Fall Applications Research Articles

Vernalization affects absorption and translocation of clopyralid and aminopyralid in rush skeletonweed (Chondrilla juncea)

AbstractThe developmental status of perennial weeds such as rush skeletonweed (Chondrilla juncea L.) can influence herbicide absorption and translocation. Differential efficacy between fall and spring applications suggests vernalization impacts herbicide absorption and translocation in other perennial asters. Clopyralid and aminopyralid absorption and translocation were quantified in nonvernalized and vernalized plants following application of 14C-labeled herbicides 2, 4, 8, 24, and 72 h after treatment. Less 14C clopyralid was absorbed, and at a slower rate, in vernalized plants. Movement out of the treated leaf was slower, with 14C clopyralid translocating more rapidly than 14C aminopyralid. More 14C moved to the roots in nonvernalized plants compared with vernalized plants, regardless of herbicide. Increased translocation to belowground survival structures is needed for effective control of C. juncea.

Efficiency of fall versus spring applied urea‐based fertilizers treated with urease and nitrification inhibitors I. Ammonia volatilization and mitigation by NBPT

AbstractMid‐ or late‐fall N fertilization is usually recommended on the Canadian prairies to reduce N losses from fall‐applied N. Yet, N fertilizers are less efficient when applied in mid‐ or late fall than in spring on crop yield. Ammonia volatilization from N fertilizers is one of the reasons for the low N use efficiency. We conducted a 2‐yr study to quantify and contrast the efficacy of a urease inhibitor, N‐(n‐butyl) thiophosphoric triamide (NBPT), with and without a nitrification inhibitor, 3,4‐ dimethylpyrazole phosphate (NI), in reducing NH3 volatilization from fall‐ and spring‐applied urea‐based fertilizers in two contrasting soils. Treatments consisted of surface‐applied urea and urea–NH4NO3 (UAN) with and without NBPT or NBPT + NI (double inhibitor, DI). We measured NH3 volatilization with acid‐charged disks during 21 (fall) or 28 (spring) d. Total NH3 volatilization (percentage of applied N) from untreated urea and UAN across sites ranged from 7 to 22% with fall application and from 3 to 29% with spring application. Addition of NBPT only or DI to urea or UAN reduced NH3 volatilization by 61 to 74% in the fall and 4 to 69% in the spring across site‐years. We found that the reduction of NH3 volatilization by NBPT was significantly greater in the fall (65%) than in the spring (40%) and with urea (61%) than with UAN (43%). Our study showed that (a) significant NH3 volatilization could occur from surface‐applied urea‐based fertilizers even under late‐fall temperatures and (b) NBPT reduced NH3 volatilization from fall‐ as well as spring‐applied urea‐based fertilizers. Therefore, farmers are encouraged to treat their urea‐based fertilizers with NBPT when considering surface application.

Pollinator exposure to systemic insecticides and fungicides applied in the previous fall and pre-bloom period in apple orchards

Pollinators provide a crucial ecosystem service by pollinating commercially cultivated crops, but they are frequently exposed to various agricultural chemicals used for pest management. In this study, we assessed the potential exposure of pollinators to various systemic insecticides and a fungicide used in apple orchards. Residue levels were determined for the whole flower as well as pollen and nectar separately for pre-bloom applications of acetamiprid, imidacloprid, sulfoxaflor, thiacloprid, thiamethoxam, and myclobutanil. Very low pesticide residue levels (2–70 parts per billion, ppb) were found in the whole flower, pollen and nectar samples compared with pesticide concentrations of 60–200 parts per million (ppm) in applied foliarly only 5 days earlier. Insecticide residues from nectar and pollen samples were below the USA EPA classification of No Observable Effect Limit (NOEL) for acute toxicity to honey bees, suggesting that a single foraging visit to flowers may not cause toxicity to bees. However, cumulative acute exposure from multiple flower visits could potentially be harmful to bees, and needs to be studied further. We also examined apple flowers for residues of several systemic insecticides that were applied for brown marmorated stink bug control late in the fall of the previous season. None of the fall sprays that contained premixed insecticide active ingredients (viz., thiamethoxam + lambda-cyhalothrin, and imidacloprid + beta-cyfluthrin), including multiple applications of individual active ingredients (viz., dinotefuran, clothianidin, and sulfoxaflor), persisted until the following spring. Based on these findings, fall applications of insecticides used for controlling invasive pests such as the brown marmorated stink bug (Halyomorpha halys) and the spotted lanternfly (Lycorma delicatula) could be considered safe to pollinator species foraging in apple orchards during the spring bloom the following season.

