Ultra-narrow row cotton studies were conducted during 1999 at two field sites in northern Florida. One site was naturally infested with Meloidogyne incognita Race 3 and the other with Rotylenchulus reniformis. The fumigant 1,3-dichloropropene (1,3-D) was applied broadcast at rates of 0, 16, 32, 48, 64, 80, and 96 kg ai./ha in replicated plots before planting Delta Pine 655 BRR cotton in 25-cm-wide rows. Post-harvest soil population densities at the root-knot nematode site had a significant (P ≤ 0.01) negative linear relationship to 1,3-D dosage level. Cotton lint yields at this site had a significant (P ≤ 0.01) positive linear relationship to 1,3-D dosage level. At the reniform nematode site, there was no relationship between post-harvest soil population densities of reniform nematodes and 1,3-D dosage level. However, significant (P ≤ 0.01) positive curvilinear relationships were found between both plant heights and lint yield to 1,3-D dosage levels.
1,3-dichloropropene; cotton; Gossypium hirsutum; Meloidogyne incognita; nematicide; reniform nematode; root-knot nematode; Rotylenchulus reniformis
Three field trials were conducted to determine response of Meloidogyne javanica to tomato cultivars containing the Mi gene for resistance in sequential tests. Trials were conducted in spring and fall 1997 and spring 1998 on the same site. Tomatoes were grown on polyethylene mulch at a site initially treated with methyl bromide and then infested with M. javanica via drip tubing. Cultivars with the Mi gene were 'PSR 8991994' and 'Sanibel', and susceptible cultivars were 'Colonial' and 'Agriset 761'. The resistant cultivars greatly suppressed root galling in the three tests. Population densities of second-stage juveniles also were low in soil samples collected from resistant cultivars. Tomato fruit yields were significantly increased in only one test when using resistant cultivars. However, the susceptible cultivars are high-yielding and recommended for north Florida production, while the cultivars containing the Mi gene are not as well adapted. In the three successive crops, no evidence of resistance-breaking biotypes of M. javanica was observed. With further incorporation into adapted cultivars, the Mi gene resistance could be a valuable tool to manage M. javanica in north Florida stake tomato production.
Lycopersicon esculentum; Meloidogyne javanica; Mi gene; nematode; resistance; root galling; root-knot nematode; tomato
In four tests conducted in loamy-sand soils in northern Florida, cotton lint yield increased and post-harvest soil populations of Meloidogyne incognita were more effectively suppressed by 1,3-dichloropropene (1,3-D) than aldicarb when both nematicides were evaluated over a range of recommended rates. Significant positive relationships existed between lint yield and rates of 1,3-D in three tests, whereas only one significant positive relationship occurred between lint yield and aldicarb rates. Yield increases ranged from 16% to 124%, depending on rate of 1,3-D, and 35% in one aldicarb-treated test. Only a weak negative relationship between post-harvest soil densities of second-stage juveniles (J2) and aldicarb rates was determined by combining data from the four tests. Aldicarb failed to suppress post-harvest J2 soil population densities in any test. All rates of 1,3-D significantly reduced post-harvest M. incognita J2 soil population densities in two tests and provided a stronger negative correlation between nematode soil densities and rates than aldicarb when all test data were combined for each nematicide.
1,3-D; aldicarb; cotton; Gossypium hirsutum; Meloidogyne incognita; nematicide; nematode; southern root-knot nematode
One grower trial and two experiment station tests were conducted to evaluate a new nematicide, fosthiazate, for management of Meloidogyne javanica in Florida flue-cured tobacco. Fosthiazate was applied broadcast and incorporated at rates ranging from 21 to 84 g/100 m² and compared with 1,3-dichloropropene at 240 and 460 ml/100 m² and fenamiphos at 67 g/100 m². All fosthiazate treatments increased tobacco yields and reduced root galling. Application of 1,3-D provided the highest tobacco yields and greatest reductions in root galling. The fenamiphos treatment outperformed all fosthiazate treatments in tobacco yield and root gall reduction. Fosthiazate may therefore have limited utility compared with 1,3-D and fenamiphos as a nematicide for tobacco in peninsular Florida.
fenamiphos; fosthiazate; 1,3-D; Meloidogyne arenaria; Meloidogyne javanica; nematicides; nematode; nematode management; Nicotiana tabacum; root-knot nematode; tobacco
Two field microplot tests were conducted in sandy soil to evaluate retention of ethoprop in relation to simulated rainfall levels. Ethoprop was applied at the equivalent of 13.5 kg a.i./ha, and simulated rainfall was added at rates of 2.5, 7.5, 15.0, and 22.5 cm over a 6-day period. Ethoprop concentration in the soil at 5-, 10-, and 40-day intervals indicated that it was depleted rapidly with increased rainfall levels. The 2.5-cm level of simulated rainfall reduced ethoprop concentration to one-half in the 0 to 15 cm depth within 10.7 days, whereas the 22.5 cm of rain shortened this period to 1.7 days. Soil samples taken 10 days after ethoprop treatment and inoculated with Meloidogyne javanica indicated that 2.5 cm of rain rendered the nematicide ineffective against M. javanica.
