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.

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.

Use of synthetic organic chemical pesticides introduced after World War II has resulted in a number of health, environmental, and socioeconomic problems discussed here. Both developed and developing countries have been affected. The problems in the developing countries of the tropics came about largely because of an error in transfer of technology. Pesticide technology developed by and for use in the developed countries was exported to countries with cultures and social structures that were not prepared to absorb this technology. Integrated pest management (IPM), an approach that reduces pest damage to tolerable levels through a variety of techniques, including natural enemies, genetically resistant crops, environmental modifications, and, when necessary and appropriate, chemical pesticides, represents an important trend toward rational management of crop pests in the developing countries. However, simply exporting IPM ‘packages’ from developed to developing countries would also be an error in transfer of technology. Each situation must be evaluated individually under actual farming conditions, and the IPM program must be tailored for the particular group of intended beneficiaries. Some of the interrelated social, attitudinal and institutional factors that should be evaluated are discussed.

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.

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.

An ecological study was conducted in two pools, one temporary and one semi-permanent at the Kenya coast to determine the relationship between infection levels of Coelomomyces indicus Iyengar in larvae of Anopheles gambiae Giles, and the species and density of copepods found in these sites. Microcyclops minutus Claus, an intermediate host of Coelomomyces indicus, was the predominant species in both pools. Other species were, Mesocyclops leuckarti Claus, Mesocyclops leuckarti pilosa Kiefer, and Mesocyclops (Thermocyclops) decipiens Kiefer. Infections occurred during the periods when M. minutus densities were above 12 cyclops per 250 ml of water. A positive relationship was shown between M. minutus density and infection levels in An. gambiae with C. indicus. The r-value for this relationship in the temporary pool was 0.726, and in the semi-permanent pool, 0.639.

Resting site preferences of the tsetse Glossina morsitans submorsitans Newstead were studied in a savanna woodland and gallery forest in the Northern Guinea Savanna of Mali. Five site-types [boles, fallen logs, undergrowth (‘bushes’), branches and tree canopies] were observed. Flies alighting to rest on these site-types were trapped on tanglefoot. Observations were made in the warm rainy, warm dry and hot dry seasons.

Boles were dominant as the preferred resting sites in the savanna woodland in all seasons; fallen logs were the next preferred site-type, while few flies were collected from the undergrowth, branches and tree canopies. Approximately 90% of flies on boles were collected below 1.0 m and none were found above 2.5 m.

During the hot dry season in the gallery forest, the undergrowth was the most preferred site-type; unshaded undergrowth accounted for approximately 98% of all flies on the undergrowth. Fallen logs and boles were the next preferred site-types; branches and tree canopies recorded very few flies. Probable reasons for the results obtained and the importance of these results in tsetse control operations are discussed.

Indoor-resting blood-fed Anopheles gambicie s.l. were collected from selected localities in Ethiopia. Anopheles arabiensis was the only sibling species identified. Paracentric chromosomal inversion polymorphisms were observed on the 2R and 3R arms. A significant excess of heterozygotes was obtained in samples from Siile carrying the 3Ra inversion. Similarly, significant variation was seen in the frequencies of the 3Ra inversion between the study localities. The observed intraspecific inversion polymorphisms relative to indoor resting behaviour are discussed.

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.

Most dissected Nezara viridula (91.6%) from night catches had their stomach filled (half-full-full) with food, and females had a higher feeding activity than males. Females outweighed males at the ratio 1.3: 1, and an individual was heavier in October than in May. Ovarian development corresponded closely with decreasing fat body of females, and immature individuals had maximum fat in the abdomen. The spent individuals with empty stomach and fat thinly spread over the venter were relatively abundant in April and May, implicating the possibility of large-scale oviposition during these seasons.

An analysis of the variation of fore-, mid- and hindgut contents in third- to sixth-instar nymphs of the African grasshopper, Zonocerus variegatus, freshly caught every hour in the field, and also left without food for 1, 6 and 12 hr, showed that gut motility and the movement of ingesta through the gut was maximal at 08.00–10.00, 13.00–14.00 and 16.00 hr. Movement of ingesta was very slow at night. A diurnal rhythm therefore governs gut emptying. Nymphs, confined in jars with leaf discs, fed from 07.00 to 19.00 hr over the temperature range 17–34°C. Most food was eaten after 13.00 hr when it is warmer. Field insects feed during the night as well. Midgut α- and β-glucosidase activity was detected at all times of testing (06.00, 12.00, 19.00 and 24.00 hr), but the levels of activity were lowest at 12.00 and 19.00 hr.

Experiments were conducted to elucidate the effect of host density on sex ratio of parasitoid offspring, using Helicoverpa armigera (Hübner) (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.

