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Abamectin offers great protection against Bursaphelenchus xylophilus, a well-known devastating pathogen of pine tree stands. Trunk injection of nematicides is currently the most preferred method of control. This study aimed to evaluate the potency of the commonly used formulations of abamectin against B. xylophilus. Twenty-one formulations of abamectin were evaluated by comparing their sublethal toxicities and reproduction inhibition potentials against B. xylophilus. Nematodes were treated with diluted formulation concentrations in multi-well culture plates. And, populations pre-exposed to pre-determined concentrations of the formulations were inoculated onto Botrytis cinerea culture, and in pine twig cuttings. Potency was contrastingly different among formulations, with LC95 of 0.00285 and 0.39462 mg/ml for the most, and the least potent formulation, respectively. Paralysis generally occurred at an application dose of 0.06 μg/ml or higher, and formulations with high sublethal toxicities caused significant paralysis levels at the tested doses, albeit the variations. Nematode reproduction was evident at lower doses of 0.00053–0.0006 μg/ml both on Botrytis cinerea and pine twigs, with significant variations among formulations. Thus, the study highlighted the inconsistencies in the potency of similar product formulations with the same active ingredient concentration against the target organism, and the need to analyze the potential antagonistic effects of the additives used in formulations.

The pine wood nematode (PWN), Bursaphelenchus xylophilus is a well-known devastating pathogen of economic importance in the Republic of Korea and other countries. In the Republic of Korea, trunk injection of nematicides is the preferred method of control. In this study, the efficacy of 16 locally produced formulations of emamectin benzoate against the PWN are compared through determining their sublethal toxicities and reproduction inhibition potentials. Nematodes were treated with varying concentrations of the tested chemicals in multi-well culture plates, and rates of paralysis and mortality were determined after 24 h. Reproduction inhibition potential was tested by inoculating pre-treated nematodes onto Botrytis cinerea, and in pine twig cuttings. Despite the uniformity in the concentration of the active ingredient, efficacy was contrastingly different among formulations. The formulations evidently conformed to three distinct groups based on similarities in sublethal activity (group 1: LC95 of 0.00768–0.01443 mg/ml; group 2: LC95 of 0.03202–0.07236 mg/ml, and group 3: LC95 of as high as 0.30643–0.40811 mg/ml). Nematode paralysis generally occurred at the application dose of 0.0134–0.1075 μg/ml, and there were significant differences in nematode paralysis rates among the products. Nematode reproduction was only evident at lower doses both on B. cinerea and pine twigs, albeit the variations among formulations. Group 1 formulations significantly reduced nematode reproduction even at a lower dose of 0.001075 μg/ml. The variations in efficacy might be attributed to differences in inert ingredients. Therefore, there is need to analyze the potential antagonistic effects of the large number of additives used in formulations.

Filenchus cylindricus (Thorne & Malek, 1968) Niblack & Bernard, 1985 was reported from the sandy rhizospheric soils of Poa pratensis and for the first time in Korea. Females and males are molecularly characterized and morphological and morphometric data supplied. Identification was made using an integrative approach considering morphological characteristics and inferences drawn from the analyses of the D2-D3 expansion segment of 28S rRNA and ITS1-5.8S-ITS2 of rRNA partial sequences. Females and males from Korea conform to the type descriptions and also to subsequent species descriptions from Iowa and Colorado USA, Sudan and Pakistan. Despite the close morphological and morphometric similarities with F. thornei (Andrássy, 1954) Andrássy, 1963, the two species can be adequately differentiated based on molecular data inference.