/pdf/rice-feeding-insects-and-selected-natural-enemies-in-west-plo6czok8y.pdf

Rice-feeding insects and selected natural enemies in West Africa: biology, ecology and identification.

The surface area of pre-oviposition female scale insects was closely correlated with their dry and wet weight biomass, and was used as a convenient, indirect method of adult size assessment. Adult females at oviposition were on average bigger when in low density populations than those in high densities, an indication of intraspecific competition in the nymphal stage. Larger females were found to be more fecund (laid more eggs), and produced larger eggs, than smaller females. No significant differences were detected between fecundities of females which had fed as nymphs on different species of host tree, and the general adult size/fecundity relationship was of sigmoid form, indicative of a maximum reproductive potential, which was independent of host tree species. Comparisons with other Hemipteran species indicated the generalist nature of P. regalis, adapted to widespread dispersal and large first instar losses from populations.

Reproductive capacity of the horse chestnut scale insect, Pulvinaria regalis Canard (Hom., Coccidae)

SeveralspeciesinthefamilyCecidomyiidae(Diptera)areknownbyaparticularreproductionmechanism called monogeny, in which all offspring of each individual female are either exclusively male or exclusively female. As a consequence, no full-sib mating occurs in monogenous populations. So offspringofeach femalemust inevitablymatewiththoseofother females,andintheworst condition, mating may occur between individuals with a common sire but different mothers, where they are only half siblings. Simulation of monogenous gall midge pedigrees, calculation of inbreeding coefficients of individuals for 20 generations, and comparing the results with those of a non-monogenous species revealed that the totalaverageinbreeding coefficients ofindividualswerenot dramatically different between these two populations. However, the maximum inbreeding coefficient of individuals per generation in non-monogenous populations was significantly higher than in monogenous populations. Despite the effect of monogeny on inbreeding, it is doubted whether inbreeding avoidance is theonlyforcethat drivestheevolutionofmonogenyingallmidges.

Monogeny, a neglected mechanism of inbreeding avoidance in small populations of gall midges

Oebalus poecilus (Dallas 1851) e uma das especies de percevejos de grande importância economica para os produtores de arroz no Brasil em sistemas de cultivo irrigados, de inundacao ou de terras altas. Estes pentatomideos sao conhecidos como percevejos das paniculas, porque ninfas e adultos alimentam-se principalmente dessas estruturas. O ataque deste percevejo resulta em graos manchados, massa inferior, reducao germinativa e graos deformados. Considerando isso, o objetivo deste estudo foi avaliar as perdas quantitativas e qualitativas na cultivar comercial de arroz de terras altas (variedade Cambara), submetidas a diferentes niveis de infestacao de percevejos de paniculas, O. poecilus, em diferentes estagios de crescimento reprodutivo das plantas de arroz. Os resultados mostram que em arroz de terras altas (variedade Cambara), os graos de arroz sao suscetiveis a danos quantitativos (numero e peso) e qualitativos (graos manchados, atrofiados, gessados e quebrados), durante todo o desenvolvimento da panicula. No entanto, quando os insetos se alimentam durante os estagios de antese/cariopse e leitosa causam percentual significativamente maior de graos vazios (ate 83%) do que quando se alimentam de graos durante as fases posteriores do desenvolvimento da panicula. Esta caracteristica foi tambem observada para a reducao de peso dos graos. Esta informacao pode beneficiar os produtores e outros pesquisadores, permitindo que concentrem os esforcos de monitoramento de O. poecilus em fases mais suscetiveis ao ataque deste inseto. Tambem serve de base para a tomada de decisao sobre quando e quais medidas de controle devem ser realizadas, a fim de controlar os percevejos das paniculas.

