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The vertical migration of second-stage juveniles (J2) of Meloidogyne floridensis and M. incognita was investigated in segmented 14-cm long PVC soil columns having their top ring in contact with soil of a potted plant. Both bottom and top rings were screened appropriately to allow only upward nematode movement and preventing root penetration from the potted plant into the soil in the column. Plants used for nematode’s stimuli were the nematode attractive tomato (Solanum lycopersicum L.) ‘Cobra’ and the nematode repellent French marigold (Tagetes patula L.) var. Petite. Host-free columns were used as control. Columns with and without plants were placed in growth chambers at 20 °C and inoculated with each root-knot nematode species by injecting 1000 J2 through a hole in the basal ring of each column. Columns were dismantled at 3, 6 and 9 days after injection and J2 were extracted from soil of each ring and the planted pot; additionally, roots in the top pot were stained to observe J2 penetration. No preferential upward migration towards either plant stimuli was observed, but M. floridensis was more migrant than M. incognita, with 4.4% and 1.6% of active J2, respectively, reaching an upward distance of more than 13 cm regardless of plant stimuli. This study supports random migration of root-knot nematode J2, even without stimulus from a host plant.

Root-knot nematodes (Meloidogyne spp.) can parasitize and reduce yields of nearly all agricultural crops. Although migration studies focus on the model species, M. incognita, there is little information about M. enterolobii, which has been a major threat for guava in Brazil. The vertical migration of second-stage juveniles (J2) of M. enterolobii and M. incognita was evaluated to determine the effect of good host and nonhost plants on nematode motility. Fourteen-cm long soil columns were constructed of PCV rings with Styrofoam cups containing a 4-week-old tomato or marigold (Tagetes patula) seedlings as plant stimuli; host-free cups were used as nontreated control. After inoculating 1000 freshly-hatched J2, the columns were placed in environmental chamber sets at 20 °C. The columns were disassembled at 3, 6, and 9 days after inoculation (DAI). The experiment was completely randomized block with four replicates. J2 were extracted from each ring and cup, while tomato and marigold roots were stained to observe J2 that penetrated roots. Data were subjected to repeated-measure MANOVA and chi-square test to compare J2 distribution along the columns. The migrations under tomato and marigold stimuli were comparable to those under host-free columns. Although both species migrated over 13 cm, M. enterolobii was more mobile than M. incognita. Juveniles of M. enterolobii infected tomato roots as early as 3 DAI, whereas marigold delayed nematode penetration. Our results show that two species of root-knot nematodes behave differently within the soil, and under the same conditions J2 of M. enterolobii migrate faster than M. incognita.

Bell and chili peppers are important vegetable and spice commodities worldwide. Significant yield reductions have been attributed to damage caused by root-knot nematodes (RKNs; Meloidogyne spp.). This study addresses the need for developing pepper varieties that have high resistance to RKN, which is now of increasing importance due to restrictions on the use of fumigant nematicides. Our goal is to provide a nonchemical alternative to sustain commercial pepper production in Florida, which is a major producer of peppers in the United States. We evaluated ‘UFRJ107(6)A3’, an advanced inbred line developed from a cross between Capsicum annuum L. ‘Jalapeno’ and ‘Round of Hungary’, for resistance against the nematode in comparison with the parental and three other Capsicum cultivars, namely, C. annuum ‘Charleston Belle’, ‘California Wonder’, and C. chinense Jacq. ‘Datil’ in two separate growth chamber experiments. Based on egg mass indices and reproduction factors, ‘UFRJ107(6)A3’ was significantly more resistant to M. incognita compared with the other five cultivars. When tested with five RKN species, ‘UFRJ107(6)A3’ showed comparably high levels of resistance to M. arenaria and M. floridensis as ‘California Wonder’ based on the nematode reproduction factor. In ‘UFRJ107(6)A3’, however, there were no detectable M. arenaria egg masses, and M. incognita reproduction was minimal compared with that of ‘California Wonder’; both cultivars supported the reproduction of M. enterolobii and M. javanica, although the reproduction factors of M. enterolobii were ≈10-fold higher than M. javanica. To characterize the mechanism of high resistance to M. incognita in ‘UFRJ107(6)A3’, we examined the extent to which infective second-stage juveniles (J2s) were able to penetrate its roots in comparison with the susceptible ‘California Wonder’ and ‘Datil’ in two independent experiments; we conducted RKN root penetration assays with a single plant in a pot and two plants in a single-pot choice test using ‘Datil’ and ‘California Wonder’, respectively, as susceptible standards. In both assays, M. incognita J2s were absent in the roots of ‘UFRJ107(6)A3’ 7 days after inoculation but were present in the susceptible cultivars, indicating that resistance has an effect at the root invasion stage. In growth chamber experiments, at constant temperatures of 28 and 30 °C, ‘UFRJ107(6)A3’ exhibited M. incognita resistance superior to its parents and to the standard resistant bell pepper ‘Charleston Belle’, thus offering the potential to enhance specialty pepper production and for use as a nematode-resistant rootstock for commercial bell peppers.

