Crop Injury Research Articles

Glyphosate, isolated or in associations, at agronomic performance and seed quality of the RR®2 soybean

ABSTRACT: The “second generation” of glyphosate-tolerant soybean (RR®2 soybean) was developed through a different technique of insertion of the glyphosate-insensitive EPSPs gene. Information on the selectivity of glyphosate, alone or in combination, in RR2 soybean is lacking. This study evaluated the effects of glyphosate, isolated or in associations, applied at post-emergence (V4), at agronomic performance and seed quality of soybean cultivar NS 6700 IPRO (RR2). The experimental design was randomized block with four replications and seven treatments, conducted in the field for two growing seasons. The treatments consisted of glyphosate herbicide, alone or in combination with clethodim, cloransulam, chlorimuron, lactofen and fluazifop, besides the control without application. Analysis was performed for crop injury, Soil and Plant Analyzer Development (SPAD) index, as well as variables related to agronomic performance (height, number of pods per plant, yield and 1,000-seed weight) and seed quality (vigor, germination, abnormal seedlings and dead seeds). An additional test was conducted with the same cultivar and treatments in a greenhouse in a completely randomized design with four replications. The herbicides did not affect agronomic performance and seed quality of RR2 soybean. Thus, the soybean cultivar NS 6700 IPRO (RR2) was tolerant to glyphosate, alone or combined with other herbicides applied in post-emergence (V4).

Early warning indexes determination of the crop injuries caused by waterlogging based on DHSVM model

Early warning on crop injuries aroused by waterlogging is the guarantee of crop yield in the middle and lower reaches of the Yangtze River. The waterlogging warning measures based on precipitation index were often inaccurate. In this literature, a new method based on DHSVM (Distributed Hydrology Soil Vegetation Model) was used for practice in summer crops at county-level, real-time and high-precision forecasting, which simulates soil groundwater depth and soil volumetric moisture content in grid unit on time step of 1 day. According to the agricultural standard of waterlogging level, the meteorology characteristic data were calculated, and then spatial distribution of the waterlogging eigenvalues was mapped. Waterlogging distribution from Jianli County was clustered into five types of regions with a 90-m spatial resolution via the unsupervised classification method (k-means) algorithm. Based on the partition statistics of waterlogging eigenvalues, the character values of each kind were extracted. Using these eigenvalues as criteria, we predicted the waterlogging in the years from 1970 to 2015. The experimental results show that the average value of kappa coefficient is between 0.87 and 0.93, which illustrates that our method is effective for warning waterlogging level.

Increasing tolerance to bispyribac-sodium is able to allow glutathione homeostasis to recover in indica rice compared with japonica rice

The high activity and broad weed spectrum of BS has made it widely used in China. However, accidental crop injuries, particularly occurring in Jiangsu, Hunan, Hubei and Heilongjiang provinces in recent years, have resulted in limiting the application of BS in China. In this study, glutathione homeostasis was measured in the contrasting sensitivity of indica and japonica rice cultivar after bispyribac-sodium (BS) treatment. The results showed that japonica rice cultivar Nanjing 9108 was more sensitive to BS than indica rice Nanjing 11 and indica-hybrid cultivar Guangliangyou 6326. In response to the exposure of BS in all rice cultivars, especially Nanjing 9108, the perturbation of glutathione homeostasis occurred, including the decreased reduced glutathione (GSH) and increased oxidized glutathione (GSSG). These results were supported by increased activities of glutathione S-transferases (GSTs) in Nanjing 11 and Guangliangyou 6326. Further tests revealed that when Nanjing 11 was pretreated with the glutathione-depleting agents L-buthionine-sulfoximine (BSO) or diethylmaleate (DEM), the GSH levels, the activity of GSTs, and the gene expression levels of GR and GSTs decreased, finally increasing the phytotoxicity of BS. The aforementioned DEM inhibitory responses were further rescued by exogenously applied GSH. In contrast, the pretreatment of glutathione or N-acetyl-L-cysteine (NAC) not only increased the contents of GSH, the activities of GSTs, and the expression level of GR and GSTs gene, but also alleviated BS phytotoxicity in Nanjing 9108. In both cultivars, DEM increased phytotoxicity and GSH partially reversed this. This study suggests that increasing tolerance to BS was able to allow glutathione homeostasis to recover in indica rice cultivar compared with japonica rice cultivar.