Ethylene regulatory treatment effects on annual bluegrass survival of freezing temperature and ice cover

AbstractAnnual bluegrass (Poa annua L.) is a golf course turfgrass species, often in a mixed stand with creeping bentgrass (Agrostis stolonifera). Annual bluegrass is more susceptible to ice cover damage than creeping bentgrass. The objective was to determine how fall applications of promotive (1‐aminocyclopropane‐1‐carboxylic acid [ACC] or ethephon) or inhibitory (ReTain or aminoethoxyvinylglycine [AVG]) substances to ethylene production influence turfgrass quality, normalized difference vegetation index (NDVI), ethylene production, canopy respiration rates, and recovery from ice encasement under field and/or growth chamber conditions. The field was monitored for fall quality and acclimation parameters, and the growth chamber study was used for ice treatments and recovery of annual bluegrass only, the winter‐sensitive species. Under field conditions, ethephon application increased ethylene production and whole plant respiration of both annual bluegrass and creeping bentgrass, and decreased turf quality and NDVI when compared to controls. Ethylene inhibition treatments did not affect turf quality, respiration or NDVI when compared to the untreated controls, but AVG treated annual bluegrass had greater ethylene production than the untreated controls after 35 and 42 d of treatment. In the growth chamber experiment, ethephon decreased annual bluegrass regrowth, while ReTain improved annual bluegrass regrowth after 40 or 80 d of exposure to −4°C with or without ice cover. Treatments that inhibit turfgrass canopy ethylene production may be viable methods to improve annual bluegrass winter survival of ice encasement conditions, and may have no negative effects on creeping bentgrass. Testing these treatments for ice survival under field conditions is still needed.

Maize yields and carbon pools in response to poultry litter, rock phosphate and P-solubilizing microorganisms

ABSTRACT: The acid release of phosphates from rock phosphates (RP) and the retention of ammonium by inorganic phosphates have been studied separately in composting; however, there is a gap in the knowledge of combined application of RP with organic residues and microorganisms. The objectives were to evaluate the combined application of fresh poultry litter (PL) with RP and P-solubilizing microorganisms (M) on soil organic matter pools, microbial biomass C (MB-C) and on whole-plant silage maize and grain yields. Two field experiments tested the effects of timing of applications of PL (8 Mg ha–1), RP (4 Mg ha–1) and microorganisms on soil organic matter pools, nutritional aspects and productive components of maize crop whole-plant silage. A second experiment evaluated the effects of RP doses (0, 3, 6 and 9 Mg ha–1) with a fixed dose of PL (8 Mg ha–1) on maize grains. Application of PL+RP decreased soil organic C, while RP alone increased the humin fraction C compared to the control. The MB-C in soil with PL and PL+RP+M increased in comparison to the control and the RP. The application of PL, based on an average of fall and spring, increased leaves + stem dry matter, while in the fall on its own, the highest cob yield was observed in the combination of PL+RP, showing synergistic effects. The best ratio of poultry litter to rock phosphate combination is 2:1 in the anticipated fall application on the maize silage crop or immediate application on the maize grain crops.

