Survival of binucleate Rhizoctonia species, biological control agents, in soil and plant debris under field conditions

• Published in: Biological control Vol. 1; no. 3; pp. 218 - 226
• Main Authors: Cubeta, M.A, Echandi, E, Gumpertz, M.L
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.10.1991
• Subjects: ecology; saprophytic colonization; ecology; saprophytic colonization
• ISSN: 1049-9644; 1090-2112
• DOI: 10.1016/1049-9644(91)90070-G

Survival of binucleate zoctoniaspp. (isolates 232-CG and JF-3N1-1) was studied in soil under field conditions. Oat kernels colonized with 232-CG and JF-3N11 were finely ground and buried 1, 15, and 30 cm deep in two field soils at Clayton (CL) and Raleigh (RA), North Carolina, and sampled monthly for 1 year. After burial for 1 month in RA soil, populations of 232-CG and JF-3N1-1 increased 49 and 29%, respectively, at 1 cm, but decreased 6 to 67% at 15 and 30 cm. Neither isolate was recovered after 5 months at 30 cm or after 7 months at 1 and 15 cm in RA soil. Populations of 232-CG and JF-3N1-1 increased 19 and 58%, respectively, after 1 month at 1 cm in CL soil, but populations of both isolates decreased between 38 and 69% after 1 month at 15 and 30 cm. Neither isolate was recovered after 9 months in CL soil. Snapbean stems colonized with 232-CG and JF-3N1-1 were buried 1 and 15 cm deep in field soils at CL and RA and were also sampled monthly for 1 year. Recovery of 232-CG and JF-3N1-1 from precolonized snapbean stems decreased by 50% after 1 month at 1 and 15 cm in CL and RA soils. After 2 and 3 months at both depths, recovery of 232-CG and JF-3N1-1 increased 10 to 40% and was followed by an irregular and gradual decline in RA soil. Recovery of 232-CG was higher ( P < 0.02) than that of JF-3N1-1 at both depths in RA soil. Recovery of 232-CG ( y = 0.71 − 0.11 x) and JF-3N1-1 ( y = 0.61 − 0.10 x) decreased over time at a similar rate, as did the recovery of both isolates from 1-cm ( y = 0.58 − 0.11 x) and 15-cm ( y = 0.65 − 0.10 x) depths. After 2 months at 1 and 15 cm in CL soil, recovery of 232-CG increased 30 and 3%, respectively, while recovery of JF-3N1-1 decreased 35 and 10%, respectively, and then decreased gradually after 3 months. Recovery of 232-CG ( y = 0.77 − 0.13 x) and JF-3N1-1 ( y = 0.51 − 0.10 x) decreased at different rates over time as did the recovery of both isolates from 1-cm ( y = 0.74 − 0.13 x) and 15-cm ( y = 0.64 − 0.10 x) depths. Recovery of both isolates was higher ( P = 0.001) at 15 cm than at 1 cm and neither isolate was recovered after 11 months in CL and RA soils. Thus, survival of isolates 232-CG and JF-3N1-1 of the binucleate Rhizoctonia spp. in field soil was dependent on the method of their amendments to soil (colonized oat kernels vs. snapbean stems) and the length of burial in the soil (1 cm vs. 15 cm). With this information it may be possible to introduce binucleate Rhizoctonia spp. in soil and implement strategies for the management and maintenance of adequate populations of these biological control agents to control diseases caused by R. solani.