1,3-Dichloropropene (1,3-D) and nonfumigant nematicides were evaluated for control of Meloidogyne spp. and soil and foliar insects in a tobacco pest management system. In a field with a high Meloidogyne spp. population density (root gall index 4.0 to 4.5 on a 0 to 10 scale in untreated controls), tobacco yields and crop values increased (482 kg/ha and $1,784/ha for 1, 3-D; 326 kg/ha and $1,206/ha for fenamiphos; 252 kg/ha and $933/ha for ethoprop) with nematicide application over an untreated control. In fields with a low population density of Meloidogyne arenaria or M. incognita (root gall index 2.3 to 2.5 in untreated controls), yields ranged from 1,714 to 2,027 kg/ha and were not altered by fumigant or nonfumigant nematicide application. Carbofuran, a soil-applied nonfumigant nematicide/insecticide, reduced the number of foliar insecticide applications required to keep insect populations below treatment threshold (3.8 vs. 4.5, respectively, for treated vs. untreated). Carbofuran reduced the cost ($23/ha) of foliar insecticide treatments when compared to an untreated control. Although nonfumigant nematicides provided some soil and foliar insect control, the cost of using a fumigant plus a lower insecticidal rate of a soil insecticide/nematicide was comparable to the least expensive non-fumigant nematicide when the cost of foliar insecticide applications was included in the cost estimates. Savings in foliar insecticide cost by use of soil-applied nonfumigant nematicide/insecticides were small ($23/ha) in comparison to potential value reductions by root-knot nematodes when the nonfumigant nematicides fenamiphos or ethoprop ($578/ha and $851/ha, respectively) were used instead of 1,3-D.
1,3-dichloropropene; Meloidogyne arenaria; M. incognita; M. javanica; nematicide; nematode management systems; Nicotiana tabacum; root-knot nematode; tobacco
The effects of crop rotation and the nematicides 1,3-dichloropropene (1,3-D), ethoprop, and fenamiphos on the relative frequency of Meloidogyne incognita race 3, M. arenaria race 2, and M. javanica and tobacco yields on a sandy loam soil were determined. Cropping sequences altered the species composition and population densities of Meloidogyne spp. Meloidogyne arenaria and M. incognita predominated when cotton, corn, sorghum, or rye-fallow preceded tobacco. Meloidogyne javanica and M. arenaria predominated when tobacco preceded tobacco. Sorghum, cotton, corn, or rye-fallow preceding tobacco enhanced yields compared to tobacco preceding tobacco in plots containing mixtures of Meloidogyne species. Sorghum supported minimal reproduction of any Meloidogyne spp. Application of 1,3-D increased tobacco yields and reduced root galling when compared to untreated controls. Both fenamiphos and ethoprop treatments were less effective than 1,3-D in controlling Meloidogyne spp. or increasing yields. A rotation crop x nematicide interaction was not observed. In continuous tobacco, use of the M. incognita-resistant tobacco cv. Coker 176 increased tobacco yields when compared to the M. incognita-susceptible cv. Coker 319 when 1,3-D was not applied.
corn; cotton; Meloidogyne arenaria; M. incognita; M. javanica; nematicide; root-knot nematode; rotation; rye; sorghum; tobacco
Wheat, cotton, and peanut were arranged in three cropping sequences to determine the effects of fenamiphos (6.7 kg a.i./ha) and cropping sequence on nematode population densities and crop yields under conservation tillage and irrigation for 6 years. The cropping sequences included a wheat winter cover crop each year and summer crops of cotton every year, peanut every year, or cotton rotated every other year with peanut. The population densities of Meloidogyne spp. and Helicotylenchus dihystera were determined monthly during the experiment. Numbers of M. incognita increased on cotton and decreased on peanut, whereas M. arenaria increased on peanut, and decreased on cotton; both nematode species remained in moderate to high numbers in plots of wheat. Root damage was more severe on cotton than peanut and was not affected by fenamiphos treatment. The H. dihystera population densities were highest in plots with cotton every summer, intermediate in the cotton-peanut rotation, and lowest in plots with peanut every summer. Over all years and cropping sequences, yield increases in fenamiphos treatment over untreated control were 9% for wheat, 8% for cotton, and 0% for peanut. Peanut yields following cotton were generally higher than yields following peanut. These results show that nematode problems may be manageable in cotton and peanut production under conservation tillage and irrigation in the southeastern United States.
