Efficacy of Fluensulfone in a Tomato–Cucumber Double Cropping System

Vegetable crops in the southeastern United States are commonly grown on plastic mulch with two crop cycles produced on a single mulch application. Field trials were conducted in 2013 and 2014 in two locations to evaluate the efficacy of fluensulfone for controlling Meloidogyne spp. when applied through drip irrigation to cucumber in a tomato–cucumber double-cropping system. In the spring tomato crop, 1,3-dichloropropene (1,3-D), fluensulfone, and a resistant cultivar significantly decreased root galling by 91%, 73%, and 97%, respectively, compared to the untreated control. Tomato plots from the spring were divided into split plots for the fall where the main plots were the spring treatment and the subplots were cucumber either treated with fluensulfone (3.0 kg a.i./ha. via drip irrigation) or left untreated. The fall application of fluensulfone improved cucumber vigor and reduced gall ratings compared to untreated subplots. Fluensulfone reduced damage from root-knot nematodes when applied to the first crop as well as provided additional protection to the second crop when it was applied through a drip system.     

Reducing Meloidogyne incognita Injury to Cucumber in a Tomato-Cucumber Double-Cropping System

The effects of a root-knot nematode-resistant tomato cultivar and application of the nematicide ethoprop on root-knot nematode injury to cucumber were compared in a tomato-cucumber double-cropping system. A root-knot nematode-resistant tomato cultivar, Celebrity, and a susceptible cultivar, Heatwave, were grown in rotation with cucumber in 1995 and 1996. Celebrity suppressed populations of Meloidogyne incognita in the soil and resulted in a low root-gall rating on the subsequent cucumber crop. Nematode population densities were significantly lower at the termination of the cucumber crop in plots following Celebrity than in plots following Heatwave. Premium and marketable yields of cucumbers were higher in plots following Celebrity than in plots following Heatwave. Application of ethoprop through drip irrigation at 4.6 kg a.i./ha reduced root galling on the cucumber crop but had no effect on the nematode population density in the soil at crop termination. Ethoprop did not affect cucumber yield. These results indicate that planting a resistant tomato cultivar in a tomato-cucumber double-cropping system is more effective than applying ethoprop for managing M. incognita.     

Use of Avermectins for the Control of Meloidogyne incognita on tomatoes

The efficacy of avermectins B₁ and B₂ for control of Meloidogyne incognita on tomato was studied in pots and field plots for two seasons. Avermectins were applied as granules and liquid in furrows or by low pressure drip irrigation systems, at rates ranging from 0.093 to 0.34 kg a.i./ha, as single or multiple applications. Levels of control comparable to those obtained by oxamyl and aldicarb at 3.36 kg a.i./ha were achieved by the avermectin with only 1/10 the volume of chemicals applied to the environment. Avermectin protection of the roots remained constant throughout the first 5 weeks giving slightly longer protection than oxamyl or aldicarb.     

Greenhouse Studies on the Effect of Marigolds (Tagetes spp.) on Four Meloidogyne Species

The effects of preplanted marigold on tomato root galling and multiplication of Meloidogyne incognita, M. javanica, M. arenaria, and M. hapla were studied. Marigold cultivars of Tagetes patula, T. erecta, T. signata, and a Tagetes hybrid all reduced galling and numbers of second-stage juveniles in subsequent tomato compared to the tomato-tomato control. All four Meloidogyne spp. reproduced on T. signata ''Tangerine Gem''. Several cultivars of T. patula and T. erecta suppressed galling and reproduction of Meloidogyne spp. on tomato to levels lower than or comparable to a fallow control. Phytotoxic effects of marigold on tomato were not observed. Several of the tested marigold cultivars are ready for full-scale field evaluation against Meloidogyne spp.     

Soil fumigation and oxamyl drip applications for nematode and insect control in vegetable plasticulture

