ABSTRACT Survey data on expected and actual prices received by individual vegetable growers in Florida, Michigan, and Texas in 1990 are used to test the rational expectations hypothesis. The use of individual grower data overcomes many of the aggregation, risk premia and model specification issues that have limited previous tests of this hypothesis in agriculture. Overall, price expectations of vegetable growers are found to be inconsistent with the rational expectations hypothesis for the majority of vegetable/state combinations studied.
ABSTRACT Horseradish has been reported to be frequently sterile and therefore difficult to improve by traditional sexual crosses. In this paper we report a simple method to perform embryo rescues on Murashige and Skoog medium without growth regulators. We then demonstrate the usefulness of the method by making crosses and self-pollinated seeds of several horseradish lines, rescuing the embryos in vitro, and growing the seedlings in soil in a greenhouse. Seedlings obtained in these experiments are being prepared for field plantings. We hope that this simple procedure will speed worldwide efforts to improve horseradish germplasm.
The Precision Cultural System (PCS) developed by the Louisiana Agricultural Experiment Station allows simple and precise cultivation of vegetable crops; however, speed of the cultivators in small vegetable crops has been limited. The standard PCS sweep cultivator was limited to about 1.6–2.4 km·h –1 in small crops because it would throw soil over the crop plants at higher speed. The standard PCS rotary tiller cultivator could operate at 3.2–4.8 km·h –1 in small crops but could not be operated faster in larger crops, due to its tendency to “walk” out of the soil at higher speeds. The standard PCS sweep cultivator was modified by replacing the sweeps between the twin drills with two pairs of straight finger-wheel (“rolling cultivator”) spiders non-angled and in tandem. The finger-wheel gangs on the bed sides were also inactivated by raising them above the soil. The resulting PCS cultivator was successfully operated in very small crop plants (≤25 mm high) at speeds of 8–10 km·h –1 with no crop damage. The cultivator could then be easily refitted for standard sweep cultivation on subsequent passes. No reductions in weed control or yield of mustard, kale, turnip, or spinach were noted when using the high-speed system.
ABSTRACT Commercial lettuce fields in Alaska were surveyed for aphid infestations and species composition. Sixteen species were collected in green tile trap pans. The majority were Lipaphis erysimi (Kaltenbach), Macrosiphum euphorbiae (Thomas), and Pemphigus spp. Pemphigus populitransversus Riley, Subacyrthosiphon, and Cryptobium Hille Ris Lambers were added to Alaska collection records. Macrosiphum euphorbiae complex were the only aphids to colonize lettuce during the 1994 season. Seedlings were infested with aphids within four days of transplanting and more alates landed on 1–3 week old seedlings than on older plants. During the 1–3 week seedling period, more alates were recorded on head lettuce than leaf lettuce. Percent infested plants averaged 9.2 and 19.3 for leaf and head lettuce, respectively, during that period. Green tile trap pans were not effective indicators of aphid activity in lettuce fields under these test conditions.
ABSTRACT Optimum age of onion (Allium cepa L.) transplants for use in current and expanding onion-growing areas in Ghana is not well understood. Field studies were conducted at two locations in Ghana during the 1996–97 and 1997–1998 onion growing seasons. Transplants that were 20, 30, 40, 50, 60 or 70 days old, and of uniform size at each age, were used. The effect of transplant age on bulb yield components of onion was determined. The tallest plants were developed from 40-day-old transplants and the shortest were developed from 70-day-old transplants. Harvest index (bulb weight/total biomass weight) of onion decreased significantly as transplant age increased. The heaviest onion bulbs, 57.2 g, were from plants derived from 40-day-old transplants, and the lightest, 26.1 g, were from plants developed from 70-day-old transplants. Plants developed from 20- to 40-day-old transplants produced the highest yields. The results indicate that using 20- to 40-day-old transplants will give optimal bulb yields.