Arachis hypogaea; cotton; crop rotation; Gossypium hirsutum; Helicotylenchus dihystera; management; Meloidogyne arenaria; M. incognita; nematicide; nematode; peanut; root-knot nematode; spiral nematode; Ttriticum aestivum; wheat
Florunner peanut was grown after 1 and 2 years of Tifton 9 bahiagrass, corn, cotton, and continuous peanut as whole-plots. Pesticide treatments aldicarb (3.4 kg a.i./ha), flutolanil (1.7 kg a.i./ha), aldicarb + flutolanil, and untreated (control) were sub-plots. Numbers of Meloidogyne arenaria second-stage juveniles in the soil and root-gall indices of peanut at harvest were consistently lower in plots treated with aldicarb and aldicarb + flutolanil than in flutolanil-treated and untreated plots. Percentages of peanut leaflets damaged by thrips and leafhoppers were consistently greater in flutolaniltreated and untreated plots than in plots treated with aldicarb or aldicarb + flutolanil but not affected by cropping sequences. Incidence of southern stem rot was moderate to high for all chemical treatments except those that included flutolanil. Stem rot loci were low in peanut following 2 years of bahiagrass, intermediate following 2 years of corn or cotton, and highest in continuous peanut. Rhizoctonia limb rot was more severe in the peanut monoculture than in peanut following 2 years of bahiagrass, corn, or cotton. Flutolanil alone or combined with aldicarb suppressed limb rot compared with aldicarb-treated and untreated plots. Peanut pod yields were 4,186 kg/ha from aldicarb + flutolanil-treated plots, 3,627 kg/ha from aldicarb-treated plots, 3,426 kg/ha from flutolanil-treated plots, and 3,056 kg/ha from untreated plots. Yields of peanut following 2 years of bahiagrass, corn, and cotton were 29% to 33% higher than yield of monocultured peanut.
Arachis hypogaea; bahiagrass; corn; cotton; Criconemella ornata; crop rotation; Frankliniella spp.; fungicide; Gossypium hirsutum; management; Meloidogyne arenaria; monocrop; nematicide; nematode; Paspalum notatum; peanut; population dynamics; Rhizoctonia solani; ring nematode; root-knot nematode; Sclerotium rolfsii; thrips; Zea mays
The efficacy of a double-cross corn (Zea mays) hybrid (Old Raccoon selection X T216) X (Tebeau selection X Mp 307) resistant to Meloidogyne incognita as a rotational crop, and fenamiphos treatment for management of root-knot nematode (M. incognita race 1) in squash (Cucurbita pepo var. melopepo) was evaluated in field tests during 1996 and 1997. Numbers of M. incognita in the soil and root-gall indices were lower on the resistant hybrid than on a commercial cultivar DeKalb DK-683. Treatment means across both corn entries had lower root-gall indices following fenamiphos treatment. In soil collected 2 September 1997, there were more colony-forming units (cfu) per gram of oven-dried soil of Pythium spp. from plots planted to DK-683 treated with fenamiphos than in untreated plots (88 vs. 59 cfu). Some corn plots had individual plants with 10% to 15% of the crown and brace roots decayed, but no differences due to fenamiphos treatment. Lodging of stalks was 40% to 50% more in the double-cross hybrid than in DK-683. Yield was greater from DK-683 than the double-cross hybrid. Based on cultivar means across fenamiphos treatments and fenamiphos treatment means across cultivars, root-gall indices and yield of squash were significantly lower following the double cross hybrid than DK-683 and in fenamiphos-treated plots than in untreated plots of squash. Yield of squash was not affected by at-planting treatment with fenamiphos on the preceding crops of corn. Nematode resistance must be transferred into the elite materials of commercial seed companies to reach its full potential as a nematode management strategy.
