Dennis P. Delaney

Glyphosate-Resistant Cotton Response to Glyphosate Applied in Irrigated and Nonirrigated Conditions

Field experiments were conducted in Alabama during 1999 and 2000 to test the hypothesis that any glyphosate-induced yield suppression in glyphosate-resistant cotton would be less with irrigation than without irrigation. Yield compensation was monitored by observing alterations in plant growth and fruiting patterns. Glyphosate treatments included a nontreated control, 1.12 kg ai/ha applied POST at the 4-leaf stage, 1.12 kg/ha applied DIR at the prebloom stage, and 1.12 kg/ha applied POST at 4-leaf and postemergence directed (DIR) at the prebloom cotton stages. The second variable, irrigation treatment, was established by irrigating plots individually with overhead sprinklers or maintaining them under dryland, nonirrigated conditions. Cotton yield and all measured parameters including lint quality were positively affected by irrigation. Irrigation increased yield 52% compared to nonirrigated cotton. Yield and fiber quality effects were independent of glyphosate treatments. Neither yield nor any of the measured variables that reflected whole plant response were influenced by glyphosate treatment or by a glyphosate by irrigation interaction. Nomenclature: Glyphosate; cotton, Gossypium hirsutum L; ‘Delta and Pine Land 458 BGRR’.

Cotton and Weed Response to Glyphosate Applied with Sulfur-Containing Additives1

Field studies were conducted to assess two sulfur-containing additives for use with glyphosate applied postemergence to glyphosate-resistant cotton for the control of sicklepod and yellow nutsedge. Neither diammonium sulfate (AMS) nor ammonium thiosulfate (ATS), both applied at 2.24 kg/ha, increased control of either species. Effective control of both species was dependent on glyphosate (isopropylamine salt) rate alone, with optimum control at 1.26 kg ae/ha. Plant-mapping data further indicated that sulfur-containing additives generally had no effect on either cotton fruiting patterns or yield. However, applying glyphosate at any rate did increase seed cotton yield in 2 of 3 yr vs. no glyphosate. In addition, applying glyphosate at any rate resulted in an increase in the number of bolls vs. no glyphosate in the following plant-mapping responses: total number of bolls per plant, number of abcised bolls per plant, bolls at the top five sympodial nodes, and bolls at positions 1 and 2 on the sympodia. Glyphosate absorption and subsequent translocation, as influenced by the addition of the sulfur-containing additives, was evaluated using radiotracer techniques. Glyphosate absorption after 48 h was 86, 63, and 37% of amount applied in cotton, sicklepod, and yellow nutsedge, respectively. Absorption by sicklepod and yellow nutsedge was not affected by the addition of either of the additives. Absorption by cotton was reduced by ATS but was not affected by AMS. In yellow nutsedge and cotton, glyphosate concentration in the treated area and adjacent tissue was not affected by either additive. A greater portion of glyphosate was translocated away from the treated area in sicklepod with glyphosate plus AMS (32%) than with glyphosate plus ATS (21%). AMS and ATS may be used in glyphosate-resistant cotton without the risk of either crop injury or yield reduction. However, their use for increased control of annual weed species, such as sicklepod and yellow nutsedge, may not be warranted. Nomenclature: Glyphosate; ammonium thiosulfate; diammonium sulfate; sicklepod, Senna obtusifolia (L.) Irwin & Barneby #3 CASOB; yellow nutsedge, Cyperus esculentus L. # CYPES; cotton, Gossypium hirsutum L. ‘Paymaster 1218 BR’. Additional index words: Ammonium thiosulfate, CASOB, CYPES, diammonium sulfate, glyphosate absorption, glyphosate additives, glyphosate-resistant cotton. Abbreviations: AMS, diammonium sulfate; ATS, ammonium thiosulfate; DAT, days after treatment.