Persistence and Movement of Fomesafen in Florida Strawberry Production

AbstractFomesafen is a protoporphyrinogen oxidase–inhibitor herbicide with an alternative mode of action that provides PRE weed control in strawberry [Fragaria×ananassa(Weston) Duchesne ex Rozier (pro sp.) [chiloensis×virginiana]] produced in a plasticulture setting in Florida. Plasticulture mulch could decrease fomesafen dissipation and increase crop injury in rotational crops. Field experiments were conducted in Balm, FL, to investigate fomesafen persistence and movement in soil in Florida strawberry systems for the 2014/2015 and 2015/2016 production cycles. Treatments included fomesafen preplant at 0, 0.42, and 0.84 kg ai ha−1. Soil samples were taken under the plastic from plots treated with fomesafen at 0.42 kg ha−1throughout the production cycle. Fomesafen did not injure strawberry or decrease yield. Fomesafen concentration data for the 0.0- to 0.1-m soil depth were described using a three-parameter logistic function. The fomesafen 50% dissipation times were 37 and 47 d for the 2014/2015 and 2015/2016 production cycles, respectively. At the end of the study, fomesafen was last detected in the 0.0- to 0.1-m depth soil at 167 and 194 d after treatment in the 2014/2015 and 2015/2016 production cycles, respectively. Fomesafen concentration was less than 25 ppb on any sampling date for 0.1- to 0.2-m and 0.2- to 0.3-m depths. Fomesafen concentration decreased significantly after strawberry was transplanted and likely leached during overhead and drip irrigation used during the crop establishment.

Insecticide Seed Treatments Partially Safen Rice to Low Rates of Glyphosate and Imazethapyr

AbstractEach year there are multiple reports of drift occurrences, and the majority of drift complaints in rice are from imazethapyr or glyphosate. In 2014 and 2015, multiple field experiments were conducted near Stuttgart, AR, and near Lonoke, AR, to evaluate whether insecticide seed treatments would reduce injury from glyphosate or imazethapyr drift or decrease the recovery time following exposure to a low rate of these herbicides. Study I was referred to as the “seed treatment study,” and Study II was the “drift timing study.” In the seed treatment study the conventional rice cultivar ‘Roy J’ was planted, and herbicide treatments included imazethapyr at 10.5 g ai ha–1, glyphosate at 126 g ae ha–1, or no herbicide. Each plot had either a seed treatment of thiamethoxam, clothianidin, chlorantraniliprole, or no insecticide seed treatment. The herbicides were applied at the two- to three-leaf growth stage. Crop injury was assessed 1, 3, and 5 wk after application. Averaged over site-years, thiamethoxam-treated rice had less injury than rice with no insecticide seed treatment at each rating, along with an increased yield. Clothianidin-treated rice had an increased yield over no insecticide seed treatment, but the reduction in injury for both herbicides was less pronounced than in the thiamethoxam-treated plots. Overall, chlorantraniliprole was generally the least effective of the three insecticides in reducing injury from either herbicide and in protecting rice yield potential. A second experiment conducted at Stuttgart, AR, was meant to determine whether damage to rice from glyphosate and imazethapyr was influenced by the timing (15, 30, and 45 d after planting) of exposure to herbicides for thiamethoxam-treated and nontreated rice. There was an overall reduction in injury with the use of thiamethoxam, but the reduction in injury was not dependent on the timing of the drift event. Reduction in damage from physical drift of glyphosate and imazethapyr as well as increased yields over the absence of an insecticide seed treatment appear to be an added benefit.