Adding a late fall application of Proxy (ethephon) before two traditional spring applications improves seedhead control of annual bluegrass

AbstractAnnual bluegrass (ABG) (Poa annua L.) is a prolific seed producer in the spring on golf courses that in turn decreases aesthetic quality and trueness of ball roll on cool‐season putting greens. Proxy (ethephon) applied twice in the spring after green‐up is the current industry standard after the loss of Embark (mefluidide) from the turf and ornamental market. However, plant growth regulators including Proxy have been used for years to help suppress ABG seedheads with inconsistent success. The primary objective of this study was to determine if ABG seedhead suppression is improved by adding a late fall application of Proxy to the two traditional spring applications of plant growth regulators at nine locations with diverse environments. A second objective was to determine the importance of including Primo Maxx (trinexapac‐ethyl) in fall and spring applications. Adding a late fall application of Proxy prior to the two spring applications (F+S+S) improved control of ABG seedheads over the traditional two spring applications (S+S), but the magnitude of improvement varied among locations. When treatments were applied F+S+S, the industry standard tank mixture of Proxy + Primo Maxx provided consistent ABG seedhead control and turf quality, similar to Proxy + Fiata (phosphonate + proprietary pigment) and equal to or better than Proxy alone.

Assessing the effects of manure application rate and timing on nitrous oxide emissions from managed grasslands under contrasting climate in Canada.

It is uncertain whether process-based models are currently capable of simulating the complex soil, plant, climate, manure management interactions that influence soil nitrous oxide (N2O) emissions from perennial cropping systems. The objectives of this study were (1) to calibrate and evaluate the DeNitrification DeComposition (DNDC) model using multi-year datasets of measured nitrous oxide (N2O) fluxes, soil moisture, soil inorganic nitrogen, biomass and soil temperature from managed grasslands applied with manure slurry in contrasting climates of Canada, and (2) to simulate the impact of different manure management practices on N2O emissions including slurry application i) rates (for both single vs. split); and ii) timing (e.g., early vs. late spring). DNDC showed "fair" to "excellent" performance in simulating biomass (4.7%≤normalized root mean square error (NRMSE)≤29.8%; -9.5%≤normalized average relative error (NARE)≤16.1%) and "good" performance in simulating soil temperature (13.2%≤NRMSE≤18.1%; -0.7%≤NARE≤10.8%) across all treatments and sites. However, the model only showed "acceptable" performances in estimating soil water and inorganic N contents which was partially attributed to the limitation of a cascade water sub-model and inaccuracies in simulating root development/uptake. Although, the DNDC model only demonstrated "fair" performance in simulating daily N2O fluxes, it generally captured the impact of the timing and rate of slurry application and soil texture (loam vs. sandy loam) on total N2O emissions. The DNDC model simulated N2O emissions from spring better than split manure application (fall and spring) at the Manitoba site partially due to the overestimation of available substrates for microbial denitrification from fall application during the wet spring periods. Although DNDC performed adequately for simulating most of the manure management impacts considered in this study we recommend improvements in the simulation of soil freeze-thaw cycles, manure decomposition dynamics, soil water storage, rainfall canopy interception, and microbial denitrification and nitrification activities in grasslands.

Efficacy of Emamectin Benzoate Trunk Injection Against the Asian Long-Horned Beetle [Anoplophora glabripennis (Coleoptera: Cerambycidae)

The efficacy of tree injected with emamectin benzoate (EB) against the Asian long-horned beetle (ALB) was tested in a heavily infested willow forest in Beijing, China. In a 1.7-ha plot, 240 out of 310 trees were treated with two EB formulations at various rates. After fall application, the larval population decreased by 89% in the following spring and by >99% during the second year detected by monitoring new frass emission from marked holes. Consequently, the number of exit holes of emerging adults decreased to 0 in the second year. Re-infestation occurred in the third year after application. This high efficacy and lasting activity might be contributed to: a) a favorable translocation of EB in trees when injected into the sapwood; b) the high intrinsic activity against ALB larvae with LC50 of 20-30 ppb; and c) a reduced lifespan of ALB adults by over 60% when feeding on twigs of EB-treated trees. On untreated control trees, the larval population decreased during the first winter. In the second year after application, the larval population was wiped out during winter and a re-infestation started from border trees by adults flying in from outside the trial plot. This pattern indicates an eradication of the ALB population in the 1.7-ha plot can be expected 2 yr after EB treatment. The benefit of treating with EB on the surrounding population was observed in both the untreated trees and imidacloprid-treated trees, suggesting that treatment of EB benefits both the treated trees and the surrounding trees in the area.

