Colored Mulches Affect Yield of Fresh-market Tomato Infected with Meloidogyne incognita

The effects of different-colored polyethylene mulches on the quantity and spectra of reflected light, earliness of fruit set, fruit yield and quality, and root-knot disease were studied in field-grown, staked tomato (Lycopersicon esculentum). White mulch reflected more photosynthetic light and a lower far-red-to-red ratio than red mulch, whereas black mulch reflected less than 5 percent of any color. Soil temperatures and fruit yields were recorded for tomato plants inoculated with Meloidogyne incognita race 3 at initial populations of 0, 1,000, 10,000, 50,000, or 100,000 eggs/plant and grown over black, white, or red plastic mulch in both spring and fall. Soil temperatures were lower under white mulch than under red or black mulch. Tomato yields declined as inoculum level increased. Plants grown over red mulch in the spring and inoculated with 50,000 eggs of M. incognita had greater early marketable yields than similarly inoculated plants grown over black or white mulch. Tomato plants inoculated with 100,000 eggs and grown over white mulch or red mulch in the spring had greater total yields per plot than similar plants grown over black mulch (7.39 kg and 7.71 kg vs. 3.65 kg, respectively).     

Reflected Far-Red Light Effects on Chlorophyll and Light-Harvesting Chlorophyll Protein (LHC-II) Contents under Field Conditions

The influence of various colors of soil cover (mulch) on the farred/red (FR/R) ratio in upwardly reflected light and on concentrations of chlorophyll (Chl) and light-harvesting Chl protein (LHC-II) were measured under field conditions. The FR/R ratios above green surfaces were higher than over white surfaces. Even though plants (Gossyplum hirsutum L. cv PD-1) were grown in full sunlight, those that received higher FR/R ratios in upwardly reflected light were taller and had thinner leaves with higher concentrations of Chl and LHC-II. A controlled environment experiment showed FR/R control of Chl and LHC-II concentrations. The results illustrate the importance of spectral distribution of reflected light on plant growth and a potential means of altering the chemistry of leaf crops under field conditions.     

Interaction of Vesicular-arbuscular Mycorrhizal Fungi and Phosphorus with Meloidogyne incognita on Tomato

The influence of two vesicular-arbuscular mycorrhizal fungi and phosphorus (P) nutrition on penetration, development, and reproduction by Meloidogyne incognita on Walter tomato was studied in the greenhouse. Inoculation with either Gigaspora margarita or Glomus mosseae 2 wk prior to nematode inoculation did not alter infection by M. incognita compared with nonmycorrhizal plants, regardless of soil P level (either 3 μg [low P] or 30 μg [high P] available P/g soil). At a given soil P level, nematode penetration and reproduction did not differ in mycorrhizal and nonmycorrhizal plants. However, plants grown in high P soil had greater root weights, increased nematode penetration and egg production per plant, and decreased colonization by mycorrhizal fungi, compared with plants grown in low P soil. The number of eggs per female nematode on mycorrhizal and nonmycorrhizal plants was not influenced by P treatment. Tomato plants with split root systems grown in double-compartment containers which had either low P soil in both sides or high P in one side and low P in the other, were inoculated at transplanting with G. margarita and 2 wk later one-half of the split root system of each plant was inoculated with M. incognita larvae. Although the mycoorhizal fungus increased the inorganic P content of the root to a level comparable to that in plants grown in high P soil, nematode penetration and reproduction were not altered. In a third series of experiments, the rate of nematode development was not influenced by either the presence of G. margarita or high soil P, compared with control plants grown in low P soil. These data indicate that supplemental P (30 μ/g soil) alters root-knot nematode infection of tomato more than G. mosseae and G. margarita.     

