In-furrow Application Research Articles

Water Productivity and Economic Analysis of Saffron Under Different Irrigation Water Salinity, Manure Application Rates and Planting Methods

The objective of the present study was to identify whether the investment in the in-furrow planting and higher application of cattle manure under irrigation water salinity condition for saffron planting is cost-effective or not. A split–split plot arrangement was conducted in complete randomized block design with irrigation water salinity levels (0.45 (fresh water, S1), 1.0 (S2), 2.0 (S3) and 3.0 (S4) dS m−1) as the main plot, cattle manure levels (30 (F1) and 60 (F2) Mg ha−1) as the sub plot and planting method (basin (P1) and in-furrow (P2)) as the sub–sub plot in three replications. Results showed that we can reach more than two-fold higher water productivity (WP) in the in-furrow planting method compared with the basin planting method. Also, application of higher cattle manure (F2 treatment) resulted in higher WP in higher salinity levels (i.e., S3 and S4 treatments).According to the net income (NI),economic water use efficiency (EWUE) and benefit-cost ratio (BCR) analysis, the production benefit of the in-furrow planting method was higher than the production cost compared with the basin method even in the first year of the planting; whereas, it was not economically feasible for basin planting method. The highest NI for the in-furrow planting method was obtained 372 × 106 Rls ha−1 that was about 3.5 times of the highest NI (12 × 106 Rls ha−1) for the basin planting method in the second year. The economic analysis results led to conclude that planting the saffron corms in furrow was found to be suitable for producing high saffron yield and consequently NI and EWUE even under high irrigation salinity levels. Therefore, it is worthwhile to change conventional basin planting method into the in-furrow planting for saffron production to achieve the higher WP and economic efficiency.

Frequency and Abundance of Selected Early-Season Insect Pests of Cotton

Abstract The use of insecticides at planting has been a common crop management practice in cotton for several decades. Historically, U.S. cotton growers relied on in-furrow applications of insecticides, such as aldicarb, to control early-season insect pests. In-furrow applications have largely been replaced with insecticide-treated seed. Since 2012, more than 60% of the U.S. cotton crop is planted with seed treated with insecticide, primarily the neonicotinoids imidacloprid or thiamethoxam. Several insects or insect groups are included on the labels of these neonicotinoids for use as seed treatments. An increased understanding of the risks associated with economically injurious populations of insect pests is needed to optimize use of early-season insecticides and reduce over-reliance on them in cotton, especially when initial decisions for insect control before planting have subsequent influence on future pest abundance. Existing literature pertaining to these early-season cotton insect pests was examined to identify factors favoring their distribution and abundance and the importance of insect control tactics used at planting. The relative importance of some of these pests is dependent on the cotton-growing region and impacted by local production practices. Thrips (predominantly Frankliniella spp.) (Thysanoptera: Thripidae) are the most prevalent early-season insect group in cotton across the United States and the primary target of initial insect control. Other targeted insects include the black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), aphids (predominantly Aphis gossypii Glover) (Hemiptera: Aphididae), plant bugs (Hemiptera: Miridae), and wireworms (Coleoptera: Elateridae).

Potential Impact of Fluopyram on the Frequency of the D123E Mutation in Alternaria solani.