corn; crop rotation; Cucurbita pepo; fenamiphos; maize; management; Meloidogyne incognita; nematicide; nematode; Pythium; resistance; Rhizoctonia solani; root-knot nematode; squash; stalk rot; Zea mays
Triticale cv. Beagle 82, cotton cv. McNair 235, and soybean cv. Twiggs were arranged in three cropping sequences to determine the effects of fenamiphos and cropping sequence on nematode population densities and crop yields under conservation tillage for 4 years. The cropping sequences were triticale (T)-cotton (C)-T-C, T-soybean (S)-T-S, and T-C-T-S. Numbers of Meloidogyne incognita second-stage juveniles declined on trificale but increased on cotton and soybean each year. Root-gall indices of cotton and soybean ranged from 1.00 to 1.08 (1 to 5 scale: 1 = 0%, 2 = 1% to 25%, 3 = 26% to 50%, 4 = 51% to 75%, and 5 = 76% to 100% of roots galled) each year and were not affected by fenamiphos treatment or cropping sequence. Numbers of Pratylenchus brachyurus were maintained on trificale and generally increased more on soybean than on cotton. Population densities of Helicotylenchus dihystera were near or below detection levels in all plots during the first year and increased thereafter in untreated plots in the T-C-T-C and T-S-T-S sequences. Generally, yields of triticale in all cropping sequences declined over the years. Yields of cotton and soybean were not affected by fenamiphos at 6.7 kg a.i./ha. Cotton and soybean were grown successfully with little or no suppression in yields caused by nematodes in conservation tillage following triticale harvested for grain.
conservation tillage; cotton; crop rotation; fenamiphos; Glycine max; Gossypium hirsutum; Helicotylenchus dihystera; lesion nematode; management; Meloidogyne incognita; nematicide; nematode; Pratylenchus brachyurus; root-knot nematode; soybean; spiral nematode; triticale; Triticosecale
In the southeastern United States, a cotton-peanut rotation is attractive because of the high value and extensive planting of both crops in the region. The objective of this experiment was to determine the effects of cotton-peanut rotations, rye, and soil chemical treatments on management of plant-parasitic nematodes, thrips, and soilborne fungal diseases and on crop yield. Peanut-cotton-rye rotations were conducted from 1988 to 1994 on Tifton loamy sand (Plinthic Kandiudult) infested primarily with Meloidogyne incognita race 3, Belonolaimus longicaudatus, Sclerotium rolfsii, Rhizoctonia solani, and Fusarium oxysporum. Continuous peanut, continuous cotton, cotton-peanut rotation, or peanut-cotton rotation were used as main plots; winter rye or fallow as sub-plots; and cotton with and without aldicarb (3.36 kg a.i./ha), or peanut with and without aldicarb (3.36 kg a.i./ha) plus flutolanil (1.12 kg a.i./ha), as sub-sub-plots. Population densities of M. incognita and B. longicaudatus declined rapidly after the first crop in continuous peanut and remained low thereafter. Neither rye nor soil chemical treatment affected M. incognita or B. longicaudatus population density on peanut or cotton. Cotton and peanut yields from the cotton-peanut rotation were 26% and 10% greater, respectively, than those from monoculmre over the 7-year study. Cotton and peanut yields were improved 9% and 4%, respectively, following rye vs. fallow. Soil chemical treatments increased yields of cotton 23% and peanut 32% over those of untreated plots. Our data demonstrate the sustainable benefits of using cotton-peanut rotations, winter rye, and soil chemical treatments to manage plant-parasitic nematodes and other pests and pathogens and improve yield of both cotton and peanut.
Arachis hypogaea; Belonolaimus longicaudatus; cotton; Criconemella ornata; crop rotation; fallow; Frankliniella spp., Gossypium hirsutum; management; Meloidogyne incognita; monocrop; nematicide; nematode; peanut; population dynamics; ring nematode; root-knot nematode; rye; Secale cereale; sting nematode; thrips
Nematicides are used to control a wide variety of nematodes on many crops; unfortunately, oftentimes the control they provide is erratic. This erratic behavior is not always predictable and has been associated with chemical, physical, and biological degradation of nematicides. Their accelerated degradation is an agricultural problem that has been observed in crop monocultures and in other crop production systems where a biodegradable compound is repeatedly applied to the same soil. The problem can occur in field soil and golf course greens; it is not unique to any single nematicide or class of nematicides, but rather to many classes of pesticides. As indicated by the population density of root-knot nematodes (Meloidogyne incognita) in the soil in a 6-year sweet corn-sweet potato-vetch rotation, the efficacy of the nematicide fenamiphos diminished during the third year. Therefore, use of the nematicide applied immediately before planting sweet corn, sweet potato, and vetch should not exceed 3 years. After 3 years, the crop rotation and(or) the nematicide should be changed.