Biomass Partitioning in Tomato Plants Infected with Meloidogyne incognita

Tomato plants were inoculated with Meloidogyne incognita at initial populations (Pi) of 0, 1, 10, 50, 100, and 200 (x 1,000) eggs per plant and maintained in a growth chamber for 40 days. Total fresh biomass (roots + shoots) at harvest was unchanged by nematode inoculation with Pi of 1 x 10⁵ eggs or less. Reductions in fresh shoot weight with increasing Pi coincided with increases in root weight. Total fresh biomass declined with Pi above 1 x 10⁵ eggs, whereas total dry biomass declined at Pi above 1 x 10⁴ eggs. The greatest reduction percentages in fresh shoot biomass induced by root-knot nematodes occurred in the stem tissue, followed by the petiole + rachis; the least weight loss occurred in the leaflets. Although biomass varied among shoot tissues, the relationship between biomass of various shoot tissues and Pi was described by quadratic equations. The linear and quadratic coefficients of the equations (stem, petiole + rachis, or leaflets on Pi) did not differ among tissues when calculations were based on standardized values. Meloidogyne incognita-infected plants had thinner leaves (leaf area/leaf weight) than did uninfected plants. Reductions in leaf weight and leaf area with nematode inoculation occurred at nodes 5-15 and 4, 6-14, respectively. Losses in plant height and mass due to nematodes reflected shorter internodes with less plant mass at each node.     

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

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

Cotton plant size and fiber developmental responses to FR/R ratio reflected from the soil surface

Cotton ( Gossypium hirsutum L.) plants were grown in irrigated field plots over red, green or white soil covers (mulches). The far-red (FR) to red (R) light ratios were higher in upwardly reflected light over the red and green surfaces than in incoming sunlight. Plants that grew over the white mulches received higher photosynhetic photon flux (PPF), but the reflected FR/R ratio did not differ significantly from that in incoming sunlight. At five weeks after emergence, seedling stern lengths were significantly longer over red and green than over white surfaces. At maturity, plants that had grown over the red and green surfaces had longer stems, larger shoots, more bolls (fruit), more seed cotton, and longer fibers than plants grown over the white surfaces even though those grown over the white surfaces had received more reflected photosynthetic light during growth and development.     

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

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

Effective Use of Marine Algal Products in the Management of Plant-Parasitic Nematodes

Algal extracts were ineffective against Meloidogyne spp., Panagrellus redivivus, and Neoaplectana carpocapsae at 1.0% aqueous concentrations, with the exception of Spatoglossum schroederi. S. schroederi killed Meloidogyne incognita, M. javanica, M. acrita, and Hoplolaimus galeatus at concentrations of 1.0, 0.75, and 0.50%. Extracts from S. schroederi at a concentration of 1.0% were ineffective against Hirschmanniella caudacrena and Belonolaimus longicaudatus. Spatoglossum schroederi, Botryocladia occidentalis, and Bryothamnion triquestrum when used as soil amendments at 0.5-1.0% concentrations (by weight) produced significant reduction of root gall development in tomato plants infected with M. incognita. Tomato plant growth was significantly improved by these algae, as well as by Caulerpa prolifera. Soil amendments of S. schroederi at concentrations of 0.5 and 1.0% significantly reduced root galling of tomato infected with M. incognita, M. arenaria, and M. javanica. Tomatoes grown in algal-soil mixture produced significantly heavier shoots and roots than plants raised in autoclaved soil. No significant differences in root-knot indices, nor in fresh and dry weights of tomato, were noted between the two concentrations of algal-soil mixture.     

Trap Crops and Population Management of Globodera tabacum tabacum

Tobacco, eastern black nightshade, and tomato were grown for 3 to 13 weeks to assess differences in invasion, development, and soil density of Globodera tabacum tabacum (tobacco cyst nematode) in field plots and microplots over three seasons. Tobacco cyst nematodes invaded roots of resistant and susceptible tobacco, nightshade, and tomato. Nematode development was fastest in nightshade and slowest in tomato, and few adults developed in roots of nematode-resistant tobacco. Soil populations of tobacco cyst nematodes were reduced up to 80% by destroying nightshade or susceptible tobacco grown for 3 to 6 weeks. Nematode populations were reduced up to 96% by destroying tomato or resistant tobacco grown for 3 to 6 weeks. Timing of crop destruction was less critical with tomato and resistant tobacco, as nematode populations did not increase after 13 weeks of growth. These studies demonstrate that trap cropping, through crop destruction, can significantly reduce G. t. tabacum populations.     