Cowpea is one of the most widely grown leguminous crops in Africa: in Kenya it occupies over 66,000 ha and Coast Province ranks second to Eastern Province with about 5200 ha. It is an important food item consumed both as a vegetable and as a grain. Unfortunately, it suffers from both preharvest and postharvest infestations which accounts for serious losses of the crop. With the introduction to Kenya of improved varieties from IITA, Nigeria, such losses would be increased due to varying susceptibility in different pest ecosystems. The objective of this study therefore was to observe the infestation of the IITA varieties and compare them with local cowpea varieties collected from different parts of Kenya. The work was conducted at C.A.R.S., Mtwapa from 1979 to 1981 inclusive. From the study, five different bruchid species were identified as infesting cowpea varieties in the field. These were Collosobruchus rhodensienus; C. phaseoli; C. chinensis; Bruchidius atrolineatus; and C. analis; in order of decreasing abundance. Over 50% of the bruchids found in the field were C. rhodensienus while Zabrotes spp. and C. maculatus (F) were never encountered in the field. Although the IITA materials were introduced because of their yield potential, it was found that some of them were as susceptible to preharvest bruchid attack as the locally available materials. The short rains season had more bruchid infestations than the long rain season. There were also fewer eggs on pods of local varieties and fewer bruchids emerging from seeds of local as compared to IITA varieties. The results however were not significantly different. Further work should be done to establish the complex of bruchids found in stored cowpea varieties, the losses caused and control measures applicable to reduce damage.

The introduction of high yielding sorghum hybrids in the mid-1960s indicated that the new cultivars were highly susceptible to insect pest attack. Use of chemicals for the control of the snootily, Atherigona soccata (Rondani), became necessary to realise a full yield potential.

This paper briefly reviews the earlier work on conventional foliar sprayings and dustings of the available insecticides which generally failed to give an effective control of the shootfly.

Work carried out in the early 1960s showed that the application of phorate, disulfoton, aldicarb and carbofuran granules in the soil at the time of sowing was very effective in controlling the pest. Recently two more insecticides, viz. isofenphos and fensulfothion have been found to be equally effective. However, the cost of applying these insecticides is rather high.

Seed treatment with carbofuran at 5 parts a.i. per 100 parts of seed proved to be highly effective and economical. It is now being widely used by farmers in the major sorghum growing area of the country. It has been found that dosage of carbofuran can be further reduced by using a 6:4 mixture of treated and untreated seed.

Trials have been conducted to determine the residues of effective insecticides in the soil and in plants at different intervals. Investigations have also been carried out to establish the correlation between the residues of different insecticides in plants and their efficacy in controlling the shootfly. A future strategy for the chemical control of the shootfly is outlined.

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.

Recent surveys have shown that ant-Homoptera associations are not limited to cocoa trees only but a large number of other plant species serve as hosts for such associations. It has been observed that some ant species may tend more than one Homopteran species on a number of different host plants. Seasonal abundance of the homopterans and their tending ants was studied on cocoa, mango and pigeon pea.

The populations of the ants tend to synchronize with the populations of the Homopterans which they tend during the season.

Progress in the adoption of biological control in the 100 years since the introduction of the vedalia beetle into California is reviewed briefly as a background to examining current trends, especially in tropical countries. Recent successful classical biological control programmes have increased interest in applying biological control to other major pest problems as has increasing public appreciation of the dangers of over-reliance on chemical pesticides. Consequently, there is an unprecedented opportunity for greater use of biological control. However, the opportunities for classical biological control are limited and greater attention to other biological control techniques is necessary, especially the development of pathogens as biopesticides and techniques to increase the impact of native natural enemies. Biological control is not a panacea and can seldom be effective on its own. It must, therefore, be integrated with other pest control techniques in integrated management programmes. International collaboration is required to increase awareness of these opportunities, facilitate the procurement of biotic agents and generally to promote the adoption of biologically sound sustainable pest and vector management procedures. Support for biological control should include training of personnel who will be involved in decision-making and in implementing control. Practitioners must be prepared to promote the use of biological control by farmers, and also address legitimate public concerns about the safety of biological control so as to ensure continuing public support and appropriate regulatory procedures.

This paper considers the status of pests and pesticides in Mauritius, including pesticide legislation and flow.

Climatic factors, namely altitude, temperature and rainfall, influence the spatial and seasonal distribution and population dynamics of economically important pests as well as their hosts (crops and livestock). The case histories of a few selected pests (leaf miner, fruit flies, stable flies), their control measures as well as research efforts in this connection are reviewed.

An appraisal is also made on some aspects of pesticide legislation along with the distribution pattern of pesticides, in relation to pesticide management. The setting up of a recent Pesticides Management Advisory Committee is regarded as a move in the right direction to safeguard pesticide misuse and abuse. Food crop production is at the expense of huge pesticides input. A series of recommendations are made with a view to improving pesticide practices in the country.

Termites are important agricultural pests in the semi-arid tropics. Conventional methods of control have relied on persistent organochloride insecticides with accompanying health and environmental problems. In contrast, cultural control methods provide untested, but environmentally sound options to farmers. This study reports results from three experiments on the use of mulches to reduce Microtermes obesi and Odontotermes spp. damage with relevance to groundnut production in India.

Termites scarification of groundnut was 80–90% lower for pods dried in neem cake or Ipomoea fistulosa mulches than for pods dried directly on the soil. Similarly, subterranean attack by termites on bamboo baits was 20–40% lower in mulched plots than in controls. However, mulches were ineffective in protecting bullock manure from removal by termites.

Successful use of mulches in termite control may be related to food source concentration. Termite location of concentrated food sources, such as bullock manure, was followed by recruitment of workers and construction of protected runways. In contrast, termites foraging on limited food sources, such as groundnut pods, did not construct runways and had greater exposure to mulches.

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.