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Butternut squash (Cucurbita moschata) plants are susceptible to defoliation and plant population (stand) reduction by insect, disease, temperature extremes, water, hail, or other mechanical damage. The timing of such losses may have variable effects on final fruit quality and yield. The objectives of these studies were 1) to determine the influence of the degree and timing of defoliation and stand reduction on the marketable yield of winter squash; 2) to determine yield compensation after stand reduction and defoliation; and 3) to explore effects of defoliation on fruit total carotenoid content. Experiments were conducted over 2 years in New York and Pennsylvania to explore these objectives. Marketable yields consistently improved with increasing plant population. If population losses occurred while plants were in the rapid vegetative growth phase, the remaining plants responded by increasing fruit number and weight per plant. Plant losses later in the season during fruit enlargement, however, did not elicit the same magnitude of response. Defoliation of 66% leaf area reduced marketable yields, and effects were most severe under high plant populations. Competition among plants restricted compensation. Moderate defoliation (33%) reduced yield in only one of three studies. This level of defoliation also increased the percentage of medium [1.0 to 1.5 kg (2.20 to 3.31 lb)] and large [1.5 to 2.0 kg (4.41 lb)] fruit and decreased the number of jumbo fruit (>2.0 kg). Total carotenoid concentration in mature fruit was unaffected by the defoliation or population treatments. Thus, butternut squash compensated for up to 33% leaf area loss at any time during the season. While the crop could compensate, under some conditions, for up to 50% plant losses, final plant population was more important than the growth stage of damage or defoliation for effects on crop yield.

The systemic nitroguanidine insecticide imidacloprid was investigated in cantaloupes, Cucumis melo L. variety reticulatus, for management of Acalymma vittata (F.) and bacterial wilt caused by Erwinia tracheiphila (E. F. Smith) Holland that is vectored by this beetle. The influence of management strategies using imidacloprid upon plant growth and development, beetle population dynamics, and bacterial wilt disease incidence and severity was evaluated. Application of imidacloprid to seedlings at higher doses caused short-term marginal leaf necrosis, and biomass of seedlings was reduced in an approximately linear pattern with increasing dose on a log scale up to 0.01 g (AI) per plant. Application to seedlings at doses low enough to avoid any phytoxicity resulted in adult A. vittata mortality rates that declined exponentially with time. Exponential decay models of bioassay data suggested ≍11d of 100%adult mortality was achieved with low rates applied to seedlings before transplanting. Applications to seedlings delayed adult immigration, and the combination of seedling application and limited foliar sprays resulted in significant increases in yield. Addition of imidacloprid at low rates to seedlings combined with 2 foliar sprays, or application to seedlings combined with an application through drip irrigation and 2 foliar sprays, was not effective in reducing the proportion of cantaloupe plants that showed bacterial wilt symptoms but did significantly reduce severity of the disease. The results suggest that low rates of imidacloprid applied before or near the time of transplanting, at times combined with few foliar sprays, could dramatically improve crop productivity via influence upon both a herbivore and a plant pathogen vectored by the herbivore.

Exposure to chilling temperatures (0-10°C) increases ethylene synthesis in several species, but it is not clear whether this increase in ethylene synthesis is involved in the development of chilling tolerance. To determine this relationship, chilling tolerance development of the ethylene-insensitive Never-ripe (Nr) tomato (Lycopersicon esculentum Mill. cv. Pearson) mutant was compared to that of a normal isogenic line. Plants were grown for 3 weeks at 25/20°C day/night, and then half the plants of each genotype were chill-hardened at 25/5°C day/night for 10 days, while the other half remained at 25/20°C. All plants were then exposed to a severe chill (5/5°C day/night) for 7 days, and a recovery period (25/20°C day/night) of 4 days. Chill hardening increased ethylene synthesis in both genotypes, but increased the rate of leaf development and dry weight accumulation during the recovery period only for the normal plants. Hardening also caused a greater decrease in lesion development in the normal plants following the severe chill. Therefore, chill hardening was more effective in the ethylene-sensitive normal plants than in the ethylene-insensitive mutants, indicating that a response to ethylene is involved in chilling tolerance development. However, chill hardening was effective for both genotypes in maintaining chlorophyll a fluorescence levels (F v /F m ), suggesting that ethylene does not control all aspects of chilling tolerance. In a separate experiment, application of a 500 ppm ethephon solution to normal 'Pearson' plants led to higher rates of ethylene synthesis and a higher rate of leaf development following a 6 day severe chill (5/5°C day/night). These results further indicate that ethylene is involved in the development of chilling tolerance.

