Control of Meloidogyne graminicola a Root-Knot Nematode Using Rice Plants as Trap Crops: Preliminary Results

Meloidogyne graminicola is one of the most harmful organisms in rice cultivation throughout the world. This pest was detected for the first time in mainland Europe (Northern Italy) in 2016 and was subsequently added to the EPPO Alert List. To date, few methods are available for the control of M. graminicola and new solutions are required. In 2019, field trials using rice plants as trap crops were performed in a Lombardy region rice field where five plots for three different management approaches were staked out: (i) Uncultivated; (ii) Treated: three separate cycles of rice production where plants were sown and destroyed each time at the second leaf stage; (iii) Control: rice was sown and left to grow until the end of the three cycles in treated plots. The results showed that in the treated plots, the nematode density and the root gall index were lower than for the other two management approaches. Moreover, the plant population density and rice plant growth were higher than the uncultivated and control plots. In conclusion, the use of the trap crop technique for the control of M. graminicola gave good results and thus it could be a new phytosanitary measure to control this pest in rice crop areas.

Crop tree release increased the density of soil nematodes and improved the food web structure

As a special thinning method, crop tree release (CTR) has a beneficial effect on forest environments and structures by changing forest light, heat, and water. However, the impact of CTR on underground biodiversity remains unclear. Therefore, we analyzed the composition, diversity, and metabolic footprints of soil nematode communities under three CTR (100, 150, and 200 trees·ha–1) treatments, as well as a no CTR treatment, in Pinus massoniana Lamb. plantations. The results showed that CTR increased the density of soil nematodes (P < 0.05), the number of omnivore–predator nematodes (P < 0.05), and the diversity (H′) of nematodes (P < 0.05) and enriched the food web structure of soil nematodes. In the medium CTR density treatment (150 trees·ha–1), the nematode density and diversity (H′) were the highest (P < 0.05), the number of omnivore–predator nematodes was also the highest (P < 0.05), and the enrichment index and structure index values of the soil nematodes reached the maximum at the depth of 0–10 cm (P < 0.05). Our results indicated that the community structure of soil nematodes became more stable and mature after CTR, which may be attributed to the changes of soil condition, especially soil organic matter, and plant diversity indirectly.

Soil nematodes in the field and fallow - density and diversity

The results presented here concern the study, which was carried out in the spring of 2009 on an arable field and a fallow. Following parameters were analysed: density, taxonomic composition, trophic and dominance structure of soil nematode communities. Shannon-Weaver diversity index, Sørensen’s index of similarity and Maturity index were also calculated. The results show that the nematode community in the soil of arable field differed from that on the fallow in respect of density and trophic structure. Nematode density was higher in the arable soil than in the fallow. The group of bacterial-feeding nematodes was the most numerous among five trophic groups recorded in the study. The higher density of that group in the arable soil than in the fallow indicates the positive response of bacterial-feeding nematodes to the higher nutrient supply after the manure applying. The results show that in three years of fallow nematode communities became more mature and diverse than in the arable soil. The study confirms the indicative value of some nematode community parameters and indices for the assessment of the varying human intervention on the functional state of the soil.

Nematicidal activity of cinnamon bark extracts and chitosan against Meloidogyne incognita and Pratylenchus coffeae

Summary In this study, we aimed to evaluate the nematicidal activity of cinnamon bark extracts (CE) and chitosan (Cs) against Meloidogyne incognita and Pratylenchus coffeae under pot and field conditions. In the pot experiments, CE mixed with Cs effectively inhibited M. incognita and P. coffeae infection on robusta coffee plants. The formulations applied, CE:Cs = 8 mg:30 mg, CE:Cs = 16 mg:60 mg and CE:Cs = 16 mg:60 mg per pot, significantly reduced the gall index and nematode number in 5 g of root and 100 g of soil. In addition, the application of CE:Cs = 48 mg:180 mg CE:Cs = 80 mg:300 mg and CE:Cs = 112 mg:420 mg plant−1 effectively reduced root gall formation and nematode density in roots and soil compared with the non-treated control under field conditions. Nematode density in the roots was positively correlated with the rate of yellow leaf disease. These results suggest that cinnamon mixed with chitosan may be used as an effective eco-friendly pesticide against plant-parasitic nematodes.