A series of experiments were conducted to evaluate the effect of oxamyl in combination with the soil fumigants 1,3-D, metam sodium and methyl bromide on nematode damage and fruit yield in vegetables. Experiments were conducted in Tifton, GA, USA over five seasons, between 2000 and 2002, using four different vegetables: squash (Cucurbita pepo), cucumber (Cucumis sativus), pepper (Capsicum annuum) and eggplant (Solanum melongend). In the eggplant experiment, insect populations were monitored. Soil fumigation alone, irrespective of application method or formulation, gave acceptable control of root-knot nematode in all experiments, except in the spring 2001 pepper experiment. Oxamyl by itself did not provide control of root-knot nematode (Meloidogyne incognita), but insect populations on eggplant were reduced. Out of three experiments that included oxamyl by itself, root galling caused by Meloidogyne spp. was reduced only on eggplant when nematode pressure was low (five nematodes per 150 cm³ soil). When oxamyl was applied in combination with pre-plant soil fumigation, small but consistent reductions in root galling were observed. Greatest reductions in galling due to oxamyl were found when fumigation provided less than optimal nematode control. The timing of application of oxamyl did not have much impact on nematode infection, but applications early in the season, preferably starting at planting, appear to be beneficial. Stubby root nematode (Paratrichodorus spp.) populations were low and variable in most experiments, but neither fumigation nor post-plant nematicide applications seemed to have any effect on soil populations at harvest. Crop yields were often significantly greater when oxamyl followed fumigation, as compared to fumigation only, which could be due to a reduction in root-knot nematode damage (and in the case of eggplant also reduced foliar damage by insects), and/or to a carbamate growth stimulant response. These experiments indicate the potential of oxamyl to reduce root-knot nematode infection and increase yields of vegetables when combined with soil fumigation by 1,3-D and/or metam sodium. More research is required to understand the effect of crop type, pest pressure, preceding fumigant (1,3-D or metam sodium) and injection timing of oxamyl.     

Effect of Soils from Six Management Systems on Root-knot Nematodes and Plant Growth in Greenhouse Assays

The effects of soil management systems on root-knot nematode (Meloidogyne incognita) eggs and gall incidence on tomato (Lycopersicon esculentum) and cucumber (Cucumis sativus) following tomato were evaluated. Soil was collected from a replicated field experiment in which six management systems were being assessed for vegetable production. Soil management systems were conventional production, organic production, bahiagrass (Paspalum notatum) pasture, bahiagrass: Stylosanthes (Stylosanthes guianensis) pasture, bare ground fallow, and weed fallow. Soil was collected from field plots and used in greenhouse experiments. Identification of egg-parasitic fungi and the incidence of root-knot nematode galling were assessed both on tomato and cucumber planted in the same pots following the removal of tomato plants. Organic, bare ground fallow and conventional production treatments reduced galling both on tomato and on cucumber following tomato. Although no treatment consistently enhanced egg-parasitic fungi, management system did affect egg viability and the types of fungi isolated from parasitized eggs.     

Control of Ditylenchus dipsaci in Infected Garlic Seed Cloves by Nonfumigant Nematicides

Different rates of granular formulations ofaldicarb, carbofuran, ethoprop, fensulfothion, and phenamiphos were applied directly onto garlic seed cloves in the seed furrow in sandy clay loam, clay loam, and loam soils at planting to assess efficacy for control of Ditylenchus dipsaci in infected seed cloves. All treatments were compared to hotwater-formalin clove dip disinfection treatment and to nontreated infected controls. Aldicarb and phenamiphos at 2.52 and 5.04 kg a.i./ ha, but not at lower rates, effectively suppressed infection by D. dipsaci and increased yields. Although both nematicides slightly slowed the rate of plant emergence, normal stands were established. Trace levels of infection occurred in all treatments, including the hotwater-formalin dip. Carbofuran at 5.04 kg a.i./ha controlled the nematode but was phytotoxic. Ethoprop was phytotoxic. Fensulfothion did not control D. dipsaci even at the highest application rate, 8.90 kg a.i./ha. Single and multiple applications of oxamyl at 1.12-8.96 kg a.i./ha, applied as a surface spray or in furrow irrigation water, slowed the early progression of disease symptoms but failed to provide season-long nematode control.     

Pasteuria penetrans for Control of Meloidogyne incognita on Tomato and Cucumber,and M. arenaria on Snapdragon

Meloidogyne incognita and Meloidogyne arenaria are important parasitic nematodes of vegetable and ornamental crops. Microplot and greenhouse experiments were conducted to test commercial formulations of the biocontrol agent Pasteuria penetrans for control of M. incognita on tomato and cucumber and M. arenaria on snapdragon. Three methods of application for P. penetrans were assessed including seed, transplant, and post-plant treatments. Efficacy in controlling galling and reproduction of the two root-knot nematode species was evaluated. Seed treatment application was assessed only for M. incognita on cucumber. Pasteuria treatment rates of a granular transplant formulation ranged from 1.5 × 10⁵ endospores/cm³ to 3 × 10⁵ endospores/cm³ of transplant mix applied at seeding. Additional applications of 1.5 × 10⁵ endospores/cm³ of soil were applied as a liquid formulation to soil post-transplant for both greenhouse and microplot trials. In greenhouse cucumber trials, all Pasteuria treatments were equivalent to steamed soil for reducing M. incognita populations in roots and soil, and reducing nematode reproduction and galling. In cucumber microplot trials there were no differences among treatments for M. incognita populations in roots or soil, eggs/g root, or root condition ratings. Nematode reproduction on cucumber was low with Telone II and with the seed treatment plus post-plant application of Pasteuria, which had the lowest nematode reproduction. However, galling for all Pasteuria treatments was higher than galling with Telone II. Root-knot nematode control with Pasteuria in greenhouse and microplot trials varied on tomato and snapdragon. Positive results were achieved for control of M. incognita with the seed treatment application on cucumber.     