Salicylic acid reduces chilling injury in post-harvest of Bird-of-Paradise

The irregular opening of the florets and susceptibility to chilling damages are the major issues of cut Bird-of-Paradise flowers (Strelitzia reginae). The salicylic acid (SA) has shown to be a promising action in reducing chilling injury in many crops; however, its effect is not well elucidated in cut flowers. The objective of this study was to determine the action of SA on the development of reduction of hilling injury during storage of Bird-of-Paradise flowers. The stems were pulsed with 200 g L-1 of sucrose in added with three concentrations of SA (2, 4 and 6 mmol L-1) and control with only 200 g L-1 of sucrose for 24 hours. Subsequently, the stems were transferred to containers with water and conditioned at 5 °C for chilling injury induction for 28 days. Water uptake rate, transpiration rate, fresh mass, electrolyte leakage, activity of peroxidase and phenolic compounds of bracts and sepals were determined weekly. The SA reduces the transpiration rate and keeps the mass fresh until 21 days. A reduction was observed in electrolyte leakage up to 14 days. All doses of SA increased POD activity of the bracts while water uptake rate, POD activity of the sepals and phenolic compound content of bracts and sepals are dependent on dose and storage period. It is concluded that the SA applied via pulsing reduces the chilling injury on Bird-of-Paradise cut flowers. In addition, it reduces the transpiration rate and maintains the fresh mass of the floral stems until 21 days. No correlation was found between POD activity and phenolic compounds.

Crescimento inicial de mudas pré-brotadas de cana-de-açúcar em duas modalidades de aplicação de herbicidas

A espécie Cyperus rotundus está entre as plantas daninhas mais difíceis de controlar, podendo causar elevados prejuízos na cultura da cana-de-açúcar. As práticas adotadas garantem os valores de produtividade, dentre elas, está o manejo de plantas daninhas. O objetivo deste trabalho foi avaliar o crescimento inicial de mudas pré-brotadas de cana-de-açúcar submetidas à aplicação de herbicidas em pré ou pós-plantio. Foram conduzidos dois experimentos (pré e pós-plantio) em casa-de-vegetação, em delineamento inteiramente casualizado, com quatro repetições. Os tratamentos correspondem aos herbicidas aplicados em três doses em pré-plantio: sulfentrazone (400, 800 e 1.600 g i.a. ha-1), diclosulam (96,6; 193,17 e 386,34 g i.a. ha-1), imazapic (66,5, 133 e 266 g i.a. ha-1) e imazapyr (250, 500 e 1.000 g e.a. ha-1) e pós-plantio: ethoxysulfuron (67,5, 135 e 270 g i.a. ha-1), halosulfuron (56,25, 112,5 e 225 g i.a. ha-1), 2,4-D (670, 1.340 e 2.680 g e.a. ha-1) e MSMA (987,5, 1975 e 3.950 g i.a. ha-1). Além de duas testemunhas sem aplicação de herbicidas. Foram avaliados os sintomas de injúrias, altura, diâmetro, número de folhas, número de perfilhos, teor de clorofila, área foliar, matéria seca da parte aérea e raiz. Os herbicidas em pós-plantio foram considerados seletivos, uma vez que os sintomas de injúrias foram baixos e os outros parâmetros avaliados não foram diferentes da testemunha. Para as aplicações em pré-plantio foram observados sintomas de injúrias até os 60 dias após a aplicação (DAA) para sulfentrazone.

