The Senegalese grasshopper, Oedaleus senegalensis (Krauss) (Orthoptera: Acrididae), is a major grasshopper pest of subsistence crops in the West African Sahel. In northern Mali, O. senegalensis spends the dry season in the egg stage in the soil and eclosion is triggered by the first rains which usually occur in May and June. Satellite imagery potentially enables rainfall, and hense O. senegalensis eclosion, to be monitored over much wider areas than those possible for ground-based observers. In 1990 and 1991, rain-gauge networks were set up at Mourdiah, northern Mali, and for each storm event, rainfall and Meteosat infra-red data were collected. The coldest convection clouds (< -70°C) produced rain 93.1% (n = 15) of the time, whereas warmer cloud (>- 10°C) produced rain only once (n = 61). The relationship between minimum cloud temperature and log transformed rainfall data was negative and highly significant (P < 0.0005). The maximum rain-gauge separation for reliable point measurements of rainfall was 8 km. Simulated rainfall experiments showed that O. senegalensis eclosion is influenced both by soil type and by the quantity of water added to the soil. A grasshopper survey after the first rain in 1994 showed that 8 mm of rain was sufficient to cause eclosion 9 days later. The implications of these results for improved O. senegalensis control are discussed.

A series of trials examining the feasibility of an attracticide technique for control of Spodoptera littoralis (Boisduval) are described. The technique combined the sex pheromone of S. littoralis with pyrethroid insecticide, λ-cyhalothrin, in 500 point-sources/ha at low rates of application of both components. It was envisaged that male moths would be attracted to contact the sources and subsequently suffer lethal or sub-lethal effects which would prevent mating. The pheromone was applied either as a sprayable microencapsulated (MC) formulation or in polyvinyl-chloride lures; emulsifiable concentrate and MC formulations of the insecticide were employed. Treatments were assessed by monitoring pheromone trap catches, mating of tethered females and, in one trial, numbers of eggmasses found in experimental areas. Mating levels and trap-catch in treatment plots were siginificantly reduced, compared to controls, for periods up to 5 and 24 nights after treatment, respectively. However despite a continuous period of mating suppression, achieved by repeated applications, no treatment-related reduction in egg-masses was observed. Two trials compared attracticide with mating-disruption treatments in which the insecticide was omitted. Similar levels of mating and trap-catch suppression were observed in the two treatments. It was concluded that the mating suppression observed in attracticide plots was due principally to disruption of chemical communication between the sexes, not to male mortality arising from contact with the insecticide sources. None of the attracticide treatments represented a viable control technique. Other practical and theoretical considerations arising from the results are discussed.

Gravid females of Lucilia cuprina (Wiedeman) in a laboratory cage orientated positively to samples of fleece. Newly-wetted fleece was significantly more attractive than dry fleece, an effect resulting from the action of water on the fleece and not just addition of water vapour to the volatile fleece kairomones. Fleece contaminated with serous exudate, resulting from myiasis by L. cuprina, was much more attractive than wet, uncontaminated fleece from the same sheep. Kairomones from wetted fleece consistently augmented the attractive effects of 2-mercaptoethanol and indole in separate experiments, and of hydrogen sulphide (released from saturated aqueous sodium sulphide solution) in one trial out of three, but not overall. It is suggested that volatile fleece kairomones play a part in eliciting orientation to sheep by gravid L. cuprina. Fleece kairomones may augment the efficacy of kairomones released by putrefactive conditions in the fleece, which are known to predispose sheep to fly strike. They may also provide an input which helps to retain L. cuprina populations in the sheep’s peridomestic precinct.

Outbreaks of the African armyworm, Spodoptera exempta (Walker), in East Africa follow a seasonal pattern related to the movement of the inter-tropical convergence zone. The season typically begins in central Tanzania with primary outbreaks that coincide with the arrival of the rains. An analysis of 27 years' light trap records shows a high negative correlation between the total number of moths caught by light traps during the season over the whole country and the number of rain days during November in central Tanzania. Out of the 27 seasons, 22 could have been correctly predicted as ‘light’ or ‘severe’, using the November rainfall at one station, Dodoma, in time to give two months' warning before the peak of the season.