Effect of phosphonate application timing and -strategy on phosphite fruit and root residues of avocado

In South Africa, phosphonate fungicides are widely used in avocado in a preventative management strategy against Phytophthora root rot (PRR), caused by Phytophthora cinnamomi. Trunk injections, curative and preventative (0.3-g a.i./m2 and 0.5-g a.i./m2 of canopy area respectively), done as two annual applications (fall and summer) are widely used to manage PRR. However, these applications have become problematic due to frequent exceedances of the European Union (EU) maximum residue level (MRL) of phosphonic acid (synonym phosphite) in fruit. Our study showed that fruit residues can be reduced by the use of specific phosphonate application methods (foliar versus trunk injections), and application timing (fall versus summer). In the 2016/17 season, trunk injections applied only in fall (1-g a.i./m2 of canopy area), or applied at the registered curative split dosage in fall (0.5-g a.i./m2) and summer (0.5-g a.i./m2), resulted in exceedances or near exceedances of the MRL for some replicates among treatments. In comparison, 3% a.i. ammonium- or potassium phosphonate foliar sprays applied only in fall had fruit residues that were consistently well below the EU MRL. The 2% a.i. foliar sprays, specifically the ammonium phosphonate formulation, done as a split application in fall (1.5% a.i) and summer (0.5% a.i.) sometimes resulted in significantly higher fruit residues than fall only applications. Some replicates of this treatment nearly exceeded the MRL. In the 2017/18 season, 2% and 2.5% a.i. foliar sprays (ammonium- and potassium phosphonate) applied only in fall yielded fruit residues that were consistently below the MRL. In contrast, the registered split dosage trunk injections (curative and preventative) sometimes resulted in exceedances of the MRL or near exceedances. In both seasons, foliar sprays at the start of the season yielded phosphite concentrations in roots that did not differ significantly from trunk injections, but towards the end of the season, concentrations were sometimes significantly lower. Foliar sprays applied only in fall have the potential to reduce fruit residues.

Properties of Nanosilica-Modified Concrete Cast and Cured under Cyclic Freezing/Low Temperatures

Abstract Cold weather concreting is one of the most challenging problems facing concrete placement in many regions. For example, in Canada, low temperatures limit the construction season to a few months, usually between May and September. The incorporation of nanosilica in concrete, which has vigorous reactivity because of its ultrafine surface area, may enhance the hydration process and properties of concrete cast at low temperatures; however, this has not been substantiated. Therefore, this study focused on developing nanomodified concrete mixtures that were mixed, placed, and cured at cyclic temperatures (−5°C and 5°C), targeting applications in early fall and late spring periods in North America. The study followed the design of experiments modeling approach to test 15 concrete mixtures based on the response surface method. Three parameters were considered in the model: incorporation of fly ash (up to 25 %) and nanosilica (up to 4 %) as well as a combination of two types of antifreeze admixtures (calcium nitrate and nitrite). The mixtures were assessed based on setting time (placement), 3- and 28-day compressive strengths (hardened properties) and absorption (infiltration of fluids). Moreover, mercury intrusion porosimetry, thermal analysis, and scanning electron microscopy were conducted to characterize the microstructural features. The results showed that nanosilica, even with the inclusion of fly ash, significantly enhanced the overall performance and development of the microstructure of concrete mixed, cast, and cured at cyclic freezing/low temperatures. Thus, nanomodified concrete has promising potential for extending the construction season during early fall and late spring periods in cold regions.

