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  • Author or Editor: L.B.J. Jensen x
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Onion (Allium cepa var. cepa L.) is extensively grown under furrow irrigation in the western United States. Wheel compaction of furrows increases water runoff and erosion, and can lead to poor lateral water movement and reduced yields. We studied the effects of 560 to 800 lb/acre (630 to 900 kg·ha-1) wheat straw mechanically applied to the bottom of irrigation furrows on yield and bulb size of sweet Spanish onions in commercial onion fields in 1988, 1990, and 1991, and at an experiment station in 1991 and 1995. Furrows in commercial fields were either compacted with tractor wheels or not. In the commercial fields, straw application increased onion yield in plots with compacted furrows in 1988 and in all plots (with or without compacted furrows) in 1990. At the experiment station, straw mulch increased onion yield 64% in 1991, and 74% in 1995. Straw application primarily increased yields of jumbo (3 to 4 inches; 76 to 102 mm) and colossal (>4 inches; 10 cm) onions, whereas there was no effect on medium (2.25 to 3 inches; 57 to 76 mm) onions. We attributed yield improvements to decreased water runoff and increased lateral water movement and soil moisture.

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Wooden fruit bins are a source of diapausing codling moth and postharvest pathogenic fungi. The redistribution of codling moths within bins is a problem where codling moth populations are being controlled by areawide codling moth sterile release programs, mating disruption programs, or both. Laboratory and fumigation chamber trials were carried out to determine the impact of relatively low levels of carbon dioxide on late-instar codling moth (Cydia pomonella L.) and two postharvest fruit pathogens, Penicillium expansum Link ex Thom and Botrytis cinerea Pers. ex Fr. Fumigation of diapausing codling moth with 40% CO2 in laboratory trials resulted in over 60% mortality after only 6 days of exposure and mortality increased with time of exposure. Significant mortality (68%) of diapausing codling moth larvae occurred after 14 days of exposure in the laboratory to 13% CO2 and a mean of 88% mortality was recorded after fumigation for 20 days. A significant number of P. expansum (46%) spores failed to germinate after laboratory exposure to 13% CO2 for 12 and 18 days respectively. Close to 100% of the P. expansum spores failed to germinate by day 20. When diapausing codling moth larvae and spores from both plant pathogens were placed in wooden fruit bins and fumigated for 21 days at 13% CO2, 75% of the diapausing codling moths died and 80% of the P. expansum spores failed to germinate. No effect on B. cinerea was observed.

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