Bloom and postbloom applications of NAD/NAA mixture have minimal effects on yield and fruit size of field-grown tomatoes and peppers

A commercial mixture of 1-naphthaleneacetamide and 1-naphthaleneacetic acid (Amcotone) was applied to tomato (Lycopersicon esculentum Mill.) and peppe r (Capsicum annuum L.) at various timings from early bloom through early fr uit development to evaluate effects on fruit size and both early and total marketable yield. Amcotone was applied at rates from 10 to 40 mg.L-1, at th ree sites for each of the species studied. Measured yield response variable s in tomato did not differ between the control and Amcotone treatments, reg ardless of location. Amcotone treatments did not affect yields or fruit siz e for pepper at the New Jersey or Texas sites. However, at Ft. Pierce, Pla. , early marketable yield of pepper was increased in plots receiving three A mcotone applications at 10 mg.L-1, but total marketable yield was significa ntly reduced in all plots receiving more than two Amcotone sprays, and mean fruit weight was reduced by all Amcotone treatments. Early and total marke table yield of pepper at Pt. Pierce were markedly reduced in plots receivin g four applications of 40 mg.L-1, which was a high rate used to assess pote ntial phytotoxicity. While minimal benefit from auxin application was obser ved in this study, earlier studies suggest that these results may have been influenced by favorable environmental conditions for fruit development or negative effects on unopened flowers during all Amcotone spray applications .