Nitrogen‐15 Evaluation of Fall‐Applied Anhydrous Ammonia: I. Efficiency of Nitrogen Uptake by Corn

Fall application of anhydrous ammonia (NH3) is a common practice for corn (Zea mays L.) production in the midwestern United States, but evaluations to date have relied entirely on yield comparisons that provide no means of distinguishing fertilizer from soil N uptake. To quantify fertilizer N uptake efficiency (FNUE) when using this practice, field trials using 15NH3 were conducted between 2016 and 2018 at four sites in a corn–soybean (Glycine max L. Merr.) rotation and at two sites under continuous corn. At each site, 224 kg N ha−1 was applied with and without the use of nitrapyrin (NP) to inhibit nitrification. Relative to grain yields without fertilizer N, response to fall N fertilization occurred at four of the six sites studied, averaging 53% (4.0 Mg ha−1) in two growing seasons with below‐normal rainfall. The use of NP was beneficial at only one site for increasing total N uptake, but resulted in a decrease at another, along with a significant reduction in grain yield. Isotopic estimates of FNUE (i.e., F15NUE) ranged from 12 to 34% (21% on average) for grain and from 16 to 42% (28% on average) for total aboveground biomass, and N derived from fertilizer ranged from 20 to 46% (32% on average). Both isotopic parameters were highest for the site lowest in native N availability, demonstrating the potential of site‐specific N management to improve fall NH3 fertilization by accounting for soil N mineralization.

Total vegetation control: a comprehensive summary of herbicides, application timings, and resistance management options

AbstractTotal vegetation control (TVC) is an essential management practice to eliminate all vegetation for the purpose of protecting infrastructure, people, or natural resources on sites where vegetation poses major fire, visibility, and infrastructure risks. TVC is implemented on sites such as railroads, power substations, airports, roadsides, and oil and gas facilities. Current research has identified that tank-mixing two effective mechanisms of action is a superior resistance management strategy compared to rotating mechanisms of action; however, effective tank mixes for TVC have not been thoroughly evaluated. A field experiment was conducted from 2013 to 2014 at five sites in Colorado to compare 32 treatment combinations to two industry standards for TVC. Research objectives were (1) to identify herbicide tank-mix combinations for TVC with multiple effective mechanisms of action for resistance management, (2) to evaluate lower use rate alternatives to minimize nontarget impacts, and (3) to determine the efficacy of fall versus spring application timings. Seven treatments were identified as top-ranking treatments, averaging 96% bare-ground (BG) across five sites and two application timings. Four out of the seven top-ranked treatments included aminocyclopyrachlor, chlorsulfuron, and indaziflam. The industry standard diuron plus imazapyr was in the top ranking, whereas the other industry standard bromacil plus diuron performed inconsistently across sites. Probability modeling was used to predict the probability of achieving 97% or 100% BG with various treatment combinations. The combination of aminocyclopyrachlor, chlorsulfuron, indaziflam, and imazapyr had the highest predicted BG probability, with 88% predicted probability of achieving 100% BG, compared to 67% and 52% predicted probabilities for the industry standards diuron plus imazapyr and bromacil plus diuron, respectively. In three of the five sites, fall applications outperformed the same treatments applied in the spring. Several top-ranking treatments represent newer, lower use rate herbicide combinations that provide multiple mechanisms of action to manage herbicide-resistant weeds and minimize nontarget impacts.

Nitrate Loss in Subsurface Drainage from a Corn-Soybean Rotation as Affected by Nitrogen Rate and Nitrapyrin.

