paint is ex- the length of some plants, but mainly dissemination, and in particular, tremely long-lasting, will not wash off at the graft union. Consequently, are Botryosphaeria spp. initially dis- during repeated rains and is not phy- grafting tools may transmit inoculum. seminated in vegetatively propagated totoxic. Nonetheless, painting is labor- Gimenez-Jaime et al. (2006) identified material that is infected but not symp- intensive for a large vineyard. We were B. obtusa and other Botryosphaeria spp. tomatic, and if so, how often? How not successful in delivering Duration in grapevine nurseries. Our isolation long are vines productive after major paint using a modified pruner due to of B. obtusa in shoots and buds also surgery? And do infections occurring Duration’s high viscosity, particularly suggests that B. obtusa might be spread below the surgical cut affect the longev- under the cooler weather conditions in propagation material. ity of the vines? when pruning is typically done. We monitored rainstorm-dissem- Surgery is being tested in some vine- In collaboration with Sutter Home inated spores over the period when yards as a means to revitalize vines Vineyards, Zinfandel vines with die- grapevines are pruned, from December with Bot canker (see sidebar, see page back symptoms — at least one dead to May. Our data indicates that B. obtusa 164). We postulate that a combination of spur — were surgically cut on the trunk conidia are disseminated during the sanitation and surgery will allow sus- approximately 12 inches above the soil entire season, including and perhaps tainable control of Bot canker. in February 2005 (table 2). The surgical especially in spring when temperatures cuts were either treated with Duration are more conducive for sporulation. or not. In the paint-treated vines, all Consequently, while later pruning will pruning cuts were painted. In 2006, an avoid exposing wounds to early-season L. Epstein is Professor of , and additional trial with surgically treated rain events and is a worthwhile compo- S. Kaur is Staff Research Associate, Department vines was started in an area with sani- nent of an integrated pest management of Plant Pathology, UC Davis; and J.S. Vander- tation. Paint coverage was good in both strategy, it may not provide sufficient Gheynst is Professor, Biological and Agricultural trials, except when there were heavy control in an infected vineyard. Engineering, UC Davis. This research was par- tially supported by a grant from the American rains and sap pushed up a new coating Research questions Vineyard Foundation. We thank Hongyun Guo, of paint. In this case, paint was reap- Romil Benyamino, Gurdev Dhahan and Burt plied. In both trials, new growth and The development of a cost-effective, Vanucci for technical assistance; Frank Zalom for the establishment of new cordons have sustainable Bot canker management insect identification; and our fantastic collabora- been excellent. However, we cannot rec- program will require additional tors and their crew at Sutter Home Vineyards. ommend Duration until data on disease incidence and yield are collected in the next several years. Currently, there is no References statistical difference between the inci- Aroca A, Garcia-Figueres F, Bracamonte L, et al. 2006. Phillips AJL. 2002. Botryosphaeria species associated dence of vines with B. obtusa symptoms Occurrence of fungal pathogens associated with with diseases of grapevines in Portugal. Phytopathol in paint-protected versus nonprotected grapevine nurseries and the decline of young vines in Mediterr 41:3–18. Spain. Eur J Plant Pathol 115:195–202. vines (table 2). Savocchia S, Steel CC, Stodart BJ, Somers A. 2007. Inoculum reduction. Our and oth- Copes WE, Hendrix FF Jr. 2004. Effect of temperature Pathogenicity of Botryosphaeria species isolated from ers’ data is consistent with the hy- on sporulation of Botryosphaeria dothidea, B. obtusa, declining grapevines in subtropical regions of Eastern and B. rhodina. Plant Dis 88:292–6. Australia. 46:27–32 pothesis that Botryosphaeria spp. may infect vines via multiple avenues. Gimenez-Jaime A, Aroca A, Raposo R, et al. 2006. Oc- Urbez-Torres JR, Leavitt GM, Voegel TM, Gubler WD. currence of fungal pathogens associated with grape- 2006. Identification and distribution of Botryosphaeria The presence of B. obtusa pycnidia on vine nurseries and the decline of young vines in Spain. spp. associated with grapevine cankers in California. deadwood on vines and the collection J Phytopathol 154:598–602. Plant Dis 90:1490–503. of conidia in funnels below infected Leavitt GM, Munnecke DE. 1987. The occurrence, dis- Van Niekerk JM, Crous PW, Groenewald JZ, et al. 2004. wood suggest that the surgical removal tribution, and control of Botryodiplodia theobromae DNA phylogeny, morphology and pathogenicity of Botry- of deadwood should reduce inoculum. on grapes in California. Phytopathol 77:1690 (abstr.). osphaeria species on grapevines. Mycologia 96:781–98. Because prunings and deadwood on Phillips AJL. 1998. Botryosphaeria dothidea and other Van Niekerk JM, Fourie PH, Halleen F, Crous PW. 2006. the vineyard floor can produce large fungi associated with excoriose and dieback of grape- Botryosphaeria spp. as grapevine trunk disease patho- vines in Portugal. Phytopath Z 146:327–32. gens. Phytopathol Mediterr 45:S43-S54. quantities of conidia, we recommend ground sanitation, such as the burial

166 CALIFORNIA AGRICULTURE • VOLUME 62, NUMBER 4