Use of the insect growth regulator (IGR) pyriproxyfen (Nemesis®) for the control of red scale Aonidiella aurantii (Maskell) (Homoptera: Diaspididae) on citrus in southern Africa has led to extensive disruption of the biocontrol of cottony cushion scale Icerya purchasi Maskell (Homoptera: Margarodidae) provided by the coccinellids Rodolia cardinalis (Mulsant) and other indigenous Rodolia spp. Similar effects on field populations of Chilocorus nigrita (Fabricius), a coccinellids predator of A. aurantii, have also been observed. The adverse effects of field-weathered residues of IGRs on the fecundity and egg viability of the coccinellids C. nigrita and Cryptolaemus montrouzieri Mulsant were determined in a laboratory bioassay. Residues of pyriproxyfen, a juvenile hormone analogue, and two chitin synthesis inhibitors, buprofezin (Applaud®) and triflumuron (Alsystin®), were tested. Exposure to residue-bearing leaves did not affect the number of eggs laid by Chilocorusnigrita, but a complete, or near complete failure of eggs to hatch ensured when adults were exposed to either 3, 7 or 19 week old weathered residues from a single application of pyriproxyfen or triflumuron. Three week old residues of buprofezin had the same effect, but both 7 and 19 week old residues no longer significantly reduced egg viability. Adults of both C. nigrita and Cryptolaemus montrouzieri commenced laying viable eggs within 20 days of being separated from all residue-bearing leaves. One week old residues of pyriproxyfen and triflumuron both significantly reduced progeny production by C. montrouzieri. Ten week old triflumuron residues were still detrimental to this species but pyriproxyfen residues of the same age were not. It was concluded that IGRs are not compatible with integrated pest management (IPM) for citrus in southern Africa, where coccinellid biocontrol agents play an important role.

Topical doses of triflumuron in acetone as low as 0.05 μg per fly induced a significant reduction in the production of viable offspring by adult Glossina morsitans morsitans Westwood, the effect being greatest in the two reproductive cycles following treatment. A dose of 0.5 μg terminated successful reproduction for the life of the fly. A single dose was as effective as the same dose split into five separate treatments. Exposure of females by tarsal contact during passage through a cotton cloth cone treated with 3% suspension concentrate of triflumuron was sufficient to terminate successful reproduction for at least four reproductive cycles following treatment. Males exposed to treated surfaces for 5 minutes could transfer effective amounts of triflumuron to females during mating for at least 2 days after treatment. Target materials, treated with 1% triflumuron in acetone and exposed to field conditions in Zimbabwe for 6 months (April to September), retained their ability to induce a peak abortion rate of 60–70% (40–45% overall) among females exposed by brief tarsal contact in the laboratory.

The life cycle of Liposcelis entomophila (Enderlein) (Psocoptera: Liposcelididae) was studied at 30 ± 1°C and 75 ± 3% r.h. The mean developmental period of the females was 22.3 days and that of the males was 18.4 days. This corresponded to the males undergoing three, and the females four, nymphal stages. A 28% developmental mortality was observed. The average number of offspring produced in the first fornight was 9.6 and the natural mortality of the females was noted only from the sixth week, increasing to 54.1% by the 12th week. An extraction and culturing regime to obtain populations of one- to three-week old adult females was developed. This procedure was also found to be ideal for L. bostrychophila Badonnel.