Succinate dehydrogenase-inhibiting (SDHI) fungicides have been widely applied in commercial potato (Solanum tuberosum L.) fields for the control of early blight, caused by Alternaria solani Sorauer. Five-point mutations on three AsSdh genes in A. solani have been identified as conferring resistance to SDHI fungicides. Recent work in our laboratory determined that A. solani isolates possessing the D123E mutation, or the substitution of aspartic acid for glutamic acid at position 123 in the AsSdhD gene, were collected at successively higher frequencies throughout a 3-year survey. In total, 118 A. solani isolates previously characterized as possessing the D123E mutation were evaluated in vitro for boscalid and fluopyram sensitivity. Over 80% of A. solani isolates with the D123E mutation evaluated were determined to be highly resistant to boscalid in vitro. However, effective concentration at which the fungal growth is inhibited by 50% values of isolates with the D123E mutation to fluopyram, ranging from 0.2 to 3 µg/ml, were sensitive and only slightly higher than those of baseline isolates to fluopyram, which ranged from 0.1 to 0.6 µg/ml. Five A. solani isolates with the D123E mutation were further evaluated in vivo for percent disease control obtained from boscalid and fluopyram compared with two wild-type isolates, three isolates possessing the F129L mutation, two isolates possessing the H134R mutation, two isolates possessing the H133R mutation, and one isolate with the H278R mutation. Relative area under the dose response curve values for boscalid and fluopyram were significantly lower for all five D123E-mutant isolates, demonstrating reduced disease control in vivo. In field trials, the frequency of A. solani isolates with the D123E mutation recovered from treatments receiving an in-furrow application of fluopyram ranged from 5 to 37%, which was significantly higher compared with treatments receiving foliar applications of standard protectants, in which the frequency of the D123E mutation in isolates ranged from 0 to 2.5%. Results suggest that A. solani isolates possessing the D123E mutation have a selective advantage under the application of fluopyram compared with SDHI-sensitive isolates, as well as isolates possessing other mutations conferring SDHI resistance. These data illustrate the importance of implementing fungicide resistance management strategies and cautions the use of fluopyram for in-furrow applications that target other pathogens of potato.

Rendimento do trigo (Triticum aestivum) em resposta a diferentes modos de inoculação com Azospirillum brasilense

The aim of this study was to evaluate the efficiency of inoculation techniques (seed treatment, in-furrow application and foliar spray) with Azospirillum brasilense on the agronomic performance and yield response of wheat. At the point of harvest, the number of seeds per ear, the thousand-seed mass, the hectoliter weight, the shoot dry matter, the N, P and K content of shoot dry matter, the grain N content, and the grain yield were evaluated. Regardless of the inoculation technique, at half the dose of N fertilizer combined with A. brasilense in liquid formulation, provided significantly superior results in agronomic performance compared to the treatment in which only the half the dose of N fertilizer was used. However, it is inferred that seed inoculation with A. brasilense associated with full nitrogen fertilization showed the highest increase in wheat development and grain yield.

English

The continuous development of soybean cultivars aiming at higher yields can result in a demand of N supply higher than the standard inoculation with Bradyrhizobium species. In this context, Azospirillum species, a nitrogen-fixing microorganism found in the rhizosphere of various plant species, may be studied as a way of providing soybean crop with the part of the N it needs. Employing a completely randomized design with four replicates, this study aimed to evaluate the agronomic performance of two different methods of standard inoculation of Bradyrhizobium spp. associated with the co-inoculation with Azospirillum spp. The tested treatments consisted of the absence of N fertilizer and inoculant, full N recommendation, two single inoculations with Bradyrhizobium spp. (in-furrow and seed-applied) combined with an in-furrow application of Azospirillum spp. At R2 growth stage, the nodule number, nodule dry weight, shoot dry biomass and shoot N content were the variables evaluated, whereas at R8 the grain yield, thousand seed weight and grain N content were assessed. The results demonstrated that the co-inoculation of Bradyrhizobium spp. with Azospirillum brasilense is beneficial to soybean yield, mainly using the in-furrow method of application for Bradyrhizobium spp., associated to the in-furrow co-inoculation with Azospirillum spp. Key words: Glycine max, inoculation, nitrogen content, yield.

