I Taller y III Seminario Internacional de Viticultura y Enolog�a Tropical

Enfermedades de la madera de la vid en am�rica. Es Eutypa lata o Botrydiplodia theobromae

Canker diseases of the grapevine in the Americas: is it Eutypa lata or Botrydiplodia theobromae

G. Leavitt

University of California, Cooperative Extension 328 Madera Avenue, Madera, CA U.S.A.

Palabras Claves: Vid, Eutypa, Botrydiplodia, Canker

Eutypa lata has been found world wide as a canker disease of grapes. Eutypa dieback, as it 15 commonly called today, is the disease of grapes infected by E. lata. The most characteristic symptoms are the wedge-shape cankers in the vine structure and the weak stunted growth characteristically observed in early spring. The leaves of the stunted shoots are small, chlorotic and misshapen. They appear to be similar to grapes suffering from zinc deficiency and often have cupped leaves with a necrotic margin. The stunted shoot symptom is generally associated with the development of a wedge-shaped canker in the woody parts of the vine and eventually dead arms and cordons. Where these symptoms have been observed, isolations have always yielded E. lata. Ascospore production generally occurs in the higher rainfall are as. With the advent of rainfall ascospore are released, and distributed by the wind. The ascospore land orfresh pruning wounds, infect the plant, ant withing 3 years a canker develops below the wound. The larger the wound the greater the opportunity for infection to occur.

Field observations and continued sampling in the Southern San Joaquin and Coachela Valleys of California in the early 1980 resulted in the discovery of numerous dead-arms which did not manifest ah of the symptoms of E. lata nor was the fungus isolated from them. Further research confirmed the pathogenicity of B. theobromae as another causal agent of dead-arm in grapes Lot canker as it is commonly known to grape growers in California, 15 also a pruning wound disease.

The subsequent wedge-shape cankers are indistinguishable from those caused by E.lata but there are no foliar symptoms. Disease development is slower than on grapes infected by E. lata. Often infections by theobromae may not be observable until the arm or cordon dies as there are no foliar symptoms. The only positive identification procedure is to culture the fungus from the margin of the cankers, as both fungi discussed he re, have been recovered from cankers found on grapes in California, Arizona, northern Mexico and southern Brasil. Based on statewide surveys of ah the grape growing are as in California, B. theobromae is the major cause of arm, cordon and vine death, from central California southward to Hermosillo, Mexico.

The physiologic races of B. theobromae designated as high and low temperature races, exist. Only the high temperature race (opt. growth temp. 30-33 C) was found in the desert area o California, Arizona ant Hermosillo, Mexico. Both races exist in the Central and northern part of California, but the low temperature race (avg. opt. temp., 27 C) was most frequently isolated (95%). Three isolates of B. theobromae, representing the high and low temperature races, were used to inocula it fresh pruning wounds of grapevine in 1983. In 1990, 90.7% of the high temperature race and 77.3% of the low temperature race were recovered fulfilling Koch's postulates. Arm death began four years after inoculation. The natural incidence of disease progress was observed for 5 years on young vines. Occurrence of the disease on vines 10 years old and older was as great as 100% with several cankers per vine. Various materials were used on pruning wound applications to prevent infection. Most fungicides tested were effective in reducing disease incidence when used on fresh pruning wounds. Latex paint reduced infections, but was significantly inferior In control to any fungicide. Springtails, (Entomobrya unostrigata), were implicated as possible vector by carrying spores to pruning wounds as they feed on vine exudates following pruning.

Pruning wounds offer easy access into the vine structure for many organisms. These two fungi appear to act in that manner. Ongoing research suggests that protection of pruning wounds against infection is vital to the long term health, vigor, and production capacity of the vine.