There is a need to identify potential biological control agents for use against noctuid pests in greenhouses. The gregarious ectoparasitoid Eulophus pennicornis (Nees) attacks a limited range of macrolepidopterous larvae, including those of some important horticultural pest species. Laboratory trials designed to investigate the biology of E. pennicornis on larvae of the tomato moth, Lacanobia oleracea Linnaeus, reveal that wasps preferentially parasitize penulitmate (fifth) or final (sixth) instar hosts. More than two-thirds of wasps lay viable eggs, and individual females oviposit on up to four hosts during their lifespan. Wasp fecundity is high, preadult development is rapid, and offspring show a markedly female-biased sex ratio. Parasitized fifth instar L.oleracea hosts do not grow as quickly as unparasitized larvae, and neither do they undergo normal ecdysis to the final larval stadium. Furthermore, the consumption of artificial diet by parasitized fifth instar hosts is greatly reduced in comparison to that of unparasitized larvae (overall feeding-reduction over a 12 day period was 64.7%). Our results suggest that E. pennicornis affects both the developmental and feeding physiology of host larvae, and that inoculative releases of this parasitoid could provide effective biological control for L. oleracea and other greenhouse pests.

In south India the cultivated oyster mushroom Pleurotus citrinopileatus Singer, which is treated as a subspecies of P. cornucopiae (Paul, ex Pers.) Rolland by some authors, is attacked by larvae of the phorid fly Megaselia tamilnaduensis Disney sp. n. The larvae feed on the mycelium. When more than 3% of the area of the surface of 2.5 kg cylindrical mushroom beds had been damaged the subsequent yields of sporophores fell from 400–500 g to 200–350 g. The new species is described and biological data are summarized.

The characteristics of feeding lesions and the relationship between cocoa pod size/age and surface area were determined as a basis for examining in detail the effects of pod age on feeding and oviposition by Helopeltis theivora Waterhouse. In no-choice and choice experiments in the field, adults made few feeding lesions on the youngest cherelles and, given a choice, made many fewer on full size, ripe yellowing pods than on old cherelles and growing pods. Old cherelles and growing pods were equally attractive based on numbers of feeding lesions per cherelle or pod, but in terms of available surface area for feeding there were more on the cherelles. These distinctions in feeding choice are even more striking for oviposition, with no eggs laid on young cherelles and old pods, and old cherelles/young pods strongly preferred on a per cherelle or pod basis, and especially per unit area of surface. It is suggested that the female chooses to oviposit on relatively old cherelles and young pods because its nymphs may benefit by feeding during a nutritious growing phase of pod development. It is also significant that eggs are rarely laid on ripe pods on which newly hatched nymphs cannot survive, nor are they laid on young cherelles, most of which, unlike the oldest, will die from cherelle wilt. The female lays a large proportion of eggs within, or very close to, feeding lesions, including those made earlier by males. Yet, this does not benefit egg viability. Males did not make feeding lesions on previously laid eggs.

Cotesia flavipes Cameron has been released several times in Africa for biological control of gramineous stem borers. Establishment has been reported on the Indian Ocean islands of Mauritius, Réunion and Madagascar, however, several attempts to introduce C. flavipes into continental Africa are reported to have failed. Recently, several cocoon masses of C. flavipes were recovered from south-western Kenya where the parasitoid was never released. Identifications of the parasitoids from south-western Kenya were based on morphological characters, allozyme frequencies, and mating experiments with laboratory populations of C. flavipes. It is hypothesized that C. flavipes became established from individuals escaping from a laboratory colony maintained in south-western Kenya in 1991.

White peach scale, Pseudaulacaspis pentagona (Targioni-Tozzetti) (Homiptera: Diaspididae), was a serious pest of mulberry until it was the subject of a successful biological control programme in Italy at the turn of the century. Since the 1950s it has returned as a sporadic pest of commercial peach and, more recently, kiwi fruit orchards. We sampled white peach scale in an unmanaged mulberry orchard in coastal Campania over a 17 month period to measure the impact, relative abundance, and interactions of the parasitoids in the absence of pesticides. Sampled scales were dissected, and the immature stages of the parasitoids identified. Mean densities of white peach scale varied with month from 3–15/9 cm2 on primary (interior) branches and 15–100/1.5–2 m secondary (exterior) branch. The generalist ectoparasitoid Aphytis proclia (Walker) was most abundant, followed by two specialist endoparasitoids, Encarsia berlesei (Howard) and Pteroptrix orientalis (Silvestri) (all Hymenoptera: Aphelinidae). Primary parasitism also varied with month from 25–85% on primary branches and 20–90% on secondary branches. Parasitism on primary branches was inversely density-dependent, but was densityindependent on secondary branches. Low levels of superparasitism were generally observed in E. berlesei and P. orientalis (0–6%), but were higher in A. proclia (0–21%). Multiple parasitism of hosts by E. berlesei and A. proclia was fairly common (up to 24% of E. berlesei immatures were found sharing a host with A. proclia), and A. proclia was the probable winner of within-host competitions. The hyperparasitoid Azotus perspeciosus (Girault) (Hymenoptera: Aphelinidae) parasitized late pre-imaginal instars of all three primary parasitoid species. There was no significant difference in hyperparasitism of the three primary parasitoid species, but the rate of hyperparasitism was inversely related to the total density of primary parasitoids.