Root-Knot Nematode Management in Double-Cropped Plasticulture Vegetables

Combination treatments of chisel-injected fumigants (methyl bromide, 1,3-D, metam sodium, and chloropicrin) on a first crop, followed by drip-applied fumigants (metam sodium and 1,3-D ± chloropicrin) on a second crop, with and without oxamyl drip applications were evaluated for control of Meloidogyne incognita in three different tests (2002 to 2004) in Tifton, GA. First crops were eggplant or tomato, and second crops were cantaloupe, squash, or jalapeno pepper. Double-cropped vegetables suffered much greater root-knot nematode (RKN) pressure than first crops, and almost-total yield loss occurred when second crops received no nematicide treatment. On a first crop of eggplant, all fumigants provided good nematode control and average yield increases of 10% to 15 %. On second crops, higher application rates and fumigant combinations (metam sodium and 1,3-D ± chloropicrin) improved RKN control and increased yields on average by 20% to 35 % compared to the nonfumigated control. Oxamyl increased yields of the first crop in 2003 on average by 10% to 15% but had no effect in 2004 when RKN failed to establish itself. On double-cropped squash in 2003, oxamyl following fumigation provided significant additional reduction in nematode infection and increased squash yields on average by 30% to 75%.     

Control of Globodera rostochiensis in Relation to Method of Applying Nematodes

Soaking potato tuber pieces for 15 min in 8,000 μg/ml of oxamyl just before planting reduced the number of Globodera rostochiensis cysts that developed on potato roots, but this treatment was phytotoxic. Five foliar applications of 1.12 kg a.i./ha of oxamyl or carbofuran at 10-day intervals beginning when 90% of the plants had emerged suppressed increase in G. rostochiensis densities. Similar foliar applications of phenamiphos were ineffective in controlling G. rostochiensis. Soil applications (in the row at planting) of aldicarb, carbofuran, phenamiphos, ethoprop, and oxamyl at 5.6 kg a.i./ha reduced the numbers of white females that developed on potato roots, but only those treatments involving aldicarb and oxamyl suppressed G. rostochiensis population increase. Combined soil and foliar treatments did not provide any advantage over soil treatment alone, as soil applications of 5.6 kg a.i./ha alone were equal to, or better than, combined soil (3.4 kg a.i./ha) and foliar (2.2 kg a.i./ha) applications in controlling G. rostochiensis.     

Control of Meloidogyne javanica by Formulations of Inula viscosa Leaf Extracts

Inula viscosa is a perennial plant that is widely distributed in Mediterranean countries. Formulations of I. viscosa extracts were tested for their effectiveness in control of Meloidogyne javanica in laboratory, growth chamber, microplot, and field experiments. Oily pastes were obtained by extraction of dry leaves with a mixture of acetone and n-hexane or n-hexane alone, followed by evaporation of the solvents. Emulsifiable concentrate formulations of the pastes killed M. javanica juveniles in sand at a concentration of 0.01% (paste, w/w) or greater and reduced the galling index of cucumber seedlings as well as the galling index and numbers of nematode eggs on tomato plants in growth chamber experiments. In microplot experiments, the hexane-extract formulation at 26 g paste/m² reduced nematode infection on tomato plants in one of two experiments. In a field experiment, a reduction of 40% in root galling index by one of two formulations was observed on lettuce plants. The plant extracts have potential as a natural nematicide, although the formulations need improvement.     