Baby corn, the young flowering ear of any Zea mays genotype, has become a familiar part of the American diet, but production of the crop occurs almost exclusively in Asia. Cultivar, planting date, and seed spacing trials were conducted in 1988 and 1989 to assess yield of baby corn. Cultivars were also evaluated for organoleptic qualities-specifically color, taste and appearance. Cultivar was the single most important factor determining the yield of baby corn in both years. Planting date and plant spacing also sign& cantly affected yield. The cultivars from 1988 that were high in yield and attributes as baby corn were re-evaluated in 1989. No single variety met all the requirements for ideal baby corn, but several cultivars met most of the characteristics. The cultivar best meeting the criteria was 'Robust 41-10', a popcorn type.

As early as 1929, university scientists began the quest to determine the ideal age at which to transplant tomatoes (Lycopersicon esculentum Mill.). Investigations have included seedlings of 2 to 15 weeks of age produced in wood, peat, plastic, or Styrofoam containers. Early researchers often omitted descriptions of soil mixes and nutrient regimes, and used a wide variety of container types. Later investigators were inclined to use commercial soilless mixes, well-defined nutrient regimes, and polystyrene trays. Pioneers of transplant age research tended to use plants of 7 weeks and older, whereas work within the past 30 years has concentrated on younger plants. Many researchers drew conclusions after only 1 year of experimentation, while others found that results varied across years. Prior to the 1980s, virtually all studies were initiated and conducted in areas far from the thriving transplant industry established in the southeastern United States. Southern-grown transplants often were not in cluded for comparison, and few studies were implemented using plants grown under commercial conditions. After more than 60 years of transplant age research, it appears that transplants of 2 to 13 weeks can produce comparable yields, depending on the many factors involved in commercial production.

Flower formation in the Cucurbitaceae family is compromised at high temperatures; both male and female flowers and therefore fruit productivity are greatly reduced as the growing temperatures for these vegetable crops are increased above 26C. This intractable phenomenon has been documented both with outdoor field experiments at various latitudes on the eastern seaboard in the USA and in a laboratory, temperature-regulated setting. We now report that an agricultural product, FP, which has been, and is used globally on many commercial crops to increase flower number and strength during blossom formation and development, overcomes the apparent refractory floral initiation and development at high temperatures. This is a new and unexpected finding. Additionally, in another facet of the experiments reported here, the parthenocarpic fruit development potential of FP was tested by eliminating bee pollination. This aspect of the study was addressed in part because of the recent concerns with bee colony collapse disorder. Flower formation, flower development and fruit yield were increased by FP over the bee-pollinated, untreated controls at high temperatures. FP was developed over a number of years of outdoor field trials as an approach to crop productivity that included hormonal regulation of floral strength and supported by mineral supplements through to the fruit production process.

Optimization of crop production can be accomplished only if successful stand establishment is achieved first, since each plant contributes to the total crop yield. Reduction of plant populations after planting will reduce yield and/or quality, even though plants compensate to some degree for stand losses. Successful stand establishment is achieved if factors that affect establishment are known, evaluated, and modified appropriately at the time of field planting. The factors that affect stand establishment are biotic and/or abiotic. Biotic factors are generally pathogens that attack plants as parasites, while abiotic factors are the environmental and physical conditions to which the plant or seed is exposed at the time of planting. Abiotic factors can be classified under three headings: soil, planting requirements, and environmental stress.