Two years of field research were conducted to determine the additive effects of weed cover and insects on pepper production. When weeds covered less than 10% of test plots, the natural insect populations reduced the marketable fruit yield of bell peppers 32% in 1983 and 22% in 1984. When weeds covered 72 or 94% of the test plots, foliage damage due to insects was from 5.8 to 12.1%, respectively. The high percent weed cover and insects reduced yield 99%. The average fresh weight of pepper foliage approached zero as weed cover approached maximum. Foliar levels of iron and aluminum were reduced greatly in peppers grown in competition with a 100% weed cover. The level of boron, copper, phosphorus, and potassium in pepper foliage increased as percent weed cover increased.

Field experiments were conducted at Frederick, MD, in 1985 and 1986 to determine effects of weed-interference periods and insects on bell peppers. Weed-interference periods of approximately 40 and 60 d reduced both bell pepper fruit number and weight 10 and 50%, respectively. Bell pepper foliage weight was reduced 10 and 50% with approximately 20- and 50-day weed-interference periods. In 1985 and 1986, insect populations were low with an average of 10 and 3% of the pepper fruit infested, respectively. Most infested fruit was damaged by European corn borer. No significant differences in insect infestation of fruit as related to time of weed-interference periods were noted.