Evaluation of an Omri-Approved Spinosad Insecticide for Control of Cabbage Root Maggot in Direct-Seeded Root Crops, 2016*

Feeding by cabbage root maggot (CRM) larvae causes stunting and collapse of plants, and tunneling damage on root crops renders them unsaleable. We evaluated the OMRI-approved spinosad product, Entrust SC, as an in-furrow drench treatment at the time of seedling emergence alone or with a follow-up application one week following. These treatments were compared to an untreated check and to a furrow drench with the industry standard, chlorpyrifos, at the time of seeding. The experiment was conducted May–Jun 2016 at the University of Massachusetts Research and Education Farm in Deerfield, MA in a field with soil classified as Hadley silt loam. Soil was amended with 50 lb/acre urea (46-0-0) (N-P-K) and 20 tons/acre manure-based compost to increase attractiveness of the site to CRM flies for oviposition. Soil was harrowed twice and a roller was used to make a fine seedbed. An RCB design with four replications of each of the three treatments and an untreated check was used, with plots measuring 10 ft of bed length with three rows per bed. Weeds were controlled by hand and, due to very high pressure, flea beetles were controlled using a single application of Wrangler at 1.5 fl oz/acre on 23 Jun. ‘Hakurei’ turnips (Johnny’s Selected Seeds, ME) were direct-seeded on 10 May using a Jang TP1 precision seeder equipped with a Y-12 seed roller and a 9/14 gear setting to achieve 0.5-inch in-row and 12-inch between-row spacing. A border of untreated turnip plants was seeded around the perimeter of the experiment and between plots within the bed, to attract CRM flies. At-plant treatments were applied on 11 May using a CO2 pressurized backpack sprayer delivering 200 gpa at 30 psi through one TeeJet TP8002E nozzle to soak the soil in the seeding band, simulating an in-furrow application. The Entrust treatments were applied on 27 May and 8 Jun in the same manner, over the sprouted turnip plants. The total number of plants per plot was recorded weekly, on 26 May, and 3, 8, 15, and 22 Jun, and provided a measure of plant stand. Marketable yield was assessed on 15 and 26 Jun by harvesting 10 plants per plot at random and making visual estimations of root damage using the following criteria: a turnip root with >25% of the surface covered with shallow tunnels or with more than one deep tunnel or other deformation was considered unmarketable. All data were analyzed with SAS 9.4 using PROC GLM and means were separated using Fisher’s LSD (α = 0.05).

Potential Interaction of Pre-emergence Herbicides and the Efficacy of Insecticide and Fungicide Seed Treatments in Cotton

The increasing presence of glyphosate-tolerant weeds has increased the use of pre-emergence herbicides in cotton, Gossypium hirsutum L., grown in Tennessee during the last 5 to 8 years. These herbicides could have negative effects on seedling growth and potentially affect thrips (Thysanoptera: Thripidae) management or seedling disease with at-planting insecticides or fungicides. Experiments were conducted in 2013 and 2014 to evaluate the potential interactions of pre-emergence herbicides on the efficacy of insecticide or fungicide seed treatments in cotton. Nontreated plots and plots treated with a thiamethoxam seed treatment generally exhibited higher number of thrips, more thrips injury, less vigor, delayed maturity, and lower yields compared to plots treated with an imidacloprid seed treatment or an in-furrow application of aldicarb. Similarly, fungicide seed treatments generally reduced the incidence of seedling disease (primarily Rhizoctonia), while improving seedling health and stand density. Negative effects of some pre-emergence herbicides on plant health also were observed. For example, combination treatments of fluometuron plus S-metolachlor or fluometuron plus fomesafen reduced plant vigor and seedling biomass and there was a tendency for higher thrips populations where pre-emergence herbicides were used. There were no substantial interactions between injury caused by pre-emergence herbicides and that caused by thrips or seedling disease suggesting that thrips, seedling disease, and herbicide injury acted independently and additively. Following herbicide label rates should reduce the risk of compounding the effects of thrips or seedling disease with herbicide injury.

Fungicide and Cultivar Effects on Sudden Death Syndrome and Yield of Soybean.

