Prevalent insect pests of upland rice and some associatednatural enemies in southeastern Nigeria

S. O. Emosairue and E. J. Usua, Crop Science Department and BiologicalSciences Department, University of Calabar (UC), Calabar, Nigeria

Rice cultivation has increased dramatically in Nigeria since 1986 because of the government ban on rice imports. Rodents, birds, and insects are major contributors to low yields in farmers’ fields in southeastern Nigeria. We conducted this study during 1990 and 1991 early seasons (May-August) and late seasons (September-December) to provide information on prevalent insect pests and natural enemies in this rice agroecosystem.

The studies were conducted at the Teaching and Research Farm, Faculty of Agriculture, UC. ITA150 and ITA257, two popular early-maturing upland rice varieties developed by the International Institute of Tropical Agriculture were used. Each variety was planted in a 28.8 m2 plot demarcated into four equal blocks of 7.2 m2 and separated by a 1.75-m path. Four seeds of each variety were sown per hill at a spacing of 30 cm within rows and between rows. Plants were thinned to two per hill 20 days after sowing (DAS). A compound NPK fertilizer (15-15-15) was applied at 450 kg/ha in a split application, the first at 20 DAS and the second at booting.

Insect collection commenced 3 weeks after crop emergence and was done twice a week, usually on Mondays and Fridays between 0700 and 0900 hours; 1200 and 1400 hours, and 1700 and 1900 hours. During each sampling, three double-stroke sweeps were made of each block using a sweep net (30 cm diameter, 75 cm deep). Total number of each insect species was recorded. This procedure was followed until rice was harvested.

One hundred arthropod species comprising insect pests, natural enemies, and a few insects with undefined roles were collected. (See table for the 15 most prevalent pests.)

Coleoptera Chrysomelidae Chaetocnema pulla chapuis (= zeae (Bryant)) Altica nigrita (Lab.) Dactylispa sp. nr. paucispina (Weise) Monolepta elegans (Allard) Coccinellidae Chnootriba similis (Mulsant)Hemiptera Pyrrhocoridae Dysdercus supertitiosus (Fabricius) Cicadellidae Cofana spectra (Distant) Nephotettix modulatus (Mel.) Pentatomidae Aspavia armigera (Fabricius) Alydidae Stenocoris claviformis (Ahmad) Mirperus jaculus (Thunbg.) Aphrophoridae Poophilus costalis Walker Coreidae Cletus notatus (Thunbg.) Cercopidae Locris erythromela (Walker)

Diptera Diopsidae Diopsis spp.

The predators encountered were reduviids, Rhinocoris segmentarius (Germ.) and R. bicolor (Fabr.); tettigoniid, Conocephalus conocephalus (L.); coccinellids, Cheilomenes sulphurea (Oliv.), Cheilomenes sp. and Scymnus sp.; and arachnids (spiders). The parasitic species encountered were the braconid, Agathis (subgenus Microdus) sp., and the eumenid, Odynerus fervidus (Suss.).

Natural enemies were found mainly between the reproductive and ripening phases of the crop. Predators such as Cheilomenes sulphurea and Cheilomenes sp. were observed mainly on rice plants infested with the rusty plum aphid, Hysteroneura setariae (Th.), while spiders were observed feeding on small dipterous insects and cicadellid bugs such as Nephottetix modulatus (Mel.). In general, the overall population of natural enemies was higher on the late season crop. The tettigoniid, C. conocephalus and the reduviid. Rhinocoris spp., were the most abundant during both seasons.

In conclusion, we believe that the high population of grain feeders (D. superstitiosus [see figure] and A. armigera) on late season rice may cause some serious damage. Future work will focus on determining yield losses caused by these prevalent pests and on assessing the role of natural enemies in suppressing pests in this upland rice agroecosystem.

Emosairue SO, EJ Usua. 1994. Prevalent insect pests of upland rice and some associated natural enemies in southeastern Nigeria. International Rice Research Notes 19 (4) 22-23.

Relative abundance of the 15 most common Insect pests associated with upland rice varieties during early and late seasons in southeastern Nigeria.

TaxonOrder

FamilySpecies

Coleoptera ITA150 ITA257 ITA150 ITA257Chrysomelidae

Chaetocnema pulla 49.6 62.3 30.3 29.7chapuis (= zeae (Bryant))

Altica nigrita (Lab.) 1.2 0.9 5.1 0Dactylispa sp. nr. 1.7 0.7 0.2 0.3

paucispina (Weise)Monolepta elegans (Allard) 1.5 2.3 0.1 0

CoccinellidaeChnootriba similis (Mulsant) 10.4 5.1 4.9 4.4

HemipteraPyrrhocoridae

Dysdercus supertitiosus 0.2 0 32.3 26.9(Fabricius)

CicadellidaeCofana spectra (Distant) 16 10.6 11.9 12

Nephotettix modulatus (Mel.) 0.3 0.9 1.2 2.2Pentatomidae

Aspavia armigera (Fabricius) 5.7 8.3 10.3 15Alydidae

Stenocoris claviformis (Ahmad) 1.7 0.7 0.6 1.8Mirperus jaculus (Thunbg.) 0.2 0 0.2 2.3AphrophoridaePoophilus costalis Walker 0.3 1.4 0.2 0.7

CoreidaeCletus notatus (Thunbg.) 0.7 1.2 0.1 0Cercopidae

Locris erythromela (Walker) 1 0.5 0.2 0.2Diptera

DiopsidaeDiopsis spp. 4 4.2 2.2 4.5

sum 94.5 99.1 99.8 100a/ Relative abundance (%) = [Total no. of each species/Total no. of prevalent species] X 100Total no. of prevalent spp. = Total no. of prevalent insect species collected from thevegetative stage to harvesting of the crop during the different cropping periods.

Early LateRelative abundance (%) as affected by planting date a/

Dysdercus superstitiosus (Fabricius) feeding on the developing grains of upland rice cultivar ITA 150 at the milky stage, Calabar, southeastern Nigeria, during the late season.