African Journals OnLine
Insect Science and its Application
The International Journal of Tropical Insect Science

ABSTRACTS (Vol 20, No1)

The Role of Different Components of the Pheromone Emission of Mature Males of the Desert Locust, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae) in Accelerating Maturation of Immature Adults

Abstract–Different blends of five chromatographically prominent components of the pheromone emission of gregarious-phase mature desert locust Schistocerca gregaria (Forskål) (Orthoptera: Acrididae) males were bioassayed for their maturation-accelerating effects on immature counterparts. The blend of all five components, namely anisole, veratrole, benzaldehyde, phenylacetonitrile and 4-vinylveratrole was as effective as the emission from live mature males in accelerating the onset of mating in immature males. Subtraction of anisole had no significant effect but that of any one of the other four components significantly reduced the acceleration potency of the resulting blends. The maximum reduction occurred in the absence of phenylacetonitrile which appears to be critical to the activity of the blend. The magnitude of reduction in maturation acceleration that resulted from the subtraction of the other three components suggests that, although present in lesser relative amounts, these compounds contribute significantly to the activity of the full blend. Some differences were found between the onset of integumental yellowing and mating which indicate that blends of slightly different compositions are involved in promoting these two physiological processes.

Key Words: desert locust, Schistocerca gregaria, maturation acceleration, phenylacetonitrile, benzaldehyde, veratrole, 4-vinylveratrole, anisole

Rôle de Facteurs Eco-Climatiques et Edaphiques sur la Fécondité au Champ de Coelaenomenodera lameensis Mineur des Feuilles du Palmier a Huile en Afrique de l'Ouest

Abstract–The leaf miner Coelaenomenodera lameensis Berti and Mariau (Coleoptera: Chrysomelidae, Hispinae) is the main oil palm pest in Africa. A study of variations in its fecundity, in space and time, was carried out at 7 plantations and 19 sites in Côte d'Ivoire. Fluctuations in fecundity, which could vary from almost 300 eggs to just a few eggs per 90-day period, were very similar at the various sites of the same plantation, and at the sites of different plantations, even when these were very far apart from each other. Fecundity increased with temperature, but other climatic factors were also important, with air saturation deficit playing a decisive role. The drier the air, the lower was the fecundity, which could even reach almost zero. As this parameter had a considerable impact on palm leaves' stomatal opening, a highly significant correlation was established between the latter and fecundity. Food supplies for larvae and adults can also affect fecundity, which seems to vary with the potassium content of the leaves.

Key Words: Coelaenomenodera lameensis, leaf miner, oil palm, Africa, fecundity, temperature, hydrous deficit, food supply

Influence of Helicoverpa armigera Hübner Diet on Its Parasitoid Campoletis chlorideae Uchida

Abstract–A study was undertaken to test the hypothesis that the quality of host plant parts determines the nutritional quality of herbivorous insects feeding on it to their parasitoids. A Gossypium hirsutum-Helicoverpa armigera-Campoletis chlorideae tritrophic system was evaluated. The superior nutritional quality of bolls and young leaves of Gossypium hirsutum (MCU-5 variety) contributes to more efficient feeding, growth and reproduction of the bollworm, Helicoverpa armigera (Hübner) and better survival of its larval parasitoid, Campoletis chlorideae Uchida. Longer total developmental duration and decrease in adult longevity were observed in H. armigera reared on senescent leaves than in those reared on bolls. Consumption, growth rate and efficiency measures were significantly lower in parasitised H. armigera larvae than in unparasitised larvae. Percentage parasitism was highest (84.1%) in H. armigera fed on bolls. The parasitoid C. chlorideae displayed shorter developmental duration and improved survival on H. armigera fed on bolls.

Key Words: Campoletis chlorideae, Gossypium hirsutum, Helicoverpa armigera, host plant chemicals, parasitisation, tritrophic interactions

Oviposition-Deterrent and Toxic Effects of Various Botanicals on the Adzuki Bean Beetle, Callosobruchus chinensis L.

Abstract–The oviposition-deterrent and toxic effects of seven plant species with known biological effects were tested against the Adzuki bean beetle, Callosobruchus chinensis L. (Coleoptera: Bruchidae) on stored faba bean seeds for two years at Holetta Research Centre, Ethiopia. Oils of Azadirachta indica, Milletiaie ferruginea and Chrysanthemum cineraraefolium were the most effective in partially or completely preventing egg laying, and no bruchids emerged from the few eggs laid. The Phytolacca dodecandra, Hagenia abyssinica and Schinus molle treatments had no significant effect on the bruchids and most of the eggs laid developed into adults. Eucalyptus globulus seed powder treatment caused the death of only emerging adult beetles.

Key Words: botanicals, Adzuki bean beetle, Callosobruchus chinensis, faba bean

Application of Capture-Recapture Models for Estimating Coffee Stemborer (Coleoptera: Cerambycidae) Abundance

Abstract–The population of coffee stemborers (Coleoptera: Cerambycidae) was estimated at six sites in south-west China using two capture-recapture models. Two sampling methods (simple and systematic random sampling), each at three sampling intensities (10, 20 and 30%) were employed for two-time capture attempts from which the capture-recapture estimates were calculated. Estimates from the models were compared with that of census data from the fields. When sampling intensity was 20%, satisfactory levels of accuracy were obtained using the two models. The level of accuracy of the estimates increased as damage rate and mean density of the insect increased. Accuracy was also increased with increasing the sampling intensity, when damage rate and density of stemborers in the plots were low.

