EVALUATION OF COLOR MULCHES AND OIL SPRAYS FOR YIELD AND FOR THE CONTROL OF SILVERLEAF WHITEFLY, BEMISIA-ARGENTIFOLII (BELLOWS AND PERRING)ON TOMATOES

Orange, yellow, and aluminum color mulches were compared to white (fal l) or black (spring) for their effect on the silverleaf whitefly, Bemi sia algentifolii (Bellows and Perring), and on the yields of staked, f resh market tomato, Lycopersicon esculentum, Mill, cv. Sunny. In addit ion, plants were sprayed weekly with a mineral oil emulsion or as need ed with a soybean oil emulsion in treatments with orange and yellow mu lches, respectively. Under high stress by the whitefly transmitted tom ato mottle virus (TMOV), plants in September and October 1990 were tal ler with the aluminum, yellow and yellow + oil, than with the other mu lch treatments (P < 0.05). Later, in November and December, plants wer e tallest on the aluminum mulch. Virus symptoms developed slower on pl ants with the orange+oil, yellow+oil, and aluminum, than with other mu lches. Yield of extra-large (> 70 mm diameter) fruit was higher with t he 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 o ther treatment except with the aluminum mulch. Yields of extra-large a nd marketable fruits also depended on the first apparent signs of viru s infection. Averaged over all mulch treatments, extra-large and marke table 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 199 1, with large whitefly populations towards the end of the season and f ew plants with virus symptoms at harvest, yields were similar with all mulch treatments. Most immature and adult whiteflies were on the whit e in the fall and on the black mulch in the spring. With other mulch t reatments, a definite trend could not be established between mulch col or and number of whiteflies observed on the plants. Yellow mulched tom ato plants, when sprayed as needed with the soybean oil emulsion or th e aluminum mulch, would be better than using black and white mulches i n the full-bed polyethylene mulch system where high whitefly populatio ns are present during the growing season. (C) 1997 Elsevier Science Lt d.