Increasing early crops of unprotected tomatoes (Lycopersicon esculentum Mill.) with naphthoxyacetic acid applied on whole plants

Abstract

A parthenocarpy-inducing preparation, Betokson, containing beta-naphthoxyacetic acid (NOA) as an active ingredient, was applied by spraying whole plants. As one of the controls, dipping the trusses in NOA solution was used according to a currently recommended technique. NOA applied by each of these treatment increased the very early yield (first 4 pickings) by 4-11 times in cv. Venture and 3-4 times in cv. New Yorker in comparison with the untreated controls. Treating the whole plant increased the very early yield more than did dipping the trusses. The early yield (first 8 pickings) was also increased in cv. Venture by NOA applied by both methods. Treatments with NOA decreased, however, the late yield. This decline was more marked with the higher NOA concentration and when the whole-plant-spray was applied. Gibberellic acid (GA₃) applied alone as a whole-plant-spray at a concentration of 25 mg·dm^-3, did not increase the very early yield but in combination with NOA, increased the early yield in cv. New Yorker. GA₃ alone, or in combination with NOA, applied as a spray on the whole plant caused marked chlorosis of the leaves and marked decline of the total yield.