Differential Vertical Movement of Nonvolatile Nematicides in Soil

When incorporated in the top 5-cm of Tifton sandy loam at 11.2 kg/ha in the field, B-68138 [ethyl 4-(methylthio)-m-tolyl isopropyl phosphoramidate] prevented galling of tomato roots by Meloidogyne sp. down to 20 cm. A similar application of 16.8 kg/ha of V-C 9-104 [0-ethyl S,S-dipropyl phosphorodithioate] was 99% effective down to 20 cm. Aldicarb [2-methyl-2-(methylthio) propionaldehyde 0-(methylcarbamoyl) oxime], B-25141 [0,0-diethyl 0-{p-(methylsulfinyl) phenyl}phosphorothioate], and carbofuran [2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate] prevented galling only in the zone of incorporation (top 5-cm of soil). When aldicarb (11.2 kg/ha) was applied to the surface of Ontario fine sandy loam contained in clay pots in the greenhouse, it prevented galling of tomato roots down to 20 cm deep. V-C 9-104 and B-68138, applied similarly, were 100% effective to a depth of 5 cm. B-25141 was 100% effective in the zone of incorporation only. D-1410 [S-methyl-l-(dimethylcarbamoyl)-N-l(methylcarbamoyl)oxy] thioformimidatel did not control 100% of the root-knot nematodes at any depth.     

Mode of Parasitism of Meloidogyne and Other Nemaiode Eggs by Dactylella oviparasitica

Hyphae of Dactylella oviparasitica proliferated rapidly through MeIoidogyne egg masses, and appressoria formed when they contacted eggs. The fungus probably penetrated egg shells mechanically, although chitinase production detected in culture suggested that enzymatic penetration was also possible. In soil, D. oviparasitica invaded egg masses soon after they were deposited on the root surface and eventually parasitized most of the first eggs laid. Occasionally the fungus grew into Meloidogyne females, halting egg production prematurely. The fungus parasitized eggs in the gelatinous matrix or eggs freed from the matrix and placed on agar or in soil. Specificity in nematode egg parasitism was not displayed, for D. oviparasitica parasitized eggs of four Meloidogyne spp., Acrobeloides sp., Heterodera schachtii, and Tylenchulus semipenetrans. In tests in a growth chamber, parasitism by D. oviparasitica suppressed galling on M. incognita-infected tomato plants.     

Efficacy of a Novel Nematicidal Seed Treatment against Meloidogyne incognita on Cotton

The efficacy of abamectin as a seed treatment for control of Meloidogyne incognita on cotton was evaluated in greenhouse, microplot, and field trials in 2002 and 2003. Treatments ranging from 0 to 100 g abamectin/100 kg seed were evaluated. In greenhouse tests 35 d after planting (DAP), plants from seed treated with abamectin were taller than plants from nontreated seed, and root galling severity and nematode reproduction were lower where treated seed were used. The number of second stage juveniles that had entered the roots of plants from seed treated with 100 g abamectin/kg seed was lower during the first 14 DAP than with nontreated seed. In microplots tests, seed treatment with abamectin and soil application of aldicarb at 840 g/kg of soil reduced the number of juveniles penetrating seedling roots during the first 14 DAP compared to the nontreated seedlings. In field plots, population densities of M. incognita were lower 14 DAP in plots that received seed treated with abamectin at 100 g/kg seed than where aldicarb (5.6 kg/ha) was applied at planting. Population densities were comparable for all treatments, including the nontreated controls, at both 21 DAP and harvest. Root galling severity did not differ among treatments at harvest.     

A Method for Field Infestation with Meloidogyne incognita

A field inoculation method was developed to produce Meloidogyne spp. infestation sites with minimal quantities of nematode inoculum and with a reduced labor requirement compared to previous techniques. In a preseason-methyl bromidefumigated site, nematode egg suspensions were delivered at concentrations of 0 or 10^x eggs/m of row where x = 2.12, 2.82, 3.52, or 4.22 through a drip line attached to the seed firmer of a commercial 2-row planter into the open seed furrow while planting cowpea. These treatments were compared to a hand-inoculated treatment, in which 10^3.1 eggs were delivered every 30 cm in 5 ml of water agar suspension 2 weeks after planting. Ten weeks after planting, infection of cowpea roots was measured by gall rating and gall counts on cowpea roots. A linear relationship between the inoculation levels and nematode-induced galls was found. At this time, the amount of galling per root system in the hand-inoculated treatment was less than in the machine-applied treatments. Advantages of this new technique include application uniformity and low population level requisite for establishing the nematode. This method has potential in field-testing of Meloidogyne spp. management strategies by providing uniform infestation of test sites at planting time.     