The effect of fungicides on severity of sudden death syndrome (SDS; caused by Fusarium virguliforme), plant establishment, and soybean yield was evaluated in 12 field experiments conducted in Illinois, Indiana, Iowa, Michigan, and Ontario in 2013 and 2014. Two soybean cultivars that differed in susceptibility to SDS were planted in fields with a history of SDS or with artificial augmentation of F. virguliforme. Efficacy of seed, in-furrow, and foliar-applied fungicides was assessed. SDS levels varied across locations and years. Fluopyram applied on the seed or in-furrow reduced foliar disease index maximum up to 95% in 5 of the 12 experiments. In three experiments with significant (P < 0.10) treatment effect, fluopyram seed treatment improved yields up to 11% compared with the base seed treatment comprising prothioconazole + penflufen + metalaxyl and clothianidin + Bacillus firmus. Meta-analysis also indicated that the fluopyram seed treatment and in-furrow application were effective at reducing SDS and increasing yield relative to the control; however, the baseline disease influenced the yield and disease response to fungicide treatments. Treatment effect was not significant when disease pressure was low. The concentration of F. virguliforme DNA in soybean roots, measured by a specific real-time quantitative polymerase chain reaction assay, was not different among fungicide treatments in 9 of 10 experiments. Moderately resistant cultivars had less disease than susceptible cultivars, indicating that resistant cultivars in combination with fluopyram seed treatment or in-furrow application could provide effective management of SDS.

Seed Treatment with Ethanol Extract of Serratia marcescens is Compatible with Trichoderma Isolates for Control of Damping-off of Cucumber Caused by Pythium ultimum.

Environmentally friendly control measures for soilborne plant pathogens are needed that are effective in different soils when applied alone or as components of an integrated disease control strategy. An ethanol extract of Serratia marcescens N4-5, when applied as a cucumber seed treatment, effectively suppressed damping-off caused by Pythium ultimum in potting mix and in a sandy loam soil. Plant stand associated with this treatment was similar to that of seed treated with the chemical pesticide Thiram in the sandy loam soil. The N4-5 ethanol extract did not consistently provide significant disease control in a loam soil. The N4-5 ethanol extract was compatible with two Trichoderma isolates, not affecting in vitro or in situ colonization of cucumber by these biological control fungi. Control of damping-off of cucumber was never diminished when this ethanol extract was applied as a seed treatment in combination with in-furrow application of the Trichoderma isolates, and disease control was improved in certain instances with these combinations in the loam soil. Data presented here indicate that the N4-5 ethanol extract is compatible with certain beneficial fungi, suggesting that this extract can be used as a component of integrated disease control strategies featuring biological control fungi.

Effects on Soybean of Prophylactic In-furrow Application of Insecticide and Fertilizer in Minnesota and Ohio

Use of crop inputs, including prophylactic application of insecticides, has increased in soybean production. A liquid fertilizer-ready formulation of the insecticide bifenthrin was recently labeled for in-furrow use with a starter fertilizer on soybean. An experiment was conducted at six sites (three in Minnesota and three in Ohio) in 2013 and two sites (Minnesota) in 2014 to evaluate effects on soybean of prophylactic in-furrow applications of a liquid fertilizer-ready insecticide (bifenthrin) and a 2-6-16 (N-P-K) liquid starter fertilizer alone and in combination. Across three site-years in Minnesota where insect injury was recorded, the insecticide decreased the percentage of plants with seedcorn maggot injury (P = 0.0291). However, across all site-years, insecticide and fertilizer had no effect (P &gt; 0.05) on plant population, plant height, or grain yield. Prophylactic use of these additional inputs under typical soybean-growing conditions in this region may not provide a return on investment. Accepted for publication 24 March 2016. Published 30 March 2016.

