Effects of plant growth retardants and mechanical topping on growth and yield of pimiento pepper (Capsicum annum L.)

The effects of growth retardants and mechanical topping were studied on pimiento pepper (Capsicum annuum L.).

In greenhouse studies, N-dimethylamino succinamic acid (Daminozide) and (2-chloroethyl) trimethylammonium chloride (CCC) at concentrations of 5x10^2-, 1x10^-2, 5x10^-3, and 1x10^-3M were applied to pimiento peppers (cv. Truhart Perfection) at seed, 2-leaf, 4-leaf, and two or three times repeated stages. CCC and Daminozide at most concentrations and times of applications were effective in increasing root length and retarding plant height. The action of these growth retardants on plant height was specific on inhibiting internodal elongation in the sub-apical region. Both retardants at most concentrations applied resulted in an increase in stem diameter. CCC was more effective than Daminozide in increasing stem diameter. Foliar application of the retardants at all concentrations and times studied resulted in an enhancement of the green color of the plant foliage. Time from transplanting to flowering was shortened by approximately 7-16 days by growth retardants. CCC was more effective than Daminozide in increasing both marketable and total yield. At all concentrations and times of applications, both retardants increased the leaf content of Mg and K and had no effect on the content of N, P, and Ca.

Mechanical topping and retardant treatments were studied in the field. Retardants increased both the early and the total yield of ripe fruits. Fruits from treated plants started to ripen about 12 days earlier than normal, a response which would be advantageous to growers of pimientos. Plants topped 1 or 2 times to a height of 23 cm yielded more ripe fruits at the first harvest than untopped plants. Seasonal yields were not influenced by topping.

Results from these studies indicate that CCC and Daminozide may be used to facilitate the mechanical transplanting of pimiento. Retardants applied at the seedling stage appear useful in preventing the development of oversized plants, a problem which is often encountered in the commercial production of pimiento transplants.