Interaction Studies Between Meloidogyne Javanica and Fusarium Oxysporum f. Sp. lycopersici (Fol) Race 3 on Different Isolines of Tomato Cv. Tasti Lee.

The Mi gene in tomato confers resistance to Meloidogyne javanica, M. incognita, and M. arenaria, the most common tropical root-knot nematode (RKN) species found in Florida. Fusarium wilt (Fol) is another major problem in Florida tomatoes which may interact with RKN and cause more plant damage. To study the interactions between RKN, Fusarium, and Mi in tomato, two greenhouse experiments were conducted. Both experiments used different isolines (with and without I-3 and Mi genes) of the tomato cultivar Tasti Lee®. In the first experiment, all four isolines were subjected to two levels of RKN (~10,000 eggs/pot and no eggs) and two levels of Fol (1000 cc soil with 1,000 cfu/g at planting and no Fol), both applied at planting. In the second experiment, the two isolines without I-3 were exposed to the same two levels of RKN as described above and three levels of Fol (50 ml Fol with 1×106 cfu/m at planting, at 10 DAT, and no Fol). Fol reduced root-knot infection and reproduction when both Fol and RKN were inoculated at planting but not when Fol was inoculated 10 days later. Plant damage from Fol was exacerbated in the presence of RKN, especially when both pathogens were present at planting. Isolines with I-3 grew better in Fol-inoculated soil but had no effect when Fol and RKN were both present. Isolines with Mi gene reduced RKN infection and reproduction but did not affect plant damage caused by Fol. In summary, while RKN reproduction was reduced in the presence of Fol, the overall plant damage was more severe when both pathogens were present.

Potential of nicotinamide adenine dinucleotide (NAD) for management of root-knot nematode in tomato.

Nicotinamide adenine dinucleotide (NAD) has been shown to induce plant defense responses to different plant pathogens, including reducing northern root-knot nematode, Meloidogyne hapla, penetration and increasing plant mass in tomato. We wanted to further evaluate NAD that are effective against the more economically important species, M. incognita and whether NAD treatments of tomato seedlings in transplant trays can protect plants in the field. Different NAD concentrations (1 mM, 0.1 mM and 0.01 mM) and three application timings (pre; post; pre and post inoculation) were evaluated in growth room and greenhouse trials. The highest tested NAD concentration (1 mM) suppressed second-stage juveniles (J2) infection for all three application methods. Root gall ratings at 30 days after inoculation (DAI) were also suppressed by 1 mM NAD compared to the other two concentrations, and egg mass number was significantly suppressed for all concentrations and application timings compared to the non-treated control. The rate of 1 mM NAD for all three application timings also improved plant growth at 30 DAI. Long-term effects of 1 mM NAD (pre, pre + post, or post applications) on nematode infection, growth and yield of tomato were evaluated in two additional experiments. All NAD applications suppressed root galls after 60 days, but only the pre + post 1 mM NAD application suppressed gall severity at 105 days, as well as suppressed egg counts by 50% at 60 DAT. No significant difference in plant biomass and fruit yield after 105 days was observed among the treatments. Two field trials were conducted in spring and fall 2020 using tomato seedlings (cv. HM 1823) treated with two different NAD concentrations (1 mM and 5 mM in spring; 5 mM and 10 mM in fall) and transplanting seedlings in fumigated (chloropicrin ± 1,3-dichloropropene) and non-fumigated plastic-mulch beds. No significant impact of NAD in terms of reducing RKN severity or overall tomato growth and production was seen in fumigated beds, but in non-fumigated beds 5 mM NAD slightly increased early fruit yield in spring, and 10 mM NAD reduced root-knot soil populations in fall.

Efficacy of metam potassium on Fusarium oxysporum, Macrophomina phaseolina, Meloidogyne javanica, and seven weed species in microcosm experiments.

BACKGROUND: Metam potassium (metam-K) is a soil fumigant widely used to control plant pathogens, nematodes, and weeds in Florida plasticulture production. The objective of the study was to determine the efficacy of metam-K against Fusarium oxysporum, Macrophomina phaseolina, Meloidogyne javanica, and seven important weed species under controlled conditions. The optimal rates generated in this study provide insight into the efficacy of metam-K for field application. RESULTS: F. oxysporum and M. phaseolina were similarly sensitive toward metam-K with a 90% effective concentration (EC90 ) of 478 and 493 µmol kg-1 soil, respectively. Meloidogyne javanica was the most sensitive pest with an EC90 of 25 µmol kg-1 which is similar to previous studies. Chenopodium album was the most sensitive weed seed with an EC90 of 260 µmol kg-1 . Geranium carolinianum and Medicago lupulina were the least sensitive weed species with EC90 values of 786 and 567 µmol kg-1 , respectively. CONCLUSION: It is apparent from these results that metam-K can effectively control important pests in Florida plasticulture production systems with the correct application rate and adequate exposure of pest to the fumigant.

Efficacy of natural products against Callosobruchus chinensis (Coleoptera: Bruchidae) in Nepal.

This study was conducted to determine the efficacy of local natural products against the beetle, Callosobruchus chinensis L. (Coleoptera: Bruchidae), in stored chickpea Cicer arietinum L. (Fabaceae) in Chitwan, Nepal. Five natural products and one synthetic pesticide (Malathion) and two storage regimes (aluminum sheet bin vs. jute bags with plastic lining) were tested for their effect on stored pulse with respect to damage by C. chinensis. The five natural products included Xanthoylum armatum DC (Rutaceae) fruit powder, Acorus calamus L. (Araceae) rhizome powder, Cinnamom camphora L. (Lauraceae) balls, oil of Sesamum indicum L. (Pedaliaceae), and leaf powder of Azadirachta indica A. Juss. (Meliaceae). Treatments of stored pulses with natural products or with Malathion all caused significantly higher mortality of C. chinensis at 15 d after treatment (DAT) than stored pulses receiving no treatments. The balls of C. camphora, rhizome powder of A. calamus and sesame oil outperformed all other treatments, including the Malathion at 45 and 75 DAT and resulted in significantly reduced damage or deterioration of stored pulses compared with other treatments. Storage regimes performed similarly, although the jute bags did protect seed integrity for some treatments. Our results indicate that incorporating these natural products into stored pulses can protect the seeds from C. chinensis for up to two generations, something that Malathion cannot do. These products are readily available to most farmers in the region and their use will lead to 1) reduction of losses to significant stored product pests, and 2) a reduction of contamination of foodstuffs and the environment by synthetic pesticides like Malathion.