Bahiagrass, corn, cotton rotations, and pesticides for managing nematodes, diseases, and insects on peanut

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.

Peanut-cotton-rye rotations and soil chemical treatment for managing nematodes and thrips

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.

Effects of irrigation, nitrogen, and a nematicide on pearl millet

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.

Efficacy and Compatibility for Fenamiphos and EPTC Applied in Irrigation Water for Nematode and Weed Control in Snapbean Production

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.

Phytoparasitic nematodes associated with three types of blueberries in arkansas

Research and commercial blueberry plantings were sampled in October 1991 to determine the population densities and species of phytoparasitic nematodes associated with rabbiteye (Vaccinium ashei), southern highbush (Vaccinium sp.), and highbusb (V. corymbosum) blueberry cultivars and the sod middles between the blueberry rows. In the research planting at Clarksville, Arkansas, samples from the highbush cv. Bluecrop, the southern highbush cv. Cooper and Gulf Coast, and the sod middles had similar numbers of total vermiform phytoparasitic nematodes (125-451/250 cm(3) soil), whereas the samples from rabbiteye cv. Climax and Tifblue had significantly lower numbers (4/250 cm(3)). The major nematode species associated with blueberries and sod was Xiphinema americanum. In a research planting at Bald Knob, Arkansas, which contained Bluecrop and rabbiteye cultivars only, samples from Bluecrop and the sod had similar numbers (288 and 334/250 cm(3)), and the rabbiteye samples had significantly lower numbers (6-14/250 cm(3)). Xiphinema americanum was the major species found in the blueberry samples, whereas Mesocriconema ornata was the major species in the sod. Nematode population densities and species distribution in commercial rabbiteye plantings in nine counties in central and southwestern Arkansas varied greatly. The average population density for rabbiteye samples was 129/250 cm(3) and for sod was 577/250 cm(3). Weed infestations in the blueberry rows in the commercial plantings probably increased the population size and species distribution.

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.

Comparison of nematode population densities on six summer crops at seven sites in north Florida

Densities of plant-parasitic nematodes were compared on six crops grown for forage during the summer of 1991 at seven sites in north central Florida. The cropping treatments were 'Howard' soybean (Glycine max), 'Deltapine 105' soybean, velvetbean (Mucuna deeringiana), 'California Blackeye #5' cowpea (Vigna unguiculata), 'Pioneer 3098' tropical corn (Zea mays), and 'Asgrow Chaparral' sorghum (Sorghum bicolor). Highest final densities (Pf) of Meloidogyne incognita and Criconemella spp. were obtained following corn or sorghum at most sites. The lowest Pf of M. incognita occurred after velvetbean at all seven sites, but Pf after cowpea were equivalent to Pf after velvetbean at four of seven sites. Cultivar choice is critical in planning rotations to suppress M. incognita because results obtained here and elsewhere have shown great differences among sorghum and cowpea cultivars. The Pf of Pratylenchus spp. were lowest following velvetbean at four of seven sites. There were no differences in densities of Paratrichodorus minor among crops, but populations increased at a greater rate if initial density (Pi) was low. Multiplication rates (Pf/Pi) of most nematode species on most crops varied inversely with Pi. An accurate impression of nematode multiplication and host status could not be obtained unless a range of Pi was examined.

Effects of Rapeseed and Vetch as Green Manure Crops and Fallow on Nematodes and Soil-borne Pathogens

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.

Nematode densities associated with corn and sorghum cropping systems in Florida

Final densities (Pf) of Meloidogyne incognita and Pratylenchus spp. increased more than ten-fold over initial densities (Pi) on corn (Zea mays) cultivars grown at three sites in north Florida. The Pf of M. incognita following sorghum (Sorghum bicolor) were much lower (P </=0.001) than Pf following corn at the two sites in which sorghum was grown. At one of these sites, Pf of M. incognita was </= 5/100 cm(3) soil, and at the other site Pf < Pi. At one site, population densities of Criconemella sphaerocephala increased to higher levels on sorghum than on corn, but Pf of Pratylenchus spp. were greater (P </= 0.01) on corn. Few differences in nematode densities were observed among the different corn cultivars tested.

Nematode population changes and forage yields of six corn and sorghum cultivars

Two temperate corn (Zea mays) hybrids (Pioneer 3320 and Northrup King 508), two tropical corn cultivars (Pioneer X304C hybrid and Florida SYN-1 experimental open pollinated cultivar), the sorghum (Sorghum bicolor) x sudangrass (Sorghum sudanense) hybrid DeKalb SX-17, and the sorghum hybrid DeKalb FS25E were compared for effect on nematode densities and forage yield in three plantings (one single-crop and one double-crop system) in Florida. Final population densities of Meloidogyne incognita in the three plantings ranged from 0 to 13/100 cm(3) soil on the two Sorghum spp. and were lower (P </= 0.001) than those obtained on the corn cultivars (range 147 to 762/100 cm(3) soil). Early planted temperate corn and sorghum generally gave higher forage yields than did tropical corn. As second crops in double-cropping systems, tropical corn cultivars generally produced greater yields than temperate corn hybrids did. At 35% dry matter, double crop forage corn yield ranged from 51.1 to 64.8 ton/ha, and sorghum ranged from 79.8 to 102.2 ton/ ha. Tropical corn, forage sorghum, and sorghum-sudangrass were profitably grown at all planting dates. Late summer planting of temperate corn was unprofitable. DeKalb SX-17 sorghum x sudangrass first crop plus the ratoon double crop gave the highest net return of $1,133/ha. Among the corn cultivars, Florida SYN-1 gave the highest double crop net return of $652/ha.