Successful N management practices for the US Midwest must optimize crop production and minimize NO-N losses from subsurface tile drainage. The objective of this study was to measure the effects of N rate, N application timing, and nitrapyrin [2-chloro-6-(trichlormethyl) pyridine] on corn ( L.) production and NO-N in tile drainage water in a corn-soybean [ (L.) Merr.] rotation in Minnesota. Anhydrous ammonia was applied at 90 and 179 kg ha with nitrapyrin in the fall and at 134 kg ha with and without nitrapyrin in fall and spring. However, drainage water monitoring was only conducted on fall treatments. Over a 5-yr period, 71% of drainage occurred in April through June and <1% occurred from November through March due to frozen soil. Averaged across N treatments and crops, annual drainage ranged from 69 to 380 mm among years. From 2001 through 2003, NO-N concentrations averaged 13.8, 15.6, and 20.0 mg L in corn and 7.3, 8.2, and 12.6 mg L in soybean when 90, 134, and 179 kg N ha was fall applied with nitrapyrin to corn, respectively. Corn grain yields were greater with spring-applied N at 134 kg ha (11.3 Mg ha) than with fall-applied N at 134 and 179 kg ha with nitrapyrin (10.5 and 10.8 Mg ha, respectively), and nitrapyrin did not affect corn production or water quality. Fall application of N is common on cold soils in Minnesota. These data showed that fall application required a greater rate of N to optimize yield than spring and that greater fall rate often increased NO-N concentration and load in tile drainage water.

Understanding the Fertilizer Management Impacts on Water and Nitrogen Dynamics for a Corn Silage Tile-Drained System in Canada.

Effective management of dairy manure is important to minimize N losses from cropping systems, maximize profitability, and enhance environmental sustainability. The objectives of this study were (i) to calibrate and validate the DeNitrification-DeComposition (DNDC) model using measurements of silage corn ( L.) biomass, N uptake, soil temperature, tile drain flow, NO leaching, NO emissions, and soil mineral N in eastern Canada, and (ii) to investigate the long-term impacts of manure management under climate variability. The treatments investigated included a zero-fertilizer control, inorganic fertilizer, and dairy manure amendments (raw and digested). The DNDC model overall demonstrated statistically "good" performance when simulating silage corn yield and N uptake based on normalized RMSE (nRMSE) < 10%, index of agreement () > 0.9, and Nash-Sutcliffe efficiency (NSE) > 0.5. In addition, DNDC, with its inclusion of a tile drainage mechanism, demonstrated "good" predictions for cumulative drainage (nRMSE < 20%, > 0.8, and NSE > 0.5). The model did, however, underestimate daily drainage flux during spring thaw for both organic and inorganic amendments. This was attributed to an underestimation of soil temperature and soil water under frequent soil freezing and thawing during the 2013-2014 overwinter period. Long-term simulations under climate variability indicated that spring applied manure resulted in less NO leaching and NO emissions than fall application when manure rates were managed based on crop N requirements. Overall, this study helped highlight the challenges in discerning the short-term climate interactions on fertilizer-induced N losses compared with the long-term dynamics under climate variability.

Application Timing Affects Tolerance of Zoysiagrass to Fluazifop‐P‐butyl and Safening Effect of Triclopyr

ABSTRACTAryloxyphenoxypropionate (AOPP) herbicides, such as fluazifop‐P‐butyl, can be used for postemergence control of grassy weeds in zoysiagrass (Zoysia spp.), although the turf might suffer transient injury. This injury can be reduced by tank mixing fluazifop‐P‐butyl with triclopyr, an herbicide that behaves as a safener for AOPP herbicides. To characterize seasonal variation in zoysiagrass injury caused by fluazifop‐P‐butyl and triclopyr applications, we conducted a 2‐yr study on three Zoysia spp. cultivars (‘Empire’, ‘Geo’, and ‘Zeon’) at Jay, FL, from August 2015 to April 2017, evaluating how injury and turf quality were affected after spring, summer, and fall applications. The level of injury and changes in turf quality were influenced by fluazifop‐P‐butyl application timing, but the most sensitive season varied with the cultivar. The seasons with the greatest injury were also the ones in which the safening activity of triclopyr was most effective. In addition, when triclopyr was applied with fluazifop‐P‐butyl, the quality of all evaluated cultivars recovered to the level of nontreated controls by 2 wk after treatment. Nonstructural carbohydrate content was not affected by herbicide applications, but there were major differences in glucose and starch content between above‐ and belowground tissue depending on cultivar and season. Overall, our study confirmed that tank mixing triclopyr can reduce fluazifop‐P‐butyl phytotoxicity in zoysiagrass, and in the case of relatively tolerant cultivars, it might allow the use of rates higher than the current labeled rate with little negative impact on turf quality while providing better control of both broadleaf and grassy weeds.

