Oryctes rhinoceros beetles were infected with an Indian isolate of Oryctes baculovirus and released into the wild population of O. rhinoceros in Minicoy island (India) for the biological suppression of rhinoceros beetle. The virus disease had established itself within 9 months and suppressed the pest population to low levels. Consequently pest damage to coconut palms also declined. A low level of pest population was maintained by the virus disease even after 3.5 years, following the introduction of Oryctes baculovirus into Minicoy island.

Ten sorghum genotypes at three plant growth stages were evaluated for antibiosis component of resistance to Peregrinus maidis expressed in terms of survival, duration and population build-up of nymphs as well as longevity and fecundity of adults. Support of nymphal survival and continued succession in mortality was evidenced on IS 18676, IS 18677 and IS 19349, indicating the influence of antibiosis factor(s) which again was supported by their prolonged duration. The growth index was consistently low at three plant growth stages on IS 18676 and IS 19349, but the genotype, IS 18677 did not express consistency on 45 days old plants. Greater longevity of adult females over males was consistent at different growth stages. Low fecundity was predominantly noticed on IS 18676, while reduced longevity was pronounced on IS 18677 and IS 19349 which was reflected in low population build-up at 15 and 30 days after infestation, when infested with 25 or 50 neonate nymphs. All these parameters contributed together suggest that antibiosis levels in IS 18676, IS 18677 and IS 19349 proportionately increased with plant age and the variability at different growth stages may be attributed to the differences in host genotypes and greatly aid as potential donors in resistance breeding programmes.

Extracts of five plants, namely Argemone mexicana, Artemisia absinthium, Cassia occidentalis, Cymbopogon citratus and Siegesbeckia orientalis were tested for their antifeedant and insecticidal effects on third-instar larvae of the cabbage webworm, Crocidolomia binotalis, which is presently one of the most important pests of cruciferous crops in Mauritius. All the five plant species investigated showed significant antifeedant properties, with A. mexicana showing the highest control potential of the five plant species studied against C. binotalis.

Studies involved the evaluation of two types of pyrethroids and two controls in a single study village settlement. A total of 1277 bednets were distributed to 75% of 420 houses in the village, in July 1989, 378 were treated with lambda cyhalothrin (Icon°), 411 with deltamethrin and 331 were untreated. A total of 336 people were not given any nets. Entomological evaluation showed that both pyrethroids have an excito-repellent and lethal effect on mosquito vector species. In assessment of malaria reduction in children as the target group, those sleeping in deltamethrin treated houses showed a greater reduction in parasite rate than those sleeping in lambda cyhalothrin nets: Overall reduction of malaria parasite rate of school children examined was 68%. Biological efficacy in both pyrethroid treated nets persisted over a period of 6 months. Another added advantage was that the individual using the net was protected against mosquitoes and other pests such as cockroaches, fleas, lice and bedbugs. Incorporation of pyrethroid impregnated nets in malaria control programmes involving community participation is recommended.

The composition and preparation of an artificial diet for the coffee berry borer, Hypothenemus hampei is described. Ten generations were obtained without any significant change in fecundity. Development at 25°C on this diet was similar to previously reported work using coffee berries. One female reared on this diet lived for 380 days. This diet will permit investigations into the genetics of insecticide resistance, potential biopesticides and other research, requiring a convenient laboratory rearing system.

A light trap was operated in Samaru, Nigeria between 1973 and 1980 to monitor populations of Coniesta ignefusalis. Two generations of the insect/year were represented by two adult peaks in July and September. In 1974, an early peak in May resulted in three generations. In cages in the field, eggs were laid between the leaf sheath and the stem in batches of 20 to 70 with a mean of 47.5 eggs/batch. Laboratory studies conducted at 25–28°C and 75–85% r.h. showed an average developmental period of 35.5 days. The average duration of the egg, larval and pupal stages were 4.5, 21.9 and 9.2 days, respectively. Unfed adults lived for 5.3 days.

