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Open access

F. W. Southwick, W. J. Lord, D. W. Greene, and L. G. Cromack

Abstract

Residual effects of single applications of 1000 and 2000 ppm succinic acid 2,2-dimethylhydrazide (SADH) in mid-July or mid-August, 1969, were determined. Mid-August treatment of 2000 ppm SADH inhibited June drop, depressed fruit size and increased fruit set; but it did not affect flowering, seed content and viability during June drop, preharvest drop, flesh firmness, or yield in 1970. Flowering and yield were often reduced in 1971 where SADH was applied in 1969. The results suggest that under some circumstances the residual effects of SADH may tend to induce biennial bearing of ‘McIntosh’ apple trees.

Open access

George C. Martin and William H. Griggs

Abstract

‘Bartlett’ pear trees were sprayed 2 weeks after full bloom or 4 weeks before harvest with a single application of succinic acid 2,2-dimethylhydrazide (Alar) at 1,000 or 2,000 ppm. Some trees that received 1,000 ppm were given a second application of Alar at 1,000 ppm 3 weeks after full bloom or 3 weeks before harvest. Alar was as effective as NAA at 10 ppm in preventing preharvest drop of fruits. Alar applied as a double spray early in the season or as a single or double spray late in the season was equally effective. Use of Alar as a preharvest drop spray provides great flexibility as it can be applied over a wide range of time. No undesirable side effects were noted from the use of Alar.

Open access

N. E. Looney, K. Williams, and G. A. Wardle

Abstract

The level of succinic acid-2,2-dimethylhydrazide (SADH) in ‘Spartan’ apples treated according to commercial practice with Alar-854 was higher in fruits treated in July or August than in fruits sprayed in late May, when measured at harvest and after storage. SADH was very persistent in apples stored at 0°C. Fruit from trees treated at comparable times in 2 seasons did not have higher SADH residues than those treated only in the second season, but fruit size reduction was more severe following some treatments applied in both years. Adding the wetting agent Tween 20 to the spray solutions increased uptake of SADH in most experiments as evidenced by increased fruit residue levels.

Open access

Jörg Schönherr and Martin J. Bukovac

Abstract

The effects of surfactants on spray retention and penetration of succinic acid-2,2-dimethylhydrazide (SADH) were determined by following growth inhibition of the first and second internode following SADH treatment of the primary leaves of an indeterminant bean (Phaseolus vulgaris L. cv. Blue Lake) plant. Surfactants (0.1%) decreased the retention of the SADH treating solution by the primary leaves thus reducing the potential dose delivered. The initial rate of SADH penetration was increased with surfactants, but the total amount penetrating was not significantly altered. Internode elongation of the ‘Blue Lake’ bean was enhanced by surfactants per se. Surfactant enhanced penetration of SADH resulted in increased inhibition of internode extension only when the absorption period was limited to 4 hr or less.

Open access

J. Thomas Raese

Abstract

Naphthenic oil with and without succinic acid-2,2-dimethylhydrazide (SADH) was applied to dormant tung trees in February or early March to delay bloom in the spring. A late frost occurred in March 1968; the only branches of the trees to flower and set fruit were those that were treated with napthenic oil and oil with SADH. By contrast, branches treated with aqueous SADH were not saved. In 1969, branch sprays of 10% oil with 1% SADH resulted in delaying bloom up to 5 days and in setting more fruit than the control. In 1970, sprays of 50% oil with 2% SADH delayed bloom on 5-year-old tung trees by approx 2 weeks.

Open access

Dennis P. Murr and Leonard L. Morris

Abstract

Postharvest discoloration of cultivated mushrooms (Agaricus.bisporus [Lange] Sing., ‘tan strain’) was significantly retarded by treatment with succinic acid-2,2-dimethylhydrazide (SADH). The optimum SADH concn was 100 ppm. The effect, however, lasted no longer than 3 days after which time all SADH treatments discolored at rates equal to or greater than controls. The decrease in discoloration was correlated with a decrease in o-diphenol oxidase (o-DPO) activity. Protease activity was higher in SADH treated mushrooms suggesting that reduction in browning was due to degradation of o-DPO rather than direct inhibition of o-DPO by SADH. In vitro SADH competes with proline for quinones produced by enzymatic or non-enzymatic oxidation of diphenols. It is proposed that in vivo SADH exerts a dual effect in reducing mushroom discoloration: first SADH induces degradation of o-DPO through an increase in proteolytic activity, and second it binds to quinones thereby removing intermediates which lead to pigment formation.

Open access

D. R. Tompkins, R. A. Norton, and C. G. Woodbridge

Abstract

‘Jade Cross’ Brussels sprouts plants treated once with a foliar spray of 3000-4500 ppm succinic acid-2,2-dimethylhydrazide (SADH) when the first 5-6 sprouts were 1.9 cm in diam were shorter, more uniform, and had yields equal to untreated plants. Treated plants, were about the same ht and yielded as well as plants where the terminal bud was removed (topped) by hand. Earlier maturity was obtained by treating plants with SADH at an earlier stage, but yields per plant were reduced. These sprouts, however, had higher levels of Ca and, generally, higher levels of Mn. Plants treated with 4500 ppm SADH, early or late, had medium size sprouts that were firmer than sprouts of the same size from untreated or topped plants.

Open access

Norman E. Looney

Abstract

Ethylene-induced endogenous ethylene production was substantial in immature pear fruits, attaining a max rate in samples harvested 60 days after full bloom and declining thereafter. Ethylene production was not dependent on the occurrence of a respiratory climacteric nor related to the rate of respiration. Field applications of succinic acid-2,2-dimethylhydrazide (SADH) suppressed both ethylene production and fruit growth.

Open access

R. D. Bartram, K. L. Olsen, and M. W. Williams

Abstract

‘Delicious’ apples treated with a 1,000 ppm spray of succinic acid-2,2-dimethylhydrazide (SADH) at 70 to 80 days after full bloom were firmer than control fruit at harvest and remained firmer throughout the 9-month storage period.

Open access

Loren D. Tukey

Abstract

The no. of berries on primary and secondary clusters of ‘Concord’ grape vines was significantly increased by succinic acid 2,2-dimethylhydrazide (SADH) at each temperature exposure in field growth chambers: natural (average day 71° F, night 53°) 51%; warm (day 80°, night 55°-60°) 61%; and hot (day 90°, night 65°-70°) 29%. The SADH treatment also caused a significant reduction in cluster length when compared to the non-treated vine-half at each temperature exposure. The smallest berries were found on the SADH treated half of each vine, and the shortest length of clusters on the vine in the hot condition.