The peach root-knot nematode, Meloidogyne floridensis, is an emerging species and may become a threat to peach growers if contamination and spread are not avoided. The influence of temperature and two plants – tomato (Solanum lycopersicum) and French marigold (Tagete patula) – on the vertical migration of second-stage juveniles (J2) of M. floridensis was studied using 14-cm long segmented soil columns. Plants were transplanted into cups attached to the top of each column. Nylon meshes were placed between cups and columns to prevent downward root growth. About 1,000 freshly hatched J2 were injected into the base of the columns and then the columns were transferred to growth chambers at 20 and 26°C under a completely randomized block design with four replicates. The number of J2 in each ring of the columns as well as inside tomato or marigold roots was recorded at 3, 6, 9, and 12 days after injection (DAI). Nematode data were subjected to a repeated measures MANOVA. The presence of plants did not improve J2 migration as compared to control. M. floridensis migration was best at 20°C at first, with J2 migrating more than 13 cm as soon as 3 DAI, while it took 9 DAI for J2 to migrate long distances at 26°C. The distribution of J2 along the columns was similar at both temperatures at 12 DAI. Temperature had no influence on J2 penetration. French marigold did not hinder J2 migration, but fewer J2 penetrated its roots.

Entomopathogenic nematodes are natural enemies and effective biological control agents of subterranean insect herbivores. Interactions between herbivores, plants, and entomopathogenic nematodes are mediated by plant defense pathways. These pathways can induce release of volatiles and recruit entomopathogenic nematodes. Stimulation of these plant defense pathways for induced defense against belowground herbivory may enhance biological control in the field. Knowledge of the factors affecting entomopathogenic nematode behaviour belowground is needed to effectively implement such strategies. To that end, we explore the effect of elicitor, elicitor dose, mechanical damage, and entomopathogenic nematode release distance on recruitment of entomopathogenic nematode infective juveniles to corn seedlings. Increasing doses of methyl jasmonate and methyl salicylate elicitors recruited more entomopathogenic nematodes as did mechanical damage. Recruitment of entomopathogenic nematodes was higher at greater rele...

Yellow (Cyperus esculentus) and purple (C. rotundus) nutsedges, and coffee senna (Senna occidentalis) are common weeds in the southern USA and each have been reported as alternative hosts for plant-parasitic nematodes. Our objective was to determine the host suitability of these weeds to plant-parasitic nematodes common in Florida agriculture and turfgrass systems. The root-knot nematode (RKN) species tested included Meloidogyne arenaria, M. enterolobii, M. floridensis, M. graminis, M. hapla, M. incognita, and M. javanica. The host status of sting nematode, Belonolaimus longicaudatus, was also evaluated, but only on the nutsedge species. All RKN species evaluated reproduced on both nutsedge species and had a reproductive factor greater than one, except for M. graminis on yellow nutsedge. However, only M. hapla, M. javanica, and M. graminis induced visual galls on yellow nutsedge and only M. graminis caused galling on purple nutsedge. Meloidogyne arenaria and M. graminis reproduced at a greater rate on purple nutsedge than on yellow nutsedge. Both nutsedge species were good hosts to B. longicaudatus. Coffee senna was a host to M. enterolobii, a poor host to M. incognita, and nonhost to the other RKN species evaluated.

