88 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 



the hardwood sawtimber. For these reasons, and because the disease 

 is usually lethal, oak wilt must be considered a serious threat to the 

 hardwood industry. 



Statewide control programs, aimed at eliminating the source of in- 

 oculum, are active in a number of States. Principal suppression meas- 

 ures include (1) the felling of diseased trees and all healthy oaks 

 within possible root graft distance (about 50 feet) and poisoning the 

 stumps; (2) felling diseased trees only, poisoning stumps, and spray- 

 ing infected trees and stumps with No. 2 fuel oil containing DDT, 

 BHC, and pentachlorophenol ; and (3) deep girdling infected trees 

 to the heartwood to hasten drying and inhibit mat production. While 

 it is expected that these measures help to suppress oak wilt, their 

 effectiveness has not been clearly demonstrated. 



Intercontinental spread may be possible through the shipment of 

 logs or lumber cut from infected trees. As a result, several countries 

 have placed embargoes on oak logs and lumber from the United States 

 unless certified disease- free. Oak lumber may be certified if kiln-dried 

 to a moisture content of 20 percent or less, and both logs and lumber 

 may be certified if originating outside the disease area. Certificates 

 are required for/shipments to Egypt, Germany, Italy, Sweden, Turkey, 

 Union of South Africa, Yugoslavia, and possibly, also Portugal. 



Range : Oak wilt is widespread throughout the eastern and midwestern 

 United States, occurring in 19 States, from Nebraska and Okla- 

 homa in the West to Pennsylvania and North Carolina in the 

 East. 

 Hosts : Fagaceae. Susceptible species indigenous to the United States 

 found naturally infected include Querent alba, Q. bicolor, Q. 

 coccinea, Q. ellipsoidalis, Q.. fcdcata, Q. ilidi 'folia, Q. imbrioaria, 

 Q. macrocarpa, Q. marilandica, Q. muehlenbergii. Q. palustris, 

 Q. phellos, Q. prinus, Q. rubra, Q. stellata, and Q. vehitina. 

 Chinese chestnut, Castanea mollissima, an exotic, was also found 

 to be susceptible through natural infections. 



Additional species, both native and exotic, which have been shown 

 to be susceptible through artificial inoculation include Quercus 

 falcata var. pagodae folia, Q. michauxii, Q. nigra, Q. shumardii, 

 Q. agrifolia, Q. chrysolepis, Q. gambelii, Q. garryana, Q. laevis, 

 Q. lauri folia, Q. lobata, Q. shumardii var. texan-a, Q. virginiana, 

 Q. virginiana var. maritima, Q. wislizenii, Q. robur, Q. acutissima, 

 Q. acuta, Q. aliena accutesserata, Q. brutia, Q. castanae folia, Q. 

 cerris, Q. dentata, Q. gardeniae folia, Q. glandulifera, Q. glauca, 

 Q. haas, Q. ilex, Q, longiux, Q. lusitamica, Q. macrolepis, Q. 

 myrsinaefolia, Q. suber, Q. thomasi, Q. variabilis, Castanea 

 dentata, C. satwa, C. piumila, Castanopsis kaioakamii, C. semper- 

 virens, Lithocarpus glabra, L. densijlorus. 

 Literature : 



Bretz, T. W. The ascigerous stage of the oak wilt fungus. Phy- 

 topathology 42 : 435^37. 1952. 



Henry, B. W. Chalwa quercina n. sp., the cause of oak wilt. Phy- 

 topathology 34 : 631-635. 1944. 



True, K. P., Barnett, H. L., Dorsey, C. K., and Leach, J. G. Oak 

 wilt in West Virginia. W. Va. Univ. Agr. Expt. Sta. Bui. 448T: 

 1-119. 1960. 



