Evaluation of color mulches and oil sprays for yield and for the control of silverleaf whitefly, Bemisia argentifolii (Bellows and Perring) on tomatoes

Abstract

Orange, yellow, and aluminum color mulches were compared to white (fall) or black (spring) for their effect on the silverleaf whitefly, Bemisia argentifolii (Bellows and Perring), and on the yields of staked, fresh market tomato, Lycopersicon esculentum, Mill, cv. Sunny. In addition, plants were sprayed weekly with a mineral oil emulsion or as needed with a soybean oil emulsion in treatments with orange and yellow mulches, respectively. Under high stress by the whitefly transmitted tomato mottle virus (TMOV), plants in September and October 1990 were taller with the aluminum, yellow and yellow + oil, than with the other mulch treatments ( P < 0.05). Later, in November and December, plants were tallest on the aluminum mulch. Virus symptoms developed slower on plants with the orange + oil, yellow + oil, and aluminum, than with other mulches. Yield of extra-large (70 mm diameter) fruit was higher with the yellow + oil, than with orange, orange + oil, and white mulch ( P < 0.05). Marketable yield was also higher with the yellow + oil, than with any other treatment except with the aluminum mulch. Yields of extra-large and marketable fruits also depended on the first apparent signs of virus infection. Averaged over all mulch treatments, extra-large and marketable yields, respectively, were 0.26 and 3.90 kg/plant when symptoms appeared during the first 30 days after planting (DAP), and 1.01 and 5.39 kg/plant when virus symptoms developed 61 to 77 DAP. In spring 1991, with large whitefly populations towards the end of the season and few plants with virus symptoms at harvest, yields were similar with all mulch treatments. Most immature and adult whiteflies were on the white in the fall and on the black mulch in the spring. With other mulch treatments, a definite trend could not be established between mulch color and number of whiteflies observed on the plants. Yellow mulched tomato plants, when sprayed as needed with the soybean oil emulsion or the aluminum mulch, would be better than using black and white mulches in the full-bed polyethylene mulch system where high whitefly populations are present during the growing season.