Efficacy of fall-applied residual herbicides on weedy rice control in rice (Oryza sativa L.)

AbstractField experiments were initiated near Colt, AR, in the fall of 2016 and continued through the summer of 2018 to evaluate rice tolerance and weedy (or red) rice control after fall-applied very-long-chain fatty acid (VLCFA)-inhibiting herbicides. A split-plot design was used for the experiment, with the whole-plot factor being winter condition (flooded or non-flooded) and the split-plot factors being herbicide and rate. Herbicide treatments included acetochlor, dimethenamid-P, pethoxamid, pyroxasulfone, andS-metolachlor applied at 1,050, 525, 420, 205, and 1,070 g ai ha−1and at 2,100, 1,050, 840, 410, and 2,140 g ha−1for low rates and high rates, respectively. Herbicides were applied in the fall, then ‘CL172’ rice was drill seeded in the spring of the following calendar year. Weedy rice control differed between years, but acetochlor and pyroxasulfone consistently provided the greatest levels of control across rates and flood conditions. Consequently, herbicides that best controlled weedy rice also caused the greatest injury to cultivated rice. Rice injury did not exceed 13% regardless of herbicide treatment at 3 wk after planting (WAP). However, the high rate of pyroxasulfone caused 20% rice injury at 5 WAP in 2018. Although it was expected that winter condition may affect residual activity of the VLCFA-inhibiting herbicides, herbicide selection and application rate both had much greater effects on rice injury and on weedy rice control. Based on these results, rice injury would be minimal or nonexistent after fall applications of the tested VLCFA inhibitors, and intermediate levels of weedy rice control may be achieved. The implementation of VLCFA-inhibiting herbicides in rice production systems would offer a novel herbicide site of action and offer a degree of selective control of weedy rice.

Integrated management strategies of Meloidogyne incognita and Pseudopyrenochaeta lycopersici on tomato using a Bacillus firmus-based product and two synthetic nematicides in two consecutive crop cycles in greenhouse

Because of the restrictions on chemical pesticide use and their negative effects on the environment, as well as on human and animal health, alternative strategies for plant pest and pathogen managements are highly desirable. The objective of this work was to evaluate the suitability of a commercial formulation of Bacillus firmus strain 1-1582, applied either alone or in combination with oxamyl or fosthiazate, to control the southern root-knot nematode Meloidogyne incognita and the fungal plant pathogen Pseudopyrenochaeta lycopersici under greenhouse conditions during two tomato crop cycles. Application of B. firmus suppressed nematode population levels during the second crop cycle and when the treatments were repeated on soil previously amended with organic matter. In contrast, fungal infection was reduced during both crop cycles regardless of the application of organic matter. The combinations of the bioformulation and chemicals induced the lowest Root Galling Index compared to all other treatments in both crop cycles. The suppression of nematode populations levels and infection rate of the fungus induced by B. firmus alone or in combination with the chemicals was more pronounced during the second tomato crop cycle than the first crop cycle, also because the temperatures during the second crop cycle were unfavorable to the nematode development. The greatest increase in tomato yield induced by the combined treatments was observed during the second crop cycle, and it was up 50% compared to the untreated control. The applications of the bionematocide and two chemicals used in this study did not result in dramatic suppression of nematode and fungal populations. However, the application of these products alone or in combination, supplemented by organic amendment increases the yield of tomato plants compared to that of the untreated control, although the plants were infected by the pest and the pathogen. These results indicate that early spring/early fall application of B. firmus is an effective biopesticide treatment for management of the southern root-knot nematode and P. lycopersici on tomato crops growing in the integrated pest management system of this experiment and in the environmental conditions of southern Italy.