Distribution of Pigeon Pea Cyst Nematode and Root-Knot Nematodes in Major Sesame Growing Areas in Myanmar

The pigeon pea cyst nematode, Heterodera cajani, is an economically important plant-parasitic nematode in sesame production. The objective of the study was to investigate distribution of H. cajani in the major sesame producing areas in Myanmar. Before cultivation, soil samples were collected in 96 local farmer’s fields: (19 fields in Magway, 20 fields in Mandalay, 14 fields in Sagaing and 43 in Nay Pyi Taw), and nematode density was quantified by real-time PCR. The cyst nematode was detected in 63.2% of the fields in Magway and the mean density was 22.6 eggs equivalent (20 g soil)−1. In Mandalay and Nay Pyi Taw, the cyst nematode was detected in 40.0% and 18.6% of the fields with the mean densities of 9.9 and 21.0 eggs equivalent (20 g soil)−1, respectively. By contrast, the cyst nematode was not detected in Sagaing fields, in which sesame is rotated with paddy rice. Infestation of root-knot nematodes (RKN, Meloidogyne spp.) was also evaluated, because sesame is generally rotated with rice and pulses, which are attacked by RKN. The results showed 25.6% infestation of RKN with a mean density of 34.3 eggs equivalent (20 g soil)−1 only in Nay Pyi Taw, while there was no infestation in Magway, Mandalay, and Sagaing. The relationships between the nematode infestation level and the cropping patterns in each sesame growing area in Myanmar were discussed.

Pratylenchus thornei: The Relationship Between Presowing Nematode Density and Yield Loss in Wheat and Barley

The root lesion nematode Pratylenchus thornei causes economic losses in wheat and barley internationally through both reduced grain yield and grain quality. This study investigated the relationships between the presowing P. thornei density and grain yield and the postharvest nematode densities. Four field experiments were conducted at the same site between 2010 and 2014. A range of presowing P. thornei densities was established in the first year by growing three cereal cultivars that ranged from resistant to susceptible. In the following year, plots were sown with the five same cereal cultivars. A linear relationship was observed between the natural log of the presowing P. thornei density and grain yield across all seasons. The results showed that grain yield losses varied between cultivars and seasons. The importance of season was significant, with this study conducted over several seasons, and it highlighted the variability in yield losses between seasons, which will need further investigation. The greatest yield losses observed were 25 to 28% when the maximum presowing P. thornei densities ranged between 150 and 250 P. thornei g of soil−1. An analysis of the relationship between the presowing and postharvest nematode densities revealed that increased presowing nematode densities resulted in decreased multiplication rates in all seasons and in all cultivars. Nematode multiplication rates also varied between seasons. These results explain why it is difficult to predict nematode levels based on cropping history, and additionally, they highlight the importance of growing resistant cultivars to maintain low levels of P. thornei to minimize risk of yield losses.

The Effectivity of Bioinoculants on Suppressing Tylenchulus semipenetrans in Citrus Growing Soil in Cao Phong, Hoa Binh

Tylenchulus semipenetrans causes serious damages related to decline on citrus in Cao Phong district, Hoa Binh province. This study evaluated the effects of EM, AMF, AT+Ketomium and Chitosan-Super in the control of nematodes. In the laboratory condition, the T. semipenetrans was isolated from the soil and assessed for survival in the liquid medium containing EM and Chitosan-Super. The larval mortality rate reached 98.57% after 72 hours when using Chitosan-Super at 2% concentration. For pot experiments, T. semipenetrans and bioinoculants were infected into Hoa Binh red grapefruit rhizospheres. The results indicated that nematode density in the soil decreased the most in CT5 (Chitosan-Super), followed by CT4 (AT+Ketomium), CT3 (AMF+EM) and CT1 (AMF), CT2 (EM); nematode density in roots was the highest at CT5 of 132±27 individuals/5g of roots, while in CT1 there was no parasitic nematode on the red grapefruit root though its density in soil was high (2.424±125 individuals/250g of soil). Citrus grew normally in all of the experience formulas. Research results are an important basis for effective use of bioinoculants in preventing nematode parasitic on citrus.

