Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/1995
Publication Date: N/A
Interpretive Summary: Pellets containing dried, living fungus have been developed using three kinds of fungi that naturally parasitize and rapidly kill nematodes in the soil. When perfected, it is hoped these pellets can be applied to soil to manage plant-parasitic nematodes. Behavioral responses of infective juveniles of the cotton root-knot nematode were studied in moist sand containing the pellets. All three kinds of pellets were found to repel th nematodes due to an unknown compound produced by the fungi. The substance was not poisonous and nematodes escaped parasitism when placed several centimeters from the pellets. Carbon dioxide is a potent nematode attractant. By slightly enriching the carbon dioxide concentration within the zone of sand where pellets were placed, nematodes were induced to accumulate near the pellets, become infected, and die within several hours.
Technical Abstract: Cylinders (38-mm-d, 40 or 72 mm long) of sand (94% less than 250-um particle size) wetted with a synthetic soil solution (10% moisture) were used to examine responses of second-stage juveniles (J2) of Meloidogyne incognita race 3 to calcium alginate pellets containing the nematophagous fungi, Monacrosporium cionopagum, M. ellipsosporum, and Hirsutella rhossiliensis. A layer of 10 or 20 pellets was placed 4 or 20 mm from one end of the column. After 0, 3, or 13 days, J2 were put on both ends, on one end, or in the center. Second-stage juveniles were extracted from 8-mm-thick sections 1 or 2 days later. All three fungal pellets were repellent; pellets without fungi were not. Aqueous extracts of all pellets and of sand in which pellets had been incubated were repellent, but acetone extracts redissolved in water were not. Injection of CO2 (20 ul/minute) into the pellet layer attracted J2 and increased mortality. In vials containing four pellets and 17 cm3 of loamy sand, the parasitism of M. javanica J2 by fungi in the soil and the suppression of nematode invasion of cabbage seedling roots occurred at similarly high levels. Moreover, efficacy obtained by adding Monacrosporium spp. as colonized Steinernema glaseri did not differ substantially from efficacy obtained with pellets. Thus, pellet repellency did not protect nematodes sufficiently to prevent a high level of biocontrol efficacy from being achieved.