Effects of new field resistant cultivars and in-furrow applications of phorate insecticide on tomato spotted wilt of peanut

Field experiments were conducted at Tifton, Georgia from 2008 to 2014 to determine the effects of new peanut (Arachis hypogaea) cultivars and in-furrow applications of phorate insecticide on severity of tomato spotted wilt (TSW) caused by Tomato spotted wilt virus. Several cultivars, including Florida-07, Georgia-06G, Georgia-07W, Georgia Greener, and Tifguard, had final incidence of TSW that were less than that of Georgia Green. In-furrow applications of phorate insecticide reduced incidence of TSW in Georgia Green in three experiments in which that cultivar was included. In-furrow application of phorate insecticide reduced incidence of TSW in most cases where incidence in nontreated plots was 10% or higher. Cultivars Georganic, and Georgia-10T, had final incidence of TSW that was lower than that of Georgia-06G, or Florida-07 within nontreated plots across 2011–2012. Georgia-10T and Georgia-12Y had final incidence that was lower than that of Georgia-06G, Georgia-07W, Georgia-09B and Georgia Greener across insecticide treatments in 2013. In-furrow application of phorate increased yields across cultivars in 2008–2009, and increased yield of Georgia-09B in 2010. In most other cases, phorate had no significant effect on yield. With higher levels of field resistance in most of these cultivars, especially those such as Georgia-12Y, benefits from use of phorate insecticide for TSW suppression were small, and typically did not result in yield increase. Based on these results, several of these cultivars should allow greater flexibility for insecticide choice for thrips management without increasing the risk of losses to TSW.

Biological control of Fusarium wilt on common beans by in-furrow application of Trichoderma harzianum

Two field trials were conducted during the summer and winter seasons of 2010 to evaluate the effect of biocontrol agents against Fusarium wilt of common bean. Treatments included six Trichoderma harzianum isolates applied in planting furrows at 1.2 × 1012 conidia/ha, and one seed treatment with carboxin + thiram. Non-treated and infested plots served as control. Three T. harzianum isolates, CEN287, CEN290 and CEN316, reduced Fusarium wilt incidence and disease severity in the summer trial; incidence averaged 43.9 and 82.4 % in effective treatments and infested control plots, respectively. During the winter season, four isolates, CEN290, 1306, CEN316 and CEN287, reduced wilt incidence by 22.4, 26.7, 41.2 and 51.3 %, respectively, compared to the infested control (92.8 %) and fungicide-treated seeds (85.8 %). In general, ranking of treatments were similar whether incidence or severity was evaluated. However, CEN287 and CEN316 were ranked as the most effective isolates in both seasons. Crop yield-related variables were not affected by the treatments. Fusarium oxysporum population in soil was positively associated with disease incidence and severity, and negatively associated with grain number per pod and 100-grain mass in the summer experiment. In the winter trial, increasing densities of Trichoderma spp. in soil were correlated with increased 100-grain mass and number of grains per pod. The results highlight the value of in furrow applications of biocontrol agents for managing Fusarium wilt of common bean.

English

Increasing fertilizer rates at sowing can provide significant increases in grain yield in vegetable crops. However, very high rates can impair root development because of increased soil salinization in the rows mainly because of KCl fertilizer. Broadcast fertilization without incorporation into soil may be a viable strategy to avoid this salinization. Therefore, we conducted a study to determine the effect of different fertilizer rates applied to the soil surface without incorporation on common bean grain yield and yield components in a no-tillage system. An irrigated field experiment with a randomized block experimental design with four replications was conducted in Brazil during the 2012 and 2013 growing seasons. The treatments consisted of four fertilizer rates of an N-P-K blend that were 0, 50, 100 (15 kg ha-1 of N, 90 kg ha-1 of P2O5 and 45 kg ha-1 of K2O) and 150% of the recommended fertilizer rate for in-furrow applications. Increasing broadcast fertilizer application provided a significant increase in common bean grain yield. The application of 300 kg ha-1 of fertilizer (100% of the recommended fertilizer rate) on the soil surface without incorporation provided a similar result as the application of the same amount in the seed row. The results document that broadcast application of a fertilizer blend on the soil surface without incorporation is a viable management tool to increase common bean grain yield in no-tillage systems in soil with high fertility, which is based mainly on its content of organic matter, phosphorus, and base saturation. Key words: Phaseolus vulgaris L., surface fertilization, Cerrado, no-tillage system.