Key Words: capture-recapture model, coffee stemborers, population sampling, China

Evaluation of Essential Oil from Six Aromatic Plants in Togo for Callosobruchus maculatus F. Pest Control

Abstract–The insecticidal activity of essential oils extracted by steam distillation from six aromatic plants from Togo, Cymbopogon schoenanthus (L.) Spreng., C. citratus (D.C.) Stapf., C. nardus (L.) Rendle, Lippia multiflora Moldemke, Eucalyptus citriodora Hook., Diplolofium africanum Turcz., was tested against the cowpea weevil, Callosobruchus maculatus F. Concentrations of 6.7; 10.0; 16.7 and 33.3 µl/l were evaluated. The chemical composition of the essential oils used was established by GC/MS analysis. Only C. schoenanthus oil showed significant insecticidal activity at 6.7 µl/l oil (LC50 2.3 µl/l). At concentrations higher than 33.3 µl/l, all test plants showed similar insecticidal activity; more than 90% of the test insects died within 24 hours of exposure. Oviposition was also reduced significantly by the essential oil treatments.

Key Words: essential oils, insecticidal activity, Cymbopogon schoenanthus, Cymbopogon citratus, Cymbopogon nardus, Lippia multiflora, Eucalyptus citriodora, Diplolofium africanum, Callosobruchus maculatus F.

Type Localities of Mosquito Species in Uganda

Abstract–A list of 88 nominal taxa of mosquito species (Diptera: Culicidae) originally described from Uganda is given. The list includes 68 valid species, 7 subspecies, 6 varieties, and 7 synonyms, within 10 tribes, 14 genera, and 13 subgenera. All 3 subfamilies of Culicidae (Anophelinae, Toxorhynchitinae, and Culicinae) are represented. The type localities of the different species are updated for quick identification based on the present political boundaries within Uganda. The species stages that are as yet not fully described in the literature, and those species whose breeding habitats are unknown are indicated.

Key Words: mosquitoes, Anophelinae, Culicinae, Toxorhynchitinae, species, type locality, type depository

Laboratory and Field Evaluation of Bacillus thuringiensis Berliner Products against the Teak Defoliator Hyblaea puera Cramer

Abstract–Commercial Bacillus thuringiensis (B.t.) Berliner products, namely Delfin^®, Agree^®, Halt^® and Spicturin^® were evaluated in the laboratory and on an intensively managed teak plantation for the control of the teak defoliator Hyblaea puera Cramer (Lepidoptera: Hyblaeidae). A 2 g/litre concentration showed highly significant lethality against defoliator larvae, the early instars being more susceptible (99.8% mortality) than late ones (63.6—81.2% mortality). The order of effectiveness was Delfin = Agree > Halt > Spicturin. At 2 g/litre the B.t. preparations were as effective as at 0.07% (2 ml/litre) monocrotophos 36 % when sprayed on one-year-old saplings in a plantation. However, at 1 g /litre concentration, monocrotophos 0.07% was superior to the B.t. products.

Key Words: Bacillus thuringiensis, commercial preparations, teak defoliator, Hyblaea puera, laboratory and field evaluations

Pièges à Tsé-Tsé en Polyéthyléne: Variation Imprévue de l'Attraction pour Glossina fuscipes fuscipes en République Centrafricaine

Abstract–The polyethylene films used in manufacturing bipyramidal tsetse traps in the Central African Republic can exhibit slight variations in colours. Experiments using a new protocol that combines a Latin square design and two competing traps in the same experiment conducted on Glossina fuscipes fuscipes show that a less intensely blue colouring decreases the attractiveness of the trap. Polyethylene is useful material for tsetse traps, but it is necessary to verify that its colouring is homogeneous.

Key Words: polyethylene, bipyramidal tsetse trap, colouring, attractiveness, Glossina fuscipes fuscipes, Central African Republic

Sex Ratio of Campoletis chlorideae Uchida in Response to Helicoverpa armigera (Hubner) Density

Abstract–Experiments were conducted to elucidate the effect of host density on sex ratio of parasitoid offspring, using Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) and its endoparasitoid Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae). The sex ratio of Campoletis chlorideae was female-biased showing a linear decrease with increasing parasitoid density at fixed host densities. However, with more hosts available, the number of parasitoids emerging increased, stabilising after a density of 32 hosts per parasitoid. To obtain a female-biased sex ratio, a low density of parasitoids should be released at a recommended site.

Key Words: Campoletis chlorideae, Helicoverpa armigera, sex ratio, parasitoid-host interaction

Effect of Post-Treatment Temperature on the Insecticidal Activity of Neem, Azadirachta indica A. Juss. Seed Extract on Schistocerca gregaria (Förskal): A Preliminary Report

Abstract–The influence of post-treatment temperature on the insecticidal activity of Azadirachta indica (A. Juss) seed extract against the desert locust Schistocerca gregaria (Forskål) is reported. In tests on adults, the toxicity of crude A. indica seed extract increased by about 10-fold when the post-treatment temperature was raised from 22ºC to 40ºC. This temperature-dependent toxicity was observed in insects treated either topically or via injection. This phenomenon could partly explain the wide variability in efficacy of neem extracts reported by different investigators.

Key Words: botanical insecticides, neem, temperature effects, Azadirachta indica, Schistocerca gregaria