Effects of Management Practices on Nematode and Fungi Populations and Okra Yield

Okra was grown in field plots of Tifton loamy sand naturally infested with the nematodes Meloidogyne incognita and Criconemoides ornalus and the pathogenic fungi Fusarium oxysporum, F. solani, F. roseum, and Pythium spp. Plots were treated with various soil pesticides and left exposed or covered with biodegradable paper film mulch under trickle irrigation. Soil was assayed for nematodes and fungi, and plant roots were examined for root-rot and insect damage. Fewer nematodes and fungi generally were recovered from soil treated with DD-MENCS (with and without film mulch) or methyl bromide-chloropicrin (2:1) (MBC) and film mulch than from nontreated soil. Funfigation with DD-MENCS or MBC suppressed populations of M. incognita, C. ornatus, F. oxysporum, F. solani, F. roseum, and Pythium spp. Ethoprop (alone or combined with other pesticides), sodium azide, and chloroneb were less effective than DD-MENCS and MBC. Plant growth anti yield were greatest when nematodes and pathogenic fungi were controlled. Yield was increased 3-fold by DD-MENCS + film mulch or MBC + film mulch in comparison with the average yield of okra produced in Georgia. The root-knot nematode-Fusarium wilt complex was most severe in nonfuntigated soil.     

Are Pathogenesis-Related Proteins Induced by Meloidogne javanica or Heterodera avenae lnvasion?

Changes in root- and leaf-soluble proteins were investigated in tomato after invasion by the root-knot nematode Meloidogyne javanica, or in barley and wheat after invasion by the cereal cyst nematode Heterodera avenae. Infection of susceptible tomato plants by M. javanica did not cause any change in the soluble-protein composition of leaves or roots compared with uninoculated plants at an early infection stage. No pathogenesis-related proteins (chitinase, glucanase, or P-14) were induced in the leaf apoplast. Changes in leaf proteins were not observed after invasion of wheat cultivars by H. avenae, whereas, in barley, a few changes in intercellular leaf proteins were recorded in resistant cultivars. These changes, however, were not the same among different H. avenae-resistant cultivars. Protein changes were found at an early stage of infection in barley and wheat roots infected with H. avenae, but no difference was found between resistant and susceptible cultivars.     

Enhanced Nematicidal Activity of Organic and Inorganic Ammonia-Releasing Amendments by Azadirachta indica Extracts

The nematicidal activities of ammonium sulfate, chicken litter and chitin, alone or in combination with neem (Azadirachta indica) extracts were tested against Meloidogyne javanica. Soil application of these amendments or the neem extracts alone did not reduce the root galling index of tomato plants or did so only slightly, but application of the amendments in combination with the neem extracts reduced root galling significantly. Soil analysis indicated that the neem extract inhibited the nitrification of the ammonium released from the amendments and extended the persistence of the ammonium concentrations in the soil. In microplot experiments, tomato plants were grown in pots filled with soils from the treated microplots. The galling indices of tomato plants grown in soil treated with ammonium sulfate or chicken litter in combination with the neem extract or a chemical nitrification inhibitor were far lower than those of plants grown in the control soil or in soil treated with chicken litter, neem extract or nitrification inhibitor alone. However, plants grown in the microplots showed only slight reductions in galling, probably because the soil amendments were inadequately mixed compared to their application in the pot experiments. The extended exposure of nematodes to ammonia as a result of nitrification inhibition by the neem extracts appeared to be the cause of the enhanced nematicidal activity of the ammonia-releasing amendments.     

