Late third stage (7-day-old) larvae and 1-day-old pupae of Anastrepha suspensa Loew (Diptera: Tephritidae) were dipped for 5 min in suspensions of 25% WP Dimilin® (diflubenzuron) at six dosages ranging from 0.003–0.1% a.i. Diflubenzuron caused significant (P < 0.05) mortality during the pupal stages of both groups treated. Consequently, the resulting adult populations were drastically reduced. The incidence of crumpled wings, deformed abdomens and ovipositors in these adults was 2–7 times and 4–9 times higher than the respective controls of treated larvae and pupae. The morphological abnormalities altered mating competitiveness of males and successful copulation and oviposition by females. Fecundity of females was reduced and diflubenzuron effects persisted into the first generation and caused decreased egg viability.

Adults fed a 0.1% a.i. diflubenzuron-treated diet for 27 days had no significant mortality, but had decreased fecundity. However, their pattern of oviposition did not differ from the control. Fecundity levels similar to the control's were achieved 6 days after the treated diet was replaced by normal diet. Diflubenzuron treatment of adults also drastically decreased the survivorship of first-generation individuals between egg-hatch and pupation. However, almost all individuals that pupated emerged as adults. No abnormalities were observed in first-generation adults or in the survivorship of their offspring.

The induction of resistance in the urban pest mosquito, Culex quinquefasciatus, to chlorpyrifos and chlorfenvinphos and the cross-resistance spectra of these selected lines to propoxur and a number of organophosphate insecticides was studied. Distinct genetic factors governing intermediate (R1) and high (R2) levels of larval resistance to organophosphates were found to be allelic according to the single locus, multiple aliele hypothesis. Adults were less susceptible to malathion and fenitrothion after larval selection with chlorpyrifos, but the degree of resistance was found to be much less than that in the larvae. The implications of these results for the control of C. quinquefasciatus in Dar-es-Salaam, Tanzania, is discussed.

Field and laboratory evidence now suggests that the African armyworm, Spodoptera exempta, is specifically adapted for survival at low population densities, providing a new basis for understanding the significance of its phase polyphenism and migratory strategy. This conclusion allows deductions to be made as to the expected extent of displacement of flying moths from low and, when they occur as a result of impeded or inadequate dispersal of parent moths, high density populations. The proposed migratory strategy which depends on the genetic determination of flight potential also provides a framework for interpreting observed patterns of armyworm outbreaks through the season and in relation to rainfall. Traits associated with a low-density, “armyworm” strategy are shared by other Noctuids which may have similar life histories.

Host location and feeding among ticks involves positioning for host findings, probing, attachment, imbibing blood and thereafter detachment. Different species of ticks fulfil this sequence of events in different ways. Behavioural differences are mainly due to sensory inputs obtained by a tick and the processing of that input by the central nervous system. Tick receptors responsible for perceiving stimuli originating in the general environment and the host in particular are located on the tarsi and mouthparts. This review gives a brief account of current knowledge on sensory receptors involved in the above behavioural patterns.

The elegant grasshopper, Zonocerus elegans Thunberg, occurs in large numbers in Kilosa district during the dry season June to January and attacks a wide range of wild and crop plants. Its impact as a pest of crop plants becomes more noticeable from the middle of the dry season when the hoppers are well advanced and the only alternative food available are vegetables in backyard gardens and river valleys. The grasshopper damage continues throughout the vuli (short) rains until the end of the oviposition period in January, thus limiting the production of green vegetables in the district. A study on the biology and ecology of the pest in Kilosa district with emphasis on short term control strategies was started in 1987. Spot spraying with insecticides to kill the early instars was found to be effective, but area-wide implementation was necessary to prevent re-invasion of cleared areas.

Studies on aspects of the biology of the kola weevil Balanogastris kolae on Cola acuminata and C. verticillata were made in the laboratory at temperatures of 28–30°C. Mated females of B. kolae oviposited a significantly higher number of eggs (238) in C. acuminata than in C. verticillata (205) when confined separately with the nuts. But when the weevil was offered the choice of three Cola species as oviposition media, significantly more eggs were oviposited in both C. nitida and C. verticillata than in C. acuminata. However, there was no significant difference between the number of eggs oviposited in C. verticillata and C. nitida.

The average total incubation, larval and pupal developmental periods of B. kolae in both C. nitida and C. verticillata were 6, 16.2 and 6.1 days, respectively. The average total developmental period in C. acuminata was 28.8 days, and 26.5 days in C. verticillata. Although the total developmental periods overlap, there was a significant difference between the periods of development of B. kolae in the two Cola species. Oviposition and development of B. kolae in the wild species, C. verticillata, coupled with its wide distribution show that it may be ecologically important in the survival of the weevils, especially when the cultivated Cola species are not available in the field.