One of the production issues that peach growers in Florida must contend with is plant-parasitic nematodes. One such species is the more recently discovered peach root-knot nematode, Meloidogyne floridensis, which is the subject of this 5-page publication. Written by Mary Ann D. Maquilan, Ali Sarkhosh, and Donald Dickson and published by the UF/IFAS Horticultural Sciences Department, July 2018. http://edis.ifas.ufl.edu/hs1320

Most commercially important rootstocks for peach [Prunus persica (L.) Batsch] had been selected for resistance to one or more of the root-knot nematode (RKN) species: Meloidogyne incognita, M. arenaria, and M. javanica. The peach root-knot nematode, M. floridensis (MF), is a relatively newly discovered threat to peach and is not controlled by resistance genes in “Nemared,” “Nemaguard,” and “Okinawa.” The “Flordaguard” peach seedling rootstock, conventionally bred to provide resistance to MF, has solely been used for low-chill peach production in Florida for over 20 years and has already shown signs of resistance breakdown. A source of high resistance to the pathogenic MF isolate (“MFGnv14”) was identified from wild peach Prunus kansuensis Rehder (Kansu peach), thereby suggesting the potential for broadening spectrum and increasing durability of resistance in peach rootstocks through interspecific hybridization with P. kansuensis. Using 12 F2 and BC1F1 populations derived from crosses between Okinawa or Flordaguard peach and P. kansuensis populations, we examined the genetic control for MF resistance by identifying associated microsatellite markers and determining genomic location of the resistance locus. One microsatellite marker (UDP98-025) showed strong and consistent association with resistance based on root-galling index. The resistance locus was mapped on the subtelomeric region of linkage group 2, co-localizing with other previously reported RKN resistance genes in Prunus. Segregation of gall-index-based resistance observed in F2 and BC1F1 populations is compatible with the involvement of a multiallelic locus wherein a dominant (Mf1) or recessive (mf3) resistance allele is inherited from P. kansuensis, and susceptibility alleles (mf2) from peach.

Nematodes, non-segmented roundworms, can cause serious yield suppression in peanut production. This 10-page fact sheet written by Zane J. Grabau and Donald W. Dickson and published by the UF/IFAS Department of Entomology and Nematology explains how to recognize a potential nematode problem in a peanut production, confirm it with an expert, and choose the best management tools to control the problem. http://edis.ifas.ufl.edu/in1199

The following work was initiated to determine the scope of application methodology and fumigant combinations for increasing efficacy of 1,3-dichloropropene (1,3-D) and metam sodium for management of root-knot nematodes (Meloidogyne spp.) in Florida. A series of five experiments were set up during spring and fall seasons to evaluate the potential of different fumigants, alone or in combination, in polyethylene film tomato production. The most promising chemical alternatives to methyl bromide, in terms of root-knot nematode management, were the combinations 1,3-D-chloropicrin, chloropicrin-proprietary solvent, and 1,3-D-metam sodium. Sprayed or injected metam sodium generally provided only short-term nematode management and by harvest nematode infection was not different from the nontreated control. Drip-applied metam sodium gave good nematode management under high nematode pressure, but needs further verification to establish (i) the importance of soil moisture and temperature on treatment efficacy and (ii) whether similar management can be obtained with fewer than three drip tubes. Broadcast applications of 1,3-D showed better efficacy as compared to applications on a preformed raised bed. Fumigation did not increase tomato yields in spring when root-knot nematode pressure was low, but during fall all chemical treatments increased yields three to five-fold, as root-knot nematode was a major yield-limiting factor.

