Applied Postemergence Research Articles

Efficacy of HPPD-inhibiting herbicides applied preemergence or postemergence for control of multiple herbicide resistant waterhemp [Amaranthus tuberculatus (Moq.) Sauer

Research was conducted in 2017 and 2018 to determine the relative efficacy of five HPPD-inhibitors, tank-mixed with atrazine, for the control of multiple herbicide resistant waterhemp. At 12 wk after application (WAA), isoxaflutole + atrazine, mesotrione + atrazine, and tembotrione + atrazine, applied preemergence (PRE), controlled waterhemp 90%, 87%, and 81%, respectively. None of the HPPD-inhibiting herbicides applied PRE controlled waterhemp similar to the weed-free control 12 WAA. Applied postemergence, topramezone + atrazine, mesotrione + atrazine, tolpyralate + atrazine, and tembotrione + atrazine controlled waterhemp 87%, 94%, 97%, and 98% 12 WAA, respectively, and were all similar to the weed-free control.

WEED MANAGEMENT WITH HERBICIDES APPLIED IN PRE AND POSTEMERGENCE ON CASTOR CROP

ABSTRACT The aim of this work was to evaluate the weed management with herbicides applied in pre and postemergence on castor crop. The treatments were constituted by management systems using herbicides in pre (PRE) and postemergence (POS): 1) S-metolachlor at 576 g ha-1 (PRE 1) and chlorimuron-methyl at 15 g ha-1 (POS 1); 2) PRE 1 + clomazone at 650 g ha-1(PRE 2) and POS 1; 3) PRE 1, POS 1 and halosulfuron-methyl at 112.5 g ha-1(POS 2); 4) PRE 1, POS 1 and ethoxysulfuron at 60 g ha-1 (POS 3); 5) PRE 1, POS 1 and ethoxysulfuron at 120 g ha-1 (POS 4); 6) PRE 1 + PRE 2, POS 1 and POS 2; 7) PRE 1 + PRE 2, POS 1 and POS 3; 8) PRE 1 + PRE 2, POS 1 and POS 4; 9) hand-hoeing control and 10) non-weeded control. The experimental design was randomized blocks with four replications. The association of the herbicides in PRE combined to sequence applications of chlorimuron-ethyl and halosulfuron-methyl or ethoxysulfuron in POS resulted in the highest control levels of Richardia scabraand Cyperus ferax. Mild phytointoxication symptoms to the crop were more persistent with ethoxysulfuron at 120 g ha-1. The acceptable control of the weed species and similar yield to the hand-hoeing control permitted to conclude that S-metolachlor + clomazone PRE, followed by chlorimuron-ethyl and halosulfuron-methyl POS proved to be more adequate as a weed management strategy on castor crop.

Response of Four Market Classes of Dry Beans to Halosulfuron Applied Postemergence at Five Application Timings

Six field trials were conducted over a three-year period (2011, 2012, 2013) at the Huron Research Station, Exeter, Ontario and University of Guelph Ridgetown Campus, Ridgetown, Ontario to determine the effect of five postemergence (POST) application timings (1 - 2 trifoliate, 3 - 4 trifoliate, 5 - 6 trifoliate, 1st flower and 1st pod stage) of halosulfuron (35 and 70 g·ai·ha-1) on the tolerance of adzuki, black, white and kidney beans. All treatments including the non-treated control were maintained weed free during the growing season. Halosulfuron applied POST in black, white and kidney bean caused as much as 8%, 8%, 7%, 4% and 2% injury 1 WAA and 4%, 4%, 2%, 2% and 1% injury 2 WAA at 1 - 2 trifoliate, 3 - 4 trifoliate, 5 - 6 trifoliate, 1st flower and 1st pod stage application timings, respectively. The injury observed was transient with 1% or less injury 4 WAA and there was no adverse effect on the shoot dry weight, plant height, seed moisture content and yield of black, white and kidney bean. Injury was substantially higher in adzuki bean at all application timings. Halosulfuron applied POST caused as much as 66%, 47%, 50%, 39% and 36% injury 1 WAA; 77%, 68%, 64%, 51% and 42% 2 WAA; and 69%, 51%, 47%, 40% and 29% 4 WAA at 1 - 2 trifoliate, 3 - 4 trifoliate, 5 - 6 trifoliate, 1st flower and 1st pod stage application timings, respectively. Halosulfuron POST decreased shoot dry weight as much as 69%, 57%, 43%, 41% and 34%; plant height as much as 17%, 15%, 14%, 13% and 10%; and seed yield as much as 47%, 46%, 45%, 56% and 55% at 1 - 2 trifoliate, 3 - 4 trifoliate, 5 - 6 trifoliate, 1st flower and 1st pod stages, respectively. Based on these results, there is an adequate margin of crop safety for halosulfuron POST in black, white and kidney beans. However, there is not an adequate margin of crop safety for halosulfuron POST in adzuki bean at the application timings evaluated.