Effectiveness of Ammonium Thiosulfate to Enhance Weed Control and Reduce Cotton (Gossypium hirsutum) Injury1

Abstract: Field experiments were conducted in 1997 and 1998 at the Prattville Experiment Field in Prattville, AL and the Wiregrass Substation in Headland, AL to determine if ammonium thiosulfate (ATS) additions to monosodium methanearsonate (MSMA) affects weed control, reduces MSMA-induced cotton injury, lessens the fruiting and maturity delay on cotton caused by MSMA, and lessens MSMA-induced yield reductions in cotton. Treatments were applied before cotton was at the pinhead square stage and the weeds were 5 cm tall. Weeds evaluated were sicklepod, morningglory species, yellow nutsedge, and Texas panicum. ATS additions to MSMA occasionally enhanced control of all weeds 5 to 20%. However, the addition of ATS did not reduce crop injury caused by MSMA, the effects of MSMA on cotton maturity, or yield reductions caused by MSMA. Nomenclature: MSMA, monosodium methanearsonate; morningglory species, Ipomoea spp. #3 IPOZZ; sicklepod, Senna obtusifolia (L.) Irwin and Barneby # CASOB; Texas panicum, Panicum texanum Buckl. # PANTE; yellow nutsedge, Cyperus esculentus L. # CYPES; cotton, Gossypium hirsutum L. Abbreviations: ATS, ammonium thiosulfate; DAT, days after treatment; POST, postemergence.

Effect of soybean vein necrosis on yield and seed quality of soybean

Abstract Soybean vein necrosis virus (SVNV) rapidly became a widespread virus of soybean (Glycine max (L.) Merr.) in the USA and Canada within a few years of its initial detection in 2008; however, the economic impact of soybean vein necrosis (SVN) symptoms caused by virus infection remains unknown. Field studies were conducted in six states in the USA during 2013, 2014 and 2015 to determine the effect of SVN on soybean yield and seed quality. Quantitative parameters, including seeds per pod, pods per plant, yield and 100-count seed weight, were assessed from plants or seeds collected from research and commercial production fields. Qualitative parameters, including protein and oil concentration, were also obtained from samples collected in Indiana and Iowa. Results from all states suggest that yield is not impacted by SVN; however, seed quality was affected in four of seven location-years. In Iowa, oil concentration decreased by 0.11% as disease incidence increased by 1% (P = 0.04). In Indiana, SVNV infected plants exhibited decreased total oil content compared with asymptomatic plants (0.16% (P = 0.04); 0.67% (P > 0.01) in 2014 and 2015, respectively. These results suggest that SVN may change soybean seed quality, which may affect the marketability of soybeans for premium markets, specifically those interested in high oleic soybeans.

Preemergence Herbicides Applied Pre- and Postcrimp in a Rye Cover Crop System for Control of Escape Weeds in Watermelon

Field studies were conducted in 2016 and 2017 in Tallassee, AL, to evaluate the effect of preemergence (PRE) herbicide applications preand postcrimp in a cereal rye (Secale cereale) cover crop for control of escape weeds in watermelon (Citrullus lanatus). Treatments were arranged in a randomized complete block design with an augmented factorial treatment arrangement with four replications. The augmented factorial arrangement included three levels of PRE herbicides, two levels of application timing, and a nontreated control. PRE herbicide treatments included ethalfluralin (18 oz/acre), fomesafen (2.5 oz/acre), and halosulfuron (0.56 oz/acre). Application timings were precrimp (herbicide applied before crimping and rolling of the cover crop) and postcrimp (herbicide applied after crimping and rolling of the cover crop). A nontreated cover crop only treatment was also included. There were no interactions among application timing and herbicide. Results indicated application timing influenced total weed coverage but not watermelon yield. Total weed coverage was lowest in precrimp applied treatments at 2, 4, and 6weeks after treatment (WAT). Comparing individual treatments revealed no significant differences among herbicides with respect to watermelon yield; however, all herbicides increased yield compared with the nontreated.