Post petal fall applications of gibberellins improve fruit set on pear

Commercial pear production has become increasingly difficult over the last decade, with low fruit set being one of the main factors leading to poor yield of pear orchards. The use of gibberellins to increase fruit set has been widely reported, but in most of the cases these applications are made at full bloom or right after a spring frost has occurred. However, the increase in fruit set due to early applications of gibberellins such as at full bloom is often lost at June drop. Aim of this study was to assess dose and timing of different gibberellin applications made after petal fall to improve the final fruit set in pear orchards. Four experiments were conducted during four years (2010–2013) in mature pear orchards with ‘Conference’ as the scion cultivar. Fruit set and yield were increased when gibberellins were applied after petal fall, with a positive relationship with dose. Applications of GA4+7+BA tended to promote higher fruit set and yield than GA3, and in addition, they were less dependent to the moment of application. GA4+7+BA showed an additive effect when performing multiple applications. Return bloom was slightly affected when gibberellins were applied after petal fall. The strategy that showed a better behavior to increase fruit set was GA4+7+BA at 500 mL·ha−1 at H + 14, which coincides with the weeks of the natural fruit drop.

Evaluation of New Oomycota Fungicides for Management of Phytophthora Root Rot of Citrus in California.

Phytophthora root rot, caused by several species of Phytophthora, is an important disease of citrus in California and other growing regions. For chemical management, mefenoxam and potassium phosphite have been available for many years, and resistance in Phytophthora spp. has been reported for both compounds. We evaluated the efficacy of the new Oomycota fungicides ethaboxam, fluopicolide, mandipropamid, and oxathiapiprolin, each with a different mode of action, against Phytophthora root rot of citrus in field and greenhouse studies. Root balls of navel orange trees on 'Carrizo citrange' rootstock were inoculated with P. nicotianae at planting in the field in fall 2013. Applications with 11 fungicide treatments were made 5 weeks after planting, in spring and fall 2014, and in spring 2015. Feeder roots and adjacent soil were collected before or after application. All of the new fungicides significantly reduced root rot incidence and Phytophthora soil populations to very low levels as compared with the control starting after the first application. Mefenoxam was only effective when a high label rate was used in the fourth application. Selected treatments also increased tree canopy size, trunk diameter, and fruit yield as compared with the control. A rate comparison with the four new fungicides was initiated in summer 2016 in another field trial using navel orange trees inoculated with P. citrophthora. Minimum effective rates to reduce Phytophthora root rot incidence and pathogen soil populations were determined after one and two applications in fall 2016 and summer 2017, respectively. Greenhouse studies confirmed the efficacy of the new fungicides. Based in part on our studies, fluopicolide recently received a federal and oxathiapiprolin a full registration for use on citrus, and registrations for ethaboxam and mandipropamid have been requested. These new compounds will provide highly effective treatment options and resistance management strategies using rotation and mixture programs for the control of Phytophthora root rot of citrus.

Preplant and Residual Herbicide Application Timings for Weed Control in No-Till Soybean

AbstractTimely herbicide applications for no-till soybean can be challenging given the diverse communities of both winter and summer annual weeds that are often present. Research was conducted to compare various approaches for nonselective and preplant weed control for no-till soybean. Nonselective herbicide application timings of fall (with and without a residual herbicide) followed by early-spring (4 wk before planting), late-spring (1 to 2 wk before planting), or sequential-spring applications (4 wk before planting and at planting) were compared. Spring applications also included a residual herbicide. For consistent control of winter annual weeds, two herbicide applications were needed, either a fall application followed by a spring application or sequential-spring applications. When a fall herbicide application did not include a residual herbicide, greater winter annual weed control resulted from early- or sequential-spring treatments. However, application timings that effectively controlled winter annual weeds did not effectively control summer annual weeds that have a prolonged emergence period. Palmer amaranth and large crabgrass control at 4 wk after planting was better when the spring residual treatment (chlorimuron plus metribuzin) was applied 1 to 2 wk before planting or at planting, compared with 4 wk before planting. Results indicate that in order to optimize control, herbicide application programs in soybean should coincide with seasonal growth cycles of winter and summer annual weeds.