A study of the effect of microenvironment on the pea leaf weevil's behaviour was made comparing a broad bean monoculture with a broad bean-oat crop mixture. It is observed that more weevils depart from the crop mixtures than from the monocultures. Microenvironment study in the two cropping systems show that temperature and wind speed are not significantly altered in the crop mixtures as compared to the monoculture, but beans growing in the mixtures were significantly more shaded than those in the monoculture. Evidence is given to show that this relative shading could be the main factor responsible for the observed increased weevil departure from the crop mixtures.

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.

Cashew nut shell liquid (CNSL) is an economically important by-product obtained from the cashew nut Anacardium occidentale L. The liquid has been found to be versatile with a wide range of uses, including as a raw material in the polymer industry, in the development of drugs (antioxidants) and in pest control. One important chemical component of CNSL known for its bioactivity is cardanol. We isolated (8Z,11Z)-3-(8,11,14-pentadecatrienyl)phenol, a cardanol from CNSL, and determined its insecticidal and progeny growth and development inhibition activities against Tribolium castaneum Hebst. We used a bioassay-guided approach for the isolation. Exposure to cardanol produced 80% mortality of adult T. castaneum in the insecticidal bioassay. In the progeny growth and development inhibition bioassay, 46.7% of larvae were killed, and only 20.7% of adults emerged without deformities after the cardanol treatment. The amount of isolated cardanol from the 1 g equivalent/ml extracted CNSL was found to be 36.55 mg with LC50 value of 47.88 mg/ml and 13.28 mg/ml against adult T. castaneum and its larvae, respectively. We conclude that cardanol can potentially be useful in managing stored product insect pests, especially T. castaneum, but with the prerequisite that one should take much care when handling and when applying the compound.

The ovipositional responses of the stem-borer, Chilo partellus (Swinhoe), to the maize cultivar Inbred A are greater than the maize cultivar, Nyamula. These responses are elicited by certain characters of the plants that are perceivable prior to the moth's arrival on the plants (distance-perceivable) as well as those perceivable after arrival on the plants (contact-perceivable). Distance-perceivable characters were not found to be responsible for the difference in the oviposition on the two cultivars tested.

The contact-perceivable characters of the maize cultivars differ in eliciting oviposition by moths. Contact with the cultivar Nyamula elicits much less oviposition than with the other cultivar tested.

Field studies on aphid species on cabbage were conducted from 1982 to 1984. Brevicoryne brassicae L. commonly occurred on cabbage in Jos Plateau. No aphids were observed on plants transplanted in November 1982 within the first 2 weeks while those transplanted in January 1984 and February 1983 and 1984 usually had a weekly mean of more than five aphids/plant which necessitated application of aphid control treatment. High uncontrolled infestations of B. brassicae on plants aged 2–3 weeks after transplanting usually resulted in stunted growth, plant death and low yields. Decis at 7.5, 12.5 and 17.5 g a.i./ha, dichlorvos at 500, 750 and 1000 g a.i./ha, carbofuran 3 G at 1000 g a.i./ha, carbaryl 85 at 1000 g a.i./ha, and hand-washing of plants with water were used in the study. Decis, dichlorvos and carbofuran applied at 12.5, 750 and 1000 g a.i./ha respectively, were more effective in B. brassicae control. The overall cumulative mean number of B. brassicae/plant on untreated plants were 1300, 1087, 1672 and 565 for crops one to four respectively. For each crop the mean aphid number on untreated plants was significantly higher (P < 0.05) than those on treated plants. For each of the 1984 crops the yields (kg/head) from treated and untreated plants, did not differ significantly (P > 0.05), but for each of the 1982 and 1983 crops, the yields from treated and untreated plants differed significantly (P < 0.05). Plants receiving the washing technique of aphid control out-yielded untreated plants while carbofuran treated plants generally out-yielded plants receiving all other treatments.

Combined effects of constant temperature (15–35°C) and relative humidity (50–90%) on longevity and total duration of life cycle of Tetrastichus pyrillae Crawford, one of the most common egg parasitoids of the sugar-cane leaf hopper, Pyrilla perpusilla Walker were determined and are discussed. Influence of the temperature both on the longevity and the developmental duration of this egg parasitoid was highly significant while the relative humidity did not produce any marked change. Average longevity of males decreased from 5.89 to 1.06 days and that of females from 9.60 to 1.04 days in response to corresponding rise in test temperature from 15 to 35 ± 1.5°C. Mean duration of its life cycle also declined from 40.5 to 9.8 days as the rearing temperature was raised from 15 to 30 ± 1.5°C. Developing parasitoid died, without attaining adulthood within its host eggs, at or above 32.5°C.

