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A. A. Csizinszky, D. J. Schuster and J. B. Kring

Field studies were conducted for three seasons, Fall 1988, and Spring and Fall of 1989 on the effect of six mulch colors: blue, orange, red, aluminum, white or black (fall or spring), and yellow on fruit yields and on insect vectors of `Sunny' tomato, In Fall 1988, in a single harvest, fruit size was greater and total marketable yields were higher with blue than with aluminum and yellow mulches. In Spring 1989 early yields of large (> 70 mm) and marketable fruit were higher with aluminum and red than with yellow and blue mulches. In Fall 1989 early yield of large fruit was higher with white than with yellow mulch. Early marketable yields were highest with white and aluminum mulches. Total yields of large fruits were highest with orange and blue mulches but marketable yields were similar with all six mulch colors. The fewest number of aphids, thrips and whiteflies were trapped on aluminum mulch. Blue mulch attracted the largest number of aphids and thrips. Red mulch attracted whiteflies. The three insects are important vectors of several virus diseases.

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A.A. Csizinszky, D.J. Schuster and J.B. Kring

In Fall 1990 and Spring 1991, the effects of four mulch colors, orange, yellow, aluminum, and white or black (fall or spring) were evaluated in the field on yields of `Sunny' tomato and numbers of insect vectors. In additional treatments, plants on the orange mulch were sprayed weekly with 2% mineral oil, and the yellow mulch was sprayed with soybean oil as needed during the season. In fall, plants were tallest (P ≤ 0.05) on the aluminum and yellow + oil treatments. The largest number of whiteflys (Bemisia argentifolii, Bellows and Perring) and the largest proportion of plants with virus symptoms were found on the white and yellow mulches. Fruit size and marketable yields were best with the yellow + oil treatment. In the spring, insect populations were low and only a few plants had virus symptoms. Plant heights, fruit size, and marketable yields were similar with all treatments.

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A.A. Csizinszky, D.J. Schuster and J.B. Kring

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.

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David J. Schuster, James B. Kring and James F. Price

The sweetpotato whitefly, Bemisia tabaci (Gennadius), was associated with symptoms of a silverleaf disorder of acorn squash (Cucurbita pepo L. cvs. Table King Bush and Table Ace) in cage studies in the greenhouse. Symptoms appeared on uninfested leaves that developed after plants were infested with the whitefly. When the infested lower leaves were removed and the young leaves protected from infestation with insecticides, new growth was asymptomatic or nearly so and symptomatic leaves remained symptomatic. Symptom expression was related more to nymphal density than to adult density since the relationship between log nymph density and symptoms was linear when adult densities were equal.

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D.J. Schuster, T.F. Mueller, J.B. Kring and J.F. Price

A new disorder of fruit has been observed on tomato (Lycopersicon esculentum Mill.) in Florida. The disorder, termed irregular ripening, was associated with field populations of the sweetpotato whitefly, Bemisia tabaci (Gennadius) and is characterized by incomplete ripening of longitudinal sections of fruit. An increase in internal white tissue also was associated with whitefly populations. In field cage studies, fruit on tomato plants not infested with the sweetpotato whitefly exhibited slight or no irregular ripening, whereas fruit from infested plants did. Fruit from plants on which a whitefly infestation had been controlled before the appearance of external symptoms exhibited reduced symptoms compared to fruit from plants on which an infestation was uncontrolled.