The impact of animal manures on the behaviour of sclerotia producing fungi infecting cotton

An investigation to determine the role of the addition of animal manure into soil on germination of sclerotia of fungi infecting cotton, including Sclerotium rolfsii, Sclerotinia sclerotiorum, Rhizoctonia solani, and Macrophomina phaseolina was conducted at the laboratory of Plant Science of Faculty of Agriculture, Forestry and Horticulture, University of Melbourne. Its effects on growth of cotton seedlings and disease severity caused by S. rolfsii was observed in a growth chamber conditions. Different source of manures affects pathogen behaviour differently. Chicken manure restrict the activity of S. rolfsii and Sc. sclerotiorum by enlarging populations of actinomycetes and bacteria in soils. When sderotia of S. rolfsii were placed on chicken manure-soil mixture, their germination was inhibited. Furthermore, hyphal lysis occurred 14 days after emerging. This manure also decreases the survival of sclerotia of S. rolfsii and Sc. sclerotiorum when the sderotia were buried for 2-3 months in it. Hence, the manure was able to reduce the severity of seedlings disease caused by S. rolfsii. Chicken manure provides a high nutrition for cotton growth when the seeds were sowed at least two months after incorporating. When cotton seeds were sowed in this mixtures soon after incorporated, however, the seedlings were suffered from severe phytotoxicity namely chlorosis and stunting. When seeds were sowed two months after incorporating of chicken manure into soil, there was none of phytotoxicity symptoms appeared. The growth of the seedlings was much better than that in soil. Cow manure, on the other hand, stimulated germination and growth of emerging hyphae of S. rolfsii in the short term of the experiment and increased disease severity. An abundance of readily available nutrients from this manure overcomes the inhibition of sclerotium germination caused by competition and provides nutrients for growth. These results indicate that chicken manure offers a good prospect to improve cotton growth as well as to control cotton seedling disease caused by S. rolfsii and probably other cotton pathogens. This could therefore be incorporated into soil as pre-sowing treatments. The best result is achieved when cotton seed was planted in this media at least two months after incorporating. By this time, some toxic substances which may be exist have degraded and sclerotia of S. rolfsii have disappeared as well