The biophysical characters of the mosquito, Culex quinquefasciatus, a dreaded vector of bancroftian filariasis was investigated. The data represents the “system” in bioaerodynamics which comprises the adult mosquito and induced air, and constitutes “action-reaction pair” for the hovering flight. Hence the static and dynamic parameters of this species are determined. An expression for moment of inertia of the flight surface (wing) is deduced considering wing design and geometry. Further aerodynamic requirements in relation to flight performance of the insect are elaborated. It is concluded that this study provides useful information on the hovering flight behaviour of the mosquito C. quinquefasciatus.

Field experiments on reduced application doses of Metarhizium anisopliae var. acridum (I 91 609: Zonocerus variegatus strain) were carried out in 1996–1997 in southeastern Benin and central Ghana. The first experiment, which took place in southeastern Benin, consisted of ULV applications of an oil based formulation of M. anisopliae on 1-ha plots of cassava, at the rates of 1 × 1011, 4.65 × 1011 2.5 × 1012 and 1 × 1013 conidia/ha. In a second experiment carried out in central Ghana, the application doses were reduced by increasing the space between spray tracks. Treatments were applied at 5, 10 and 20m track spaces, corresponding to doses of 2.5 × 1012, 1.25 × 1012 and 0.625 × 1012 conidia/ha, respectively. After application, samples of L4–L6 larvae and adults of Z. variegatus were collected using sweep nets and their mortality monitored in small cages. Zonocerus variegatus population density was monitored at three-day intervals over a 21-day period. In southeastern Benin, analysis of survival time, resulting from the first sampling, did not reveal any significant difference between the various dose treatments. In central Ghana, for treatments at different doses and track spaces, there was no difference between 5 and 10m track spaces, corresponding to 2.5 × 1012 and 1.25 × 1012 conidia/ha. But the 1.25 × 1012 conidia/ha treatment at 10 m-track space reduced the application time by half (17 min instead of 34 min).

The sternal gland shows significant differences in size and activity in different instars of the worker caste of Trinervitermes bettonianus. Gland size (volume and surface area) was not significantly different between instars 1 and 2, and 2 and 3; but was significantly different between these age groups and instars 4–7. The potential trail-laying activity of the gland of a worker increased from zero to 50 trail units in the course of development from the first to seventh instar. The relatively high biological activity of the gland in the older instars 5–7 may be of ecological significance, since these stages were found to constitute over 90% of foragers under field conditions.

Desmodium tortuosum (Sw) DC (Papilionaceae) is a preferred wild host of Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) which is an important pest of cotton in Tolima, Colombia. From November 1976 until March 1979, cotton and D. tortuosum were compared and contrasted in the field as hosts of the pest. A very high infestation level of H. virescens in cotton in 1977 was preceded by an extremely low infestation level of the insect in D. tortuosum previous to the cotton-growing season. In 1978 and 1979 moderate infestation levels in cotton were preceded by moderately low infestation levels of H. virescens in D. tortuosum previous to the cotton growing season in both years.

Progressively less eggs were laid on cotton versus D. tortuosum as the cotton plants aged. Peak numbers of H. virescens occurred during the latter part of the cropping season and immediately after. A mean of 13% of first-instar larvae of H. virescens on D. tortuosum were found stuck by the glandular trichomes of the plant. On cotton significantly more eggs were found during the week of full moon than new moon or first quarter. Apparent sterility and pre-hatch mortality of eggs of H. virescens varied between 1–5 and 0 and 7%, respectively, for both hosts combined.

Egg parasitism by Trichogramma sp. (Hymenoptera: Trichogrammatidae) in cotton was 1.5% in 1977, presumably due to excess use of pesticides, and 23.5% in 1978 when pesticides were not used much. Parasitism of eggs on D. tortuosum by the same parasite averaged 1%; the glandular trichomes of D. tortuosum trapped and killed adult Trichogramma.

The fact that infestation levels of H. virescens in cotton were very high in the year that they were very low in D. tortuosum previous to the cotton-growing season, and moderate in cotton during 2 years that they were not as low previously in D. tortuosum suggests that the continued presence of the pest many aid its natural regulation, perhaps by providing a source of hosts to H. virescens specific parasites.

