Seed production systems for daikon or Chinese winter radish (Raphanus sativus L., Longipinnatus Group) were investigated in the Winter Garden of southwest Texas in 1992 and 1993. Planting dates ranged from October through March. Bed configurations (number of rows × bed spacings) were 2 × 0.96 m, 2 × 1.93 m, 3 × 1.93 m, and 4 × 1.93 m. Within-row spacings were 5, 10, and 15 cm. Crops were grown using minimum fungicide and insecticide amounts, while no attempt was made to control weeds chemically. Seed was harvested between May and June. Seed yields (kg·ha–1) increased for planting dates of October to November. Lower seed yields from the January or later plantings appear to be related to increased disease and insect pressures. Total and medium class size (≥3 and ≤4 mm in diameter) seed yields were highest at 40 rows × 1.93 m bed spacings and 10 cm within-row plant spacings. Germination and percent coatless seeds were unaffected by bed configuration and within-row plant spacings. The closest within-row spacings (5 cm) increased the risk of plant lodging and delayed plant maturity.
Azadirachtin (ATI), an insect growth regulator derived from extracts of neem (Azadirachta indica A. Juss) seed, was evaluated for the control of cabbage looper (Trichoplusia ni Hübner), diamondback moth (Plutella xylostella L.), and silverleaf whitefly (Bemisia argentifolii Bellows and Perring) in cabbage (Brassica oleracea L. Capitata Group) grown in southwestern Texas. In Fall 1992, ATI was tested with the a.i. at 0, 22, 33 and 44 g·ha–1. In 1993, ATI was evaluated at 33 g·ha–1 and in combination with M-Pede (1%, v/v), an organic insecticide based on potassium salts of fatty acids at 49%. Two commercial (Align and Neemix) and one experimental hydrogenated (LDF) ATI formulations were evaluated at 11 g·ha–1 in 1994. Insect populations were monitored weekly before and after treatment application. Plant damage was evaluated immediately before harvest, and marketable yields were determined. In 1992, large (>6 mm long) and total cabbage looper counts were reduced by ATI compared with the nontreated control. Insect mortality was similar for all ATI rates tested in 1992. In 1993, ATI at 33 g·ha–1 + M-Pede reduced the number of cabbage looper and diamondback moth larvae. ATI efficacy against cabbage looper and diamondback moth was enhanced when crop oil (polyol fatty acid esters with polyethoxylated derivatives) was tank-mixed with Align or LDF formulations in 1994. ATI did not reduce the number of silverleaf whitefly nymphs compared to the control. In all seasons, ATI-treated plants had lower insect-induced plant damage and higher marketable head weights than the nontreated control. Using ATI on lepidopterous pests appears to be beneficial for integrated pest management strategies.