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In Wisconsin, the cranberry plant (Vaccinium macrocarpon Ait.) is protected from freezing temperatures by flooding and sprinkle irrigation. Due to the high value of the crop, growers typically overprotect by taking action at relatively warm temperatures. Our goal is to provide recommendations for improved frost protection strategies by studying seasonal hardiness changes in different parts of the cranberry plant (leaves, stems, buds, flowers, fruit). Stages of bud growth were defined and utilized in the hardiness determinations. Samples were collected from mid-April to mid-Oct. 1996 and cuttings were subjected to a series of freezing temperatures in a circulating glycol bath. Damage to plant parts was assessed by visual scoring and observation, ion leakage, and evaluation of the capability to regrow. The following results were obtained: 1) Overwintering structures, such as leaves, stems, and buds, can survive temperatures <–18°C in early spring, and then deacclimate to hardinesses between 0 and –2°C by late spring. 2) In the terminal bud floral meristems are much more sensitive to freeze–thaw stress than are the vegetative meristems. 3) Deacclimation of various plant parts occurred within 1 week, when minimum canopy temperatures were above 0°C, and when the most numerous bud stage collected stayed the same (bud swell). 4) Fruits >75% blush can survive temperatures of –5°C for short durations. By collecting environmental data from the same location we are attempting to relate plant development, frost hardiness, and canopy temperatures (heat units).
Watermelon growers are advised to grow melons in a given field no more than 1 year out of 4. Bermudagrass pastures are abundant in the southern U.S., but ranchers are reluctant to destroy a pasture for 1 year and plant it with melons if they must then re-establish a sod. A project was designed to develop a system for growing watermelon in a permanent pasture with only a minimal amount of tillage, and without destroying the established forages in the pasture. The approach is to compare and evaluate several techniques for growing watermelons in strip-tilled areas within a permanent pasture. These techniques include cultivation, plastic mulches, and herbicides applied to 2-m strips separated by untilled bermudagrass. Research was done in 1996 at two university research centers in Oklahoma and Texas. The treatments with greatest watermelon yields, in decreasing order, were black polyethylene mulch, hand-weeded control, photodegradable mulch, biodegradable mulch, cultivation plus sethoxydim, sethoxydim alone, cultivation alone, and the weedy check. At harvest, 63% of the area in the cultivation alone treatment, 40% of the area in the plastic mulch treatment, and 1% of the area in the sethoxydim treatment were covered with a regrowth of bermudagrass. Forage was also collected from row areas of plots. Forage amounts, in decreasing order, were from cultivation alone, weedy check, sethoxydim alone, photodegradable mulch, polyethylene mulch, biodegradable mulch, cultivation plus sethoxydim, and the clean control.
Two distinct syndromes have emerged in some production areas that have caused losses of sweetpotato (Ipomoea batatas) storage roots during postharvest storage: a complex of fungal rots (end rots) progressing from either end of storage roots and a necrotic reaction (internal necrosis) progressing internally from the proximal end of storage roots. This study was conducted in multiple environments to evaluate whether the use of preharvest ethephon application and storage with or without curing after harvest could be used to screen sweetpotato breeding lines for susceptibility/resistance to these two disorders. Treating vines with ethephon 2 weeks before harvest and placing harvested roots directly into storage at 60 °F without curing resulted in the greatest incidence of end rots in each state and there were significant differences in incidence among the sweetpotato genotypes evaluated. However, when ethephon was not used and roots were cured immediately after harvest, the incidence of end rots was low in all the genotypes evaluated except for one breeding line. Incidence and severity of internal necrosis were greatest when ethephon was applied preharvest and roots were cured immediately after harvest, but two cultivars, Hatteras and Covington, had significantly more internal necrosis than all others.