If relative levels of oviposition in cotton could be predicted by lunar cycles this would aid in planning control strategies, such as massive liberations of egg parasites and more intensive monitoring of infestation levels during predicted peak periods.

Acetylcholinesterase (AChE), arylesterase (AE), carboxylesterase (CE), and cholinesterase (ChE) activities were determined in six adult populations of the lesser grain borer, Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) collected from grain warehouses in various areas of Punjab, namely Lahore (L), Sialkot (S), Wazirabad (W), Multan (M), Chkhawatni (C), and Karachi (K). The multiple forms of esterases were resolved by polyacrylamide gel electrophoresis (PAGE) and activities determined biochemically, using a spectrophotometer. All the strains had the same AChE activity except Sialkot strain, which had 46% more activity than the susceptible K strain. Similarly K, S, W, L, and C strains exhibited almost the same AE level, whereas the M strain showed 29% lower activity than K strain. The CE activity of L (352%), S (198%) and C (214%) strains and ChE activity of L (178%) and C (317%) strains were significantly higher than that of K strain. The total esterases of L, S and C strains showed respectively 152%, 63% and 73% higher activity than the susceptible K strain. The PAGE pattern of various esterases coincided with the biochemical analysis. The variable thickness of the bands in the gel indicated relative esterase induction that could be correlated with the development of resistance in R. dominica.

Studies on the spatial distribution and sampling of infestation of the blister midge, Erosomyia indica Grover, were carried out in a mango orchard at Bangalore, India. The spatial distribution of the infestation on the panicles were studied using the parameters variance-mean ratio, and Lloyd's index of patchiness. It was found that the midge infestation tended to follow a random distribution pattern. The infestation was not significantly different among the sections of the canopy delineated horizontally and vertically. However, infestations in east lower, south lower and south upper were significantly correlated to the total infestation. The sample sizes were apportioned to these sections using regression analysis, thus arriving at a sectional random sampling plan for better precision estimates. For the data on percentage infestation, angular transformation was found to be satisfactory. These results have application in field studies leading to the management of the pest on mango.

Studies were conducted on the biology of the recently described Goniozus sensorius Gordh (Hymenoptera: Bethylidae), a gregarious ectoparasitoid of Diaphania indica (Saunders) (Lepidoptera: Pyralidae). Eggs are laid after temporarily paralyzing the host. Mean development time from egg to adult is 11.96 days at 26.43 and 65.08% r.h. The female lays an average of 50.1 eggs during its life time and parasitizes 7.26 hosts on average. The sex ratio is 1:3.91, males:females. Mean adult longevity is almost similar for males (8.55 days) and females (9.81 days). Aphanogmus fijiensis (Ferriere) (Hymenoptera: Ceraphronidae) was recorded as a hyperparasitoid through G. sensorius.

The population dynamics of busseola fusca (Fuller) was studied from 1997 to 1999 at Halhale and Halhal Begos, located at altitudes of 1960 and 1850 m above sea level respectively in the highlands of Eritrea. Sowing was done in early April in Halhale and late June in Halhal Begos throughout the study period. All agronomic practices recommended for sorghum production in the two areas were followed to ensure good crop stand, except for application of pesticides. A total of 15 generations, nine in Halhale and six in Halhal Begos were observed during the study periods. Busseola fusca had three and two generations per year in Halhale and Halhal Begos, respectively. Peak egg laying at Halhale was in early May, July and early September, while at Halhal Begos it was in July and early September. The study revealed that stage-specific mortalities of B. fusca were caused by infertility, disappearance (predation by ants and earwigs, lack of suitable host, abiotic factors), residuals and parasitoids. The key mortality factor was disappearance of small larvae (35–66 % mortality). The mortality of the other stages was low but had a composite effect on the overall generation mortality. The mortality of small larvae was density-dependent and density-independent at Halhale and Halhal Begos, respectively. The changes in population between generations were due to small larval mortality of B. fusca from one generation to the next. The life table study showed that mortality due to natural factors did not reduce B. fusca population below the damage level. Integrated management strategies are discussed to reduce the damage caused by B. fusca on sorghum.