As a background to an IPM project, this paper describes pesticide treatment of cotton in Sudan Gezira, starting in 1945/46. Until the end of the 1950's, one treatment per season was sufficient to control the only important pest, the jassid, Empoasca lybica, but the number of treatments increased during the 1960's (from 3 to 5) and has since the early 1970's been 6–9.

The continuous use of pesticides has resulted in changes of the pest complex, ultimately creating “hyper” pests such as the whitefly (Bemisia tabaci), cotton bollworm (Heliothis armigera) and aphids (Aphis gossypii). The increase in number of applications of pesticide is coupled with the rising costs of pest control and a stagnant yield. The stickiness problem created by the honey dew of whitefly and aphids increased with the rising number of sprays. The exclusive use of chemical control not only failed to improve the quality or quantity of the yield, but put a great strain on the national economy as well.

The Sudan therefore requested the FAO to initiate an IPM project starting in 1979, with financial support from the Netherlands. During the past 2 years support has also been given by the World Bank. The IPM approach has given very valuable results during the last two seasons when large (more than 100 acres) plots in the Gezira and Rahad Schemes were left unsprayed with the objective of investigating the potential of the natural enemies in the absence of pesticides, and to compare findings with population trends of pest and beneficial organisms in the fields subjected to conventional chemical control.

The first significant finding was that Bemisia tabaci and Aphis gossypii can be managed at desirable levels by their indigenous natural enemies, and that their outbreaks are attributed to the decimation of these natural enemies by chemical treatment. Populations of beneficial arthropods were consistently much lower in the fields which received regular pesticide applications.

The result of the large-scale experiments indicate that Empoasca lybica is the only really damaging pest (“key pest”) in the Gezira because of the absence of natural enemies to regulate its population. Control of E. lybica in the 1940's and 1950's resulted in the creation of Heliothis armigera as a major pest. This situation necessitated early season applications of pesticides to suppress H. armigera, which further reduced the role of the natural enemies of B. tabaci and A. gossypii. Both have developed into major pests of regular occurrence.

Cotton farmers in Gezira are now faced with a complex of very serious pests. In order to solve this problem, we will have to make drastic changes in pest control strategies and to adopt an IPM approach as soon as possible. The biological control H. armigera is considered as first priority in order to avoid the early season application of pesticides. Trichogramma pretiosum was introduced from the USA and released in the Rahad Scheme in 1988/89. The preliminary results are very promising.

Cultural and biological control of E. lybica will be attempted in order to further reduce pesticide applications. The control of this pest by the use of “milder” pesticides is also included in the programme.

The presently used threshold levels for all major pests are very low, and are under revision through properly conducted large-scale experiments.

Flight activity in strain 16cSS of Anopheles gambiae (sensu stricto) has been investigated using an acoustic actograph. The peak activity was concentrated within the first hour after light off. After recording their activity, individual mosquitoes were examined for their chromosome inversion karyotype. No significant relationship was found of any of the karyotypes to total activity over the 2 hr after light off or the time at which 50% of their activity had been completed.

The results are discussed in relation to the possible widespread introduction of mosquito bednets and the possible selection of mosquitoes biting abnormally early before people go to bed.

A basic study of the behavioural responses of the harvester termite, Hodotermes mossambicus (Hagen) to poison baits was undertaken. Laboratory trials revealed that the collected baits were not incorporated into the termite nest food stores. The baits were never eaten because the nest-bound larval caste selects the food to be consumed by the entire colony, from the material collected by the foraging caste. Moreover, field observations have shown that the commercial bait, Kamikaze®, bears no resemblance to the grass collected by the termite foragers. This study revealed that observations of foraging and feeding behaviour of the termites are necessary before designing control measures.

The red locust, Nomadacris septemfasciata (Serville) (Orthoptera: Acrididae), is a threat to agricultural productivity in Malawi. The country has a single known red locust outbreak area, the Lake Chilwa flood plains in southern Malawi, in addition to several other areas where the locust occasionally breeds. Activities of the red locust in Malawi during the period 1988 to 1998 are discussed. Four major outbreaks occurred during the period—in 1993, 1995, 1996 and 1997. Control of these outbreaks was conducted by air except for the 1995 outbreak in Mpatsanjoka River Valley which was controlled by spot treatment on the ground. The use of both a helicopter and a fixed-wing aircraft, where the helicopter locates locust swarms and their concentrations and guides the spray aircraft, appears to be the most efficient and effective strategy for controlling locust outbreaks in Malawi.

Plant resistance research requires many entomological and plant breeding techniques and methodologies of which some are critical to the success of the programme. The entomologist has the responsibility of developing techniques for: providing sufficient numbers of insects for screening and other plant resistance studies; creating uniform and controlled populations of the test insect for identifying and developing resistant germplasm; measuring resistance; and determining mechanisms and bases of resistance. A thorough knowledge of the insect-host plant relationship is essential for developing efficient techniques. Some of the considerations involved in developing these techniques are discussed with selected examples to illustrate various techniques employed in plant resistance to insects research.