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Quantitative and qualitative damage caused by Oebalus poecilus (Hemiptera, Pentatomidae) to upland rice cultivated in new agricultural frontier of the Amazon rainforest (Brazil)

Rice is an important cereal crop and is cultivated virtually in all agro-ecological zones in Nigeria. However, production capacity is far below national requirement. One of the major reasons for the low yields of rice in Nigeria is depredation by pests, particularly the insect pests. The rice plant is an ideal host for a large number of insect pests-root feeders, stems borers, leaf feeders and grain feeders. High yield losses associated with these insect pest categories portray the role of the insects in low rice yield in Nigeria and sub-Saharan Africa as a whole. Unfortunately, the potential for proper management of rice insect pests to enhance yield has not been fully realized in Africa. Proper management of rice pests therefore is a pre-requisite for enhanced and sustainable rice production amidst smallholder farmers that typify the rice production industry in Nigeria. In this review, major insect pests of rice were identified with emphasis on their pest status, distribution and control methods. Cultural, biological, host plant resistance and chemical controls and the development of integrated pest management programmes were reviewed. The long-term and wide adoption of integrated insect pest management of rice in Nigeria was advocated, emphasizing the use of host plant resistance and biological control but the current cultural practices should be evaluated from time to time for enhanced efficiency.

Incidence of Insect Pests on Rice in Nigeria: A Review

The development and pest status of Aspavia armigera on two cowpea varieties viz: Ife Brown and TVU1890 and alsoon two upland rice varieties viz: ITA 128 and ITA 257 were studied under ambient conditions in the laboratory and at the roof-top garden, Department of Agricultural Biology, University of Ibadan, Nigeria.The oviposition periods on rice were 15.1 and 6.0 days respectively on ITA 257 and ITA 128; and on cowpea 10.6 and 8.5 days respectively on Ife Brown and TVU 1890. Fecundity was low. Mated females laid the highest number of eggs (24.6) on the cowpea Ife Brown and this was significantly higher than in the other cultivars. Mated and unmated males and females lived longer on Ife Brown and ITA 257 than on ITA 128 and TVU 1890.The developmental period (nymph to adult), was shorter on ITA 257 (23.3 days) and Ife Brown (22.9 days) than on ITA 128 (23.3 days) and TVU 1890 (25.3 days). There were five nymphal instars and the mean growth ratio of head capsule measurements was 1.32.Infestation at the level of two A. armigera per peduncle caused total seed losses in the two cowpea varieties whereas four and eight bugs per panicle caused 39.1 and 31.7 % grain yield losses in ITA 257 and ITA 128 rice varieties respectively.

The development of Aspavia armigera Fabricius (Hemiptera: Pentatomidae) and its status as a pest of cowpea and rice.

The biology of the African rice gall midge Orseolia oryzivora Harris and Gagne was investigated in screenhouse and laboratory studies, and its incidence on cultivated wet-season rice was studied in farmers’ fields during the 2006 and 2007 rice-growing seasons at two localities in Nigeria. This insect is nocturnal, and mating takes place immediately after emergence. Both mated and unmated females lay eggs, with mated females laying on average 389 eggs each, and unmated females laying about 87 sterile eggs. The egg stage takes on average 2.5 days. Larval development takes 3.6, 3.3 and 3.0 days for the first, second and third instars, respectively, while the pre-pupal and pupal stages take 2.8 and 6.1 days, respectively. Adult females live for 48–78 h, while males live for 24–30 h. The life cycle of O. oryzivora is completed within 21–24 days under screenhouse conditions. The adult male is slender and about 3 mm long, while the female is more rounded with a 4 mm long body and a bright red abdomen. The insect produces unisexual progeny. Field incidence is low at the beginning of the rainy season, peaking with the peak in rainfall and humidity that concurs with the vegetative stage of the crop. The population of the midge declines as temperatures rise. In conclusion, prediction models may be developed based on weather parameters, to aid in forecasting the field incidence of O. oryzivora and its management strategies. Furthermore, it maybe possible to reduce the damage caused by O. oryzivora to rice crops by altering planting period and taking into account environmental factors.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1742758410000044

Biology of the African rice gall midge Orseolia oryzivora (Diptera: Cecidomyiidae) and its incidence on wet-season rice in Nigeria.