Corn Response to POST-Applied HPPD-Inhibitor Based Premix Herbicides with In-Furrow and Foliar-Applied Insecticides

In recent years injury has been reported in numerous Tennessee corn fields treated with an organophosphate (OP) insecticide and either a mesotrione- or tembotrione-based herbicide premix. Research was conducted with the objective to determine if corn treated with an in-furrow application of chlorpyrifos or a foliar application of chlorpyrifos or bifenthrin, or a combination of in-furrow and foliar treatment, would be more predisposed to injury when either a premix ofS-metolachlor, mesotrione, and glyphosate (meso premix) or a premix of tembotrione plus thiencarbazone (tembo premix) was applied. The main effects of insecticide or herbicide, the two-way interaction of insecticide by herbicide, and the three-way interaction of herbicide by insecticide by application type of insecticide were all significant for injury as well as yield. When chlorpyrifos was used both in-furrow and foliarly on corn treated with the tembo premix, injury was increased to 56% and yield was reduced 58% compared with corn that had not been treated with that insecticide. This use pattern of chlorpyrifos utilized in-furrow followed by chlorpyrifos applied foliarly with the tembo premix essentially doubled the injury (29 to 56%) and increased yield loss from 41% where chlorpyrifos was only utilized foliarly to 49% when chlorpyrifos was applied in-furrow and foliarly. Corn injury was negligible (&lt; 6%) and yield was similar where the meso premix was examined in combination of both types of insecticide applications. This study clearly demonstrated the phytotoxic interaction between these two herbicide premixes and the OP insecticide chlorpyrifos. Therefore, growers need to be mindful of which herbicides are utilized when OP insecticides are used for insect management.

Effect of In-Furrow and Early-Season Banded Applications of Fungicides on Incidence of Early Leaf Spot of Peanut

Field experiments were conducted in Tifton, GA, in 2012-2014 to determine the effect of in-furrow applications of prothioconazole and early-season banded applications of prothioconazole or pyraclostrobin on incidence of early leaf spot (Cercospora arachidicola) of peanut (Arachis hypogaea). In each year, border rows were planted in May as a source of inoculum for plants in the treatment plots. Plots were planted in August or September after epidemics of early leaf spot were severe in the border plots. Fungicide application regimes included two rates (100 and 200 g a.i./ha) of prothioconazole applied in-furrow at planting, and 200 g a.i./ha of prothioconazole or 164 g a.i./ha of pyraclostrobin applied concentrated in a 30-cm band 21 days after planting (DAP). Incidence (percent of leaflets with one or more leaf spot) of early leaf spot was monitored until 54 to 57 days after planting in each year. In all years, disease incidence was below 10% at 28 DAP in plots treated with 200 g a.i./ha of prothioconazole in-furrow compared to over 40% in nontreated plots at the same time. In-furrow applications of 100 g a.i./ha of prothioconazole were less effective, but suppressed leaf spot incidence compared to the control. Banded applications of either fungicide at 21 DAP resulted in a decrease in leaf spot incidence, and prevented increase in leaf spot incidence for 19 days or longer. Accepted for publication 30 November 2015. Published 3 December 2015.

Evaluation of insecticides and application methods to protect onions from onion maggot, Delia antiqua, and seedcorn maggot, Delia platura, damage

