Incidence and relative abundance of rice stem borers in three selected rice fields in Lagos and Ogun States, Nigeria

Bolajoko Bolarinwa Adewoye,Winifred Ayinke Makanjuola,Joseph Chuks Anikwe

doi:10.4314/br.v19i1.9

Abstract

This study was conducted to investigate the incidence of rice stem borer infestations and the species composition present in the selected rice fields. Data were collected between April 2017 and November 2018 across three locations, which include the upland rice field in Agbajege, Ogun state, rainfed lowland in Itoikin and Mangrove swamp in Igbogun, Lagos state, respectively. The incidence of rice stem borers was indicated by dead heart and white heads symptoms, while tillers were excised for rice stem borer identification and population. Results showed a high and low incidence of rice stem borers with no significant difference(p>0.05) at p= 0.29 and 0.37 between the early and late planting seasons in the rainfed lowland and upland rice fields respectively. Planting seasons were significant in the incidence of rice stem borers in mangrove swamp rice fields at p<0.05, p=0.01). This study showed that the predominant species of rice stem borers present in the three study sites were Chilo zacconius and Sesamia calamistis. C. zacconius was the most abundant species at 89% while S. calamistis was 11%. Rice stem borer populations were significantly higher at (p<0.05, p=0.000) in flooded zones while the highest rice stem borer populations were observed at the reproductive phase of the rice plants. Thisstudy showed that the planting seasons coincided with the peak period of the development of rice stem borers. Hence, conservation of natural enemies, monitoring and surveillance should be adopted in insect pest management in rice agroecosystems

Highlights

Rice stem borers are a major group of insects that cause significant economic damage in paddy fields globally
Symptoms indicating the presence of rice stemborers infestations: The incidences of rice stemborer is indicated by the symptoms observed during survey which include the deadheart symptom, which occurs during the vegetative phase and whiteheads which occurs during the booting/panicle initiation stage and grain filling stage of the reproductive phase (Plate 1)
This study reveals that rice stemborers in rice fields varied across locations and growth stages, rice stem borers are highly abundant in flood-prone areas and in rice fields where pesticides use is inevitable with enabling factors

Summary

Introduction

Rice stem borers are a major group of insects that cause significant economic damage in paddy fields globally. Different species of rice stem borers of the order Diptera (Flies) and Lepidoptera(moth) have been reported as major pests across all rice agroecosystems They cause significant yield losses in paddy rice ranging from 22-100% during major outbreaks (Ukwungwu,1984; Pathak and Khan,1994; Kega et al, 2016). During the vegetative phase in rice plants, larvae of rice stem borers damage the leaves by feeding on the central whorl of the young plants This causes the leaf to wither, turn brown, and later die off, termed “dead heart” (Ogah and Nwilene, 2017). Rice stem borers bore into the tillers during the panicle initiation or grain-filling stage, leading to an abortion of the panicle development or grain filling process respectively This causes uniformly empty and chaffy panicles, known as “whiteheads”. The most significant damage of rice stem borer infestations occurs during the reproductive phase, in which the rice plants are unable to compensate for the damages inflicted at this stage

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Conclusion