Inter-row hoeing for weed control in organic spring cereals—Influence of inter-row spacing and nitrogen rate

Abstract Inter-row hoeing has become increasingly important for weed control in organic spring cereals since the introduction of automatic steering systems. The technology requires a widening of current inter-row spacing for spring cereals in order to provide sufficient room for accurate operation of a hoe share between crop rows. However, there is considerable uncertainty about the optimal combination of inter-row hoeing, inter-row spacing and nitrogen (N) rate in terms of weeding effectiveness and crop yield. The aim of this study was to investigate the effect on weed and crop growth of the interaction between five inter-row spacings (125, 150, 200, 250, and 300 mm) and two N rates (50 and 100 kg NH4-N ha−1). Three field experiments were conducted in spring barley and two in spring wheat. One hoeing pass was applied for each inter-row spacing using a share width that worked 15–47 mm from the crop row. The immediate effect on weed numbers following hoeing was a 80–90% reduction in barley and a 63–80% reduction in wheat, but with no significant differences between spacings and N rates. However, the effect on weed biomass at crop anthesis was minor in barley because the crop itself substantially suppressed weed growth. Spring wheat was less competitive and inter-row hoeing reduced weed biomass by 60–70% compared to the standard 125 mm spacing without hoeing. The widening of inter-row spacing appeared not to reduce crop yield or grain quality. Prerequisites for successful inter-row hoeing in spring cereals include retained crop stands when increasing inter-row spacing and the avoidance of crop injuries from inaccurate steering.

Adsorption, desorption and persistence of fomesafen in soil.

Fomesafen provides control of glyphosate-resistant Palmer amaranth in cotton but frequent seedling injury has been reported. This study evaluated soil adsorption, desorption, and field persistence of fomesafen. The Freundlich distribution coefficient (Kf ) for fomesafen on seven US soils varied from 1.30 to 9.28 µg1-1/n g-1 mL1/n . The pesticide distribution coefficient (Kd ) and soil organic carbon normalized adsorption coefficient (KOC ) varied from 1.11 to 12.76 mL g-1 and 58 to 1467 mL g-1 , respectively. The soils evaluated had desorption rates of 11.06% to 81.31% after a single desorption cycle. Soil pH, organic matter, sand, silt and clay content had a significant impact on fomesafen adsorption and desorption. Fomesafen field half-lives (DT50 ) in Cecil sandy loam were 47 and 34 days, compared with 6 and 4 days in Tifton loamy sand when fomesafen was applied at 1× and 2× the label rate, respectively. The fomesafen dissipation rate decreased significantly under low-density polyethylene (LDPE) mulch compared with bare ground. Fomesafen soil adsorption to soils was not strong and was affected by multiple soil properties. Fomesafen field persistence varied significantly between soil types and under ground cover. The data suggest that soils with a lower pH and higher clay content are less likely to produce crop injury due to greater fomesafen adsorption. © 2018 Society of Chemical Industry.

Clean the Sprayer to Avoid Crop Injury

The objective of this 5-page document is to present the correct clean-out procedure for spray equipment following pesticide use. Written by Frederick M. Fishel and published by the UF/IFAS Agronomy Department, August 2018. http://edis.ifas.ufl.edu/pi277

Injury Criteria Associated with Soybean Exposure to Dicamba

AbstractResearch conducted in the field identified 14 injury criteria associated with dicamba (Clarity® diglycolamine salt) applied at 0.6 to 280 g ae ha–1(1/1,000 to 1/2 of 560 g ha–1use rate) to indeterminate soybean at V3/V4 or R1/R2. For each criterion, injury was rated using a scale of 0=no injury, 1=slight, 2=slight to moderate, 3=moderate, 4=moderate to severe, and 5=severe. Greatest crop injury 15 d after treatment (DAT) was observed for dicamba rates of 0.6 to 4.4 g ha–1for upper canopy pale leaf margins (3.8 to 4.2) at V3/V4 and for terminal leaf cupping (4.1 to 5.0) at R1/R2, and for rates of 0.6 to 8.8 g ha–1for upper canopy leaf cupping (3.8 to 4.8) and upper canopy leaf surface crinkling (3.4 to 4.4) at V3/V4. Injury 15 DAT was equivalent to the nontreated control for dicamba rates as high as 4.4 g ha–1for lower stem base swelling at V3/V4 and for upper canopy leaf rollover/inversion and terminal leaf necrosis at R1/R2; for rates as high as 8.8 g ha–1for leaf petiole base swelling and stem epinasty at R1/R2, and lower stem base lesions/cracking (V3/V4 and R1/R2 average); and for rates as high as 17.5 g ha–1for lower leaf soil contact at V3/V4 and leaf petiole droop at R1/R2. The response to increasing dicamba rate observed for the injury criteria was in contrast to the steady increase in visual injury and plant height reduction rated as 0 to 100%. The moderate to severe upper canopy leaf cupping, pale leaf margins, and leaf surface crinkling, and terminal leaf cupping 15 DAT with dicamba at 0.6 to 4.4 g ha–1corresponded to soybean yield loss of 1% to 9% for application at V3/V4 and 2% to 17% at R1/R2.