Compatibility of Acephate with Herbicides Applied Postemergence in Peanut

Compatibility of Acephate with Herbicides Applied Postemergence in Peanut

Weed Control with Halosulfuron Applied Preplant Incorporated, Preemergence or Postemergence in White Bean

Four field trials were conducted over a three-year period (2011-2013) at various locations in Ontario to evaluate the level of weed control provided by halosulfuron applied PPI,PREor POST at 17.5, 35 and 70 g&middotai&middotha-1 in white bean. Halosulfuron applied PPI or PRE at 17.5, 35 and 35 g&middotai&middotha-1 caused 2% or less visible injury 1 and 4 WAA in white bean. However, halosulfuron applied POST at 17.5, 35 and 70 g&middotai&middotha-1 caused 2% - 8% and 1% - 3% white bean injury at 1 and 4 WAA, respectively. There was no decrease in white bean seed yield relative to the weed free check due to weed interference with halosulfuron applied PPI or PRE at doses evaluated, except when applied PRE at 17.5 g&middotai&middotha-1 which resulted in a decrease in seed yield of 25%. Weed interference caused a decrease in white bean yield of 47%, 42% and 44%, when halosulfuron was applied POST at 17.5, 35 and 70 g&middotai&middotha-1, respectively. Halosulfuron applied PPI, PRE and POST controlled AMARE 92% - 100%, 85% - 99% and 47% - 75%; CHEAL 95% - 100%, 83% - 99% and 36% - 51%; and SINAR 97% - 100%, 99% - 100% and 100%, respectively. Halosulfuron applied PPI and PRE reduced AMARE density 93% - 97% and 75% - 95%; CHEAL density 89% - 98% and 81% - 93%; and SINAR density 99% - 100% and 99% - 100%, respectively. Halosulfuron applied PPI and PRE reduced dry weight of AMARE 96% - 98% and 86% - 96%; CHEAL 96% - 98% and 87% - 93%; and SINAR 100% and 100%, respectively. Halosulfuron applied POST at rates evaluated reduced SINAR density and dry weight 100% but caused no significant reduction in AMARE and CHEAL density or dry weight compared to the weedy check. Based on these results, halosulfuron applied PPI orPREat 35 g&middotai&middotha-1 can be used safely for the control of selected broadleaf weeds in white bean production.

Compatibility of Acephate with Herbicides Applied Postemergence in Peanut

ABSTRACT Numerous agrochemicals can be applied in peanut to control pests. Field and laboratory experiments were conducted in North Carolina during 2009 and 2010 to determine peanut response to paraquat and tobacco thrips (Frankliniella fusca Hinds.) when acephate was applied in combination with chloroacetamide and contact herbicides. Experiments were also conducted during 2011 to determine peanut response to acephate applied alone or with paraquat when peanut was planted either without aldicarb or when aldicarb was applied in the seed furrow at planting. Visible peanut damage caused by tobacco thrips feeding was greater when chloroacetamide herbicides were applied without acephate compared with application with acephate regardless of paraquat treatment. Visible injury caused by paraquat was higher when chloroacetamide herbicides were included compared with paraquat alone in one of two years. Visible injury by paraquat was lower when applied with acephate compared to paraquat alone in one of two years. Acephate applied to peanut foliage and aldicarb applied in the seed furrow at planting protected peanut similarly from damage associated with tobacco thrips feeding. Acephate alone or with chloroacetamide herbicides changed solution pH from slightly acidic to highly acidic. Several combinations of pesticides formed either transient or permanent precipitates.