Per cent survival, larval period and weight, pupal duration and weight, emergence, adult longevity and fecundity of Heliothis armigera (Hubner) were affected by the pulse species on which it was reared. The pulses could be classified into two groups i.e. pigeon pea and chick pea which were suitable for growth, development and fecundity and black gram, sweet pea, green gram, broad bean and lentil which were unsuitable.

The systematics of phlebotomine sandflies have significantly advanced in the last two decades through the incorporation of a growing body of information on the biology of sandflies and the introduction of new techniques: chromosome analysis, enzyme electrophoresis, detailed morphological studies, laboratory rearing and colonization, and multivariate morphometrics. These techniques have been used mainly in the study of intra-specific variation of vector species. The rôle of sandfty systematics in the epidemiology of leishmaniasis is discussed.

Crude fractions of aerial parts of Andrographis paniculata (Burm.f.) (Acanthaceae) were evaluated for antifeedant, growth-inhibitory and oviposition-deterrent activity against larval and adult stages of the Bihar hairy caterpillar, Spilarctia obliqua (Arctiidae). The methanol fraction had the highest growth-inhibitory activity. Further fractionation resulted in nine sub-fractions of which the most active, identified as the diterpene andrographolide, displayed significant growth-inhibitory and antifeedant properties with GI50 and FD50 values of 100.4 and 159.7 μg/g diet respectively. The ethyl acetate fraction possessed the highest oviposition-deterrent activity.

Larval dispersal and establishment of Chilo partellus (Swinhoe) was studied on different maize cultivar combinations at the whorl stage. Dispersal was increased 2-fold when the infested cultivar ICZ2-CM (resistant) was surrounded by the more susceptible Inbred A, and decreased when Inbred A plants were surrounded by ICZ2-CM. A negative relationship (r = 0.89) was found between the proportions of larvae establishing on infested plants and those unaccounted for. The influence of a cultivar on increased larval dispersal could be exploited in resistance breeding strategies. The possible role of such an effect in pest management strategies is discussed.

The relationships between estimates of tsetse challenge and trypanosome prevalence in trypanotolerant and susceptible cattle were examined at sites of the African Trypanotolerant Livestock Network. Estimates of tsetse challenge were determined as the product of tsetse relative densities, their trypanosome infectionrates and the proportions of feeds taken by them from cattle. Trypanosome prevalence in both trypanotolerant and susceptible breeds of cattle was estimated from monthly examination of groups of ear-tagged cattle. Regression equations between estimates of trypanosome prevalence and tsetse challenge were fitted using an arcsin transformation of trypanosome prevalence and a log10 transformation of tsetse challenge. Highly significant relationships between estimates of tsetse challenge and trypanosome prevalence were found for sites with trypanotolerant cattle (P < 0.0001) and sites with susceptible cattle (P < 0.01). Mean trypanosome prevalence at a given level of tsetse challenge was at least twice as high in susceptible as in trypanotolerant cattle. The slopes of the regression lines for the two groups of cattle were significantly different (P < 0.05). The results confirm the superior ability of trypanotolerant cattle to withstand tsetse challenge in the field. The curves obtained for the two groups of cattle illustrate the necessity in tsetse control campaigns for a major reduction of tsetse populations to take place before significant decreases in trypanosome incidence in livestock can be achieved.

This bibliography on diseases of insect pests of rice contains 287 references. Major groups of insect pathogens are briefly discussed. Available records on diseases, insect hosts and locations of collections are tabulated. Additionally, references are grouped by subject.

Twenty-three insecticide formulations were bioassayed for toxicity against the eggs and larvae of H. hampei in maturing and ripe berries of C. arabica L. Var. typica. The infested berries were dipped in different concentrations of individual formulations, dissected 24 hr later for recording larval mortality and transferring the eggs to wet filter papers where larval hatching was recorded for the next 4 days. The order of toxicity and LC50 (% a.i. × 103) values for the eggs in maturing and ripe (figures in parenthesis) berries were: thiodan EC 35, 5.1 (6.2) > perfekthion, 5.9 (8.1) > decis, 7.2 (9.4) > carbicron, 7.3 (9.8) > actellic, 10.6(12.9) > thiodan EC 3, 14.7 (17.4); > folimat > aldicarb > dursban > tiovel > supona > dimilin > methomyl > kelthane > phosdrin > sevin > methoxychlor > dieldrin > azordrin > fenitrothion > bimarit > chlorpyrifos > gardona, 39.7−1043.7 (44.3−2642.2). The order of toxicity remained almost the same for the larvae, the LC50 values being 2.1−12.7 (2.9−21.8) for the top six and 14.8−1920.4 (47.1−2738.6) for the remaining 17 formulations. Generally, the formulations were 1.1−2.7-fold more toxic to larvae than to eggs infesting the maturing berries but 0.47−3.57 more toxic to eggs than larvae in the ripe berries.