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 Paratrichodorus allius and Corky Ringspot Disease in Potato with Shank-injected Metam Sodium

Corky ringspot disease (CRS) of potato produces necrotic areas in tubers that are considered quality defects that can lead to crop rejection. CRS is caused by tobacco rattle virus that is vectored by stubby-root nematodes (Paratrichodorus spp., Trichodorus spp.) at very low population densities, making disease management difficult and expensive. Fumigation with metam sodium (MS) is a common practice to control soil-borne fungi and increase potato yield. MS is generally applied in water via chemigation (water-run, WR) but is ineffective at controlling CRS when WR-applied, even at high rates. Therefore, WR MS is often used in combination with 1,3-dichloropropene (1,3-D), aldicarb or oxamyl to attain adequate CRS control. Between 1996 and 2000, fields with a history of CRS were treated with WR MS, shank-injected MS, and/or 1,3-D, and tubers were evaluated for symptoms of CRS. Shank injection of MS (SH MS) at depths of 41 cm, 15 and 30 cm, or 15, 30 and 45 cm controlled CRS over 3 years of testing. All rates of 280 liters/ha or greater were effective. Shank injection of metam potassium (MP) at rates of 448 liters/ha was also effective. 1,3-D controlled CRS alone or in combination with WR or SH MS. Proper shank application of MS or MP may adequately control CRS without the additional cost of other nematicides at low (<10 P. allius/250 g soil) to moderate (10 to 30 P. allius/250 g soil) populations of the nematode vector. Although SH MS was superior to WR MS, additional research is necessary to determine if this practice would be sufficient at higher CRS disease pressure or if addition of other nematicides would be necessary.     

Effects of Application Strategies of Fumigant and Nonfumigant Nematicides on Cantaloupe Grown in Deep Sand Soils in Florida

A 2-year study was conducted in which three treatment tactics of oxamyl (at planting application, application every 2 weeks, and rescue applications, as determined by crop symptoms) were compared to fumigant treatments with methyl bromide, 1,3-dichloropropene (1,3-D), and 1,3-D plus chloropicrin for management of Meloidogyne spp. In 2002, treatments that included 1,3-D produced higher yields as determined both by number and weight of marketable fruit. All treatment tactics relying solely on oxamyl, at planting, scheduled treatments, and rescue, were not different from untreated controls for both marketable yield and number of fruit. Gall ratings in 2002 were lowest for 1,3-D at the 112-liters/ha rate, followed by 1,3-D at 84 liters/ha with and without oxamyl. All treatments of oxamyl, except when combined with 1,3-D, had gall ratings not different from untreated plots. In 2004, treatments of methyl bromide and 1,3-D plus chloropicrin had the highest total number of both marketable fruit and highest marketable yields. All treatment strategies relying solely on oxamyl had yields equivalent to the untreated controls. Mean root-gall ratings were lowest for methyl bromide plus chloropicrin and 1,3-D plus chloropicrin treatments. Root-gall ratings for all treatment tactics relying solely on oxamyl were not different from untreated controls.     

Control of Meloidogyne chitwoodi in Potato with Shank-injected Metam Sodium and other Nematicides

Metam sodium (MS) is often applied to potato fields via sprinkler irrigation systems (water-run, WR) to reduce propagules of soil-borne pathogenic fungi, particularly Verticillium dahliae, to prevent yield loss from potato early dying disease. However, this procedure has not been effective for controlling quality defects in tubers caused by Columbia root-knot nematode (Meloidogyne chitwoodi). In five trials from 1996 to 2001, application of MS by soil shank injection (SH) provided better control and tuber quality than that generally obtained by WR MS, in three of five trials. Results were similar when SH MS was injected at one (41–45 cm), two (15 and 30 cm) or three (15, 30 and 45 cm) depths. In the two trials where SH metam potassium was tested, culls were reduced to 3% and 0% and were equivalent to those resulting from a similar rate in kg a.i./ha of SH MS. A shank-injected tank mix of MS plus ethoprop EC and SH MS plus in-season chemigation applications of oxamyl provided acceptable control in trials where SH MS alone was inadequate. In-furrow application of aldicarb at planting following SH MS did not appear to increase performance. Most consistent control (0–2% culled tubers in five trials) occurred when SH MS at 280 liters/ha was used together with 1,3- dichloropropene (140 liters/ha), applied simultaneously or sequentially. This was similar to combinations of 1,3-D and WR MS, but SH MS may be preferred under certain conditions.     