Control of Nematodes and Soil-borne Diseases in Florida Potatoes with Aldicarb and 1,3-D

Yields of U.S. Size A potato tubers were increased by 1,3-dichloropropene (1,3-D) (56 liters/ha) and 1,3-D (56 liters/ha) + aldicarb (3.4 kg/ha) in 1982 and 1983 and by aldicarb (3.4 kg/ha) in 1982. Treatments that included aldicarb provided the best control of corky ringspot disease, whereas those including 1,3-D were more effective against bacterial wilt. The most effective nematode control (nematodes included Meloidogyne incognita, Belonolaimus longicaudatus, trichodorids, Criconemella ornata, Tylenchorhynchus claytoni, and Helicotylenchus sp.) was provided by the combination of 1,3-D + aldicarb.

Effect of Soil pH on Nematicide Efficacy on Soybean

To determine the efficacy of selected nematicides under different soil pH regimes in a sandy soil, soil pH ranges were achieved by adding lime or sulfur. Nematicides increased soybean yields, and their efficacy was generally not influenced by soil pH. Belonolaimus longicaudatus was negatively correlated (r = -0.58, P = 0.01) with yield in 1977.

Tillage and multiple cropping systems and population dynamics of phytoparasitic nematodes

The effect of two cropping and tillage systems on the population dynamics of four nematode species was evaluated on a loamy sand. Hairy vetch succeeded by corn or grain sorghum was seeded in split plots randomized within whole plots of no-tillage versus conventional tillage over four growing seasons (1980-83). The vetch-corn cropping system increased the density of Meloidogyne incognita 2.9 x more than the vetch-grain sorghum cropping system. In contrast, the vetch-grain sorghum cropping system increased the density of Criconemella ornata 0.7 x more than the vetch-corn cropping system. Meloidogyne incognita and C. ornata were affected more by these cropping systems than were Pratylenchus brachyurus or Paratrichodorus minor. Multiple cropping systems, vetch varieties, and crop host preference affected nematode population densities, whereas tillage treatments, conventional or no-tillage, had little effect on them.

Behavior, Parasitism, Morphology, and Biochemistry of Criconemella xenoplax and C. ornata on Peach

Host-parasite relationships of Criconemella xenoplax and C. ornata on Nemaguard peach and common bermudagrass were determined in the greenhouse. Criconemella xenoplax reproduced on peach and reduced root volume, height, and dry stem weight after 6 months, compared with the noninfested check. Numbers of C. ornata did not increase on peach or influence peach growth, but they did reduce dry top weight and root volume of common bermudagrass, compared with C. xenoplax. Criconemella xenoplax and C. ornata produced the enzyme beta-glucosidase and were capable of metabolizing prunasin, but only C. xenoplax produced beta-cyanoalanine synthase to detoxify the cyanide released from prunasin. The apparent inability of C. ornata to detoxify cyanide is one explanation why numbers of this species did not increase on peach. Criconemella xenoplax and C. ornata can be distinguished by using stylet length, vaginal configuration, and shape of the anterior head region.

Management of Root-knot Nematodes by Phenamiphos Applied through an Irrigation Simulator with Various Amounts of Water

Phenamiphos (6.7 kg a.i./ha) was applied via an irrigation simulator to squash at planting (AP) and 2 weeks after planting (PP), and to corn AP and 1 week PP to manage root-knot nematodes (Meloidogyne incognita). The nematicide was applied with 0.25, 0.64, 1.27, and 1.91 cm surface water/ ha to a Lakeland sand in which the soil moisture was at or near field capacity. Based on efficacy and crop response, no additional benefits resulted when phenamiphos was applied in volumes of water greater than 0.25 crn/ha. The cost of applying each 0.25 cm of water over a hectare is approximately $1.08, or a 92% reduction in nematicide application cost over conventional methods ($13.50/ha). Low root-gall indices and high yields from squash and corn indicate more effective nematode management when phenamiphos was applied AP rather than PP. Results from this method of applying phenamiphos suggest that certain nematicides could be used as salvage alternatives when nematodes are detected in crops soon after planting. For multiple-pest management, nematicides, other compatible biocides, and fertilizers could be applied simultaneously with sprinkler irrigation.