Effects of Tagetes patula on Active and Inactive Stages of Root-Knot Nematodes

Although marigold (Tagetes patula) is known to produce allelopathic compounds toxic to plant-parasitic nematodes, suppression of Meloidogyne incognita can be inconsistent. Two greenhouse experiments were conducted to test whether marigold is more effective in suppressing Meloidogyne spp. when it is active rather than dormant. Soils infested with Meloidogyne spp. were collected and conditioned in the greenhouse either by 1) keeping the soil dry (DRY), 2) irrigating with water (IRR), or 3) drenching with cucumber (Cucumis sativus) leachate (CL) for 5 wk. These soils were then either planted with cucumber, marigold or remained bare for 10 wk. Suppression of nematode by marigold was then assayed using cucumber. DRY conditioning resulted in the highest number of inactive nematodes, whereas CL and IRR had higher numbers of active nematodes than DRY. At the end of the cucumber bioassay, marigold suppressed the numbers of Meloidogyne females in cucumber roots if the soil was conditioned in IRR or CL, but not in DRY. However, in separate laboratory assays, marigold root leachate slightly reduced M. incognita J2 activity but did not reduce egg hatch (P > 0.05). These finding suggest that marigold can only suppress Meloidogyne spp. when marigold is actively growing. This further suggests that marigold will more efficiently suppress Meloidogyne spp. if planted when these nematodes are in active stage.     

Interaction of Population Levels of Fusarium oxysporum f. sp. vasinfectum and Meloidogyne incognita on Cotton

In autoclaved greenhouse soil without Fusarium oxysporum f. sp. vasinfectum, Meloidogyne incognita did not cause leaf or vascular discoloration of 59-day-old cotton plants. Plants had root galls with as few as 50 Meloidogyne larvae per plant. Root galling was directly proportional to the initial nematode population level. Fusarium wilt symptoms occurred without nematodes with 77,000 fungus propagules or more per gram of soil. As few as 50 Meloidogyne larvae accompanying 650 fungus propagules caused Fusarium wilt. With few exceptions, leaf symptoms appeared sooner as numbers of either or both organisms increased. In soils infested with both organisms, the extent of fungal invasion and colonization was well correlated with the extent of nematode galling and other indications of the Fusarium wilt syndrome.     

Effect of Application Timing of Oxamyl in Nonbearing Raspberry for Pratylenchus penetrans Management

In 2012, the Washington raspberry (Rubus idaeus) industry received a special local needs (SLN) 24(c) label to apply Vydate L^® (active ingredient oxamyl) to nonbearing raspberry for the management of Pratylenchus penetrans. This is a new use pattern of this nematicide for raspberry growers; therefore, research was conducted to identify the optimum spring application timing of oxamyl for the suppression of P. penetrans. Three on-farm trials in each of 2012 and 2013 were established in Washington in newly planted raspberry trials on a range of varieties. Oxamyl was applied twice in April (2013 only), May, and June, and these treatments were compared to each other as well as a nontreated control. Population densities of P. penetrans were determined in the fall and spring postoxamyl applications for at least 1.5 years. Plant vigor was also evaluated in the trials. Combined results from 2012 and 2013 trials indicated that application timing in the spring was not critical. Oxamyl application reduced root P. penetrans population densities in all six trials. Reductions in P. penetrans population densities in roots of oxamyl-treated plants, regardless of application timing, ranged from 62% to 99% of densities in nontreated controls. Phytotoxicity to newly planted raspberry was never observed in any of the trials. A nonbearing application of oxamyl is an important addition to current control methods used to manage P. penetrans in raspberry in Washington.     

Drip Irrigation as a Delivery System for Infestation of Field Plots with Nematodes

A drip irrigation delivery system was used to infest field sites with the plant-parasitic root-knot nematodes, Meloidogyne incognita. Juvenile or egg inocula passed through the system without blockage of emitters or harm to the nematodes. Field sites so infested were available for experimentation. Delivery of approximately 5 x 10⁴ to 10⁵ juveniles or 10⁵ to 3 x 10⁵ eggs per emitter through the drip system resulted in heavy root galling of tomatoes planted next to the drip emitters. Nematodes feeding on bacteria (Acrobeloides sp.) and on fungi (Deladenus durus) also were successfully applied through the drip system. This method has potential for uniformly infesting experimental sites with plant-parasitic or entomogenous nematodes and for manipulation of nematode community structure for soil ecological studies.     

Effects of Management Practices on Meloidogyne incognita and Snap Bean Yield

Phenamiphos applied at 6.7 kg ai/ha through a solid set or a center pivot irrigation system with 28 mm of water effectively controlled root-knot nematodes, Meloidogyne incognita, and resulted in greater snap bean growth and yields irrespective of growing season, tillage method, or cover crop system. The percentage yield increases attributed to this method of M. incognita control over nontreated controls were 45% in the spring crop, and 90% and 409% in the fall crops following winter rye and fallow, respectively. Root galling was not affected by tillage systems or cover crop, but disk tillage resulted in over 50% reduction in bean yield compared with yields from the subsoil-bed tillage system.