Selected squash and pumpkin cultivars and breeding lines were evaluated for reaction to powdery mildew in a trial conducted at the Hancock Agricultural Research Station, in central WI. Seeds of 26 lines were planted in the greenhouse on 5 Jun (Jiffy-7~R pellets, 4-5 seeds per pellet). Seedlings were transplanted into the field on 28 Jun and later thinned to leave one plant per hill. Each plot consisted of a single row containing three hills, spaced 3 ft apart in the row. Rows were 12 ft apart with 18 ft wide alleys between the ends of adjacent plots. The trial was designed as a randomized complete block (entries were not blocked by cucurbit type) with three replications. The soiltype was Plainfield sand with pH 7.0. Fertilizer consisted of 0-0-60, 500 lb/A, broadcast 4 Apr, 6-24-24, 100 lb/A, placed in the furrow 28 Jun when rows were marked for transplanting, and a sidedress application of 34-0-0, 100 lb/A, 17 Jul. Insects werecontrolled with Admire 2F incorporated in the fertilizer at planting (16 fl oz/500 lb) and foliar application of Capture 2 EC (4 fl oz/A, 3 Jul, 1 Aug), and Ambush 25W (4 oz/A, 15 Aug). Plants were not inoculated; only natural inoculum of the powdery mildew fungus contributed to disease establishment. No fungicide was applied at any time during the season. Powdery mildew severity was rated on a Horsfall-Barratt scale of 0 (no symptoms) to 11 (all foliage and stems dead), and ratings were converted to percentages. Whole plot assessment was done for four areas (approximately 3 ft by 3 ft) in each plot on 31 Jul, 7 Aug, 14 Aug, 22 Aug, 29 Aug, 5 Sep, 12 Sep and 18 Sep. On 22 Aug, 29 Aug, 5 Sep, 12 Sep and 18 Sep, six older leaves, six middle-aged leaves,and six new leaves in each plot were chosen arbitrarily and rated. Individual leaves were rated only for powdery mildew severity but the whole plot rating included severity of powdery mildew as well asany other cause of defoliation. Summer squash (yellow and zucchini) were harvested every 3-5 days throughout the growing season when fruit reached 6-8 in. in length. Acorn squash and pumpkins were harvested 4 Oct. Weight, and fruit quality (marketable orimmature)were recorded for each pumpkin. Number of fruit, total weight per plot, and whether fruit were marketable or immature were recorded for acorn squash. The number of rotting fruit was recorded for each line but these fruit were not weighed. Rainfall recorded during thegrowing season (in.) was: Jul, 2.08; Aug, 3.17; Sep 2.78. An additional 7.7 in. of water was applied as overhead sprinkler irrigation in 15applications (30 Jun – 31 Aug).
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