Interest in specialty melons (Cucumis melo) with distinctive fruit characteristics has grown in the United States in recent years. However, disease management remains a major challenge in specialty melon production. In this study, grafting experiments were conducted to determine the effectiveness of using Cucumis metulifer, a species known for its genetic resistance to root-knot nematodes (RKNs; Meloidogyne spp.), as a potential rootstock for managing RKNs in susceptible specialty melon cultivars. In the greenhouse experiment, honeydew melon ‘Honey Yellow’ was grafted onto C. metulifer and inoculated with M. incognita race 1. The grafted plants exhibited significantly lower gall and egg mass indices and fewer eggs compared with non- and self-grafted ‘Honey Yellow’. Cucumis metulifer was further tested as a rootstock in conventional and organic field trials using honeydew melon ‘Honey Yellow’ and galia melon ‘Arava’ as scions. ‘Honey Yellow’ and ‘Arava’ grafted onto C. metulifer exhibited significantly lower galling and reduced RKN population densities in the organic field; however, total and marketable fruit yields were not significantly different from non- and self-grafted plants. Although the improvement of RKN resistance did not translate into yield enhancements, incorporating grafted specialty melons with C. metulifer rootstock into double-cropping systems with RKN-susceptible vegetables may benefit the overall crop production by reducing RKN population densities in the soil. At the conventional field site, which was not infested with RKNs, ‘Honey Yellow’ grafted onto C. metulifer rootstock had a significantly lower total fruit yield than non-grafted ‘Honey Yellow’ plants; however, fruit yields were similar for ‘Arava’ grafted onto C. metulifer rootstock and non-grafted ‘Arava’ plants. Although no significant impacts on the fruit quality attributes of ‘Honey Yellow’ were observed, grafting onto C. metulifer decreased the flesh firmness of ‘Arava’ in both field trials and resulted in a reduction in total soluble solids content under conventional production. In summary, grafting RKN-susceptible melons onto C. metulifer rootstock offers promise for growing these specialty melons; however, more studies are needed to elucidate the scion–rootstock interaction effect on fruit yield and quality.

Methyl bromide controls three major problems in crop production: weeds, nematodes and phytopathogenic fungi. An alternative system was investigated that used various colored plastic mulches with Telone C35 (63.4% 1,3-dichlropropene, 34.7% chloropicrin, 1.9% inert ingredients). This alternative to methyl bromide was to investigate: 1) control weeds through wavelength selective plastic mulches, 2) control fungi by chloropicrin, and 3) control weeds and nematodes by 1,3-dichloropropene. These mulches control weeds by a thickness that prevented weed penetration, especially nutsedges, by retaining phytotoxic fumigant longer, or by allowing infra-red and red light to penetrate through the film while restricting other photo synthetically active wavelengths. Infra-red and red light changed the morphology of nutsedges from a hard plastic-penetrating point to a soft leafy structure that cannot tear the film. The mulches tested were blue virtually impermeable film (VIF), black VIF, black polyethylene film (PE), as well as blue, green, olive, brown, and metalized PE. Conclusions after a two-year study were: 1) that there was no direct correlation between the amount of light transmitted through colored mulch with tomato yield per plant, 2) that the use of fumigation with plastic mulches led to an average increase of 40% in crop yield compared to non-fumigated beds, and 3) finally, that if the grower decided not to use any pesticide, fungicide, or herbicide, then metalized PE mulch would maximize weed control and crop yield.

Identification of forage legumes well adapted to the southeastern United States is complicated by climatic, soil, and biotic factors. Among the pests that impact forage legume persistence are root-knot nematodes (RKNs) (Meloidogyne spp.). We hypothesized that legumes native to the region should have higher levels of resistance to RKN species that are common in this region due to long-term natural selection pressure. The objective of this research was to evaluate the response of 10 southeastern U.S. native legumes to M. arenaria (Neal) Chitwood race 1, M. incognita (Kofoid and White) Chitwood race 3, and M. javanica (Treub) Chitwood. Legumes were grown in Cone-tainers in a greenhouse for 3 wk, inoculated with a given RKN isolate, and after an additional 9 wk were uprooted and evaluated for root galling and nematode egg mass production responses. The level of root galling and egg mass production varied among native legumes, but in general was lower than previously observed on introduced legumes. Desmodium paniculatum (L.) DC., Galactia regularis (L.) Britton et al., and Centrosema virginianum (L.) Benth. varied among the three RKN species in their root galling and egg mass production responses. The accession of D. incanum DC. used was immune to all three RKN isolates, and could be a potential source of RKN resistance genes. The perennial native legumes evaluated all had either a fleshy taproot or a strong rhizome system.

