Assessment of incidence of collar rot disease of groundnut in Andhra Pradesh and evaluation of bioefficacy of Trichoderma spp. against Aspergillus spp.

Roving survey was conducted during Kharif, 2018-19 in three major groundnut growing districts of Rayalaseema in Andhra Pradesh to know the status of collar rot (caused by Aspergillus spp.) incidence under field conditions. Effect of variety, seed treatment, farming situation, soil type and cropping pattern on disease incidence was studied. Maximum collar rot incidence was observed in Anathapuramu district (17.24%) followed by Chittoor district (15.90 %) and Y.S.R. Kadapa district (12.56%). Even though fungicides were reported to be effective against collar rot of groundnut, there is limited data available on biological control of collar rot. Hence, a study was also conducted to isolate and test Trichoderma spp. that is effective against the collar rot pathogen. Eight Trichoderma spp. isolates were evaluated against six virulent Aspergillus spp. isolates (i.e., two isolates of A. niger, two isolates of A. flavus and two isolates of A. terreus) using dual culture technique. From the results it was revealed that, Trichoderma spp. isolate GT2 (88.64 %) exhibited highest overall mean per cent inhibition followed by GT1 (85.17 %) and GT7 (84.20 %). Whereas, the lowest mean per cent inhibition was recorded in GT3 (45.59 %).