Developmental biology and field performance of Platygaster diplosisae Risbec (Hymn: Platygasteridae) an egg-larval parasitoid of african rice gall midge Orseolia oryzivora Harris and Gagné (Diptera: Cecidoymiidae)

The developmental biology and field performance of Platygaster diplosisae an endoparasitoid of African rice gall midge (AfRGM) Orseolia oryzivora were investigated. Experiments were conducted in the screen house, laboratory and fields during 2006/2007 farming seasons. The pre-oviposition period averaged 12.1 h. The mean number of eggs laid per female was 95.2 and mean oviposition period was 3.5 days. The average incubation period was 13.0 days with a hatchability of 67.3%. There were three larval instars with developmental duration averaging 2.2, 0.5 and 2.5 days for the 1st, 2nd and 3rd larval respectively. The prepupa and pupa developmental period lasted for 2.4 and 6.7 days respectively. The longevity of males and females were 3.0 and 4.1 days respectively without food, which varied when food was given. The parasitoid has total developmental period of 27.3 days. The results showed that P. diplosisae has an impact as a bio-control agent of AfRGM, but the percentage parasitism of the host was low at the beginning of the season and increased significantly later in the season with a peak in October of each season. It was recommended that mass rearing or conservation of the parasitoid be adopted to improve its efficiency in control of AfRGM.Keywords: Biology, Platygaster diplosisae, bio-control, field impact, Orseolia oryzivora

Developmental response of tropi cal warehouse moth, Ephestia cautella (Walker) (Lepidoptera: Pyralidae)'s larvae to stored cocoa beans fermented at varied degrees

Developing larvae of major insect pests like Ephestia cautella rapidly degrade stored cocoa beans through feeding and other biological activities on the beans. Completion of developmental stages of insects may be influenced by a number of biochemical factors triggered by the primary post-harvest processing of cocoa beans prior to storage. Hence, this study assessed the development of E. Cautella from first instar larval stage to adult stage on cocoa beans fermented at varied degrees. Fresh ripening pods of Amelonado variety (N38) were harvested and fermented variedly at 0 - 7 days, and sun-dried to about 5 - 6% moisture content. The variedly fermented cocoa beans (300g/treatment) were infested with newly hatched first instar larvae of E.cautella (N=10) in a completely randomized design with four replications at 28±2°C and 70±5% relative humidity(RH). Days to adult emergence of the larvae of E.cautella on the cocoa beans varied significantly (P>0.05) between 0 day and 76.50 days in 4 days and 7 days-fermented beans, respectively. Significant variations occurred (P>0.05) in the total adult emergents of E. cautella, ranging between 0 and 8.25 in 4 days and 1 day fermented beans, respectively. This study reveals that the fermentation period of cocoa beans prior to drying and storage influenced adult emergence of E.cautella on stored cocoa beans, with 0 - 3 days fermented beans highly susceptible to E.cautella’s development to adult stage. Cocoa beans need to be fermented adequately for 4 to 7 days before drying to prevent insects’ damage. Notably, 4-days fermented cocoa beans did not support E.cautella development to adult stage at 90 days post larvae-introduction. The 4-days fermented cocoa beans require further investigations for its nutritional suitability and importance in human diets.Keywords: Varied fermentation, Ephestia cautella, total adult emergents, days to adult emergence

Effect of Neem Seed Kernel Extracts in the Management of Rice Stem Borers in the Field in Nigeria

Stem borers are economic pests of rice and its management through conventional methods has not given the desired results. Hence in this study field experiments were conducted to determine the comparative efficacy of neem seed kernel extracts (Azadirachta indica; (Neem) and synthetic insecticide (Carbofuradan) against rice stem borers in Nigeria during 2006/07 farming season. The effect of these sprayings was also recorded on natural enemies and yield attributes. Results showed that the two pesticides significantly (p < 0.01) reduced stem borers damage (number of dead hearts, white heads) compared to untreated check, and also significantly (p < 0.05) increased number of productive tillers with resultant increase in grain yield than the control plots. Maximum numbers of different natural enemies were found in neem extract treated plots against the carbofuran treated plots. It is suggested that on the basis of infestation of borer, high yield and conservation of natural enemies, neem seed extract can be regarded as suitable alternative to synthetic insecticides for the management of rice stem borers in the field.Keywords: Botanical/insecticide, stem borer controlNig J. Biotech. Vol. 23 (2011) 13- 2

Population structure of Vitelaria paradoxa Gaertn. F. and Parkia biglobosa(Jacq.) Benth.in the Agroforestry Parklands of Nigerian humid Savanna

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