SELECTIVITY OF HERBICIDES APPLIED SEPARATELY OR IN COMBINATION IN THE POST EMERGENCE OF RR2 MAIZE

The goal was to evaluate the tolerance of maize hybrids 2B810 PW and 30F35 HR to herbicides applied alone and in combination. Trials were carried out in the field in a randomized block design with four replicates. The treatments were three herbicides, alone or in combination, in addition to the control. Herbicides were: atrazine (2000 g ai ha-1); nicosulfuron (50 g ai ha-1) and glyphosate (1080 g ae ha-1). Crop injury was evaluated at 7, 14, 21, and 28 days after application and also SPAD index, height, ear height, stem diameter, 1000-grain weight, and yield. In general, the variables were not affected by the treatments. Hybrids 2B810 PW and 30F35 HR showed tolerance to the application in post-emergence (V4) of the herbicides used.

Residual Activity of ACCase-Inhibiting Herbicides on Monocot Crops and Weeds

AbstractField experiments were conducted in 2014 and 2015 in Fayetteville, Arkansas, to evaluate the residual activity of acetyl-CoA carboxylase (ACCase)–inhibiting herbicides for monocot crop injury and weed control. Conventional rice, quizalofop-resistant rice, grain sorghum, and corn crops were evaluated for tolerance to soil applications of six herbicides (quizalofop at 80 and 160 g ai ha–1, clethodim at 68 and 136 g ai ha–1, fenoxaprop at 122 g ai ha–1, cyhalofop at 313 g ai ha–1, fluazifop at 210 and 420 g ai ha–1, and sethoxydim at 140 and 280 g ai ha–1). Overhead sprinkler irrigation of 1.3 cm was applied immediately after treatment to half of the plots, and the crops planted into the treated plots at 0, 7, and 14 d after herbicide treatment. In 2014, injury from herbicide treatments increased with activation for all crops evaluated, except for quizalofop-resistant rice. At 14 d after treatment (DAT) in 2014, corn and grain sorghum were injured 19% and 20%, respectively, from the higher rate of sethoxydim with irrigation activation averaged over plant-back dates. Conventional rice was injured 13% by the higher rate of fluazifop in 2014. Quizalofop-resistant rice was injured no more than 4% by any of the graminicides evaluated in either year. In 2015, a rainfall event occurred within 24 h of initiating the experiment; thus, there were no differences between activation via irrigation or by rainfall. However, as in 2014, grain sorghum and corn were injured 16% and 13%, respectively, by the higher rate of sethoxydim, averaged over plant-back dates. All herbicides provided little residual control of grass weeds, mainly broadleaf signalgrass and barnyardgrass. These findings indicate the need to continue allowing a plant-back interval to rice following a graminicide application, unless quizalofop-resistant rice is to be planted. The plant-back interval will vary by graminicide and the amount of moisture received following the application.

