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  • Author or Editor: L.G. Wilson x
  • Journal of the American Society for Horticultural Science x
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Temperatures recorded by weather stations and within the canopy of tomato (Lycopersicon esculentum Mill.) crops were compared in fields near Davis, Calif., during Summer 1983 (60 days) and 1987 (50 days). For both years, the average maximum and minimum temperatures, daily temperature ranges, degree days per day, and total accumulated degree days were compared. In 1983, the mean maximum temperature at the weather station did not differ significantly from that in the canopy, but the mean minimum temperature at the weather station was significantly lower than that in the canopy. In 1987, the mean maximum temperature at the weather station was significantly higher than that in the canopy, but mean minimum temperatures did not differ significantly. Temperature ranges were significantly narrower for the weather station toward the end of the 1983 season, and significantly wider for the weather station at midseason 1987. Comparisons of degree days per day showed significant differences between means at the weather station and in the canopy in 1983, and among those at the weather station and the two degree day calculation methods used for temperatures recorded in the canopy. Total accumulated degree days based on temperature records at the weather station were lower than those in the canopy in 1983 but higher in 1987. In 1987, the single sine degree day calculation method overestimated degree days compared to the 2-hr triangulation method. The phenology of the tomato crop as predicted by weather station temperatures indicated that tomato maturation was underestimated in 1983 and overestimated in 1987. The rate of development for hypothetical populations of Heliothis zea (Boddie) and Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) within the tomato crop was again underestimated in 1983 and overestimated in 1987, as based on temperature data of the weather station.

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Water solutions of commercial formulations of growth regulators were pressure-injected into the trunks of topped American elm (Ulmus americana L.) trees in June to evaluate their ability to reduce sprout regrowth. Regrowth was significantly reduced by methyl 2-chloro-9-hydroxyfluorene-9-carboxylate (chlorflurenol), N-[4-methyl-3-[[(trifluoromethyl)sulfonyl]amino] = phenyl]acetamide (fluoridamid), l,2-dihydro-3,6-pyridazine-dione (maleic hydrazide), succinic acid,2,2-dimethylhydrazide (daminozide) and 2,3,5-triiodobenzoic acid (TIBA); α-cyclopropyl-α-(4-methoxypenyl)-5-pyrimidine = methanol (ancymidol) and (2-chloroethyl)trimethyl-ammonium chloride (chlormequat) were ineffective. Some undesirable effects on the tree and foliage were observed. Maleic hydrazide (MH) and daminozide (SADH) were selected for additional field tests at 3 concentration levels on topped American elm and American sycamore (Platanus occidentalis L.). Regrowth was significantly reduced and foliage condition was acceptable for the high concentration of SADH and the low concentration of MH. Successive measurements in both experiments showed that sprout regrowth was reduced by an amount equivalent to at least 1 year of growth during the first 2 seasons following treatment.

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