Damage caused by fungi and insects to stored peanut seeds before processing

Franciele Dos Santos,Ignácio José De Godoy,André Luiz Lourenção,Priscila Fratin Medina,João José Dias Parisi

doi:10.1590/1678-4499.182

Abstract

The aim of this study was to gather data on the incidence of fungi associated with peanut seeds stored in their pods, before being processed by the State of Sao Paulo seed-producing companies, and the relation of the fungi to the seed damage caused by insects and to the quality of the stored seeds. Samples were taken from seed lots of cultivars IAC 886 and IAC 503 stored by these companies at the beginning and end of a six-month storage period. The peanut seeds were shelled and half of each sample was treated with fludioxonil + metalaxyl. Untreated and treated seeds were analyzed for moisture content, germination, vigor and health. The following insects were found to damage the peanut seeds: Cyrtomenus mirabilis (Perty) (Hemiptera: Cydnidae) and Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae). Both species reduced seed quality. When present, fungi of the genera Aspergillus, Fusarium, Penicillium and Rhizopus infected seeds and seedlings during the germination process and were considered the main limiting factor for obtaining normal seedlings. Nevertheless, despite their presence, peanut seeds maintained their germination capacity and vigor after six months of storage in their pods.

Highlights

The State of São Paulo accounts for 89% of the Brazilian peanut crop production (CONAB 2014)
Most of the reported damage caused by insects was attributable to C. mirabilis, which occurs in the field, and to C. cephalonica, which is present during storage (Table 1)
The predominant fungi associated with peanut seeds were Aspergillus spp., Fusarium sp., Penicillium spp. and Rhizopus sp. (Tables 2, 3)

Summary

Introduction

The State of São Paulo accounts for 89% of the Brazilian peanut crop production (CONAB 2014). During the postharvest management process developed by these companies, the seeds are stored in their pods in “big bags” or in bulk for at least six months without receiving any fungicidal or insecticidal treatment between harvesting and processing Because of their thin, fragile seed coat; large, brittle cotyledons; and the placement of the tip of the radicle near the basal surface of the cotyledons, these seeds are very susceptible to mechanical damage and insect infestations, which, in turn, promotes the entry of fungi into the seeds. High relative humidity promotes the reinitiation of metabolic activity in the embryo, whereas high temperatures increase respiratory activity, which depletes reserves These conditions may favor fungal and insect activity, reducing seed quality (Christensen and Kaufmann 1965). In São Paulo, the occurrence of peanut seed lots with germination percentage is often lower than the standard established for marketing (60%), due to high rates of infection caused by fungi and insects (Santos et al 2013)

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