control; degradation; enhanced degradation; fenamiphos; management; Meloidogyne incognita; nematicide; nematode; root-knot nematode; rotation
The efficacy of clean fallow, bermudagrass (Cynodon dactylon) as a rotational crop, and fenamiphos for control of root-knot nematode (Meloidogyne incognita race 1) and soilborne fungi in okra (Hibiscus esculentus), snapbean (Phaseolus vulgaris), and pepper (Capsicum annuum) production was evaluated in field tests from 1993 to 1995. Numbers of M. incognita in the soil and root-gall indices were greater on okra than on snapbean or pepper. Application of fenamiphos at 6.7 kg a.i./ha did not suppress numbers of nematodes on any sampling date when compared with untreated plots. The lack of efficacy could be the result of microbial degradation of the nematicide. Application of fenamiphos suppressed root-gall development on okra following fallow and 1-year sod in 1993, but not thereafter. A few galls were observed on roots of snapbean following 2- and 3-year fallow but none following 1-, 2-, and 3-year bermudagrass sod. Population densities of Pythium aphanidermatum, P. myriotylum, and Rhizoctonia solani in soil after planting vegetables were suppressed by 2- or 3-year sod compared with fallow but were not affected by fenamiphos. Yields of snapbean, pepper, and okra did not differ between fallow and 1-year sod. In the final year of the study, yields of all crops were greater following 3-year sod than following fallow. Application of fenamiphos prior to planting each crop following fallow or sod did not affect yields.
Bermudagrass; Capsicum annuum; Gynodon dactylon; Cyperus esculentus; fenamiphos; Hibiscus esculentus; management; Meloidogyne incognita; nematicide; nematode; nutsedge; okra; pepper; Phaseolus vulgaris; resistance; root-knot nematode; snapbean; sod-based rotation
The objective of this experiment was to determine the effects of fenamiphos 15G and short-cycle potato (PO)-sweet potato (SP) grown continuously and in rotation with peanut (PE)-grain sorghum (GS) on yield, crop quality, and mixed nematode population densities of Meloidogyne arenaria, M. hapla, M. incognita, and Mesocriconema ornatum. Greater root-gall indices and damage by M. hapla and M. incognita occurred on potato than other crops. Most crop yields were higher and root-gall indices lower from fenamiphos-treated plots than untreated plots. The total yield of potato in the PO-SP and PO-SP-PE-GS sequences increased from 1983 to 1985 in plots infested with M. hapla or M. arenaria and M. incognita in combination and decreased in 1986 to 1987 when root-knot nematode populations shifted to M. incognita. The total yields of sweet potato in the PO-SP-PE-GS sequence were similar in 1983 and 1985, and declined each year in the PO-SP sequence as a consequence of M. incognita population density increase in the soil. Yield of peanut from soil infested with M. hapla increased 82% in fenamiphos-treated plots compared to untreated plots. Fenamiphos treatment increased yield of grain sorghum from 5% to 45% over untreated controls. The declining yields of potato and sweet potato observed with both the PO-SP and PO-SP-PE-GS sequences indicate that these crop systems should not be used longer than 3 years in soil infested with M. incognita, M. arenaria, or M. hapla. Under these conditions, these two cropping systems promote a population shift in favor of M. incognita, which is more damaging to potato and sweet potato than M. arenaria and M. hapla.
Arachis hypogaea; crop rotation; fenamiphos; grain sorghum; Ipomoea batatas; Meloidogyne arenaria; Meloidogyne hapla; Meloidogyne incognita; Mesocriconema ornatum; nematode; peanut; potato; root-knot; root-knot nematode; Solanum tuberosum; Sorghum vulgare; sweet potato
Recoverable fenamiphos in the soil and residue in squash following different simulated rainfall treatments after nematicide application were determined in a 2-year study. Efficacy of fenamiphos also was evaluated. Fenamiphos treatments (3 SC and 15 G) were broadcast (6.7 kg a.i./ha) over plots and incorporated into the top 15 cm of soil immediately before planting 'Dixie Hybrid' squash. Simulated rainfall treatments of 0, 2.5, and 5.0 cm water were applied 1 day after fenamiphos application. Soil samples from 0- to 8-cm, 8- to 15-cm, and 15- to 30-cm soil depths were collected 1 day after the simulated rainfall applications and analyzed for fenamiphos, fenamiphos sulfoxide (FSO), and fenamiphos sulfone (FSO₂). Squash was analyzed for total fenamiphos residue. Greater concentrations of fenamiphos were present in the 0- to 8-cm soil layer following application of 15 G than 3 SC formulation. Simulated rainfall treatments did not alter fenamiphos concentrations in any soil layer (except for the 0- to 8-cm depth in 1992) or concentration of FSO and total fenamiphos residue in the 15- to 30-cm soil layer. Root-gall indices were greater from untreated than most fenamiphos-treated plots, but were not affected by formulations of fenamiphos or simulated rainfall treatments. Concentrations of total residue in squash ranged from 1 to 4 μg FSO₂/g.