Nematodes Associated with Two Species of Mentha (Lamiaceae) in Balochistan, Pakistan

Nematodes associated with Mentha spicata L. and Mentha longifolia L. were investigated in Balochistan in various localities so as to assess the variation in density of different nematode species found in the rhizosphere. Ten species of nematodes were found associated with Mentha spicata while four species were found in the rhizosphere of M. longifolia. Significant differences in nematode density were recorded (p at the most p < 0.01). The dominant nematodes associated with Mentha spicata were Pratylenchus projectus and Merlinius khuzdarensis while those associated with Menthe longifolia were Xiphinema americanum and Pratylenchus thornei.

A Predictive Risk Model Analysis of the Potato Cyst Nematode Globodera pallida in Idaho

Globodera pallida is a major nematode pest of potato (Solanum tuberosum) and is of great economic importance for the potato industry. Assessing potato yield loss caused by the Idaho G. pallida population under field conditions was not performed due to its quarantine status in Idaho, where it is prohibited by regulatory statutes to grow potato in any infested fields. The experimental data came from three trials that were conducted under greenhouse conditions. A predictive risk model analysis was performed to: (i) determine the effect of the Idaho population of G. pallida on potato yield; (ii) estimate reproduction rate from different initial nematode densities; and (iii) simulate potato yield losses in Idaho field conditions by integrating the coefficients of potato yield into the SUBSTOR-DSSAT crop simulation model. Experiments were conducted under greenhouse conditions using five initial G. pallida soil infestation levels (0, 10, 20, 40, and 80 eggs/g soil). The coefficients of potato yield achieved under each initial nematode density were integrated into the SUBSTOR-DSSAT potato growth simulation model. The model showed that tuber weight reached a maximum yield of 96 ton/ha in noninfested soil. Based on the greenhouse trials, the model predicted a minimum yield of 12 and 58 ton/ha in trial 1 and trial 2/3 respectively, when initial nematode density was 80 eggs/g soil. In trial 1, tuber weight was significantly reduced by 44% at 40 eggs/g soil and by 87% at 80 eggs/g soil, and 20% at 40 eggs/g soil and by 39% at 80 eggs/g soil in trial 2/3. The outputs of this study should facilitate common understanding between regulators, policymakers, and potato growers on the challenges and opportunities for controlling this economically important pest in Idaho.

Pre-Plant Fumigation of Soils for Nematode Control Affects the Seedling Production and Morphological Properties of Pine and Larch Seedlings

Using a fumigation sterilizer (Dazomet) for nematode control, this study determined the effect of soil sterilization on the quantity and quality of the growth of Pinus densiflora Siebold & Zucc. and Larix kaempferi (Lamb.) Carrière seedlings in an open-field nursery at Jeongseon-gun, Kangwon-do, Republic of Korea. Most soil nematodes disappeared after fumigant sterilization. The organic matter content, cation exchange capacity, and Mg2+ content of the soil increased significantly, but the electrical conductivity (EC) decreased. The quantity of pine and larch seedlings was highly correlated with the soil nematode density. The soil properties changed due to soil fumigation, which affected the growth of both species. Pine seedling growth was affected by the soil chemical properties, such as available phosphorus (AP), Ca2+, Mg2+, and EC, and the growth of larch seedlings was affected by the EC and nematode density. The quality of the pine seedlings improved, whereas that of larch did not. This was a result of the difference in their tolerance to soil salinity. The seedling quality index (SQI) of the two species was related to the EC, but the pine seedlings were more affected by the EC, indicating that the control of soil nematodes by fumigant treatment significantly increased the quantity of seedlings produced and partly improved their quality. Soil management using a fumigant treatment was more efficient for producing pine seedlings than larch. Our results can be used to improve agricultural and forestry economics.