Effect of soil and seed application of Trichoderma harzianum on pigeonpea wilt caused by Fusarium udum under field conditions

Abstract

The efficacy of the biological control agent Trichoderma harzianum was tested on various levels of Fusarium udum, the pigeonpea wilt pathogen. Field plots infested with the pathogen at three inocula levels (log 3.04, log 4.98 and log 5.34 colony-forming units (cfu)/g of soil) were identified. Trichoderma harzianum was applied as a seed treatment (10 and 20 g/kg seed) and as a soil amendment (10 and 20 g/9 m 2). The Trichoderma population increased to more than 10 8 cfu/g soil by 60 days in treated plots, whereas for seed treatments, fungal population reached a maximum of 10 4.62 cfu/g soil within 45 days, and thereafter started to decline. At log 3.04 pathogen concentration, soil amendment, with T. harzianum at 10 and 20 g gave 42.9% and 61.5% disease control, respectively. Seed treatments resulted in less than 30% disease control when compared to the check. The disease control achieved with fungicide seed treatment was insignificant. At log 4.98 and log 5.34 pathogen concentrations, disease control ranged between 22% and 35.3% for soil treatments. Even at the highest pathogen density (log 5.34), soil amendment with T. harzianum at 10 g gave about 30% disease reduction. In seed treatment plots, disease control ranged between 4.36% and 13.7%. In general, soil application of T. harzianum was found to be more effective than seed treatment for disease suppression. These results suggest the need to augment soil applications of T. harzianum for obtaining effective control of pigeonpea wilt.