* Corresponding author. Crop Protection 19 (2000) 217}224 Incidence and management of virus diseases of cucurbits in Lebanon Y. Abou-Jawdah*, H. Sobh, S. El-Zammar, A. Fayyad, H. Lecoq American University of Beirut, FAFS, Beirut, Lebanon INRA, Station de Pathologie Vegetale, BP 94, 84143 Montfavet Cedex, France Received 3 August 1999; accepted 14 December 1999 Abstract Virus diseases are the major cause of economic losses in commercial cucurbit production in Lebanon. This survey revealed that Zucchini yellow mosaic Potyvirus (ZYMV) and Cucurbit aphid-borne yellows Polerovirus (CABYV) are the most common viruses of "eld-grown cucurbits in Lebanon. They are followed by Watermelon mosaic Potyvirus (WMV), Papaya ringspot Potyvirus-watermelon strain (PRSV-W) and to a lesser extent Cucumber mosaic Cucumovirus (CMV). Cross-protection with a mild strain of ZYMV-WK gave signi"cant protection of squash plants against severe virus symptoms and resulted in signi"cant yield increase as compared to the control. Silver plastic mulch also gave a signi"cant protection against viral diseases and a higher total yield than controls. However, the best protection and highest total yield were obtained with #oating row covers. The integration of cross-protection with silver mulch or with #oating row covers improved the protection obtained with either approach.  2000 Elsevier Science Ltd. All rights reserved. Keywords: Squash; Cross-protection; ZYMV; Integrated management 1. Introduction Viral diseases cause important economic losses throughout the world. More than 35 viruses have been isolated from cucurbits (Provvidenti, 1996). These viruses constitute complex and dynamically changing problems as described by Nameth et al. (1986). Cucurbits are among the major vegetables grown in Lebanon. Several virus diseases inducing mosaic symptoms were pre- viously reported including Watermelon mosaic Potyvirus (WMV), Zucchini yellow mosaic Potyvirus (ZYMV), Pa- paya ringspot Potyvirus * watermelon strain (PRSV-W), Zucchini yellow yeck Potyvirus (ZYFV), and Cucumber mosaic Cucumovirus (CMV) (Makkouk and Lesemann, 1980; Lesemann et al., 1983; Katul, 1986). The incidence of leaf mosaic and deformation symptoms on squash and cucumber and the associated loss of yield are so high that summer and fall crops have been largely abandoned in the coastal region of Lebanon. More recently severe yellowing symptoms of older leaves of cucumber, melon and squash were observed in open "elds and in green- houses. Viruses that cause similar yellowing symptoms on cucurbits have been reported in several countries, and they are transmitted either by aphids (Lecoq et al., 1992) or by white#ies (Wisler et al., 1998). Several management practices for the control of virus diseases of cucurbits have been reported including the use of di!erent types of plastic mulch (Brown et al., 1993; Summers et al., 1995), mineral oil (Simons and Zitter, 1980), #oating row covers with "ne mesh placed directly over the plants (Perring et al., 1989; Orozco et al., 1994) and cross-protection using mild strains of the predomi- nant virus or viruses (Lecoq et al., 1991; Walkey et al., 1992; Rezende and Pacheco, 1998). However, in cucur- bits, the evaluation of the e$cacy of cross-protection as compared to other management practices and its in- tegration with other management practices have received limited attention. This paper presents the results of a survey of cucurbit viruses of major economic importance in Lebanon and of a comparison, under "eld conditions, of the e$cacy of some management practices alone or in combination with cross-protection. 0261-2194/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S 0 2 6 1 - 2 1 9 4 ( 9 9 ) 0 0 1 0 0 - 3