Submitted to: Compost Science and Utilization
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 22, 2004
Publication Date: January 3, 2005
Citation: Entry, J.A., Strausbaugh, C.A., Sojka, R.E. 2005. Compost amendments decrease Verticilliuam dahliae infection in potato. Compost Science & Utilization. 13(1):43-49. Interpretive Summary: The major challenge facing commercial production of biological control of plant pathogens is to obtain effective, reproducible, and economically and environmentally acceptable disease control. The lack of disease control by organic treatments and biological control microorganisms is often ascribed to environmental factors, which are often difficult to define. We used wood chip-polyacrylamide (PAM) cores to alter the soil environment in a greenhouse study to favor indigenous soil microorganisms in vegetable and manure compost to reduce Verticillium dahliae infection of potato plants. Soil amended with wood chip cores and wood chip-vegetable compost cores had lower visible infection rates than all other treatments. Soil amended with wood chip-PAM-dairy compost soils amended with vegetable compost only had lower Verticillium dahliae infection rates than the control soil or soil amended with dairy compost. The control, vegetable compost and dairy compost treatments had lower microbial biomass/Verticillium dahliae biomass (MB/VB) ratios than the other three treatments. Visible infection curvinlinearly correlated with the MB/VB ratio in a negative relationship (4**2=0.76). As the MB/VB ratio increased visible infection of Verticillium dahliae decreased. The use of wood chip-PAM-vegetable compost treatments may be a possible method to control soilborne diseases in high value crops. This study provides some evidence that changing the soil environment to favor biological control or indigenous soil microorganisms to control soil pathogens may give produces a viable alternative to soil fumigants.
Technical Abstract: The lack of success of biological control with soilborne diseases is primarily due to the introduction of the biological control organism into a sub-optimal environment. Indigenous soil microorganisms contribute to disease suppression in cropping systems by reducing and competing with pathogen populations limiting disease severity. Various communities of indigenous microorganisms in any particular soil have adapted to the specific environmental conditions. If the soil around the plant roots could be altered to favor the indigenous soil microorganisms relative to the plant pathogen, the survival and proliferation of indigenous soil microorganisms and thus effectiveness of biological control may be increased. We used wood chip-polyacrylamide (PAM) cores to alter the soil environment in a greenhouse study to favor indigenous soil microorganisms in vegetable and manure compost to reduce Verticillium dahliae infection of potato plants. Potato plants gorwing in soils amended with vegetable compost-wood chip-PAM cores had substantially lower visible and isolation Verticillium dahliae infection rates than control soils and soils with dairy or vegetable compost alone. Soils with wood chip-PAM cores and soils with wood chip-PAM-vegetable compost had higher microbial biomass/Verticillium dahliae biomass (MB/VB) ratios in soil than control soils or soils amended with compost. MB/VB ratios in wood chip-PAM cores and wood chip-PAM-vegetable compost were higher than in wood chip-PAM-dairy compost cores. Verticillium dahliae infection negatively correlated curvinlinearly with the MB/VB ratio (r**2=0.76).