Onion maggot, Delia antiqua (Meigen), and seedcorn maggot, Delia platura (Meigen), are important pests of spring-sown onions, Allium cepa L. Larvae of both species feed on developing epicotyls and roots of young onion plants often resulting in seedling mortality. Cultural controls used in combination with the insecticide chlorpyrifos are currently the standard practice for maggot control in the western USA. However, cultural controls are only partially effective and reliance on chlorpyrifos has several potential problems including future availability and development of resistance. Insecticides including clothianidin, imidacloprid, spinosad, and thiamethoxam were evaluated in California, USA in 2011–2013 to identify efficacious alternatives to chlorpyrifos. Some insecticides were applied in multiple ways including seed treatment, in-furrow application at planting, and rototiller incorporation prior to planting. Onion plant population, vigor, and yield were measured to assess insecticide efficacy. Maggots reduced onion plant populations by more than 65% of the seeding rate in the untreated controls. Seed treatments with spinosad or clothianidin + imidacloprid were the best alternative to chlorpyrifos for minimizing onion mortality from maggot feeding. Onions treated with both seed treatments had similar or higher plant populations and bulb yields compared to chlorpyrifos. The efficacy of spinosad was greatly improved when applied as a seed treatment compared to an in-furrow application at planting or when incorporated into the soil with a rototiller prior to planting. Spinosad seed treatment increased onion plant populations by 256%, 76%, and 853% compared to untreated controls in 2011, 2012, and 2013, respectively. Conversely, in-furrow and rototill-incorporated applications of spinosad were similar to the untreated control in terms of onion plant population and yield. Seed treatments with newer chemistries could provide an efficacious alternative to chlorpyrifos for protecting onions from maggot damage in western onion production systems.

Tecnologia de aplicação de agrotóxicos no controle de fitonematoides em soja

O objetivo deste trabalho foi avaliar o efeito de diferentes sistemas de aplicação tratamento de sementes (TS), sulco de semeadura (Sulco) e associação de ambos (TS + Sulco) e tratamentos químicos no controle de Pratylenchus brachyurus e Meloydogine javanica, em condição de campo e ambiente controlado em vaso. O delineamento utilizado foi de blocos ao acaso, com parcelas subdivididas, em que, nas parcelas principais, foram alocados três sistemas de aplicação: tratamento de sementes, aplicação no sulco + tratamento de sementes (duas vezes a dose) e aplicação no sulco. As subparcelas foram constituídas de diferentes tratamentos químicos: testemunha; abamectina + tiametoxam + fludioxonil + metalaxil-M + tiabendazol (30+42+1,5+1,2+9g i.a. ha-1); imidacloprido + tiodicarbe + carbendazim + tiram (63+189+18+42g i.a. ha-1); fipronil + tiofanato-metílico + piraclostrobina (30+27+3g i.a. ha-1); carbofurano + carbendazim + tiram (420+18+42g i.a. ha-1). Avaliou-se a população de fitonematoides no sistema radicular (campo e ambiente controlado), área foliar e massa seca de parte aérea (ambiente controlado). A associação de TS + sulco resultou em maior eficácia e efeito residual de controle dos nematoides. O tratamento com abamectina + tiametoxam + fludioxonil + metalaxil-M + tiabendazol promoveu os maiores níveis de controle, com benefícios expressivos no desenvolvimento das plantas.

Thrips and Cotton Response to Relay Intercropping with Wheat in North Carolina

In North Carolina, double cropping cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) often results in sub-optimal cotton yield and minimal investment return, most often due to lack of sufficient stand as a result of moisture limitations and a short growing season. Relay intercropping of cotton in wheat prior to harvest may be an alternative to traditional double cropping. A relay intercropping system was tested at five locations over three years in North Carolina to determine thrips infestation, cotton yield, and economic return following relay intercropping of cotton and wheat. Relay intercropped wheat yield ranged from 65% to 85% of conventional wheat plantings. Cotton yields were not affected by the presence of relay-intercropped wheat, but plant maturity was delayed in some experiments. Intercropped cotton plants exhibited similar morphology to cotton planted in a traditional strip tillage system with wheat terminated two wks prior to planting with increased nodes above cracked boll, suggesting delayed plant development. In four of five locations, thrips (Thysanoptera: Thripidae) populations were lower in the intercropped cotton, most likely due to interference of the ability of thrips to locate cotton seedlings. Thrips levels when seed was treated with abamectin plus thiamethoxam plus azoxystrobin and an additional in-furrow application of aldicarb or acephate applied to foliage were less than that of seed treated with azoxystrobin alone. Estimated economic return of intercropped cotton and wheat equaled that of conventional cotton planting and exceeded double cropping of wheat followed by soybean [Glycine max (L.) Merr.] most years when cotton, soybean, and wheat prices were set at $1.98 kg-1 lint, $0.44 kg-1, and $0.25 kg-1, respectively.