Abstract A total of 327 root samples collected from horticultural and agronomic crops, and weeds associated with these crops in Florida crop production regions, were examined. Isozyme phenotypes, esterase (EST) and malate dehydrogenase (MDH) phenotypes were used to characterise and identify the species of Meloidogyne present in these samples. At least 26 females from each sample were examined using polyacrylamide gel electrophoresis. Sixteen major bands of EST activity were found, corresponding to 12 phenotypes. A species-specific EST phenotype was consistently associated with each of the Meloidogyne spp. identified: Meloidogyne arenaria, M. floridensis, M. graminicola, M. hapla, M. incognita, M. javanica, M. mayaguensis and M. partityla. Two unique EST phenotypes, which have not been described, were found associated with three unidentified nematode populations. Five bands of MDH activity and four phenotypes were also found among the populations. During this study, new host records were determined for M. floridensis and M. mayaguensis, two recently reported Meloidogyne spp. in Florida. Plant species found as new hosts of M. floridensis were Cucumis sativus, Phaseolus sp., Solanum melongena and one weed species, Emilia sonchifolia, and the M. incognita-resistant peach rootstock ‘Flordaguard’. New hosts for M. mayaguensis were Carica papaya, Capsicum annuum var. Longum, and six weed plants, including Eclipta prostrata, Fatoua villosa, Panicum sp., Poinsettia cyathophora, Solanum americanum and also one unidentified weed species belonging to the family Acanthaceae. To our knowledge, Florida is the only geographic area of North America where M. floridensis and M. mayaguensis have been detected.

Plant defense pathways play a critical role in mediating tritrophic interactions between plants, herbivores, and natural enemies. While the impact of plant defense pathway stimulation on natural enemies has been extensively explored aboveground, belowground ramifications of plant defense pathway stimulation are equally important in regulating subterranean pests and still require more attention. Here we investigate the effect of aboveground stimulation of the salicylic acid pathway through foliar application of the elicitor methyl salicylate on belowground recruitment of the entomopathogenic nematode, Steinernema diaprepesi. Also, we implicate a specific root-derived volatile that attracts S. diaprepesi belowground following aboveground plant stimulation by an elicitor. In four-choice olfactometer assays, citrus plants treated with foliar applications of methyl salicylate recruited S. diaprepesi in the absence of weevil feeding as compared with negative controls. Additionally, analysis of root volatile profiles of citrus plants receiving foliar application of methyl salicylate revealed production of d-limonene, which was absent in negative controls. The entomopathogenic nematode S. diaprepesi was recruited to d-limonene in two-choice olfactometer trials. These results reinforce the critical role of plant defense pathways in mediating tritrophic interactions, suggest a broad role for plant defense pathway signaling belowground, and hint at sophisticated plant responses to pest complexes.

ADDITIONAL INDEX WORDS. Fragaria ◊ananassa, ring nematode, nutsedge, methyl bromide, 1,3-dichloropropene, chloropicrin, metam, napropamide SUMMARY. Field studies were conducted in three Florida locations (Bradenton, Gainesville, and Quincy) during 1998-99 and 1999-2000 to: 1) compare the performance of two transplant systems under diverse MBr alternative programs in 'Chandler' strawberry (Fragaria ◊ananassa), and 2) determine the effi cacy of these treatments on soilborne pest control in strawberry. Fumigant treatments were: 1) nonfumigated control, 2) methyl bromide plus chloropicrin (MBr + Pic) at a rate of 350 lb/acre, 3) Pic at 300 lb/acre and napropamide at 4 lb/acre, 4) 1,3-dichloropropene (1,3-D) plus Pic at 35 gal/acre and napropamide at 4 lb/acre, 5) metam sodium (MNa) at 60 gal/acre and napropamide at 4 lb/acre, and 6) MNa followed by 1,3-D at 60 and 12 gal/acre and napropamide at 4 lb/acre, respectively. Strawberry transplants were either bare-root or container- ized plugs. There were no signifi cant fumigant by transplant type interactions for strawberry plant vigor and root weight per plant, whereas ring nematode (Criconema spp.) and nutsedge (Cyperus rotundus and C. esculentus) populations, and total marketable fruit weight were only infl uenced by fumigant application. The nonfumigated plots had the lowest strawberry plant vigor and root weight per plant in all three locations. In most cases, plant vigor and root biomass per plant increased as a response to any fumigant application. With regard to the transplant type, bare-root transplants had similar plant vigor as plugs in two of the three locations. Fumigation improved nutsedge and ring nematode control. All fumigants had higher early and total marketable yield than the nonfumigated control, whereas transplant type had no effect on total fruit weight.

