In a replicated field test in 1982 where natural virus incidence was 25% watermelon mosaic virus 1 (WMV-1) and 75% WMV-2, we observed mosaic symptoms at harvest in leaves and fruit of the yellow-fruited Cucurbita pepo L. ‘Butterbar’, ‘Early Prolific Straightneck’, and ‘Multipik’. The range in percentage of diseased plants among the cultivars was small (26–33%), but total diseased fruit exceeded 40% in ‘Butterbar’ and ‘Early Prolific Straightneck’ and was less than 10% in ‘Multipik’. In a replicated field test in 1983, ‘Early Prolific Straightneck’ and ‘Multipik’ squash plants mechanically inoculated at early flowering with WMV-1, WMV-2, and zucchini yellow mosaic virus (ZYMV) became 97–100% foliar diseased. Production of diseased fruit was significantly greater in virus inoculated ‘Early Prolific Straightneck’ plants (all 3 viruses) than in uninoculated plants, and significantly greater in ‘Multipik’ plants inoculated with ZYMV or WMV-1 than in those inoculated with WMV-2 or not inoculated. In both tests, there were significant delays in the development of fruit symptoms in virus infected ‘Multipik’ when virus infection was mainly WMV-2. The evidence suggests fruit symptoms were caused by viruses other than WMV-2, and that WMV-2 does not induce symptoms in fruit of ‘Multipik’.