003 Epidemiology and Control of Pepper Stip

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  • 1 Monterey Counties, Calif
  • | 2 San Joaquin Counties, Calif.
  • | 3 Dept. of Vegetable Crops, University of California, Davis, CA 95616

Pepper stip is a physiological disorder manifested as gray-brown to greenish spots occurring on the fruit of bell, pimento, Anaheim, and other types of peppers, most noticeably on red fruit that mature under fall conditions. Most hybrid bell cultivars are resistant to the malady; the problem is most severe for pepper growers reliant on less-expensive, open-pollinated cultivars. In 1995, we initiated studies to evaluate the possible link between mineral nutrition and this disorder. Two susceptible open-pollinated cultivars and two resistant hybrid cultivars were grown in randomized plots at seven sites. Significant correlations were seen between the levels of potassium (r = 0.59) and calcium (r = -0.37) in whole leaves and the incidence of stip (P = 0.05). The stip-resistant cultivars also maintained less total nitrogen in the whole leaves than susceptible cultivars (P = 0.05). In 1996 and 1997, we undertook field studies to evaluate the effects of varying calcium and nitrogen application rates. Inconsistent results were observed with calcium applications. Moderate reductions in stip incidence was observed at some sites and no reduction at others following foliar calcium applications. Nitrogen nutrition had no effect on stip severity. In 1998, evaluation of a large number of open-pollinated cultivars was undertaken; `Gusto' showed excellent tolerance to pepper stip, followed by `Taurus' and `Cal Wonder 300'. We conclude that growers that are reliant on open-pollinated cultivars can utilize these cultivars to minimize the incidence of pepper stip.

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