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%.     

Efficacy of Various Application Methods of Fluensulfone for Managing Root-knot Nematodes in Vegetables

Fluensulfone is a new nematicide in the flouroalkenyl chemical group. A field experiment was conducted in 2012 and 2013 to evaluate the efficacy of various application methods of fluensulfone for control of Meloidogyne spp. in cucumber (Cucumis sativus). Treatments of fluensulfone (3.0 kg a.i./ha) were applied either as preplant incorporation (PPI) or via different drip irrigation methods: drip without pulse irrigation (Drip NP), pulse irrigation 1 hr after treatment (Drip +1P), and treatment at the same time as pulse irrigation (Drip =P). The experiment had eight replications per treatment and also included a PPI treatment of oxamyl (22.5 kg a.i./ha) and a nontreated control. Compared to the control, neither the oxamyl nor the fluensulfone PPI treatments reduced root galling by Meloidogyne spp. in cucumber. Among the drip treatments, Drip NP and Drip +1P reduced root galling compared to the control. Cucumber yield was greater in all fluensulfone treatments than in the control. In a growth-chamber experiment, the systemic activity and phytotoxicity of fluensulfone were also evaluated on tomato (Solanum lycopersicum), eggplant (Solanum melongena), cucumber, and squash (Curcurbita pepo). At the seedling stage, foliage of each crop was sprayed with fluensulfone at 3, 6, and 12 g a.i./liter, oxamyl at 4.8 g a.i./liter, or water (nontreated control). Each plant was inoculated with Meloidogyne incognita juveniles 2 d after treatment. There were six replications per treatment and the experiment was conducted twice. Foliar applications of fluensulfone reduced plant vigor and dry weight of eggplant and tomato, but not cucumber or squash; application of oxamyl had no effect on the vigor or weight of any of the crops. Typically, only the highest rate of fluensulfone was phytotoxic to eggplant and tomato. Tomato was the only crop tested in which there was a reduction in the number of nematodes or galls when fluensulfone or oxamyl was applied to the foliage compared to the nontreated control. This study demonstrates that control of Meloidogyne spp. may be obtained by drip and foliar applications of fluensulfone; however, the systemic activity of fluensulfone is crop specific and there is a risk of phytotoxicity with foliar applications.     

Establishing a Corky Ringspot Disease Plot for Research Purposes

A method to establish two experimental corky ringspot disease (CRS) plots that had no prior CRS history is described. CRS is a serious disease of potato in the Pacific Northwest caused by tobacco rattle virus (TRV) and transmitted primarily by Paratrichodorus allius. ‘Samsun NN’ tobacco seedlings were inoculated with viruliferous P. allius in the greenhouse before they were transplanted into the field soil at the rate of 3,000 plus seedlings/ha. Care was taken to keep soil around plants in the greenhouse and transplants in the field moist to avoid vector mortality. The vector population in the soil of one of the fields was monitored by extraction, examination under microscope and bioassay on tobacco seedlings to ascertain that they were virus carriers. Presence of virus in tobacco bioassay plants was determined by visual symptoms on tobacco leaves and by testing leaves and roots using ELISA. Although TRV transmission was rapid, there was loss of infectivity in the first winter which necessitated a re-inoculation. After two years of planting infected tobacco seedlings, 100% of soil samples collected from this field contained viruliferous P. allius. In the second field, all five commercial potato cultivars, known to be susceptible, expressed symptoms of CRS disease indicating that the procedure was successful.     