Based on a longitudinal survey performed in 1982–1983, a vector control strategy was implemented from 1985 onwards in a malarial-dense area of Burundi. One annual round of indoor spraying with malathion greatly reduced both the parasite load and the parasite rate in the population until 1989. However, from 1990 to 1993, a progressive resurgence of malaria was observed in most villages. For the present study, two villages were selected on the basis of their differential response to house spraying. In the village of Mulira surrounded by rice fields, the excellent results observed in the past have been followed by recent increases in parasite rates. In the village of Murengeza, also located in the rice growing area but near a river, the spraying had less impact. The inoculation rate was found to be similar in both villages, but the transmission peak occurred at the end of April in Mulira, and two months earlier in Murengeza. Indoor spraying with lambdacyhalothrin was carried out on 26 April 1993, one month too late according to the strategy intended. As no sporozoite mosquitoes were observed during the six months following spraying, this strategy should be maintained but, in villages near rivers, the application should commence much earlier, in mid-January. Anopheles gambiae Giles sensu stricto (Diptera: Culicidae) and A. funestus Giles were found to be very endophilic species, whereas the dominant A. arabiensis. Patton was highly exophilic. Therefore it is recommended that treatments should not only be applied to human dwellings but also to other structures such as animal sheds, kitchens, etc, shown by earlier studies to be resting sites of A. arabiensis. This study underlines the need for regular reassessment in vector control programmes.

The use of the random amplified polymorphic DNA (RAPD) polymerase chain reaction to characterize individual Lucilia sericata Meigen from southern England was evaluated. Some simple techniques which allowed the preservation and extraction of DNA to be optimized without the complications of transporting liquid nitrogen were investigated. The RAPD results show that closely related L. sericata, including those from a single strike, can be readily distinguished from each other on the basis of their RAPD profiles resolved using electrophoretic analysis; profiles were defined with ten random primers. Analysis of these RAPD data using a similarity coefficient method and a recently developed randomization test to detect the non-random association of alleles at different loci, allowed the genetic homogeneity of L. sericata within southern Britain to be explored. This study shows that while a number of factors can complicate the use and interpretation of RAPD fragments as genetic markers, RAPD fingerprinting can be a valuable technique for studies of intraspecific genetic variation in L. sericata.

Field experiments in which clip-caged apterae of Myzus persicae (Sulzer) (Homoptera: Aphididae) were monitored on sugarbeet revealed that leaf age, plant age and infection of the host with beet yellows closterovirus (BYV) had very large effects on aphid performance (development, reproduction and survival). On healthy plants performance was much better on young, expanding heart leaves than on older leaves. Performance on senescent leaves was poor. When apterae were kept on young heart leaves all their lives (by moving clip-cages to younger leaves every 4 days) there was a strong negative relationship between aphid performance and plant age (measured as plant leaf number at birth). On plants inoculated with BYV apterae showed large improvements in performance. These occurred so rapidly that nymphs born at the time of virus inoculation could benefit as much as those born later. The sizes and between-leaf distributions of M. persicae populations which developed from standard numbers of colonists on whole plants in cages were consistent with the results of the clip-cage experiments. Alatae were less sensitive than apterae to differences in plant and leaf age. Implications of the results for BYV epidemiology and control are discussed.