Spring wheat response to simulated glyphosate drift

The nearly ubiquitous use of glyphosate‐resistant soybean, corn, sugar beet, and/or canola cultivars in the Northern Great Plains can result in off‐target movement to sensitive crops like spring wheat. The objective of this study was to measure the effect of simulated glyphosate drift at a concentration of 0.07 lb acid equivalent/acre on spring wheat crop injury, crop residue, and yield. Earn 0.5 CEUs in Integrated Pest Management by reading this article and taking the quiz at www.certifiedcropadviser.org/education/classroom/classes/554.

Regional pest suppression associated with widespread Bt maize adoption benefits vegetable growers

Transgenic crops containing the bacterium Bacillus thuringiensis (Bt) genes reduce pests and insecticide usage, promote biocontrol services, and economically benefit growers. Area-wide Bt adoption suppresses pests regionally, with declines expanding beyond the planted Bt crops into other non-Bt crop fields. However, the offsite benefits to growers of other crops from such regional suppression remain uncertain. With data spanning 1976-2016, we demonstrate that vegetable growers benefit via decreased crop damage and insecticide applications in relation to pest suppression in the Mid-Atlantic United States. We provide evidence for the regional suppression of Ostrinia nubilalis (Hübner), European corn borer, and Helicoverpa zea (Boddie), corn earworm, populations in association with widespread Bt maize adoption (1996-2016) and decreased economic levels for injury in vegetable crops [peppers (Capsicum annuum L.), green beans (Phaseolus vulgaris L.), and sweet corn (Zea mays L., convar. saccharata)] compared with the pre-Bt period (1976-1995). Moth populations of both species significantly declined in association with widespread Bt maize (field corn) adoption, even as increased temperatures buffered the population reduction. We show marked decreases in the number of recommended insecticidal applications, insecticides applied, and O. nubilalis damage in vegetable crops in association with widespread Bt maize adoption. These offsite benefits to vegetable growers in the agricultural landscape have not been previously documented, and the positive impacts identified here expand on the reported ecological effects of Bt adoption. Our results also underscore the need to account for offsite economic benefits of pest suppression, in addition to the direct economic benefits of Bt crops.

Effectiveness of mechanical weed control on Italian flint varieties of maize

AbstractWeed control is one of the most important practices for a satisfying crop performance. In organic farming, weeds are mainly controlled by using mechanical methods, which may result in incomplete crop selectivity. Maize is one of the crops for which mechanical weed control is commonly applied. To assess weed control efficacy and the possible crop injuries caused by mechanical interventions (harrowing, hoeing and ridging), a field experiment was carried out in 2013–2014 on traditional flint Italian varieties of maize (Marano, Ottofile, Pignoletto, Nostrano and the hybrid Maranello) suited for organic food production. The study included the following treatments: weed control with a spring tine harrow + hoeing and ridging (STH), manual weed removal all season long (MWR), spring tine harrowing + manual weed removal (STH + MWR) and an untreated check (CHK). In the 2 years, the experiment was carried out in two similar fields in which 60 plots (6 × 10 m) were arranged in a RCBD with three replications. Weed control efficacy was assessed by determining weed density, weed species composition and weed cover after each mechanical intervention in the STH and CHK plots. Weed diversity indices were also calculated at the final assessment. The possible crop injuries caused by mechanical means were assessed by determining maize plant height, number of leaves, and plant density after each mechanical intervention. At maturity, maize yield and other yield-related traits (1000-seed weight, hectolitre weight, and grain moisture) were determined. The results showed that the mechanical treatments lowered the weed infestation, without changing weed species dominance and slightly lowering species richness; even though they were not able to completely control the weeds. In both years, the final weed density in STH plots was of about 50 plants m−2. Better weed control was obtained when weeds were at early growth stages and with a repeated number of harrowing. Mechanical weeding did not cause significant injury in terms of plant height nor density; however, for Marano and Maranello, a delay in the crop cycle was observed as shown by the lower number of leaves in STH compared with MWR. Yield ranged from 0.3 t ha−1 for Marano CHK to 10.4 t ha−1 for the hybrid Maranello in MWR + STH. Yield and yield-related traits were not affected by mechanical weeding.

