Search Results
Abstract
Increasing herbicide selectivity between weeds and economic crops has facilitated row crop production with a decreasing demand for labor to be used for mechanical weed control. However, selectivity has been identified in several cases (1, 2, 3) to be of an intra-specific nature. Intra-specific selectivity by growth regulating compounds (i.e. herbicides) provides interesting academic concepts for more adequate physiological models (4, 5, 6) than inter-specific comparisons. The increased selectivity does creat problems in the use of herbicides in commercial production practices because several cultivars of a crop are usually available. Robinson (3) has suggested that with close selectivity and the rapid changing of cultivar utilization, inbred lines may be the most appropriate indicator plants to utilize in determining herbicide tolerances.
Abstract
The measurement of carbon dioxide under field conditions is difficult by alkali titration (5) and colorimetric methods (2,4). Static absorption by alkali can be utilized for inplace measurements but is dependent on ambient turbulence. The common colorimetric method (2) is temperature dependent and requires a constant temperature for absorption.
Abstract
Oxyfluorfen exhibited intraspecific selectivity among cabbage (Brassica oleracea L. var capitata) cultivars. The wettable powder (WP) and granular (G) formulations were less toxic to cabbage plants than the emulsifiable concentrate (EC) formulation when applied at 0.56 kg ai/ha. Susceptibility to oxyfluorfen injury decreased with plant age. Plants treated with 0.56 kg ai/ha of the WP formulation at the 2-leaf growth stage showed greater injury than plants treated at the 6–8 leaf stage. Oxyfluorfen injury symptoms from an application of 0.28 kg ai/ha EC formulation were increased when plants were treated previously with 1.12 kg ai/ha EPTC. Selectivity may be provided by cuticular wax on the cabbage leaves which prevents spray retention and penetration. Cultivars with increased cuticular wax showed reduced injury from oxyfluorfen application.
Abstract
Carbon dioxide levels were higher under polyethylene, paper-polyethylene, and paper-aluminum foil mulches than over bare soil. Higher levels of CO2 were found over plant holes in the mulch than over the mulch itself. CO2 levels a short distance from plant holes did not differ significantly from the levels over bare soil. Fresh manure as a potential source of CO2 did not increase ambient CO2 levels and lowered broccoli and cucumber yields. Yields were greater with mulches in broccoli, lettuce, and cucumbers because mulches caused higher soil temperatures. Greater growth and yields of test species were attributed primarily to soil temperature modification by mulches; atmospheric CO2 levels were not a factor.
Abstract
2,4 Dichlorophenyl-p nitrophenyl ether (nitrofen) was more injurious to field transplanted cabbage at the 3 leaf than at the 6 or 9 leaf stages; ‘Hybelle’ was more tolerant than ‘Rio Verde’. 2,4 Dinitro-p-trifluoromethyl phenyl ether (fluorodifen) caused greater injury than nitrofen when applied as a preemergence treatment on direct-seeded cabbage or as a postemergence treatment on transplanted cabbage.
Abstract
Starvation tests demonstrated that the purslane sawfly (Schizocerella pilicornis Holmgren) feeds only on common purslane (Portulaca oleracea L.) and winter purslane (Montia perfoliata (Donn) Howell). Carbaryl, malathion, and Bacillus thuringiensis (insecticides) and DCPA, trifluralin, and nitrofen (herbicides) kill all sawfly larvae when applied directly to them and their food supply at field recommended rates. Chlorothalonil and maneb (fungicides) had little effect. Herbicides applied to soil with pupating sawflies had no effect on the pupae.
Abstract
Rest period reduction in non-stored onion (Allium cepa L.) sets is favored by post-harvest temperatures of 5° and 25°C for periods of 1 to 10 days. A short-term post-harvest temperature of 45°C favored rest period reduction, but periods over 24 hr at 45° did not reduce the rest period. Reduction of sprouting attributable to the 45° storage was more pronounced with the White Portugal cultivar than with Yellow Ebenezer. Zero to 800 rad gamma irradiation (of freshly harvested sets) did not influence time of sprouting but doses from 1,600 to 12,800 rad decreased sprouting. Potassium gibberellate (A3)(applied as a dip treatment on sets) increased weights of plants grown from sets stored at 5°C for 72 hr before planting. High post-harvest storage temperatures (45°) negated the subsequent growth promoting effects of GA. Application of these findings has resulted in commercial shipments of freshly harvested onion sets under refrigeration.