Effect of Halosulfuron Applied Preplant Incorporated, Preemergence, and Postemergence on Dry Bean

Five field trials were conducted over a 2-yr period (2007, 2008) at various locations in Ontario to evaluate the tolerance of black, cranberry, kidney, otebo, pink, pinto, small red Mexican (SRM), and white bean to halosulfuron applied PPI, PRE, and POST at 35 and 70 g ai/ha. There was minimal injury (3% or less) with halosulfuron applied PPI or PRE in dry bean. At Exeter and Ridgetown, halosulfuron applied POST at 35 and 70 g/ha caused 3 to 5% and 4 to 8% injury in dry bean, respectively at 1 wk after herbicide application (WAA). The injury was transient with no significant injury at 2 and 4 WAA. At Harrow, halosulfuron POST at 35 and 70 g/ha caused as much as 4% injury at 35 g/ha and 14% injury at 70 g/ha in dry bean. Halosulfuron applied PPI, PRE, and POST at 35 and 70 g/ha caused no decrease in plant height of dry bean except for kidney bean, which was reduced 6% at 70 g/ha, and white bean, which was reduced 3% at both 35 and 70 g/ha. Halosulfuron applied PPI, PRE, and POST at 35 and 70 g/ha caused no decrease in dry bean yield except for kidney bean, which was reduced 9% at 35 g/ha and 10% at 70 g/ha; otebo bean, which was reduced 3% at 70 g/ha; and white bean, which was reduced 7% at both 35 and 70 g/ha. On the basis of these results, there is an adequate margin of crop safety in dry bean to halosulfuron applied PPI or PRE at 35 and 70 g/ha. In addition, there is an adequate margin of crop safety in black, cranberry, pink, pinto, and SRM bean to halosulfuron applied POST at 35 and 70 g/ha. However, further research is required to ascertain the tolerance of kidney, otebo, and white bean to halosulfuron applied POST.

Further Evidence of a Genetic Basis for Varied Levels of Injury to Sweet Corn Hybrids from Cytochrome P450-metabolized Herbicides Applied Postemergence

Over the last two decades, sweet corn injury from postemergence herbicides has resulted in routine screening of combinations of new and existing hybrids and herbicides. Sensitivity of sweet corn to several cytochrome P450-metabolized herbicides is simply inherited and has a common genetic basis, a single P450 locus that may account for a large amount of the variation in sweet corn injury commonly observed among screening trials. Using data from 13 hybrid-herbicide screening trials, the objective of this work was to determine the extent to which injury from P450-metabolized herbicides was associated with the genotypes of hybrids at a locus affecting herbicide sensitivity. Of the 703 hybrids evaluated in the University of Illinois sweet corn hybrid nurseries from 2002 to 2007, previous work showed that a total of 104, 70, and nine of the hybrids were known to be homozygous-tolerant, heterozygous, or homozygous-sensitive, respectively, for an allele affecting herbicide response. Nurseries from 2002 to 2007 included six trials with mesotrione, three trials with nicosulfuron, and one trial each with foramsulfuron, tembotrione, halosulfuron, and carfentrazone. When means of hybrids in genotypic classes were compared, homozygous-sensitive hybrids were consistently injured more severely than homozygous-tolerant and heterozygous hybrids. When environmental conditions favored crop injury, heterozygous hybrids had an intermediate response that was closer to homozygous-tolerant hybrids than homozygous-sensitive hybrids. These data are further evidence that the probability of injury from several P450-metabolized herbicides, including mesotrione, nicosulfuron, foramsulfuron, tembotrione, halosulfuron, and carfentrazone, is highest in homozygous-sensitive hybrids and least in homozygous-tolerant hybrids and that variability of responses among sweet corn hybrids to these P450-metabolized herbicides can be explained largely by the genotype of a hybrid at a single locus.

Inheritance of Cross-sensitivity in Sweet Corn to Herbicides Applied Postemergence

Some sweet corn (Zea mays L.) hybrids and inbreds can be severely injured by applications of postemergence herbicides. An association was observed between the responses of sweet corn hybrids and inbreds to nicosulfuron and mesotrione, and F2 families derived from a cross of a sensitive (Cr1) and a tolerant (Cr2) sweet corn inbred segregated for response to these two herbicides. These observations prompted us to examine the inheritance of sensitivity in sweet corn to multiple postemergence herbicide treatments with different modes of action and to determine if there was a common genetic basis for cross-sensitivity to these herbicides. The sensitive and tolerant inbreds, progeny in the F1, F2, BC1, and BC2 generations, and BC1S1, BC2S1, F2:3 (S1:2) and F3:4 (S2:3) families were screened for responses to eight herbicide treatments. Based on segregation of tolerant and sensitive progeny and segregation of family responses, our data indicate that a single recessive gene in Cr1 conditioned sensitivity to four acetolactate synthase (ALS)-inhibiting herbicides (foramsulfuron, nicosulfuron, primisulfuron, and rimsulfuron), a 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide (mesotrione), a growth regulator herbicide combination (dicamba + diflufenzopyr), and a protoporphyrinogen oxidase (PPO)-inhibiting herbicide (carfentrazone). Based on highly significant positive correlations of phenotypic responses among BC1S1, BC2S1, F2:3, and F3:4 families, the same gene (or closely linked genes) appeared to condition responses to each of these herbicide treatments. The dominant allele also conditions tolerance to bentazon [a photosystem II (PSII)-inhibiting herbicide] although another gene(s) also appeared to affect bentazon tolerance.

