UNICONAZOLE CONTROLS GROWTH AND YIELD OF GREENHOUSE TOMATO

Tomato (Lycopersicon esculentum cultivar 'Summer Flavor') seedlings received a single uniconazole soil drench at 0, 12.5, 25, 50, 100, 200 or 400 μg per plant at the five-leaf stage. After 2 weeks of growth, plant height, length and area of the fifth leaf, and plant fresh and dry weights progressively decreased with increasing rates of uniconazole. The rate of leaf production was unaffected at low rates of the retardant. Another group of seedlings received soil drenches at the above rates at the onset of flowering. Uniconazole applied at both stages resulted in short final plant height at all rates. Total fruit yield was reduced by uniconazole at the 12.5 μg per plant rate, with further reduction as rates increased. Yields of large fruits (≥ 110 g) increased at the two lower rates of uniconazole. The incidence of blossom-end rot (BER) was nearly eliminated by this retardant at all rates. Foliar application of uniconazole at the flowering stage with rates of 0, 25, 50, 100, 250, 500, 750 or 1000 μg per plant had less control on plant height compared with their respective rates as a soil drench. Total fruit yield was not affected until the rate exceeded 100 μg per plant. The incidence of BER decreased sharply with increasing rates of uniconazole. The number and weight of fruits ≥ 110 g were doubled at rates between 25 and 250 μg per plant. Plant fresh and dry weights were lower as a result of uniconazole foliar spray. Fruit number was reduced regardless of the rate and stage of uniconazole application. © 1990.