Cucurbita melopepo; efficacy; fenamiphos; leaching; management; Meloidogyne incognita; nematicide; nematode; root-knot; root-knot nematode; squash
Pearl millet is used mainly as a temporary forage crop in the southern United States. A new pearl millet hybrid has potential as a major grain crop in the United States. The effects of nematodes, irrigation, a nematicide, and nitrogen rates on a new pearl millet grain hybrid, HGM-100, and nematode population changes were determined in a 2-year study. Root-knot nematodes (Meloidogyne incognita race 1) entered the roots of pearl millet and caused minimal galling, but produced large numbers of eggs that hatched into second-stage juveniles. Root-gall indices ranged from 1.00 to 1.07 on a 1-5 scale and were not affected by irrigation or rates of nitrogen. Yield of pearl millet was up to 31% higher under no supplemental irrigation than under irrigation, 16% higher in fenamiphos-treated plots than untreated plots, and 56% higher in plots treated with 38 kg nitrogen/ha than plots treated with 85 kg nitrogen/ha. In southern Georgia, pearl millet appears to be resistant to ring nematode (Criconemella ornata) but favors development and reproduction of M. incognita.
chemical control; Criconemella ornata; irrigation; Meloidogyne incognita; millet; nematode; nitrogen; Pennisetum glaucum; ring nematode; root-knot nematode
The efficacy of fallow and coastal bermudagrass (Cynodon dactylon) as a rotation crop for control of root-knot nematode (Meloidogyne incognita race 1) and soilborne fungi in okra (Hibiscus esculentus cv. Emerald), squash (Cucurbita pepo cv. Dixie Hybrid), and sweet corn (Zea mays cv. Merit) was evaluated in a 3-year field trial. Numbers of M. incognita in the soil and root-gall indices were greater on okra and squash than sweet corn and declined over the years on vegetable crops following fallow and coastal bermudagrass sod. Fusarium oxysporum and Pythium spp. were isolated most frequently from soil and dying okra plants. Numbers of colony-forming units of soilborne fungi generally declined as the number of years in sod increased, but were not affected by coastal bermudagrass sod. Yields of okra following 2-year and 3-year sod and squash following 2-year sod were greater than those following fallow. Yield of sweet corn was not different following fallow and coastal bermudagrass sod.
coastal bermudagrass; Cucurbita pepo; Cynodon dactylon; fallow; Hibiscus esculentus; management; Meloidogyne incognita; nematode; okra; root-knot; rotation; squash; sweet corn; Zea mays
There is increasing concern in the United States about the pesticide movement in soil, groundwater contamination, and pesticide residue in food. The objective of this study was to determine the efficacy, degradation, and movement of fenamiphos (Nemacur 15G) in the soil and residues in squash fruit as influenced by four simulated rainfall treatments (2.5 or 5.0 cm each applied 1 or 3 days after nematicide application) under field conditions. In 1990, concentrations of fenamiphos were greater in the top 15 cm of soil in plots with no rainfall than in those treated with rainfall. Eighty to 95 % of the fenamiphos recovered from treated plots was found in the 0-15-cm soil layer. The concentration of fenamiphos recovered from the 0-15-cm soil layer in 1991 was approximately one-half the concentration recovered in 1990, but greater concentrations of fenamiphos sulfoxide (an oxidation product of fenamiphos) were recovered in 1991 than in 1990. Concentrations of fenamiphos, fenamiphos sulfoxide, and fenamiphos sulfone were near or below detectable levels (0.002 mg/kg soil) below the 0-15-cm soil layer. Rainfall treatments did not affect the efficacy of the nematicide against Meloidogyne incognita race 1. The concentration of fenamiphos in squash fruit in 1991 was below the detectable level (0.01 mg/kg).
