Etiology of Peanut Pod Rot in Nicaragua: I. The Effect of Pod Size, Calcium, Fungicide, and Nematicide

Pod rot is one of the most important peanut (Arachis hypogaea L.) diseases in the pacific coast region of Cosiguina in Nicaragua. The region receives excessive rainfall during the peanut growing season and fields with high pod rot incidence often have moderate to high infestations of stem rot (Sclerotium rolfsii) and lesion nematode (Pratylenchus spp.). It was hypothesized that soilborne fungi, nematode damage and/or soil calcium deficiency could be involved in peanut pod rot. Flutolanil (1.2 kg a.i./ha, two applications), aldicarb (3.4 kg a.i./ha, one application), and calcium (670 kg/ha, two applications of gypsum) were evaluated on small (Georgia Green) and large (C-99R) seeded, runner cultivars in field experiments from 2005 to 2007 to help determine disease etiology. Experiments were split-split-plot or split-plot designs and treatments were replicated five times. There were no differences in pod rot between the two cultivars. Flutolanil did not decrease pod rot and only increased yield when associated with aldicarb nematicide. Gypsum application did not decrease pod rot, or increase yield or pod calcium content. Aldicarb had no effect on pod rot, but significantly increased yield by 22%, apparently by suppression of pod and/or root damage by lesion nematode. Neither calcium deficiency nor lesion nematode damage increased pod rot. Accepted for publication 19 October 2009. Published 15 February 2010. Pod rot is one of the most important peanut diseases in the pacific coast region of Cosiguina in Nicaragua. The objectives of the study were to understand the etiology of pod rot in Nicaragua, and to determine the effect of cultivar selection, fungicide, nematicide, and gypsum applications on pod rot and peanut pod yield.