This study was conducted to determine the suppressiveness of obligat parasite P. penetrans against the peanut root-knot nematode Meloidogyne arenaria race 1 in vegetable growing site and to find out whether the field site have infested with other root-knot nematode species, causing the suppression to break down. The study were carried out at four vegetable crops grown sites tomato Lycopersicon lycopersicum cv. Bella Rosa, cucumber Cucumis sativus L. cv. Cobra, okra Abelmoschus (=Hibiscus) esculentus (L.) Moench cv. Clemson Spineless and squash Cucurbita pepo L. cv. Golden Summer at the Plant Science Research and Education Unit-Citra, University of Florida, US. The field site was arranged in a split plot design with eight replicates. To determine the effect of 1,3dichloropropene (1,3-D) on P. penetrans, the split plot was fumigated with 1,3-D (Telone II)at dose of 112 L/ha.. Plant and soil samples were collected from each plot at harvest time. The percentages of M. arenaria race 1 infective juvenile (J2) with endospores attached ranged from 40%to 10%.. Only a very low incidence of M. incognita was extracted from tomato roots galls.. The results indicate that P. penetrans is likely to be one of the important effective agent in the nematode suppression and the reduction M. arenaria race 1 damage, Bu çalışmanın amacı, obligat parazit olan Pasteuria penetrans bakterisinin sebze yetiştirilen alanlarda kök-ur nematodu Meloidogyne arenaria ırk 1’e karşı baskınlığını ortaya çıkarmak, bu baskınlığın etkisinin kırılmasına neden olan diğer kök-ur nematod türlerinin alanda bulunup bulunmadığını tespit etmektir. Bu amaçla 2011 yılının Mart ayında, daha önceden P. penetrans bulaştırılmış ve M. arenaria race 1’e karşı baskın olduğu bilinen Florida Üniversitesi’nin araştırma arazisinde, domates Lycopersicon lycopersicum cv. Bella Rosa, salatalık Cucumis sativus L. cv. Cobra, bamya Abelmoschus (=Hibiscus) esculentus (L.) cv. Clemson Spineless ve kabak Cucurbita pepo L. cv. Golden Summer gibi dört farklı sebze çeşidi yetiştirilmeye başlanmıştır. Çalışma bölünmüş parseller deneme deseninde 8 tekerrürlü olarak yürütülmüştür. Her bir sebze çeşidi için biri ilaçlı diğeri ilaçsız olacak şekilde parseller hazırlanmıştır. Ilaçlı parseller 112 lt/ha oranında 1,3-dichloropropene (1,3-D) (Telone II) ile ilaçlanmıştır. Tüm deneme parsellerinden hasat sonunda bitki kökleri ve toprak örnekleri alınarak inceleme yapılmıştır. Alınan toprak örneklerinden elde edilen M. arenaria ırk 1 juvenillerinin P. penetrans’ın endosporları ile bulaşıklık oranı en yüksek %40 olarak kimyasal uygulanmış kabak parselinde, en düşük endospor bulaşıklık oranı ise kimyasal uygulanmayan bamya parselinde yaklaşık %10 olarak gözlenmiştir. Deneme alanlarında yetiştirilen sebzelerden yalnızca domates bitkisi köklerinde çok düşük oranda diğer nematode türlerinden M. incognita tespit edilmiştir. Çalışmadan elde edilen sonuçlar, sebzelerde M. arenaria race 1 tarafından meydana gelen zararın azaltılmasında ve bu nematodun baskı altında tutulmasında P. penetrans’ın önemli bir etmen olduğunu ortaya koymuştur

A field trial in 2012 indicated a possible disease complex between Pythium aphanidermatum and the root-knot nematode (RKN) Meloidogyne incognita in cucumber. Two growth chamber trials were conducted to investigate this potential disease complex. The results indicate that control of RKN may be important for managing Pythium damping-off in cucumber. Accepted for publication 29 August 2016.