Abstract
A new leaf blight disease of yard long bean caused by Diaporthe sp. was identified during a survey of polyhouses in Thiruvananthapuram district of Kerala. Maximum incidence (80%) and severity (45.77%) of the disease were noticed in the variety NS 621.The disease causing fungus was identified to be Diaporthe sp. based on morphological and molecular studies. A varietal screening was conducted in the polyhouse of Integrated Farming System Research Station (IFSRS), Karamana using five varieties viz. Lola, Vellayani Jyothika, Gitika (KAU Varieties), VS 50 (KAU prerelease culture) and NS 621 (Namdhari Seeds Private Limited) to assess the natural incidence and severity of the leaf blight disease. The most susceptible variety to natural incidence of Diaporthe leaf blight disease (PDI - 58.66) was NS 621. In vitro evaluation of organic preparations, botanicals and non-hazardous compounds in inhibiting the mycelial growth of Diaporthe sp. revealed that, fermented leaf extract of the commonly available weed,Setaria barbata (10%) and sodium bicarbonate (0.5%) resulted in cent per cent inhibition of the mycelial growth of the fungus. The pot culture experiment conducted in the variety NS 621 in the polyhouse of IFSRS, Karamana revealed that soil applicationof arbuscular mycorrhizal fungi (AMF) (KAU isolate) @ 5g plant-1 at the time of planting followed by foliar application of fermented leaf extract of S. barbata (10%) at 20, 40 and 60 days after planting resulted in significant control of the leaf blightdisease (PDI - 11.35). The next best effective treatment in reducing the disease incidence (PDI - 18.33) was soil application of AMF @ 5g plant-1 at the time of planting followed by foliar application of sodium bicarbonate (0.5%) at 20, 40 and 60 days after planting.
NSTL