The length of the reproduction cycle of Lasioderma serricorne (F.) under ambient laboratory conditions (temperature range 28.0–32°C and 72.5–80.5% r.h.)was shown to depend on the identity and state of division of various cereal grains, cowpeas, groundnuts and dried root crops. Cut dried yams allowed the shortest cycle andwholericethelongest.The rate of population increase by L. serricorne was also assessed and this was maximal when cut wheat and minimal when whole rice was provided. Fecundity was highest with sorghum and lowest with rice as food source. Females of the species lived longer than males.

This is a description of species area effects for Agromyzidae associated with leguminous plants. The data on geographic area was extracted from the National Museums of Kenya (Herbarium section). The geographic area species plots showed an effective partial correlation of 16%. The correlation was unfortunately low and could be attributed to inadequate botanical and agromyzid records in Kenya. Generally, geographical area explained most of the species richness in Kenya. Other variations not accounted for by the logarithmic plot of species-area effects were derived from residuals. The plots between residuals and different variables showed that leaf-form, habitat variation, altitude and taxonomic isolation also explained variation in species area plots.

Experiments on development of Amblyseius longispinosus Evans (Acari:Phytoseiidae) as influenced by castor pollen as an alternate food and its interaction with sorghum mite, Oligonychus indicus Hirst (Acari:Tetranychidae) were conducted under laboratory conditions. A. longispinosus showed poor growth on castor pollen. Female and male developmental periods were 2.6 ± 0.30 and 2.42 ± 0.21 days on spider mites, 2.70 ± 0.89 and 2.68 ± 0.39 days on spider mites + castor pollen and 5.12 ± 2.03 and 3.89 ± 1.80 days on castor pollen alone, respectively.

At interaction A. longispinosus suppressed populations of O. indicusat 1:10, 1:20, 1:30, 1:40 and 1:50. Prey elimination was on 12th day in 1:10, 18th day in 1:20, 20th day in 1:30, 24th day in 1:40 and on 30th day in 1:50 ratio.

Successive extraction of the green alga, Scenedesmus acutus 276–3a with different solvents indicated that the petroleum ether extract was the most repellent to the hatched larvae of Spodoptera littoralis. The application of spray emulsified 1 % petroleum ether extract inhibited egg laying. At 0.25% concentration the moths laid only 52.4 of their egg masses on the treated oviposition sites in comparison to the untreated control. Concentration of 1% was protective against the immature stage by hindering the third instar larvae to feed on treated leaf discs. In addition, the water emulsion of petroleum ether extract was insecticidal. The percentage mortality was directly proportional to the concentration applied and to the duration of exposure.

Normal variations of ovarian glycogen content and the effect of different doses of thyroxine (T4) on this cellular constituent were investigated from 3rd day of fifth larval instar to adult emergence in Bombyx mori L. Ovarian glycogen remained higher during fifth larval stage with a peak on 7th day. At the end of 5th larval stage the glycogen content declined and this lower level continued upto 4th day of pupal age. Thereafter, this cellular constituent again sharply increased and reached a peak on pupal day 6, followed by a fall upto adult emergence. A single injection of different doses (0.5, 1, 2 and 5 μg/g body weight) of thyroxine, caused a significant decrease in glycogen content of ovary, during larval stage and an increase during pupal and adult stages of development with few exceptions. Thyroxine at the doses of 0.1 and 0.25 μg/g remained ineffective throughout the study period with an exception on day 2 after injection. The specific pattern of variation of the ovarian glycogen content as observed during normal stages of development was not altered by thyroxin though this hormone changed the level of glycogen. Thus, the results indicated that both glycogenolysis and glycogenesis occur in ovary after thyroxine treatment.

In laboratory assays, two Bacillus thuringiensis var. kurstaki preparations, HD-263a WP and HD-263c WP, were highly effective against larvae of the honeydew moth, Cryptoblabes gnidiella Millière (Lepidoptera: Pyralidae), especially against the first and second instars. Both preparations were more effective than DipelR WP at most concentrations tested. Two viral preparations, AcMNPV and Amorbia cuneana NPV, were ineffective.