Cross-sensitivity in Sweet Corn to Nicosulfuron and Mesotrione Applied Postemergence

Nicosulfuron and mesotrione are herbicides from different chemical families with different modes of action. An association between the sensitivity of sweet corn (Zea mays L.) to nicosulfuron and mesotrione was observed when hybrids, inbreds, and S1 families (S2 plants) were evaluated for herbicide sensitivity in field trials. In 2003 and 2004, 50% and 53% of mesotrione-sensitive hybrids were sensitive to nicosulfuron compared with only 6% and 1% of mesotrione-tolerant hybrids that were sensitive to nicosulfuron. In trials with inbreds in 2003 and 2004, 88% and 78% of nicosulfuron-sensitive inbreds had some injury from mesotrione but 0% and 5% of nicosulfuron-tolerant inbreds were injured by mesotrione. Among S1 families, 77% of the mesotrione-sensitive families were nicosulfuron-sensitive but only 5% of the mesotrione-tolerant families were sensitive to nicosulfuron. Segregation of S1 families for response to mesotrione was not significantly different from a 1:2:1 pattern of sensitive: segregating: tolerant families (chi square value = 2.25, P = 0.324) which would be expected if sensitivity was conditioned by a single recessive gene. Segregation of S1 families for response to nicosulfuron was 15:23:26 (sensitive: segregating: tolerant) which was slightly different from an expected 1:2:1 ratio (chi square value = 8.84, P = 0.012). Segregation of S1 families probably was affected by the relatively small number of S2 plants sampled from each family. Similar responses of the S1 families to nicosulfuron and mesotrione lead us to hypothesize that the same recessive gene is conditioning sensitivity to both herbicides. Possibly, this gene is common in the inbreds and hybrids that were sensitive in these trials. These hypotheses will be tested by examining segregation in S2 families and other segregating generations and by conducting tests of allelism among sensitive inbreds and inbred parents of sensitive hybrids. Chemical names: 2-(4-mesyl-2-nitrobenzoyl)-3-hydroxycyclohex-2-enone, (mesotrione); 2-[[[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]-N,N-dimethyl-3-pyridinecarboxamide, (nicosulfuron).

Influence of Application Rate and Timing on Efficacy of DPX-PE350 Applied Postemergence

Broadleaf weed control with DPX-PE350 at 56, 84, 110, 140, and 170 g ae ha−1applied postemergence was evaluated. DPX-PE350 was less effective and higher rates were required when applied to three- to six-leaf weeds compared to one- to two-leaf weeds. Listed in order of increasing susceptibility are sicklepod, tall morningglory, pitted morningglory = palmleaf morningglory, and entireleaf morningglory = hemp sesbania = velvetleaf.

Bentazon Applied Postemergence for Economical Control of Common Cocklebur in Soybeans

Effectiveness of bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide] for control of common cocklebur (Xanthium pensylvanicumWallr.) in soybeans [Glycine max(L.) Merr.] was evaluated in field research over a 3-yr period. Bentazon, applied over-the-top at 0.6 to 1.1 kg/ha, controlled common cocklebur more effectively than over-the-top or directed applications of dinoseb (2-sec-butyl-4,6-dinitrophenol) at 0.8 to 1.7 kg/ha or 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] at 0.2 kg/ha. Single applications of bentazon were highly effective for control of common cocklebur, but multiple applications usually provided the best control and highest soybean yields. A preemergence treatment of metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] at 1.1 kg/ha and a postemergence application of bentazon at 1.1 kg/ha provided 92 to 99% control of common cocklebur. Control of common cocklebur with bentazon reduced discounts in harvested soybean seed caused by excessive moisture content and foreign material. The reduction in discounts improved soybean seed grades.