Assessment of New Herbicide Programs for Cowpea Production

Cowpea is a major specialty crop in the southern US. In recent years, no new herbicide programs have been evaluated for cowpea despite additional herbicide registrations. Studies were conducted from 2014 to 2016 at Fayetteville and Kibler, Arkansas to assess new herbicide programs for cowpea production. The herbicide programs included: three commercial standard programs; fomesafen (PPL, 0.21 kgha−1)-, flumioxazin (PPL, 0.21 kgha−1)-, and halosulfuron (PPL, 0.054 kgha−1)-based programs with or withoutS-metolachlor (1.12 kgha−1) fb imazethapyr (0.07 kgha−1); and two sets of sulfentrazone (PPL/PRE)-based programs applied alone (0.21 kgha−1) or as a pre-mixture with carfentrazone (0.11 kgha−1+0.01 kgha−1) with or withoutS-metolachlor (1.12 kgha−1). The sulfentrazone-based programs included POST applications of imazethapyr fb sethoxydim (0.32 kgha−1) or fluthiacet-methyl (0.0067 kgha−1) and sethoxydim as necessary. In 2014 and 2015, crop stand loss was minimal and crop injury was generally low (<20%). Weed control from sulfentrazone- and flumioxazin-based programs was excellent (>90%). In 2016, with heavy rainfall around planting time, sulfentrazone-containing programs reduced cowpea yield 45% to 60%. Flumioxazin-based programs caused >85% injury at Kibler early-season, which lasted until harvest. Heavy rainfall also reduced efficacy of residual herbicides. In general, the sulfentrazone- and flumioxazin-based treatments consistently yielded similar to the weed-free controls. The majority of the programs had <60% weed control in Fayetteville early in the season. POST herbicides improved weed control to >90% in most treatments. Palmer amaranth and annual grass control was generally better in Kibler, with >80% control at harvest. Sulfentrazone is registered for cowpea and is effective on Palmer amaranth, but growers need to be careful about where and when to use it. Flumioxazin should be considered for registration in cowpea once its use pattern and location-specific recommendations are well defined.

Insecticide Seed Treatments Reduced Crop Injury from Flumioxazin, Chlorsulfuron, Saflufenacil, Pyroxasulfone, and Flumioxazin + Pyroxasulfone + Chlorimuron in Soybean

With increased instances of weed resistance to applications of postemergence herbicides, the use of soil-applied herbicides that offer residual activity is becoming popular. Unfortunately, under some conditions, the use of residual herbicides can result in unintentional injury to crops. However, there are a number of ways to reduce these risks, including the use of in-crop herbicide safeners. Based on previous research conducted on rice, the potential may exist for crop injury from certain soil-applied herbicides to be reduced (safened) in seeds treated with insecticides. Field trials were conducted in Marianna, Arkansas, in 2015 and 2016, and near Colt, Arkansas, in 2016, to explore this possibility in soybean. Soybean seeds were treated with the insecticide thiamethoxam and subsequently the herbicides metribuzin, saflufenacil, pyroxasulfone, sulfentrazone, chlorimuron, flumioxazin, flumioxazin + pyroxasulfone + chlorimuron, mesotrione, and chlorsulfuron were applied immediately after planting. Of the nine herbicides evaluated, the insecticide reduced crop injury for flumioxazin, chlorsulfuron, saflufenacil, pyroxasulfone, and flumioxazin + pyroxasulfone + chlorimuron. The highest degree of injury reduction was seen 1 week after emergence (WAE) at Marianna, where injury from flumioxazin + pyroxasulfone + chlorimuron was reduced from 15% to 5%. Based on the results from this study, the insecticide seed treatment thiamethoxam may have the potential to safen soybean to applications of some soil-applied herbicides.