We tested the effectiveness of volatile oils of Lippia adoensis Hoschst, Cymbopogon citratus (DC) Stapf., Eugenia uniflora L., Lantana camara L., and Chromolaena odorata (L.) King and Robinson at a dose range of 5 to 50 p.1 in protecting 9.9 g (50 seeds) of stored cow pea from infestation by the cowpea weevil, Callosobruchus maculatus F. The effectiveness of the oils as fumigants ranked as follows: L. adoensis > C. citratus > E. uniflora. Oils of L. camara and C. odorata were unsuitable for fumigation purposes. At doses of 5 to 20 μl, oil of L. adoensis protected cowpea from weevil attack. At 5 μl, volatile oil of L. adoensis was as effective as 20 μ1 each of E, uniflora and C. odorata, and only slightly inferior to C. citratus. Insecticidal activity of L. adoensis against C. maculatus was unequalled by any other oils tested. The effective doses of these oils did not impair the viability of treated cowpea.

Larval parasitism of the sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), by Neotrichoporoides nyemitawus Rohwer (Hymenoptera: Eulophidae) was studied in the laboratory. Ten shoot fly larvae of each instar (3) and two periods of exposure (24, 48 h) were used in a factorial design with four replicates. Significant differences of parasitism were observed with respect to instars, periods of exposure, and the interaction instar-period of exposure. The second larval instar was most parasitized (68.75 and 85% of parasitism after 24 and 48 h, respectively), followed by the first instar (46.25% of parasitism) exposed for 48 h to adult parasitoids. N. nyemitawus was an effective shoot fly endo-larval parasitoid. Observations on N. nyemitawus searching sorghum seedlings for shoot fly larvae are summarized.

Observation of the damage caused by Mussidia nigrivenella (Pyralidae) on corn cobs and cotton bolls begun in Togo in 1988 was continued in 1990 and 1991. The study was conducted at IRCT's Anié-Mono station at the Dalanda, Notsé and Kouvé test and on small holdings in the Notsé region. M. nigrivenella is the main pest on corn (over 90% of the caterpillars observed). Its larvae populations were higher in 1991 than in the previous year, owing to favourable climatic and cropping conditions.

On immature cotton bolls, C. leucotreta remains the dominant species. However, the extent of M. nigrivenella activity on mature bolls was revealed for the first time. In certain locations, over 90% of the caterpillars and chrysalids observed in attacked mature bolls belong to this species. Hence, cotton plants which are not destroyed after harvests can act as reservoirs for pyralid pests.

Tetramethrin, deltamethrin and cypermethrin formulated as fumigant tablets or spray(ing) solutions showed flushing out activity on Triatoma infestans. Fumes arising from the tablets were analysed by gas chromatography. The proportion of pyrethroid liberated was between 10 and 20% of the original amount formulated. The flushing out activity shown was dependent on the pyrethroid compound, insect stage and sex. In general deltamethrin proved the most active flushing out agent and cypermethrin the least active. Maximal activity was shown in the combination of nymphs and tetramethrin. Nymphs of Rhodnius prolixus were only flushed out by deltamethrin. In all cases, deltamethrin and cypermethrin yielded 100% mortality 7 days after exposure to the pyrethroid fumes, while tetramethrin was not a killing agent.

