Response of tomatoes, Lycopersicon esculentum Mill., cv. Flora-Dade, to insecticides applied weekly or on demand and to 3 fertilizer levels, low (1 ×), medium (2 ×), and high (3 ×), was investigated in fall 1979 and spring 1980. Insecticide spray schedules had no effect on fruit size, marketable yield, and number of fruit per ha. The application of fertilizers above the 1 × level (148 kg/ha N, 30 P, 171 K, and 10 Mg) did not improve fruit size or increase tomato yields, but increased residual salt content of soil.
Cabbage (Brassica oleracea L. Capitata Group ‘Market Prize’) was grown in the spring (February to April) 1981 and fall-winter (October to January) 1981–82 with 2 insecticidal spray schedules conducted weekly and on demand; 2 in-row spacings, 23 and 38 cm; and 2 fertilizer rates, low (152N–53P–139K and 8 Mg kg/ha), and high (257N–99P–261K and 15 Mg kg/ha). Fenvalerate [Cyano (3-phenoxyphenyl) methyl-4-chloro-alpha-(1-methylethyl) benzeneacetate] at 0.112 kg a.i./ha was applied either weekly or when a threshold of 0.5 lepidopterous larval feeding injuries/plant was equalled or exceeded. With the weekly insecticide treatment, 12 and 10 sprays were applied, respectively, in the spring and fall, vs. 1 and 2 applications, respectively, for the 2 seasons in the demand plots. Insect damage ratings were lower in the weekly sprayed than in the demand plots; however, marketable yields (kg/ha) and average head size were not affected by spray schedules. In both seasons, marketable yields were greater at the 28 cm spacing than at 38 cm, whereas average head sizes were greater at 38 cm than at 23 cm. The high fertilizer rate increased head size in both seasons, but increased marketable yields only in the spring.
Field studies were conducted for three seasons, Fall 1988 and Spring and Fall 1989, on the effect of six mulch colors: blue, orange, red, aluminum, yellow, and white (fall) or black (spring), on fruit yields and on insect vectors of Sunny' tomato (Lycopersicon esculentum Mill.). Plant growth and yields were inconsistent with mulch colors during the three seasons. In Fall 1988, in a once-over harvest, extra-large (≥ 70 mm diameter) and marketable fruit yields were higher (P ≤ 0.05) on blue than on the conventional white mulch. In Spring 1989, early marketable yields on red mulch were higher than on black mulch, and in Fall 1989, under high stress from tomato mottle virus (TMoV) transmitted by silverleaf whitefly [Bemisia argentifolii (Bellows and Perring)], seasonal yield of extra-large fruit was better on orange than white mulch. In Fall 1988 and 1989, fruit size and marketable yields were reduced on yellow mulch. Aphids (Aphididae), thrips (Thripidae), and whiteflies were counted monthly in traps placed on the mulched beds. Aphids were least numerous on the aluminum and yellow and most numerous on the blue mulch. Where differences occurred, the fewest thrips were captured on aluminum and the fewest whiteflies were captured on the yellow, aluminum and orange mulches. Although differences were not always significant, the fewest adult whiteflies also were observed on foliage of tomato plants grown on these latter three mulches. Later in the seasons, as plant foliage covered the mulch, differences in the number of insects captured were similar for all mulch colors. Low numbers of whiteflies on the orange and aluminum mulches early in Fall 1989 delayed virus symptom development and increased yields. Virus symptom development was not delayed and yields were low on the yellow mulch, in spite of the low number of whiteflies. When averaged over all mulch colors, extra-large and marketable fruit yields increased linearly with delayed symptom development. It is proposed that, under high insect stress, mulches should be selected for their effects on insects in addition to their effects on soil temperature and plant morphology.