Niche Distribution of Paratrichodorus minor and Belonolaimus longicaudatus Following Fumigation on Potato and Cabbage

An experiment was conducted to determine population changes and niche variation in the soil at two depths (0 to 20 cm and 20 to 40 cm) of Paratrichodorus minor and Belonolaimus longicaudatus populations following fumigation. Eight plots each of potato (Solanum tuberosum) and cabbage (Brassica oleracea var. capitata), fumigated with 1, 3-dichloropropene or nonfumigated, were established. Eight plots of sorghum-sudangrass hybrid (Sorghum bicolor × S. arundinaceum var. sudanense) were also used to monitor depth distribution (0 to 20 cm and 20 to 40 cm) of B. longicaudatus and P. minor following each cabbage/potato season. Soil samples were taken 0 to 20 cm and 20 to 40 cm deep during the potato/cabbage, and sorghum-sudangrass growing seasons. During the 1993-94 and 1994-95 potato/cabbage seasons, P. minor was found at highest numbers at 20 to 40 cm, whereas numbers of B. longicaudatus were highest at 0 to 20 cm. During the 1994 and 1995 sorghum-sudangrass growing seasons, B. longicaudatus numbers were highest at 0 to 20 cm. Paratrichodorus minor numbers were highest at 0 to 20 cm and at 20 to 40 cm deep in the 1994 and 1995 sorghum-sudangrass growing seasons, respectively. Reduction by soil fumigation of B. longicaudatus at 0 to 20 cm deep did not affect depth distribution or cause P. minor populations to increase in potato or cabbage plots. Paratrichodorus minor numbers increased at 20 to 40 cm deep in the 1994-95 cabbage season after soil fumigation.     

Abundance and Vertical Distribution of Longidorus breviannulatus Associated with Corn and Potato

Longidorus breviannulatus was detected in a field planted to corn after 13 years of potato. Nematode populations were maintained in this field in adjacent corn and potato plots for 2 years but did not increase significantly on either crop. Population levels increased until approximately 60 days after planting and then declined until the end of the growing season. Overwinter mortality was negligible. The vertical distribution of the nematode population changed during the course of the season. More nematodes were recovered from depths of 0-15 cm in early season samples and from depths of 15-30 cm in late season samples. Data indicated that this redistribution was due to nematode migration.     

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.     

Supplementary foliar N, P and K, applied individually or in combinations, and the tolerance of potatoes to infection by the potato cyst nematodes Globodera rostochiensis and G. pallida

The use of supplementary foliar N, P and K to ameliorate the reduced nutrient uptake of potato plants infected by potato cyst nematode (PCN) were investigated. The potato cv. Pentland Dell achieved yields in plots not treated with oxamyl similar to those found in plots treated with oxamyl when supplementary foliar N or N plus K was applied to plots infested with 13 eggs g^-1 soil of Globodera pallida. Yield improvements from foliar N applications were attributed to increased leaf area index but the reason for yield increases from foliar N plus K applications could not be clarified. In a second experiment, where PCN infestation was 76 eggs g^-l soil, the potato cv. Sante gave yields up to 19% higher than a standard fertiliser practice when supplementary foliar N was applied to plots not treated with oxamyl. Nutrient analysis showed that without oxamyl there were significantly lower concentrations of N, P and K in whole plant dry matter at 58 days after planting (DAP) but higher levels of N in the fourth leaf dry matter at 98 DAP. Emergence was significantly advanced by the use of oxamyl in both experiments. Sante dramatically reduced populations of Globodera rostochiensis from an average of 76 eggs g^-1 soil to 7 eggs g^-1 soil. Foliar application of nutrients is a promising method of ameliorating the effects on potatoes of PCN invasion but the nutrient concentrations and timing of individual sprays need to be more closely matched to crop requirement than was possible in our experiments     

Decline of Globodera rostochiensis as Influenced by Potato Root Diffusate Movement and Persistence in Soil