Antixenotic and antibiotic components of resistance to the cassava mealybug, Phenacoccus manihoti Matt. Ferr. were evaluated in different varieties of cassava (Manihot esculenta Crantz), in Poinsettia (Euphorbia pulcherrima Wild), Talinum (Talinum triangulare Jack) and Faux-caoutchouc (hybrid of M. esculenta and M. glaziovii Mull. Arg.). Resistance, was estimated in the field on 25 varieties of cassava by means of varietal screening. Although we were unable to identify varieties ofcassava totally resistant to P. manihoti, there was evidence of partial resistances. Thus the Incoza variety is the most resistant, followed by the Moudouma and Zanaga varieties. On the other hand we found very susceptible varieties, such as Dikonda, Kataoli, 3M8 and 1M20. Laboratory evaluations of the antibiotic component of resistance, made by estimating the intrinsic capacity for increase rc, showed that the host-plantshave a considerable effect on the multiplying capacity of the mealybug. Indeed rc ranges from 0.038 (Poinsettia) to 0.160 (Ganfo cassava variety), i.e. a ratio of 1 to 4 between the two extreme values. If the cassava varieties alone are considered, the percentage of maximum variation is 20% between the Incoza (rc = 0.133) and Ganfo (rc = 0.160) varieties. The Incoza cassava variety is the most resistant, in terms of both antixenosis and antibiosis. Classification of the other cassava varieties, from the most to the least resistant, differs according to the resistant component under consideration. Poinsettia and Talinum both have a very strong antixenotic component, but their antibiotic component differs (rc = 0.038 and 0.150 respectively). Our results suggest that the resistance mechanisms of the host-plants of P. manihoti intervening in the fixation of the pest (antixenosis), are different from those acting on the development of the mealybug (antibiosis). We established significant correlations between the size of the mealybugs and their demographic characteristics for all the plants studied: the duration of the prereproductive period is shorter and the net reproduction rate is higher when the mealybugs are large-sized. These results are discussed in the context of an integrated monitoring programme.

A study of the noxiousness of the African white rice stem borer, Maliarpha separatella Rag carried out under controlled field conditions has revealed that the impact of this pest on the yield and its components is assessable. For mean infestation rates up to 68% during the period of highest sensitivity of a paddy rice culture (second half of tillering to panicle initiation), no significant decrease could be observed in the number of panicles, nor any significant increase in the number of white heads and the number of empty grains per hill. However, with increasing infestation rates, the number of immature panicles increased and the number and weight of filled grains per hill decreased. An explorative analysis of the infestation rate-yield loss relationship, showed that a sigmoid model describes this interdependence appropriately. The proposed economic injury level (EIL), is here considered more the result of an approach, which had as its goal the re-definition of the status of the pest than as an instrument of a chemical control programme with treatments based on an action threshold.

Five-to six-day old male pupae of Ectomyelois ceratoniae Zeller were irradiated with 0, 20, 25 and 30 krad of gamma rays. When the radiated males were mated with normal females there were deleterious effects on fertility without extreme effects on mating or fecundity. Percentage of embryonated eggs and progeny per female decreased to two thirds of the control by 25 and 30 krad treatments. Productivity of the female mated with irradiated males was decreased and significant reductions in egg viability, egg hatch and larvae per female were observed in F1 generation. Similar pattern of sterility was observed in sibling crosses of F2 at the three doses.

Sesamia calamistis Hampson and Eldana saccharina Walker larvae were reared at 25°C on pieces of stem from five indigenous African grasses. All five, Andropogon sp., Panicum maximum Jacq., Pennisetum polystachion (L.) Schult., P. purpureum L. and Sorghum arundinaceum (Desv.) Stapf. have been reported as host plants for one or both species. Larval survival, larval and pupal period and pupal weight were recorded and compared to values of these parameters for larvae reared on stems of maize and on artificial diet. S. calamistis larval survival was less than 10% on each grass species compared to 95% on artificial diet and 30% on maize stems. Larval period was similar on maize and the grasses, but was 50% faster on artificial diet. Pupal periods were similar for larvae reared on grasses, maize and artificial diet. Pupal weights were highest for larvae reared on artificial diet, followed by maize and then grasses. E. saccharina larval survival was less than 5% on each grass species compared to 60% on artificial diet and 19% on maize stem. Larval development was 25% faster on artificial diet than on maize or grasses. Larvae reared on grasses, maize and artificial diet had similar pupal periods. Pupal weights were lowest on grasses and highest on artificial diet.