No abstract

Parasitic nematodes are a major threat to global food security, particularly as the world amasses 10 billion people amidst limited arable land. Most traditional nematicides have been banned due to poor nematode-selectivity, leaving farmers with inadequate controls. Here, we use the model nematode Caenorhabditis elegans to identify a family of selective imidazothiazole nematicides, called selectivins, that undergo cytochrome p450-dependent bioactivation exclusively in nematodes. At low parts-per-million concentrations, selectivins perform comparably well with commercial nematicides to control root infection by Meloidogyne incognita – the world’s most destructive plant-parasitic nematode. Tests against a wide range of phylogenetically diverse non-target systems demonstrate that selectivins are more nematode-selective than nearly all marketed nematicides. Thus, selectivins are first-in-class bioactivated nematode controls that provide efficacy as well as much-needed nematode selectivity.

The Pacific Northwest (PNW) of the United States (Idaho, Oregon, and Washington) is a diverse agricultural production area with over 400 different commodities grown in the region. Plant-parasitic nematodes are a constraint to the production of many of these commodities. Soil sample data from 2012 to 2016 were obtained from nematode diagnostic laboratories in the region to assess trends in occurrence, population densities, and distribution of plant-parasitic nematodes in the PNW. A total of 38,022 unique data points were analyzed. The number of plant-parasitic nematode samples processed in the PNW by diagnostic laboratories has significantly increased from 2012 to 2016. Fifteen genera of plant-parasitic nematodes were identified by diagnostic laboratories, with 86% of the samples in the PNW containing at least one plant-parasitic nematode genus. These laboratories provide a valuable service to agriculture in the PNW. Additionally, they serve as a rich source of information on plant-parasitic nematode distribution, occurrence, and abundance that, when analyzed, provides an empirical basis upon which to interpret individual grower reports and make management recommendations.

Phytophthora ramorum, the causal agent of sudden oak death on oak and tanoak and Ramorum blight or Ramorum shoot dieback on ornamentals, is a recently emerged pathogen. Viburnum is a genus of commonly grown ornamental shrubs known to be susceptible to P. ramorum. The entire genus has been placed on the P. ramorum host list. The range of susceptibility of genotypes in the genus is currently not understood. We evaluated whether or not cultivars in the genus Viburnum differ in susceptibility to P. ramorum in controlled, detached leaf inoculations using two isolates belonging to the two clonal lineages found in Oregon. The genus Viburnum shows remarkable differences in susceptibility to infection by P. ramorum. Viburnum genotypes differed significantly in susceptibility to P. ramorum in detached leaf inoculations. V. × burkwoodii was consistently the most susceptible host genotype, followed by V. plicatum ‘Mariesii’ and V. lentago. Most cultivars evaluated for resistance to P. ramorum were not susceptible or developed only small lesions as determined with a detached leaf assay. Our work only provides information on leaf based resistance, and inferences on epidemic development in whole canopies and under field conditions cannot currently be made.

Nematode parasites of humans, livestock and crops dramatically impact human health and welfare. Alarmingly, parasitic nematodes of animals have rapidly evolved resistance to anthelmintic drugs, and traditional nematicides that protect crops are facing increasing restrictions because of poor phylogenetic selectivity. Here, we exploit multiple motor outputs of the model nematode C. elegans towards nematicide discovery. This work yielded multiple compounds that selectively kill and/or immobilize diverse nematode parasites. We focus on one compound that induces violent convulsions and paralysis that we call nementin. We find that nementin stimulates neuronal dense core vesicle release, which in turn enhances cholinergic signaling. Consequently, nementin synergistically enhances the potency of widely-used non-selective acetylcholinesterase (AChE) inhibitors, but in a nematode-selective manner. Nementin therefore has the potential to reduce the environmental impact of toxic AChE inhibitors that are used to control nematode infections and infestations.