Browsing Cotton Report 2005 by Title
Now showing items 15-18 of 18
Transitioning Lygus Chemical Controls to More Selective Options for Arizona CottonLygus hesperus (Knight) has been the number one pest of Arizona cotton since 1998. With advances in the selective management of Arizona cotton’s other two key pests (i.e., Bemisia tabaci and Pectinophora gossypiella), there has been less opportunity for collateral control of this yield-limiting pest. There has also been a new premium placed on locating less disruptive, even selective, control methods that are compatible with existing selective technologies. Our laboratory routinely screens candidate compounds for efficacy against Lygus hesperus under desert conditions. Promising leads are further developed and evaluated in the field for efficacy, spectrum of activity and safety for beneficial arthropods. Our recent findings have identified three compounds with potential for delivering economic control of Lygus hesperus with greater safety for beneficial arthropods than current standards of control. At the same time, our work has importantly identified many compounds that are ineffective against our Lygus, despite reported success against a related species, the tarnished plant bug, Lygus lineolaris (e.g., acetamiprid, imidacloprid, indoxacarb, pyrethroids, thiamethoxam). Flonicamid, a pyridine carboxamide, is under development by FMC in the U.S. This aphicide has shown excellent results in controlling our Lygus in cotton. Novaluron, a chitin inhibitor under development by Uniroyal (as Diamond®) in the U.S., has rate sensitive activity against Lygus in cotton. Metaflumizone (BAS320I), under development by BASF in the U.S., is a semi-carbazone chemistry with significant efficacy against Lygus hesperus. These three or potentially other new leads in insecticide discovery may play an important role in transitioning Arizona cotton growers away from neuro-toxic, broad-spectrum, and disruptive organophosphates and carbamates currently used to control Lygus in cotton. The potential benefits to natural enemy conservation should help stabilize insect pest management in Arizona cotton, thus minimizing the chances of secondary pest outbreaks and costly pest resurgences. Until selective alternatives are found and registered, acephate (e.g., Orthene 97 by Valent USA) and oxamyl (Vydate C-LV by DuPont) remain our standard recommendations for Lygus control in Arizona cotton.
Twin Line Cotton Production in a Conservation Tillage SystemTwo experiments were conducted in 2004 evaluating twin line cotton production using a conservation tillage system approach. DPL 451 BR Upland cotton was planted into oat hay stubble on April 30 and May 5, 2004 at commercial cooperator sites at Tonopah and Tolleson AZ, respectively. The two primary experimental objectives were to determine whether cotton planted into previous crop residue initiated fruiting on the mainstem once the cotton seedling grew above the crop stubble and whether there were differences in lint yield between the single and twin line system. Previous twin line cotton production research had been conducted by authors at 30 locations from 2001-2003. In almost all cases, the harvest of low set bolls presented problems with the twin line system. In 2004, the initiation of the first fruiting branch was independent of the stubble height at both locations. In addition, there were no differences in lint yield in either a single or twin line cotton production system when planting into previous crop residue using conservation tillage.
Upland Variety Testing Evaluation in Southeastern ArizonaTwo separate variety evaluations were conducted in southeastern Arizona during the 2004 cotton growing season. The two locations were on grower-cooperator fields in the Upper Gila River Valley located in Thatcher, AZ (Graham County) and in the Sulfur Springs Valley in Kansas Settlement, AZ (Cochise County). Twelve varieties were selected for the Graham County evaluation and fifteen in the Cochise County evaluation. These varieties included several transgenic varieties and ranged in maturity from early to full-season varieties. Several Acala varieties were also evaluated in both the Graham and Cochise County tests. Both evaluations were conducted using a randomized complete block design with each variety replicated four times. Plant measurements were collected in season on several dates from the Graham County evaluation. End of season plant measurements were collected from the Cochise County evaluation. Lint yield was estimated at each location by harvesting the entire plot and weighing the harvested seed cotton with a weigh wagon equipped with load cells. Sub samples were collected from each plot for fiber quality and percent lint determinations. Total crop value for each variety was calculated by using the fiber quality premium/discount and using a $0.52 per pound price. The total price is then multiplied by total lint yield to obtain the total value for that particular variety. Results observed in the Graham County evaluation were similar to those in 2003. Lint yield ranged from 1200 to over 1600 lbs. lint/acre. The FiberMax variety FM991BR produced the highest lint yield and also the highest total crop value at over $950/acre. Results from the Cochise County evaluation demonstrated the potential that high fiber quality can have on total crop value. Lint yields ranged from 600 to over 1200 lbs. lint/acre. The highest yielding variety (ST5242BR) did not produce the highest crop value. Because of the higher fiber quality of the Acala varieties, they produced the highest value at approximately $630/acre.
Weed Management and Agronomic Performance of a Cotton-Barely Double Crop RotationThe tillage operations required to grow an annual barley and cotton crop rotation were reduced by eliminating tillage prior to planting cotton, eliminating cultivations for weed control in cotton, and especially by eliminating tillage following cotton. A light activated, weed sensing automatic spot-spray system reduced the amount of spray volume and herbicide used by 40% to 60% at Marana and 36% to 56% at Maricopa in 2004. At Maricopa, a large number of volunteer cotton plants in the furrows of early planted no-till cotton reduced the spray volume savings from using the weed sensing automatic spot-spray system. Weed control was similar with the weed sensing, automatic spot-spray system compared to the conventional continuous spray system for most weed species but weeds with narrow leaf, upright leaf canopies such as sprangletop, barley and skeleton weed were more difficult to detect and control. In both Marana and Maricopa, there were yield differences between treatments related to planting date, with late-planted cotton yielding less than early-planted cotton. At Marana, the early-planted conventional tillage cotton out-yielded the barley cover crop, early-planted no-till cotton treatment. At Maricopa, there were no yield differences between the two early planted cotton treatments; however, the late-planted conventionally tilled cotton yielded 28% more than the late-planted no-till cotton. Although the yield comparisons are not yet definitive, it appears that in some situations no-till cotton may yield less than conventionally tilled cotton. At Maricopa, the height of cereal crop stubble did not affect subsequent cotton establishment, field populations, plant height or lint production (2003 and 2004) and the position or node of the first fruiting branch and the first retained boll were similarly unaffected in 2004.