Cucurbita pepo var. melopepo; degradation; efficacy; fenamiphos; leaching; Meloidogyne incognita; nematicide; nematode; pesticide residue; root-knot nematode; squash
The effects of irrigation on the efficacy of nematicides on Meloidogyne incognita race 1 population densities, yield of sweet corn, and the carry-over of nematicidal effect in the squash crop were determined in a sweet corn-squash-vetch cropping system for 3 years. Fenamiphos 15G and aldicarb 15G were applied at 6.7 kg a.i./ha and incorporated 15 cm deep with a tractor-mounted rototiller. Ethylene dibromide (EDB) was injected at 18 kg a.i./ha on each side of the sweet corn rows (total 36 kg a.i./ha) at planting for nematode control. Supplemental sprinkler irrigation (1.52-4.45 cm), applied in addition to natural rainfall (4.60-10.80 cm) within l0 days after application of nematicides, did not affect nematicide efficacy against M. incognita or yield of sweet corn. Soil treatment with fenamiphos, EDB, and aldicarb increased the number and total weight of sweet corn ears and the weight per ear each year over untreated controls (P ≤ 0.05). All nematicides provided some control of M. incognita on squash planted after sweet corn, but yields were consistently greater and root-gall indices lower on squash following sweet corn treated with fenamiphos than other nematicides.
aldicarb; chemical control; Cucurbita pepo; ethylene dibromide; fenamiphos; irrigation; Meloidogyne incognita; nematicide; nematode; root-knot nematode; squash; sweet corn; Zea mays
A nematicide (fenamiphos) and a herbicide (EPTC) were injected into a sprinkler irrigation system separately and as tank mixtures and applied in 25.4 kl water/ha for nematode and weed control on snapbean. There were no differences (P = 0.05) between methods of injection of fenamiphos + EPTC on efficacy or crop response. The root-gall indices of cultivars Eagle and GV 50 were lower in fenamiphos-treated plots than those treated with EPTC alone and untreated plots. The yield and crop value were greater (P = 0.05) for cultivars Eagle and Nemasnap than GV 50. Fenamiphos 4.48 kg a.i./ha + EPTC 3.36 kg a.i./ha controlled root-knot nematodes, Meloidogyne incognita, ring nematodes, Criconemella ornata, and weeds, and resulted in greater plant growth, yield, and crop value than those from untreated plots. No benefits (P = 0.05) resulted from treatment with fenamiphos at 6.72 kg a.i./ha + EPTC treatment compared with fenamiphos at 4.48 kg a.i. + EPTC.
Criconemella ornata; EPTC; fenamiphos; Meloidogyne incognita; nemagation; nematode; Phaseolus vulgaris; root-knot nematode; snapbean; weeds
Management ofMeloidogyne incognita by chemigation with fenamiphos was studied in an infested field planted to M. incognita-suscepfible yellow summer squash cv. Dixie Hybrid. Fenamiphos (VL 73.1% a.i. manufacturing concentrate in propylene glycol) was mixed with Unitol DSR-90 or used as fenamiphos 3 SC (spray concentrate). Both formulations, applied with 63.5 kl irrigation water per hectare, decreased numbers of M. incognita second-stage juveniles in the soil and root-gall indices, and increased yield of squash compared with the untreated control. There was no benefit achieved by mixing the fenamiphos concentrate with Unitol DSR-90 over the use of fenamiphos 3 SC formulation. Fenamiphos application rates between 3.36 and 6.72 kg a.i./ha could provide control of M. incognita comparable to that obtained with 6.72 kg a.i./ha. Reduced rates of fenamiphos applied with irrigation water used to control plant-parasitic nematodes could reduce the potential for groundwater pollution as well as cost to the grower.
Cucurbita pepo; fenamiphos; Meloidogyne incognita; nemagation; nematicide; nematode; root-knot nematode; summer squash
Field and greenhouse experiments were conducted to determine the extent to which fenamiphos and its degradation products, fenamiphos sulfoxide and fenamiphos sulfone, are available to contact nematodes in the soil. Water extraction provided a relative measure of each chemical's availability to the soil water where the chemicals could contact nematodes, and methanol extraction provided a relative measure of the total amount of each chemical present in the soil. Only small amounts of fenamiphos and fenamiphos sulfone could be extracted by water, even when much larger amounts were present in the soil. In contrast, virtually all of the fenamiphos sulfoxide present in the soil was extractable by water several days after nematicide application. Three days after fenamiphos (3EC) was applied at 6.7 kg a.i./ha to field plots, 6.4% of the fenamiphos, 14.4% of the fenamiphos sulfone, and 100% of the fenamiphos sulfoxide present in the soil was extracted by water. In greenhouse experiments with soil from these field plots, a 15G formulation of fenamiphos containing 98.7% fenamiphos and 1.3% fenamiphos sulfoxide was added to the soil. After an initial period of 3-4 days, the sulfoxide which formed by oxidation of fenamiphos became completely available for water extraction, whereas fenamiphos remained relatively unextractable by water. Fenamiphos sulfoxide is much more available to soil water, thus available for contact with nematodes, than are fenamiphos or fenamiphos sulfone. Based on this availability in water, it seems likely that fenamiphos sulfoxide is the major component for controlling nematodes.