The effect of light quality on leaf production and development of in vitro-cultured plants of Alternanthera brasiliana Kuntze

We investigated the influence of light quality on the leaf development of Alternanthera brasiliana Kuntze (Amaranthaceae) grown in vitro. Growth parameters including specific leaf mass, thickness, and leaf density were lowest in plants grown under red light. Blue light induced the largest number of leaves/plant, and the largest thickness and area of the leafblade. Green and red lights induced the smallest leaf areas. The thickness of the abaxial-face epidermis and spongy parenchyma of the plants was significantly reduced in plants grown under red light. The thickness of the palisade parenchyma and upper epidermis were significantly increased in plants grown under blue light, compared to the other fluorescent-light treatments. The specific spectral band also influenced the differentiation of mesophyll cells. In the dark and under red light, the mesophyll was homogenous; and in the dark and under green light, the leaves were more compact. Under blue light, the cells displayed the characteristic palisade morphology. The results showed that the increase of a specific parenchyma type was related to a specific spectral band. All spectral-quality treatments reduced the numbers of stomata and trichomes. The results for green light were in some respects similar to those for red light, and in other respects similar to those for blue light, probably because phytochromes and cryptochromes are green-light receptors. This study indicated that Alternanthera plants have strong morphological plasticity induced by light. The results suggest that high-quality Alternanthera can be achieved by culturing the plants in vitro under a combination of blue and red light.     

An In Vitro Test for Temperature Sensitivity and Resistance to Meloidogyne incognita in Tomato

An in vitro root explant tissue culture technique is described for determining susceptibility of tomato (Lycopersicon esculentum Mill.) breeding lines and cultivars to the root-knot nematode Meloidogyne incognita. Root explants were taken from 2-day-old seedlings cultured for 30 days at 28 C on Gamborg''s B-5 medium with or without nematode inoculum. The remaining portion of the root and stem from the excised root explants was transferred to soil in pots and grown to maturity in the greenhouse. In vitro root explants were evaluated for growth and occurrence of juveniles, adults, and egg masses. The regenerated plants were used to produce more seed, The proposed technique is simple, reliable, and adapted to routine screening of large numbers of F₁ and F₂ samples, and it utilizes less space than tests performed on intact plants in the greenhouse or growth chamber. Evidence is presented also on the breakdown of resistance to M. incognita under high temperature stress using this in vitro root explant technique.     

Comparison of Reproduction by Meloidogyne graminicola and M. incognita on Trifolium Species

The reproductive potential of Meloidogyne graminicola was compared with that of M. incognita on Trifolium species in greenhouse studies. Twenty-five Trifolium plant introductions, cultivars, or populations representing 23 species were evaluated for nematode reproduction and root galling 45 days after inoculation with 3,000 eggs of M. graminicola or M. incognita. Root galling and egg production by the two root-knot nematode species was similar on most of the Trifolium species. In a separate study, the effect of initial population densities (Pi) of M. graminicola and M. incognita on the growth of white clover (T. repens) was determined. Reproductive and pathogenic capabilities of M. graminicola and M. incognita on Trifolium spp. were similar. Pi levels of both root-knot nematode species as low as 125 eggs per 10-cm-d pots severely galled white clover plants after 90 days. Meloidogyne graminicola has the potential to be a major pest of Trifolium species in the southeastern United States.     

Effects of Chicken-excrement Amendments on Meloidogyne arenaria

The effects of chicken litter on Meloidogyne arenaria in tomato plants cv. Rutgers were determined in the greenhouse. Tomato seedlings were transplanted into a sandy soil amended with five rates of chicken litter and inoculated with 2,000 M. arenaria eggs. After 10 days, total numbers of nematodes in the roots decreased with increasing rates of chicken litter. After 46 days, egg numbers also decreased with increasing litter rates. In another experiment, soil was amended with two litter types, N-P-K fertilizer, and the two primary constituents of chicken litter (manure and pine-shaving bedding). After 10 days, numbers of nematodes in roots were smaller in chicken-excrement treatments as compared to nonexcrement treatments. At 46 days, there were fewer nematode eggs in chicken-excrement treatments compared to nonexcrement treatments. Egg numbers also were smaller for fertilizer and pine-shaving amendments as compared to nonamended controls. Chicken litter and manure amendments suppressed plant growth by 10 days after inoculation but enhanced root weights at 46 days after inoculation. Amendment of soil with chicken litter suppressed M. arenaria and may provide practical control of root-knot nematodes as part of an integrated management system.     

