Days Before Harvest Research Articles

Efficacy of Selected Conventional and Experimental Insecticides for Control of European Corn Borer on Snap Beans, 1997

Abstract Trials were arranged in a RCB design with four replications. Each replicate had a plot consisting of four 30-inch-wide, 20-ft-long rows. Twenty-five-foot-wide alleys were established between each of the four replications. Insecticides were applied to the middle two rows of each plot, leaving two untreated rows between each plot. Eight insecticide treatments were compared with two untreated checks after multiple manual infestations of ECB egg masses. The two untreated check plots were averaged for the ANOVA. Treatments were to be applied at 28, 21, 14, and 7 days before harvest (DBH); however, because of slow plant development, applications were made at 33, 27, 20, and 12 DBH, every six to eight days beginning on 31 Jul. All insecticide treatments were applied with a modified John Deere 6000 high-clearance vehicle (HCV) with a rear-mounted boom. Six Conejet (TX VS-6) hollow cone nozzles (three per row) were calibrated to deliver 25.2 gpa at 40 psi and a speed of 2.5 mph, utilizing a compressed air system. Four nozzles (2 per row) were attached to drops and directed toward the under surface of the snap bean canopy, area, a third nozzle (one per row) was mounted directly over the row. In one of the center two rows of the 4-row plot, a seven-foot section of row was marked and manually infested (by pinning) with black-headed stage ECB egg masses on wax paper disc, to the foliage of the snap bean plants. Four eggs masses per foot of row were attached i on the following dates: 25 Jul, 1, 8, 15, and 22 Aug.

Preharvest Watersprout Removal Influences Canopy Light Relations, Fruit Quality, and Flower Bud Formation of `Redskin' Peach Trees

Three separate blocks of mature, nonirrigated trees of `Redskin' peach [Prunus persica (L.) Batsch] on `Lovell' rootstock, all uniformly dormant-pruned to an open center, were summer pruned 43, 31, and 21 days before harvest (DBH) in 1988, 1989, and 1990, respectively, and compared to unpruned controls in respect to light penetration and fruit characteristics. Summer pruning consisted of watersprout removal (WSR), selectively including all shoots more upright than 45° on scaffolds from the crotch to the top of the tree. WSR increased photosynthetic photon flux density (PPFD) in the center of the fruiting zone of the canopy to four times the level measured in unpruned trees, but only to an average of 16% of above-canopy PPFD. The greatest effect of WSR on PPFD occurred in the center of the tree, increasing light levels from <10% full sun before WSR to 90% full sun following WSR. WSR resulted in higher PPFD in the center of the tree for the remainder of the season. Fruit ground color and red pigmentation were not affected by WSR. WSR increased the percentage of fruit that exceeded 62 mm in diameter and decreased the percentage of fruit < 55 mm in diameter in 1988 and 1990. In 2 of the 3 years, WSR increased flower count per cm shoot length in the fruiting zone of the canopy.

Peach Fruit Quality Is Affected by Shade during Final Swell of Fruit Growth

Girdled or nongirdled `Biscoe' peach (Prunus persica [L.] Batsch) secondary scaffold branches were covered with shade fabric to provide a range of photosynthetic photon flux densities (PPFD) from 44 to 20 days before harvest (DBH), from 20 to 0 DBH or 44 to 0 DBH. Fruit quality was affected differently by the various periods of shade during the final swell of fruit development. Shading 40 to 20 DBH did not affect fruit weight or quality, whereas shading 44 to 0 DBH had the greatest effect on fruit weight and quality. Fruit quality was generally similar on branches exposed to 100% and 45% incident PPFD (IPPFD). Fruit on” girdled branches generally responded to shade more than fruit on nongirdled branches. Fruit weight was positively related to percent IPPFD for girdfed but not nongirdled branches shaded 20 to 0 DBH and 44 to DBH. On nongirdled branches, fruit exposed to 45% IPPFD for 44 to 0 DBH had 14% less red color and 21% lower soluble solids content (SSC) than nonshaded fruit. Harvest was delayed >10 days and preharvest fruit drop was increased by shading to <23% IPPFD. Shading branches for 20 to 0 or 44 to 0 DBH altered the relationship between flesh firmness and ground color: Firmness declined as ground color changed from green to yellow for fruit shaded 44 to 20 DBH, but firmness declined with little change in ground color for fruit shaded 20 to 0 or 44 to 0 DBH. Girdling results indicated that fruit weight and SSC partially depended on photosynthate from nonshaded portions of the canopy, whereas fruit redness, days from bloom to harvest, and ground color depended on PPFD in the vicinity of the fruit.

Preharvest Desiccation of Rice With Paraquat1

Studies to determine the suitability of paraquat (1,1′dimethyl‐4,4′‐bipyridinium ion) as a preharvest desiccant were conducted on rice (Oryza sativa L.) cultivars ‘Brazos’ and ‘Labelle’. Under hot, clear weather conditions, paraquat rates of 0.14 kg/ha or above desiccated the leaves within 1 day. Under cool, cloudy conditions 2 to 3 days were required for desiccation. Paraquat applied to rice after the grains were fully developed at rates up to 0.56 kg/ha up to 10 days before harvest (DBH) did not reduce grain yields. Grain moisture, however, was reduced when a minimum of 0.14 kg/ha paraquat was applied at least 4 DBH. Percent whole kernels after milling was not lowered, or lowered only slightly, by application of up to 0.56 kg/ha paraquat up to 10 DBH. These results suggest that paraquat could be a valuable preharvest desiccant for rice if toxic residues are not found in the grain.