Showing papers on "Trichoderma harzianum published in 1978"
TL;DR: No single treatment provides a satisfactory damping-off of radish and on the inoculum density of R. solani, so the effect of single treatments of soil and direct introduction of biological antagonists into soil was examined.
Abstract: HENIS, Y., A. GHAFFAR, and R. BAKER. 1978. Integrated control of Rhizoctonia solani damping-off of radish: Effect of successive plantings, PCNB, and Trichoderma harzianum on pathogen and disease. Phytopathology 68:900-907. When applied to soil at rates of 0.04-0.15 g/ kg (dry weight permitted no increase in inoculum density. With high basis), wheat-bran cultures of Trichoderma harzianum inoculum levels (80 propagules/ g soil) T. harzianum protected radish seedlings from damping-off induced by accelerated reduction in population of R. solani in Rhizoctonia solani and also increased radish germination in comparison with nontreated controls. After four or five noninfested soils. Protection lasted for five successive weekly successive plantings of radish in infested, nonamended soil, plantings. Pentachloronitrobenzene (PCNB) at 4 /Ag/g soil however, incidence of Rhizoctonia damping-off decreased (active) added with T. harzianum inoculum had an additive substantially. A conduciveness test was developed and used effect on disease control and a synergistic effect on the for quantitative evaluation of the ease with which disease decrease in inoculum density of R. solani propagules. In the increased in a given soil. Soil conduciveness declined to a absence of T. harzianum PCNB alone delayed the decrease of minimum in the nonamended, infested treatment after five viable R. solani propagules. At a relatively low initial successive plantings. The concept of incorporating soil inoculum density (five propagules/g soil) when radishes were conduciveness (along with inoculum quality and inoculum replanted every week, inoculum concentration rose during concentration) into the capacity portion of the inoculum the first 3 wk. Cultures of T. harzianum added to this soil potential is suggested. Additional key words: biological control. The literature on biological (3, 5) and chemical (16, 20, pellet sampler (12) for the study of population dynamics 21) control of Rhizoctonia solani Kuihn is voluminous. It of R. solani in soil, it became possible to study the covers seed treatments, soil fungicides, modification of combined chemical-biological effect on both the cultural practices, amending soil with plant residues and pathogen population and the incidence of root diseases in specific substances to induce changes in soil microflora, the soil. In this study, the effect of single treatments of soil and direct introduction of biological antagonists into soil. with Triehoderma harzianum Rifai, PCNB, or both on However, no single treatment provides a satisfactory damping-off of radish and on the inoculum density of R. control of R. solani. Fungicides are practical and widely solani was examined. Observations were made following used, but can favor other pathogens (10). Moreover, the successive plantings of radish seeds in a soil with an use (often extensive and excessive) of chemicals for pest initially low-to-medium population density of R. solani, control is a growing concern to public health authorities as compared with those in a soil infested with a high and environmentalists. With the exclusion of crop population of that fungus. sequence and fertilization practices (7, 16), however, practical use of biological control of root diseases has MATERIALS AND METHODS been doubted on both theoretical and practical grounds (1). The successful introduction of integrated, chemicalInoculation and assessment of disease.-An axenic biological control in entomology has encouraged plant culture of chopped potato-soil (CPS) inoculum of R. pathologists to renew their efforts towards this goal (3). solani isolate R-3 was prepared (12). A Fort Collins The few reports so far on integrated control of R. solani loamy sand (sieved through a 2-mm sieve) was infested by deal with the combined effect of chemical or physical mixing it with the inoculum in a twin-shell blender. After factors and the indigenous microflora (8, 18, 19, 21). adjusting moisture to 15% (about -0.7 bars water Attempts to control R. solani by simultaneous use of potential), 100-g portions were distributed in 80-mmpentachloronitrobenzene (PCNB) and Trichoderma sp. deep, conical, plastic pots, (78 mm diameter at the bottom were reported recently (6). With development of the soiland 110 mm diameter at the top). Soil in each pot was 00032-949X/78/000155$03.00/0 planted with 10 radish (Raphanus sativus 'Early Scarlet Copyright © 1978 The American Phytopathological Society, 3340 Globe') seeds having 99% germinability. Seeds were Pilot Knob Road, St. Paul, MN 55121. All rights reserved, planted at a depth of 1 cm. The pots were covered with
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