Efficacy of Fluensulfone in a Tomato–Cucumber Double Cropping System

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

Control of Root-knot Nematodes on Tomato in Stone Wool Substrate with Biological Nematicides

The efficacy of four biological nematicides on root-galling, root-knot nematode (Meloidogyne incognita) reproduction, and shoot weight of tomato (Solanum lycopersicum) grown in stone wool substrate or in pots with sandy soil was compared to an oxamyl treatment and a non-treated control. In stone wool grown tomato, Avid® (a.i. abamectin) was highly effective when applied as a drench at time of nematode inoculation. It strongly reduced root-galling and nematode reproduction, and prevented a reduction in tomato shoot weight. However, applying the product one week before, or two weeks after nematode inoculation was largely ineffective. This shows that Avid® has short-lived, non-systemic activity. The effects of Avid® on nematode symptoms and reproduction on soil-grown tomato were only very minor, probably due to the known strong adsorption of the active ingredient abamectin to soil particles. The neem derived product Ornazin® strongly reduced tomato root-galling and nematode reproduction only in stone wool and only when applied as a drench one week prior to nematode inoculation, suggesting a local systemic activity or modification of the root system, rendering them less suitable host for the nematodes. This application however also had some phytotoxic effect, reducing tomato shoot weights. The other two products, Nema-Q™ and DiTera®, did not result in strong or consistent effects on nematode symptoms or reproduction.     

Hatch and Reproduction of Globodera tabacum tabacum in Response to Tobacco,Tomato, or Black Nightshade

The effects of broadleaf tobacco, tomato, and black nightshade on juvenile hatch and reproduction of Globodera tabacum tabacum were determined in laboratory and greenhouse experiments. Root exudates from nightshade stimulated greater egg hatch than those from either ''Rutgers'' tomato or ''86-4'' tobacco. Hatch was greater at higher proportions of root exudates for all three plant species. Root exudates from plants greater than 3 weeks old stimulated more hatch than younger plants. No regression relationships existed between plant age and nematode batch. In other experiments, hatch from eggs in cysts was higher for tomato and nightshade after 10 weeks in greenhouse pots compared to tobacco and bare soil. Numbers of second-stage juveniles in eggs in cysts produced from a previous generation on the same host were highest on nightshade and less on tomato and tobacco. Cysts of variable age recovered from field soil had increased hatch in both root exudates or water compared to recently produced cysts from plants in growth chambers. Globodera t. tabacum may be subject to both host and environmentally mediated diapause.     

Effects of Film Mulch and Soil Pesticides on Nematodes,Weeds, and Yields of Vegetable Crops

Field plots in Tifton loamy sand were treated with various soil pesticides in 1973 and 1974 and either left exposed or covered with biodegradable flint mulch. Test crops were cantaloup, slicing and pickling cucumber, squash, and sweet corn. Overhead sprinkler irrigation was used in 1973, and trickle irrigation under the film mulch was used on sweet corn in 1974. Soil was assayed for nematodes, and roots of plants were evaluated for damage by root-knot nematodes. Nematode populations were reduced by soil treatment with an organic phosphate or carbamate nematicide-herbicide-fungicide combination (NHF), DD-MENCS, methyl bromide-chloropicrin (MBR-CP), ethoprop, carbofuran, and sodium azide + ethoprop or carbofuran. Sodium azide, sodium azide + ethoprop or carbofuran, ethoprop, and carbofuran were less effective than DD-MENCS, MBR-CP, attd the NHF combination. The NHF combination controlled grasses and broadteaf weeds as effectively as the herbicide alone. Growth and yield were greatest when nematodes and weeds were controlled. Yields of marketable vegetables were highest from plants in plots treated with DD-MENCS with a film mulch.