Decline of Globodera rostochiensis populations occurring naturally in soil and those added to potato hills and furrow centers in nylon bags was correlated with root weight of Hudson, Rosa, and Katahdin potatoes at two locations in New York. Cysts in bags were added to soil at planting and at 1, 3, 5, 7, and 9 weeks after emergence (AE). Fallow decline required only 2-4 weeks in soil and did not increase with time. Decline due to growing potatoes was greater in hills than in furrow centers, and resistant Hudson potatoes stimulated greater nematode hatch for longer times in both hills and furrows than did resistant Rosa and susceptible Katahdin. Potato root diffusate (PRD) was produced in highest concentration early in the season; decreased egg hatch with time was probably the result of declining PRD production and inactivation of PRD in soil. Decreasing potato row spacing from 92 cm to 46 and 23 cm between rows increased G. rostochiensis decline in furrow centers, with the majority of decline occurring within 1-3 weeks AE. Replanting potatoes after 1 week of trap crop growth failed to favor population reduction over a single full season crop.     

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.     

Basal fertiliser application method, tuber initiation nitrogen, foliar NPK and the tolerance of potatoes to infection by the potato cyst nematodes Globodera rostochiensis and G. pallida

The effects of broadcast granular, placed liquid and foliar fertilisers on the tolerance of potatoes to infection by potato cyst nematodes were investigated. The tolerance of the potato cv. Pentland Dell was not significantly improved by fertiliser application type but placed liquid fertiliser, with or without foliar applications, increased the concentrations of N, P and K measured in whole plant dry matter of PCN infected plants. The tolerance of the potato cv. Sante was not statistically improved by altering the balance of fertiliser nitrogen applications between planting and tuber initiation or by applying foliar nitrogen. Nitrogen applications of 120 kg N ha^-1 at planting and a further 120 kg N ha^-1 at tuber initiation supplemented with foliar N, however, achieved a larger tuber yield than the same nitrogen programme without foliar N and gave a significantly greater yield than the application of 240 kg N ha^-1 at planting plus foliar N. The emergence of both cultivars was delayed in the absence of oxamyl. N, P and K concentrations within whole plant dry matter were significantly higher in plants from oxamyl treated plots and both N and K concentrations were significantly increased by increasing the quantity of N at planting, at 56 DAP. Splitting the fertiliser N between planting and tuber initiation appears to be important in maintaining the availability of this nutrient to PCN infected plants throughout the season.     

Population Dynamics of Plant-parasitic Nematodes on Cover Crops of Corn and Sorghum

Buildup of plant-parasitic nematode populations on corn (Zea mays), soybean (Glycine max), and sorghum (Sorghum bicolor) were compared in 1991 and 1992. Final population densities (Pf) of Meloidogyne incognita were lower following sorghum than after soybean in both seasons, and Pf after sorghum was lower than Pf after corn in 1992. In both seasons, Pf differed among the sorghum cultivars used. No differences in Pf on corn, sorghum, and soybean were observed for Criconemella spp. (a mixture of C. sphaerocephala and C. ornata) or Paratrichodorus minor in either season. Pf levels of Pratylenchus spp. (a mixture of P. brachyurus and P. scribneri) were greatest after corn in 1992, but no differences with crop treatments were observed in 1991. When data from field tests conducted with corn and sorghum during the past four seasons were pooled, negative linear relationships between ln(Pf/Pi) and ln(Pi) were observed for Criconemella spp. and P. minor on each crop, and for M. incognita on corn (Pi = initial population density). Although ln(Pf/Pi) and ln(Pi) were not related for M. incognita with pooled sorghum data, separate relationships were derived for various sorghum cultivars. Regression equations from pooled data were used to obtain estimates of equilibrium density and maximum reproductive rate, and these estimates were used to construct models expressing nematode Pf across a range of initial densities. Many of these models were robust, encompassing a range of sites, season, crop cultivars, and planting dates. Quadratic models derived from pooled field data provided an alternative method for expressing Pf as a function of Pi.     

