Pepper seedlings can be infested with broad mites prior to transplanting. Transplanted seedlings may not present visible mite damage symptoms and few microscopic mites will be undetected by growers. A rapid increase of the mite population can subsequently result in yield losses in greenhouse-grown crops. Control of broad mites based on biological (N. californicus) and conventional (sulfur) methods were evaluated after infested transplants were introduced into a production greenhouse. Seedlings were artificially infested with two broad mites, 3 days before they were transplanted in mid-September in a passively ventilated greenhouse in Florida. Plants had either two predatory mites released once [4 days after transplanting (DAT)], or twice (4 and 22 DAT), or were sprayed with sulfur (four weekly applications starting 13 DAT when first damage symptoms were noticed). Damage on plants was assessed by an injury scale transformed into percentage values, with 100% being total damage on untreated infested plants. Broad mites were absent in all plants 38 DAT but the damage caused to the plants at this time was negatively correlated (r= –0.95) with marketable yield at 90 DAT. Plants produced no marketable yield where broad mites were not controlled. One or two releases of predators led to respective damages of 56% and 45%, and fruit yields of 2.0 and 3.0 kg·m-2. Plants sprayed with sulfur had a damage of 7% after reaching a maximum of 74% at 18 DAT; however, yields were 4.3 kg·m-2, which was similar to the yield obtained in the uninfested control treatment (4.6 kg·m-2). Releases of predators prior to transplanting and/or higher predator release densities may be needed under similar conditions and will be evaluated in a subsequent experiment.
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