Epidemiology of spotted wilt disease of peanut caused by Tomato spotted wilt virus in the southeastern U.S.

Spotted wilt disease of peanut ( Arachis hypogaea) (SWP), caused by Tomato spotted wilt virus (TSWV) (genus Tospovirus, family Bunyaviridae), was first observed in Alabama, Florida, and Georgia in the late 1980s and rapidly became a major limiting factor for peanut production in the region. Tobacco thrips ( Frankliniella fusca) and western flower thrips ( Frankliniella occidentalis) both occur on peanut throughout the southeastern U.S., but F. fusca is the predominant species that reproduces on peanut, and is considered to be the more important vector. Several non-crop sources of potential primary vectors and TSWV inoculum have been identified, but their relative importance has not been determined. The peanut growing season in Alabama, Florida, and Georgia is from April through November, and ‘volunteer’ peanut plants can be present for much of the remainder of the year. Therefore peanut itself has huge potential for perpetuating both vector and virus. Symptoms are often evident within a few days of seedling emergence, and disease progress is often rapid within the first 50–60 days after planting. Based on destructive sampling and assays for TSWV, there is often a high incidence of asymptomatic infections even in peanut genotypes that produce few and mild symptoms of infection in the field. Severity of SWP epidemics fluctuates significantly from year to year. The variability has not been fully explained, but lower incidences have been associated with years categorized as “La Niña” in the El Niño-Southern Oscillation. Planting date can have a large effect on disease incidence within a location. This may be linked to the thrips reproductive cycle and environmental effects on the plant and plant–thrips–virus interactions. Row pattern, plant population, and in-furrow applications of phorate insecticide can also affect epidemics of SWP. Considerable progress has been made in developing cultivars with natural field resistance to TSWV. Use of cultivars with moderate field resistance combined with other suppressive measures has been very successful for managing spotted wilt disease. Several new cultivars with higher levels of field resistance can improve control and allow more flexibility in the integrated management programme. Although effects of these factors on epidemics of SWP have been documented, mechanisms responsible for disease suppression by most factors have not been fully elucidated.

A meta-analysis of severity and yield loss from ascochyta blight on field pea in Western Australia

A meta-analysis of severity and yield loss from ascochyta blight (AB) on field pea was performed using 18 field experiments conducted over eight seasons in 13 locations in Western Australia (WA). The severity of AB, across the WA grain-belt, reached its maximum limit (AB severity 5) during mid-April sowing and linearly declined to almost nil by mid-July sowing. Pre-sowing rainfall had a significant effect on AB severity: the more rainfall events that occurred the less was the disease severity. The regional and seasonal difference in the rate of decline of the AB severity (slope of the regression line) with delay in sowing was not significant, whereas the intercepts were largely significant indicating there were differences in the initial AB severity status between the regions and seasons. Fungicide control [Impact® in-furrow (flutriafol) application or fortnightly sprays of Bravo® (chlorothalonil)] did not reduce the disease severity in early sowing (week ending 7 May). The yield loss due to AB was calculated as 10.3% per AB severity unit, indicating that a loss of ≥50% could occur with the highest severity. Magnet showed significantly higher yield loss compared to all other varieties. The differences in yield loss between the five regions were not significant. On the other hand, a dry finishing season resulted in significantly higher yield loss than a wet finishing season. These analyses will help design improved strategies for AB management in field pea in Western Australia.