Effect of urea and ammonium sulphate applied before sowing on sudangrass seedlings

SUMMARYStudies were conducted to determine possible leaching or fixation problems in growing sudangrass (Sorghum Sudanese Stapf.) when urea, ammonium sulphate plus triple superphosphate, and ammonium polyphosphate fertilizer were applied as a seed-bed application to the very sandy soils of the Libyan Sahara near the Kufra Oasis. The effectiveness of the nitrogen source was measured by plant colour, leaf analysis, and seedling height.The urea nitrogen plus single superphosphate when applied and watered-in did not supply enough nitrogen to obtain a vigorous green seedling compared with ammonium polyphosphate (21% N, 53% P 2O6), which produced excellent vigorous green seedlings. The ammonia source supplied more nitrogen than the urea imder the conditions of these trials.The application of urea 1, 2, 4, and 8 days before sowing was inadequate in supplying nitrogen to meet the early demand of the sudangrass seedlings. Sudangrass seedlings after 26 days were only 5–6·3 cm tall. With a seed-bed application of 36–72 kg N/ha as ammonium sulphate under comparable circumstances, sudangrass seedling height was 21·7 cm. The plants receiving no nitrogen applied before sowing were 6·7 cm high, similar to those which received urea.Under these virgin sandy soil conditions, the ammonium sulphate and ammonium polyphosphate (21% N, 53% P2O5) fertilizers applied to the seed bed were retained within the root zone in sufficient amounts to give a vigorous, non-deficient sudangrass seedling. Nitrogen from urea was deficientand presumed leached beyond reach of the seedling root when applied to the seed bed. Applied post-emergence, however, urea was a very satisfactory source of nitrogen.

Effects of Herbicides Applied Postemergence on Weeds and Sunflowers1

Herbicides were applied as postemergence treatments either as early over‐the‐top spray or late‐directed spray to sunflowers (Helianthus annuus L.) for weed control and crop tolerance determinations at Experiment, Ga. Treatments of RP 17623 (2‐tertiobutyl‐4‐(2,4‐dichloro‐5‐ isopropyloxyphenyl)‐5‐oxo‐l,3,4‐oxadiazoline) were applied to sunflowers in the cotyledon, first leaf, and second leaf growth stages. Several herbicides commonly used on other crops were applied late postemergence directed spray to sunflowers when they were 25 to 35 cm tall.were obtained from early postemergence treatments of RP 17623 when applied as over‐the‐top spray at either the cotyledon or the first‐leaf stage of sunflower growth. Weed control results were similar to RP 17623 from several herbicides that were applied as late‐directed postemergence sprays. Early postmergence treatments with RP 17623 caused some early injury to sunflower plants and a reduction in achene oil percent when compared with achenes from untreated plants, but achene yields were not reduced. None of the herbicides applied as late‐directed postemergence sprays injured sunflowers, reduced achene yield, or achene oil percent.

Root and Foliar Absorption of Atrazine Applied Postemergence to Broadleaf Weeds

Results from both growth chamber and field experiments indicate that root absorption of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) applied postemergence to small broadleaf weeds is not a requisite for their control. Though broadleaf weeds absorb toxic quantities of atrazine from wet soil, they can be killed by foliar absorption alone because all of their meristems are exposed to a foliar spray. They are particularly sensitive when foliar penetration is enhanced by high relative humidity and wet foliage.

Foliar and Root Absorption of Atrazine Applied Postemergence to Giant Foxtail

In growth chamber studies, high relative humidity and rewetting crystalline spray deposits of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) increased absorption by and phytotoxicity to giant foxtail (Setaria faberii Herrm.), but phytotoxicity was restricted to expanded (unrolled) leaves unless some atrazine was absorbed by the roots. Though phytotoxicity was increased by simulated rainfall when root absorption was prevented, an appreciable number of the plants were killed only when atrazine residues were washed into the soil. In field studies, atrazine applied to a wet soil surface was as effective as the same rate of atrazine foliarly applied. In other field experiments, atrazine applied to giant foxtail on a wet soil and followed by simulated rainfall reduced stand and dry weight, but on a dry soil and not followed by simulated rainfall, atrazine reduced dry weight less and did not reduce stand. These results are due to root absorption of atrazine from wet soil. Spray additives increased phytotoxicity.