ethoprop; Meloidogyne javanica; nematicide; nematode; rainfall
A survey was conducted in four major flue-cured tobacco producing countries to determine use of nematicides for control of plant-parasitic nematodes on flue-cured tobacco. Included in the survey were scientists from Brazil, Canada, the United States, and Zimbabwe. Nematicides were used on 60-95% of the flue-cured tobacco crop in these regions. The choice of fumigant and nonfumigant nematicides, however, varied greatly as influenced by the edaphic factors, nematode species, and other pests present. The major nematicides, application methods, and efficacy evaluation systems used in these countries were addressed.
chemical control; Globodera tabacum; Meloidogyne spp.; nematicide; Nicotiana tabacum; Pratylenchus spp.; survey; tobacco
Greenhouse lysimeter and field microplot tests were conducted to evaluate the effects of Meloidogyne incognita and M. javanica on plant water relations and growth performance of NC 2326 flue-cured tobacco. In the greenhouse, afternoon leaf water potential values at 8-11 weeks after transplanting were lower by as much as 0.22 MPa in plants infected with either nematode than in the control plants. From 11 to 22 weeks, leaf water potential values were similar in all treatments. Over the course of the 22-week experiment, all infected plants showed similar evapotranspiration patterns, and plants in these treatments used 87-88% of the water utilized by noninfected plants. Biomass production from nematode-infected plants, however, was only about 50% of the biomass of control plants. The field microplot study showed water use patterns similar to those in the lysimeter study.
evapotranspiration; leaf water potential; Meloidogyne incognita; Meloidogyne javanica; Nicotiana tabacum
The motility of Meloidogyne incognita second-stage juveniles (J2) and their ability to induce root galls in tomato were progressively decreased upon exposure to nicotine at concentrations of 1-100 μg/ml. EC₅₀ values ranged from 14.5 to 22.3 μg/ml, but J2 motility and root-gall induction were not eliminated at 100 μg/ml nicotine. Nicotine in both resistant NC 89 and susceptible NC 2326 tobacco roots was increased significantly 4 days after exposure to M. incognita. The increase was greater in resistant than in susceptible tobacco. Root nicotine concentrations were estimated to be 661.1-979.1 μg/g fresh weight. More M. incognita were detected in roots of susceptible than in roots of resistant tobacco. Numbers of nematodes within resistant roots decreased as duration of exposure to M. incognita was increased from 4 to 16 days. Concentrations of nicotine were apparently sufficient to affect M. incognita in both susceptible and resistant tobacco roots. Localization of nicotine at infection sites must be determined to ascertain its association with resistance.
Nicotiana tabacum; root-knot nematode; resistance; alkaloid; Meloidogyne incognita; nicotine; tobacco
nematode management; plant resistance; cultural practices; nematicides; crop rotation; sanitation; allelopathy; conservation tillage; soil amendments
A field trial was conducted for 2 years in an Arredondo fine sand containing a tillage pan at 15-20 cm deep to determine the influence of subsoiling on the distribution of corn roots and plant-parasitic nematodes. Soil samples were taken at various depths and row positions at 30, 60, and 90 days after planting in field corn subsoiled under the row with two chisels and in non-subsoiled corn. At 30 and 60 days, in-row nematode population densities to 60 cm deep were not affected by subsoiling compared with population densities in nonsubsoiled plots. After 90 days, subsoiling had not affected total root length or root weight at the 20 depth-row position sampling combinations, but population densities of Meloidogyne incognita and Criconemella spp. had increased in subsoiled corn. Numbers of Pratylenchus zeae were not affected. Subsoiling generally resulted in a change in distribution of corn roots and nematodes in the soil profile but caused little total increase in either roots or numbers of nematodes. Corn yield was increased by subsoiling.
subsoiling; field corn; Zea mays L.; cultural practices; Meloidogyne incognita; Pratylenchus zeae; Criconemella spp.; root-knot nematode; lesion nematode; ring nematode; nematode ecology
A 2-year field study evaluated the influence of subsoiling and nematicide application, alone and in combination, on the growth and yield of field corn in a sandy soil in north-central Florida. The field had a 25-30-cm-deep tillage pan (plowpan) and was infested with Belonolaimus longicaudatus, Hoplolaimus galeatus, Trichodorus christei, and Pratylenchus spp. Subsoiling increased corn yield both years, and the residual effect of subsoiling in the first year increased yields in the second year. Preplant application of DD injected in-row increased yields and reduced nematode populations. At-planting applications of DD injected in-row and carbofuran in-furrow or in a band were less effective than subsoiling in increasing yields and reducing nematode numbers. Interactions between subsoiling and nematicide treatments occurred in the second year.
