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Purple nutsedge is a difficult weed to eradicate due to extensive underground growth. One eradication strategy is to inhibit tuber formation for preventing reproduction, In developing this strategy, soil applications of paclobutrazol (PA) were conducted to suppress rhizome and tuber development in Hawaii. Factors examined were 4 PA levels at 0, 0.5, 2 and 8 mg ai·liter-1 (medium) and 4 application types: a) soil drench, fresh tuber, b) soil incorporation, fresh tuber, c) soil drench, stored tuber for 1 month at 4C, and d) drench to a synthetic medium (vermiculite: perlite = 2: 1 by volume), fresh tuber. Treatment design was 4×4 factorial with 5 replications, and experimental unit was a tuber planted 2 cm deep in a 1-liter plastic container. Two months after planting tuber numbers and rhizome lengths were recorded and analyzed for regression and orthogonal comparisons. Control means were 11.1 tubers and 1178 mm total rhizome length. PA reduced both measurements as no tuber was formed at 2 or 8 mg ai·liter-1 and total rhizome lengths were limited to 8 and 3 mm, respectively. PA was less effective in the synthetic medium than in the soil, while application methods and tuber storage did not result in significant differences.
Abstract
Time intervals between leaf emergence, flower stalk emergence, and flower cut were determined for 550 Strelitzia reginae Ait. (Bird of Paradise) flowers during 1977–80 at an elevation of 25 m in Hawaii. The interval between leaf emergence and flower stalk emergence averaged 186 days with a range of 173 to 204. The interval between flower stalk emergence and flower cut averaged 64 days with a range of 54 to 74. Seasonal differences in the duration of development did not account for the seasonal differences in yield. Dissection of flowering fans revealed sequences of flower bud abortion which occurred during June to October, and accounted for low flower production during winter and early spring months in Hawaii.
Abstract
A harmonic model, consisting of growth and seasonal components, accounted for 80% of the variation in flower production of Strelitzia reginae Ait. (bird of paradise). Time series analyses showed low temperatures to be most closely associated with flower production. A model of flower stalk development indicated the mechanism of seasonal flower production in the increasing phase of the model, low temperature (14° to 16°C) retarded floral differentiation and subsequent elongation prior to flower emergence. A temperature threshold of 27° was the source of seasonal flower production in the decreasing phase of the model by causing flower bud abortion.