Collar rot of groundnut caused by lasiodiplodia theobromae in North Vietnam

Collar rot of groundnut (Arachis hypogaea), caused by Lasiodiplodia theobromae (Pat.) Griffon & Maubl. (syn Botryodiplodia theobromae Pat., Diplodia natalensis Pole-Evans and Diplodia gossypina Cooke), the anamorph of Botryosphaeria rhodina (Berk. & M.A. Curtis) Arx, was first recorded in the early part of the 20th century by Miller and Harvey (1932). In USA, L. theobromae caused severe damage in North Carolina in 1947 (McGuire and Cooper 1965) and some other sites. After these instances, there were no further reports of collar rot in USA until 1998 when the disease caused severe losses on groundnut in Virginia (Phipps and Porter 1998). Lasiodiplodia theobromae has now been isolated from stems, shells and seeds of groundnut from a number of countries including Australia (Bell et al. 2003), Chad (Sougnabe and Foko 2003), Egypt (El Habbaa et al. 2002), Gabon (Ndzoumba et al. 1990), India (Ramakrishna and Kolte 1984, Rao and Pande 1992), Indonesia (Dharmaputra and Retnowati 1996), Ivory Coast (Savary 1987) and Nigeria (Osuinde and Daibo 1999). In Vietnam, collar rot was first reported on groundnut by Dan et al. (2000) and was especially severe in spring 2003, when the disease was found on more than 20% of plants at Dong Anh, Hanoi. Instances of this disease seem to be increasing especially in areas that have sandy soil and two crops of groundnut during one season. In this article, we present a description of the pathogen, the symptoms that it causes on groundnut in Vietnam and media for its culture.