Belonolaimus longicaudatus (sting); Hoplolaimus galeatus (lance); Pratylenchus spp. (lesion); Trichodorus christei (stubby-root); carbofuran; chemical control; DD; tillage pan
flowering; root-knot nematodes; M. incognita; M. arenaria; M. javanica; Nicotiana tabacum L.; microplots; nematicides; ethoprop (Mocap); D-D (Shell D-D)
Growth of flue-cured tobacco as influenced by Meloidogyne javanica and the effectiveness of DD and ethoprop to manage this nematode were evaluated over two growing seasons. Populations of M. javanica, root galling, plant height, steam crown diameter, whole plant weight, and yield were monitored at approximately 2-week intervals beginning 28 days after transplanting. Treatment influence on nematode population development, root galling, and plant growth generally followed a pattern in descending order of efficacy: DD (187 liters/ha), ethoprop (27, 18, or 9 kg a.i./ha), and control. In all treatments, nearly season-long increases in M. javanica populations and root galling were observed. Correlation coefficients relating nematode populations or root galling to final tobacco yield suggested either method may be used successfully to evaluate nematicide efficacy in research plots. Plant growth parameters most affected by M. javanica in order of decreasing severity were cured leaf yield, whole plant weight, plant height, and stem diameter.
root-knot nematode; nematicides; Nicotiana tabacum
The effects of Meloidogyne incognita and M. javanica on a susceptible tobacco (Nicotiana tabacum L.) cv. McNair 944 were investigated in field microplots during 1978 and 1979. Three initial inoculum levels—4, 16, and 64 nematode eggs and/or second-stage larvae per 100 cm³ of soil—were used for each nematode species. Data obtained from the experiments included plant yield and the amount of reproduction of the two nematode species. At comparative inoculum levels, M. javanica was more aggressive than M. incognita on tobacco and caused approximately twofold more yield suppression than M. incognita. The calculated initial population of M. incognita, derived from the average for 2 yr, which produced a 7% suppression in plant yield was four eggs and/or second-stage larvae per 100 cm³ of soil; whereas less than one M. javanica egg and/or second-stage larvae per 100 cm³ of soil was needed to achieve similar suppression. Nematode reproduction varied in the 1978 and 1979 tests, but similar trends were observed. Early season M. javanica populations were greater than those of M. incognita, but late season populations of M. incognita were twice anti three times those of M. javanica.
aggressiveness; injury levels; Nicotiana tabacum
Root invasion, root galling, and fecundity of Meloidogyne javanica, M. arenaria, and M. incognita on tobacco was compared in greenhouse and controlled environment experiments. Significantly more M. javanica than M. arenaria or M. incognita larvae were found in tobacco roots at 2, 4, and 6 d after inoculation. Eight days after inoculation there were significantly more M. arenaria and M. javanica than M. incognita larvae. Ten days after inoculation no significant differences were found among the three Meloidogyne species inside the roots. Galls induced by a single larva or several larvae of M. javanica were significantly larger than galls induced by M. incognita: M. arenaria galls were intermediate in size. Only slight differences in numbers of egg masses or numbers of eggs produced by the three Meloidogyne species were observed up to 35 d after inoculation.
Meloidogyne arenaria; M. incognita; M. javanica; root invasion; fecundity; gall size; tobacco
Greenhouse tests were conducted to determine the effects of soil temperature and texture on development of Pratylenchus scribneri and the pathogenicity and reproductive rates of this nematode on selected crop plants. In a sandy loam soil, greatest numbers of P. scribneri were found at 30 and 35 C on sudangrass and sugarbeet, respectively. In a silty clay loam, the nematode reproduced best at 35 C on sugarbeet. Higher populations of P. scribneri were found in the sandy loam than silty clay loam soil at corresponding temperatures. In a pathogenicity test, top and root growth of sudangrass and barley were suppressed by the nematode, whereas no significant growth inhibition was found on wheat and alfalfa. Tests with other vegetable and field crops indicated wide variance in nematode reproduction.
Lesion nematode; pathogenicity; soil temperature; soil type; sudangrass; sugarbeet; barley; wheat; and alfalfa
The pathological effects of Pratylenchus scribneri on susceptible snap bean and resistant lima bean were studied. In a pathogenicity test, the nematode increased nearly 75-fold on snap bean and suppressed top growth. On lima bean, P. scribneri reproduced slowly and did not significantly affect top growth. Discreet lesions formed on lima bean roots, but no lesions developed on snap bean roots. Paraffin sections taken 2, 5, 13, 25, and 32 days after inoculation showed little cellular necrosis in snap bean roots, whereas cells surrounding the nematode in lima bean were extensively necrotic. Cortical cells of infected snap bean roots were almost completely invaded and killed 25 and 32 days after inoculation. The cortex of lima bean tissues was intact, although localized necrotic areas remained at sites of nematode invasion.
host resistance; lesion nematode; Phaseolus lunatus; Phaseolus vulgaris
Foliar applications of oxamyl (methyl N', N'-dimethyl-N-[(methylcarbamoyl)oxy]-l-thiooxamimidate) were applied 24 hr before transplanting seedlings to soil infested with Rotylenchulus reniformis. With a single application of oxamyl, tomato seedlings required 600 ppm to significantly inhibit R. reniformis penetration. Cotton seedlings, however, required a single application of 2400 ppm for significant inhibition of penetration, but only 600 ppm when two or more applications were used.
Gossypium hirsutum; L ycopersicon esculentum; Vydate®