Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 4, 2000
Publication Date: N/A
Interpretive Summary: More than 100 species of small worms, known as plant-parasitic nematodes, infect nearly every agronomic and horticultural plant important to agriculture. In the United States, these pests cause annual economic losses from decreased food, fiber, and ornamental production estimated at $10 billion. At the present time, only a small array of chemicals, which are frequently inadequate, unsuitable or too costly for certain crops or soils are available to control these pests. Therefore, a safe, effective, and economic means to control these worms is badly needed. This investigation showed that when harmless commercial product, which acts to freeze water droplets at temperatures a few degrees higher than they would normally freeze, was added to droplets containing nematodes, the droplets froze thereby killing the nematodes. In the absence of this product, the droplets remained liquid and the nematodes were unaffected. The results suggest that tin geographical areas where soils remain unfrozen at subzero temperatures, the addition of this commercial product to soil could induce freezing and thereby reduce the nematode population. This procedure has potential use by farmers as an alternative to chemical nematicides.
Technical Abstract: Juveniles of five species of nematodes were added to solutions with (treatment) and without (control) a commercial ice nucleating activity (INA)agent. Ten microliter drops of these nematode solutions were placed on glass microscope slides and transferred to a freeze plate where the temperature was reduced to -6 degrees to -8 degrees C. Droplets containing the INA agent froze while those without the agent remained liquid. After 2 min, the temperature of the plate was raised to 24 degrees C and the slides were examined with a light microscope to determine the viability of the juveniles. The results showed that the majority of juveniles (43% to 88% depending on species) in solutions that did not contain the INA agent (controls) were active and deemed living. This result indicated that the nematodes were capable of supercooling thereby protecting them from the subzero temperatures. Alternatively, less than 10% of the juveniles that had frozen for 2 min in solutions containing the INA agent remained viable indicating that inoculative freezing of the solution was lethal to the supercooled juveniles. Our results suggest that in geographical areas where soils remain unfrozen but supercooled, the addition of an INA agent could induce ice nucleation and thereby reduce the populations of nematode species that would be capable of surviving by supercooling but unable to survive when the soil solution is frozen.