Phytochemical screening of crude methanol extract of Acalypha fimbriata was done to check for presence of secondary metabolites. The result indicated that the plant contained alkaloids, tannins, saponins, flavonoids, resins and glycosides. Extracts at different concentrations of (10, 20, 30 and 40 %v/v) with a solvent-treated control (0 %v/v) were also bio-assayed for their insecticidal potential against Sitophilus zeamais on stored maize. Five pairs (1 male :1 female) of adult insects were used to infest 50 g TZPB-SR-W maize grains stored for three months. Experiment was laid out in a completely randomised design, in four replicates, in the Entomology Research Laboratory, University of Ibadan, under an ambient conditions of 27 ± 2?C and 65 ± 5% relative humidity. Parameters assessed were insect mortality, oviposition, progeny emergence as well as percentage grain damage and seed viability. Results showed that the plant extract significantly (P 0.05) in the germination of tested seeds among all treatments including the control. Keywords :  Phytochemical screening, Acalypha fimbriata , protectant, Sitophilus zeamais

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Qualitative Phytochemical screening of Acalypha fimbriata, and its methanol extract as protectant against Sitophilus zeamais (Coleoptera: Curculionidae) on stored maize

Three different solvents namely; hexane, ethyl acetate and ethanol were used in partitioning the extracts obtained from Piper guineense seeds and solvent extracts were investigated for the presence or absence of secondary metabolites. Extracts were further evaluated on adult maize weevils, Sitophilus zeamais. Experiment was carried out under laboratory conditions at 27 ± 2 C ambient temperatures and 65 ± 5% relative humidity and was arranged in a completely randomised design in four replicates. Parameters assessed, including contact toxicity, repellent effects as well as effect of solvent extracts on the germination of maize seeds. Results obtained showed that the solvent extracts contained all the secondary metabolites tested except flavonoids and steroids. As well, all the solvent extracts were lethal and possessed high repellent action against S. zeamais, with ethanol fraction being the most potent. There was no significant difference in the germination of seeds treated with the solvent extracts as well as the ethanol control. The results obtained from this study reveal P. guineese as a potential candidate for bio insecticide and could serve as an alternative to synthetic insecticides.

http://jcp-old.modares.ac.ir/article_16308_288a6164070e3cc874281a6272ad8aff.pdf

Phytochemical investigations of Piper guineense seed extract and their effects on Sitophilus zeamais (Coleoptera: Curculionidae) on stored maize

Termites are one of the key pests attacking Eucalyptus species and also play important roles in ecological processes. A better understanding of the roles of termites in ecosystem processes requires information on termite diversity and could also provide useful information to identify noxious species. There is inadequate information on the termite diversity associated with Eucalyptus plantations in Nigeria. Therefore, occurrence and diversity of termite species in four Eucalyptus species plantations in Afaka, Nigeria was investigated. Termite samples were collected from E. camaldulensis , E. cloeziana , E. citriodora and E. tereticornis plantations in five micro-habitats: epigeal mound, leaf litters, wood litters, soil and under stem bark. The results showed that seven termite species, Macrotermes bellicosus , Macrotermes subhyalinus , Odontotermes obesus , Nasutitermes germinatus , Amitermes evuncifer , Microtermes sp., and Ancistrotermes sp., were identified from the four Eucalyptus plantations. All the identified termite species were distributed across E. cloeziana , E. citriodora and E. tereticornis plantations. Macrotermes subhyalinus , Nasutitermes germinatus , Amitermes evuncifer , Microtermes sp., and Ancistrotermes sp., were present in E. camaldulensis plantation while M. bellicosus and O. obesus were absent. All the termite species encountered in this study are soil dwellers while 85.71% occurred among the leaf litters. The percentage (57.14%) of the termite species in epigeal mounds, wood litter and under the stem bark was the same. Members of the sub-family Macrotermitinae represented 71.4% of the total termite species identified while members of the sub families Termitinae and Nasutermitinae each represented 14.3%. Keywords: Occurrence, Diversity, Termite Species, Eucalyptus , Plantations

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F. K. Ewete

Papers

The development of Aspavia armigera Fabricius (Hemiptera: Pentatomidae) and its status as a pest of cowpea and rice.

Biology of the African rice gall midge Orseolia oryzivora (Diptera: Cecidomyiidae) and its incidence on wet-season rice in Nigeria.

Qualitative Phytochemical screening of Acalypha fimbriata, and its methanol extract as protectant against Sitophilus zeamais (Coleoptera: Curculionidae) on stored maize

Phytochemical investigations of Piper guineense seed extract and their effects on Sitophilus zeamais (Coleoptera: Curculionidae) on stored maize

Occurrence and diversity of termite species in Eucalyptus plantations in Afaka, Kaduna State, Nigeria