Life Cycle of the Golden Cyst Nematode,Globodera rostochiensis,in Quebec,Canada

In 2006, the golden cyst nematode, Globodera rostochiensis, was discovered in the province of Quebec, Canada. We report here the life cycle of G. rostochiensis under the climatic conditions of southwestern Quebec. Only one full generation was completed per year under these latitudes. On susceptible potato cv. Snowden, G. rostochiensis needed a minimum of 579 growing degree units (GDU) (base 5.9°C) to complete its life cycle and the first mature cysts were observed 42 to 63 days after planting (DAP). In soil, second-stage juveniles (J2) were first observed 14 to 21 DAP, whereas both white females on roots and males in soil appeared synchronously after 35 to 42 days. The duration of the life cycle was affected by temperature but not by soil type. A second wave of hatching systematically occurred later in the season and a second generation of males was observed during the 2011 growth season. No complete second cycle was observed before plant senescence. Climate change and later maturing cultivars/crops could allow the development of a full second generation in the future.     

Occurrence and Diversity of Yeasts in the Mangrove Ecosystems in Fujian, Guangdong and Hainan Provinces of China

Mangrove wetland is a unique ecosystem and has rich bioresources. In this article, the roots, stems, branches, leaves, barks, fruits, and flowers from 12 species of the mangrove plants and six species of the accompanying mangrove plants, seawater and sediments in mangrove ecosystems in China were used as sources for isolation of yeasts. A total of 269 yeasts strains were obtained from the samples. The results of routine identification and phylogenetic analysis showed that they belonged to 22 genera and 45 species. Of all the 269 strains, Candida spp. was predominant with the proportion of 44.61%, followed by Kluyveromyces spp. (8.55%), Pichia spp. (7.44%), Kodamaea ohmeri (5.58%), Issatchenkia spp. (4.83%) and Debaryomyces hansenii (4.46%). We also found that strains N02-2.3 and ST3-1Y3 belonged to the undescribed species of Pichia sp. and Trichosporon sp. respectively while strain HN-12 was not related to any known yeast strains. This means that different yeast strains of Candida spp. especially C. tropicalis were widely distributed in the mangrove ecosystems and may have an important role in the mangrove ecosystems. The results also showed that some of them may have potential applications.     

Control of Heterodera schachtii with Foliar Application of Nematicides

Foliar applications of ethyl 4-(methylthio)-m-tolyl isopropylphosphoramidate (phenamiphos) or S-methyl 1-(dimethylcarbamoyl)-N-[(methylcarbamoyl)oxy] thioformimidate (oxamyl) retarded infection of sugarbeets by the sugarbeet nematode, Heterodera schachtii under greenhouse conditions. Maximum nematode control was obtained when treatments were applied previous to, or at the time of, inoculation of plants with the nematode. Consecutive foliar applications inhibited nematode development, with four applications giving greatest inhibition of maturation. A treatment with either phenamiphos or oxamyl at 2,000 μg/ml (ppm) resulted in the greatest increase in plant growth, and 4,000 μg/ml gave the best nematode control. A treatment of 4,000 μg/ml of either phenamiphos or oxamyl was phytotoxic. However, this was due to container confinement of the chemical since phytotoxicity at this rate has not been observed under field conditions.     

Vertical Distribution of Plant-parasitic Nematodes in Sandy Soil under Soybean

Vertical distribution of five plant-parasitic nematodes was examined in two north Florida soybean fields in 1987 and 1988. Soil samples were collected from 0-15 cm, 15-30 cm, and 30-45 cm deep at each site. Soil at the three depths consisted of approximately 96% sand. More than 50% of Belonolaimus longicaudatus population densities occurred in the upper 15-cm soil layer at planting, but the species became more evenly distributed through the other depths as the season progressed. Criconemella sphaerocephala was evenly distributed among the three depths in one field but was low (< 20% of the total density) in the upper 15 cm at a second site. Maximum population densities of Pratylenchus brachyurus were observed at 15-30 cm on most sampling dates. Vertical distributions of Meloidogyne incognita and Paratrichodorus minor were erratic and showed seasonal variation. A diagnostic sample from the upper 0-15 cm of these soybean fields revealed only a minority of the populations of most of the phytoparasitic species present.