fenamiphos; fenamiphos sulfone; fenamiphos sulfoxide; metabolite; nematicide; nematode; soil solution; water
The degradation of fenamiphos, fenamiphos sulfoxide, and fenamiphos sulfone was determined in a greenhouse experiment using autoclaved and nonautoclaved soil from field plots treated or not treated with fenamiphos. Fenamiphos degradation and formation of fenamiphos sulfoxide was faster in uonautoclaved soil than in autoclaved soil. In nonautoclaved soil, previous exposure to fenamiphos was associated with increased rate of degradation of fenamiphos snlfoxide. Fenamiphos total toxic residue degraded more rapidly in nonautoclaved soil previously exposed to fenamiphos than in nonautoclaved soil never exposed to fenamiphos. This accelerated degradation was due to more rapid degradation of fenamiphos sulfoxide and appears to be biologically mediated.
accelerated degradation; degradation; enhanced degradation; fenamiphos; fenamiphos sulfone; fenamiphos sulfoxide; metabolite; microbial degradation; nematicide; nematode; pesticide degradation
Nematode population densities and yield of sweet corn and sweet potato as affected by the nematicide fenamiphos, in a sweet corn-sweet potato-vetch cropping system, were determined in a 5-year test (1981-85). Sweet potato was the best host of Meloidogyne incognita of these three crops. Fenamiphos 15G (6.7 kg a.i./ha) incorporated broadcast in the top 15 cm of the soil layer before planting of each crop increased (P ≤ 0.05) yields of sweet corn in 1981 and 1982 and sweet potato number 1 grade in 1982 and 1983. Yield of sweet corn and numbers of M. incognita second-stage juveniles (J2) in the soil each month were negatively correlated from planting (r = - 0.47) to harvest (r = -0.61) in 1982. Yield of number 1 sweet potato was inversely related to numbers of J2 in the soil in July-October 1982 and July-September 1983. Yield of cracked storage roots was positively related to the numbers of J2 in the soil on one or more sampling dates in all years except 1985. Some factor(s), such as microbial degradation, resistant M. incognita development, or environment, reduced the effect of fenamiphos.
fenamiphos; Ipomoea batatas; Meloidogyne incognita; nematicide; nematode; root-knot nematode; sweet corn; sweet potato; vetch; Vicia sativa; Zea mays
Tank mixes of a fungicide (metalaxyl) and a nematicide (fenamiphos) with herbicides (isopropalin or pendimethalin) and an insecticide (chlorpyrifos) were applied by soil incorporation or irrigation to control the black shank-root knot complex and weeds on four tobacco cultivars. The disease complex was more severe on cultivars McNair 944, NC-2326, and K-326 than on Speight G-70. The disease complex was reduced (P ≤ 0.05) on all cultivars with the pesticide combinations containing metalaxyl + fenamiphos. On most cultivars, percentage disease, disease index, root-gall index, yield, and weed control did not differ (P ≤ 0.05) between the tank mixes containing isopropalin or pendimethalin or among methods of application. Generally, the most effective method of treatment application for control of the disease complex and weeds was preplant incorporated followed by postplant irrigation and preplant irrigation.