Weed control effect of unmanned aerial vehicle (UAV) application in wheat field

Wheat is a major food source throughout the world.  However, biological factors like pests and weeds can lead to lower crop yield. Most crop protection nowadays involves pesticide and herbicides application. This is commonly conducted with knapsack in China, which is inefficient and high labor intensive. Unmanned aerial vehicle (UAV) are an aerial spraying technology recently-developed. Using UAV application is more flexible and standardized, the spraying efficiency is 60 times more than knapsack sprayer. However, weed management using UAV is still a challenge. Low spray volume and droplet density with less penetration may affect weed control efficacy. High droplet concentration may induce crop injury. This study focused on discovering crop safety and weed control efficacy of UAV in wheat fields. Different herbicides, rates and spray volume were tested for pre-emergence (PRE) and post-emergence (POST). The results show that no crop injury was induced for PRE. While 10%-20% injury on wheat was found for POST. All herbicides treatments showed significant effects on weed management compared to untreated control. However, the efficacy was not stable between years and fields. Weed management for PRE can reach 98%-100% when the soil is humid, smooth and with no straw coverage when using diflufenican + isoproturon (120 + 1200 g ai ha -1 ). For POST application via UAV, weed injury ranged from 10% injury to 70%, in which isoproturon + clodinafop-propargyl + mesosulfuron (120 + 7.5 + 0.9 g ai ha -1 ) injured weed the most in 2018 (reached 70%). Knapsack sprayer showed relatively better weed control efficacy in many cases for POST applications. Weeds showed certain degree of resistance. In general, PRE application with UAV showed better potential, but herbicide spraying needs to be combined with field management to achieve better weed management efficacy. Keywords: unmanned aerial vehicle (UAV), herbicide application, weed management, wheat DOI:  10.33440/j.ijpaa.20190202.45.  Citation: Chen Y, Qi H L, Li G Z, Lan Y B.  Weed control effect of unmanned aerial vehicle (UAV) application in wheat field.  Int J Precis Agric Aviat, 2019; 2(2): 25–31.

Effect of Thiamethoxam on Injurious Herbicides in Rice

Increases in the number of herbicide-resistant weeds in rice has led to the need for new herbicides and modes of action to control these troublesome weeds. Previous research has indicated that insecticide seed treatments can safen rice from herbicide drift. In 2014 and 2015, two field experiments were conducted at the Rice Research and Extension Center (RREC) near Stuttgart, Arkansas, and at the University of Arkansas Pine Bluff (UAPB) farm near Lonoke, Arkansas, to determine if insecticide seed treatments could prevent unacceptable levels of herbicide injury from preemergence (PRE)- and postemergence (POST)-applied herbicides that are typically injurious to rice. Both studies were planted with the imidazolinone-resistant, inbred variety CL151. ‘Treated’ plots contained the insecticide seed treatment thiamethoxam while ‘nontreated’ plots contained no insecticide seed treatment. Seven herbicides were evaluated in the PRE experiment: clomazone, pethoxamid, fluridone, S-metolachlor, thiobencarb, clethodim, and quizalofop to determine crop injury, stand counts, groundcover, and rough rice yield with and without an insecticide seed treatment compared to plots with no herbicide treatments. Overall, an insecticide seed treatment provided increased rice stands and less herbicide injury than the ‘nontreated’ seed while increasing yield by 500 kg ha-1. Of the herbicides tested, clomazone-, thiobencarb-, clethodim-, and quizalofop-treated plots had equivalent yields to the no-herbicide plots. The POST experiment evaluated propanil, saflufenacil, carfentrazone, and acifluorfen in various tank-mixtures and application timings. Similar to the PRE experiment, plants from treated seed had less herbicide injury 1 and 5 weeks after treatment (WAT) along with an increased canopy height and groundcover percentage. Plants having treated seed also had increased yields when used with some herbicide programs. Overall, the use of an insecticide seed treatment can give the added benefit of less injury from injurious herbicides as well as increased groundcover.