Ethylacetate-soluble fraction of methanol extract of the stems of two cowpea cultivars TVu 946 and Vita 1 were examined by high performance liquid chromatography (HPLC) and tested for antifeedant properties for larvae of Maruca testulalis by applying the extract on the leaf discs from the susceptible cowpea variety Vita 1. Extracts derived from TVu 946 showed significantly greater feeding inhibition than extracts from Vita 1 in all the tests. HPLC analysis gave different elution profiles for the two extracts. Together, these observations implicate allelochemical factors in general, and feeding deterrents in particular, as a basis of TVu 946 stem resistance to Maruca.

The susceptibility of 23 cotton genotypes to spotted bollworm, Earias vittella, was studied under natural infestation during 1977 and 1978 rainy season at Delhi, India. There were substantial differences in bollworm damage and larval population in different genotypes. Damage in shed squares and bolls was higher than in green bolls picked up from the plant. The damage/larval population in the less susceptible cultivars (Hindiweed, XG-15, HR-26 # 8XH · HG-6-IN and Sanguineum) was lower than in the susceptible check (BJR) and the trial mean. The differences in susceptibility were more pronounced at the moderate damage levels and that the damage in less susceptible cultivars increased or decreased according to the insect pressure.

There were significant differences in the gossypol, tannins, moisture, phenols and sugar content among the genotypes tested. Gossypol, tannins and moisture content of bolls and squares were negatively correlated with bollworm damage and larval population. Free phenols showed negative, but lower correlation coefficients with bollworm damage. Sugars contributed towards susceptibility while nitrogen content of bolls did not show any effect on bollworm damage. The less susceptible cultivars had higher amounts of gossypol and tannins. Some genotypes showed ovipositional non-preference because of smooth leaves.

Many factors appeared to influence the genotypie susceptibility to spotted bollworm, of which gossypol, tannins and ovipositional non-preference (due to smooth leaves) were the major factors. Gossypol and smoothness are genetically inherited and can be manipulated through crop improvement. The rating of the number and size of pigment glands on the calyx tubes and hairiness on the under surface of leaves can be used as important marker characters in breeding for spotted bollworm resistance.

The leaf miner Coelaenomenodera lameensis Berti and Mariau (Coleoptera: Chrysomeiidae, 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'lvoire. 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.

Studies were conducted at the ICRISAT Sahelian Centre, Niger, to assess damage and yield loss by the millet stemborer, Coniesta ignefusalis (Lepidoptera: Pyralidae) on Pennisetum glaucum (L.) R. Brown. Although 78% of stems were infested, late attack by the millet stemborer on millet plants resulted in bored stems yielding more than unbored ones. Artificial infestations with 5 and 10 larvae per plant at 2 weeks after plant emergence (WAE) resulted in 50 to 70% plants with deadhearts and 24 to 100% avoidable yield loss. At 4 weeks after plant emergence, infestations with 5 larvae and 10 larvae per plant resulted in 7% increase in yield and 16% yield loss, respectively. Therefore, both the age of plant and density of borer population at the time of infestation can influence resulting stemborer damage and yield loss on pearl millet.

The current phenological study in sorghum fields has shown that Busseola fusca is bivoltine in eastern Ethiopia. The first generation begins at the end of April, while early August marks the beginning of the second (Diapause) generation. The second generation passes through the dry season in stalks and stubble as diapause larvae, of which a considerable proportion survive in the stubble until the next crop. The onset of pupation of the diapause larvae is in the middle of April. A progressive increase in the mortality of the larvae of both generations is observed towards the later stages. Five hymenopterous parasitoids, Bracon sesamiae (Cameron), Cotesia (= Apanteles sensu lato) sesamiae (Cameron), Dolichogenidea (= Apanteles sensu lato) sp. near laevigatus, Pediobius furvus (Gahan) and Procerochasmias nigromaculatus (Cameron) and one dipterous parasitoid (Sarcophaga sp.), attacking larvae and pupae of B. fusca at Alemaya, eastern Ethiopia, were identified.

A two-choice type bioassay has been used to screen extracts from a number of plants of the sagebrush community for their antifeeding properties against the Colorado potato beetle, Leptinotarsa decemlineata Say. The extracts of Artemisia tridentata, Purshia tridentata and Chrysothamnus nauseosus have been fractionated for their antifeeding constituents. Known constituents of these plants (deacetalmatricarin, coumarins, cucurbitacins, polyphenols, polyacetylenes, and essential oils) were also screened. The results indicate that several chemical classes of compounds are responsible for antifeeding activity in each plant. Water soluble substances present in the waste marc after steam distillation of peppermint oil were highly active, too.