black shank; chemigation; Meloidogyne spp.; nematode; Nicotiana tabacum; Phytophthora parasitica; root-knot nematode
In a rapeseed-squash cropping system, Meloidogyne incognita race 1 and M. javanica did not enter, feed, or reproduce in roots of seven rapeseed cultivars. Both nematode species reproduced at low levels on roots of the third crop of rapeseed. Reproduction of M. incognita and M. javanica was high on squash following rapeseed, hairy vetch, and fallow. The application of fenamiphos suppressed (P = 0.05) root-gall indices on squash following rapeseed, hairy vetch, and fallow; and on Dwarf Essex and Cascade rapeseed, but not Bridger and Humus rapeseed in 1987. The incorporation of 30-61 mt/ha green biomass of rapeseed into the soil 6 months after planting did not affect the population densities of Criconemella ornata, M. incognita, M. javanica, Pythium spp., Rhizoctonia solani AG-4; nor did it consistently increase yield of squash. Hairy vetch supported larger numbers of M. incognita and M. javanica than rapeseed cultivars or fallow. Meloidogyne incognita and M. javanica survived in fallow plots in the absence of a host from October to May each year at a level sufficient to warrant the use of a nematicide to manage nematodes on the following susceptible crop.
Brassica napus; Criconemella ornata; Cucurbita pepo; fungus; Meloidogyne incognita; M. javanica; nematode; Pythium spp.; rapeseed; Rhizoctonia solani; ring nematode; root-knot nematode; squash
The effects of planting date, rye (Secale cereale cv. Wren Abruzzi) and wheat (Triticura aestivum cv. Coker 797), crop destruction, fallow, and soil temperature on managing Meloidogyne incognita race 1 were determined in a 2-year study. More M. incognita juveniles (J2) and egg-producing adults were found in roots of rye planted 1 October than in roots of rye planted 1 November and wheat planted 1 November and 1 December. Numbers of M. incognita adults with and without egg masses were near or below detectable levels in roots of rye planted 1 November and wheat planted 1 November and 1 December. Meloidogyne incognita survived the mild winters in southern Georgia as J2 and eggs. The destruction of rye and wheat as a trap crop 1 March suppressed numbers of J2 in the soil temporarily but did not provide long-term benefits for susceptible crops that followed. In warmer areas where rye and wheat are grown in winter, reproduction of M. incognita may be avoided by delaying planting dates until soil temperature declines below the nematode penetration threshold (18 C), but no long-term benefits should be expected. The temperature threshold may be an important consideration in managing M. incognita population densities in areas having lower winter soil temperatures than southern Georgia.
fallow; Meloidogyne incognita; root-knot nematode; rye; Secale cereale; trap crop; Triticum aestivum; wheat
Seven cultivars of wheat, five of oat, one of rye, and four of barley were tested as hosts for Meloidogyne incognita, M. javanica, or M. arenaria under greenhouse conditions where soil temperature ranged from 21 to 34 C. Reproduction rates of all nematode species were high on all cultivars, except M. javanica and M. arenaria on 'Brooks' and 'Florida 501' oat. Meloidogyne incognita and M. javanica produced more eggs on roots of 'Rutgers' tomato than on cultivars of wheat, oat, rye, or barley.
Avena sativa; barley; Hordeum vulgare; Meloidogyne arenaria; M. incognita; M. javanica; oat; root-knot nematode; rye; Secale cereale; Triticum aestivum; wheat
Nematode population densities and yield of sweet potato and onion as affected by nematicides and time of application were determined in a 3-year test. Population densities of Meloidogyne incognita race 1 in untreated plots of sweet potato increased each year, but Helicotylenchus dihystera and Criconemella ornata did not. Ethoprop (6.8 kg a.i./ha) incorporated broadcast in the top 15-cm soil layer each spring before planting sweet potato reduced population densities of nematodes in the soil and increased marketable yield in 1982, but not in 1983 and 1984. When DD, fenamiphos, and aldicarb were applied just before planting either sweet potato or onion, nematode population densities at harvest were lower in treated than in untreated plots. No additional benefits resulted when the nematicides were applied immediately before planting both sweet potato and onion. Correlation coefficients (P ≤ 0.05) between yield of marketable and cracked sweet potato storage roots vs. densities of M. incognita juveniles in the soil at harvest among years ranged from r = -0.33 to r = -0.54 and r = 0.31 to r = 0.54 (P ≤ 0.05), respectively. Temperatures of -6 to -8 C in December 1981 and - 11 to - 13 C in December 1983 killed the onion crops. Correlation coefficients for marketable yield of onion seeded in 1982 and harvested in 1983 vs. densities of M. incognita juveniles and H. dihystera in the soil at harvest were r = -0.42 and r = -0.31 (P ≤ 0.05), respectively.
aldicarb; Allium cepa; chemical control; crop rotation; DD; ethoprop; fenamiphos; Ipomoea batatas; Meloidogyne incognita; root-knot nematode