Pyrethroids are the insecticides of choice for the treatment of bednets for malaria control. Pyrethroid resistance in Anopheles spp. vectors may adversely impact malaria control measures, and therefore it is important to know the initial level of pyrethroid resistance before pyrethroid-treated bednets are introduced. Furthermore, a search for replacement insecticides is necessary to manage any eventual high-resistance levels to pyrethroid insecticides that may affect the effectiveness of treated bednets. This study reports on the susceptibility of Anopheles gambiae s.s. exposed for 1 h to the pyrethroid insecticide permethrin and the carbamate insecticide propoxur, at eight localities in the Greater Accra region of Ghana. The observed mortality rates ranged between 21–92% and 92–100% to permethrin and propoxur, respectively. The results also showed a reduction in the knockdown time (KD50 and KD95) in propoxur (mean KD50 = 20 min and mean KD95 = 31 min) when compared with permethrin (mean KD50 = 47 min and mean KD95 = 87 min). The results suggest that permethrin may not be effective in all areas. Where pyrethroid resistance is a problem, propoxur could be an alternative for indoor residual spraying and for insecticide-treated materials such as curtains and eave screens.

To investigate the existence of inter-strain fecundity in the groundnut beetle Careydon serratus, the fecundity and larval survival of crosses of beetle strains from Bauhinia, Cassia, Piliostigma and Tamarindus were studied. The crosses produced viable eggs, but the fertility of beetles mated within strains was significantly higher than that of inter-strain matings, the former being nearly double the latter. Differences in larval mortality between the various crosses were also observed.

The possibility of the involvement of pod wall toughness in the resistance of cowpea, Vigna unguiculata (L.) Walp., to the legume pod borer, Maruca testulalis was studied. The toughness of non-intact and intact pod wall increased with age, but the rate varied at different growth stages of the pod as well as between cultivars. There was a positive and significant correlation (r = 0.82**) between pod age and pressure required to penetrate pod wall. No significant differences (P > 0.05) were observed in non-intact pod wall toughness between TVu 946 (resistant) and IT82D-716 (susceptible) at all the growth stages tested. However, significant differences (P < 0.05) were observed between these two cultivars for only 6-day-old intact pods where IT82D-716 recorded a higher value than TVu 946. Correlation between pod damage severity by M. testulalis and toughness of non-intact and intact pod wall of these cultivars at different growth stages were not significant.

While pod wall toughness would be a desirable trait, it is concluded from this study that pod walls of the cultivars studied did not play any appreciable role on cowpea resistance to the larvae of M. testulalis.

We studied the mite complex—consisting of Tetranychus cinnabarinus (Boisduval), T. urticae (Koch) and Aculops spp.—on three varieties of carnation (Finesse, Optima and White Barbara) in a flower farm in Kenya. Over a period of 24 months, those carnations established in a soilless substrate (pumice in gunny bags) harboured on average less than five mites per leaf as compared to over 20 per leaf on plants established on bare soils. This was the case whether the crop was judiciously or prolifically sprayed with acaricides. The study further established that the economic gain was the same when lower volumes of pesticides were used, whether sprayed judiciously or prolifically. The variety White Barbara generally harboured higher mite numbers than Finesse or Optima. Furthermore, there were fewer rejections, and higher market value when plants were established on pumice substrate compared to bare soils. The study further showed that planting in pumice holds promise for mite control in flower farms. Furthermore, predatory natural enemies of the pest mites, including phytoseiid mites and Orius spp., were conserved in plots where pumice was used with minimum spray.

The band-legged ground cricket group comprises a pair of very closely related species; Dianemobius fascipes occurs widely over tropical and subtropical regions of Southeast Asia, while D. nigrofasciatus is restricted to temperate regions. A similar situation is found in the lawn ground cricket group; the tropical/subtropical species D. taprobanensis is replaced by D. mikado in temperate regions. In both southern species, tropical strains were almost homodynamic, but they produced a few delayed eggs independently of photoperiod and a variable proportion of macropters in response to photoperiod; subtropical strains showed clearer responses. Both northern species controlled egg diapause, nymphal development and wing form by various photoperiodic responses. The two species groups showed parallel geographical profiles of size variation, and the adults and eggs were smaller in the southern than in the northern species. In the absence of strong climatic selection for larger growth rate, size increase in tropical regions would be counteracted by predation pressure. The optimal adult size thus seems to be smaller in tropical than in temperate regions, being determined by the geographically variable balance between counteracting selecting forces.

A large pond, up to 2000 m2 area, adjacent to the sea at Jimbo, near Vanga, on the south coast of Kenya was studied for salinity and the presence of mosquito larvae 1980–1981. Rainfall peaked in November–December 1980 and again in March–May 1981, while salinity of the pond-water fluctuated inversely from dryness in February, more than 100% seawater equivalent in months before main rains, to below 13% seawater after the onset of rain in March.

Five types of mosquito larvae occurred in the pond: Aedes albocephalus mostly at 21–30% salinity (range 13–30%); Culex sitiens mostly at 31–40% salinity (range 13–54%); Culex tritaeniorhynchus and Culex thalassius mostly at 41–50% salinity (range 13–50%) and the Anopheles gambiae complex from 13 to 54% salinity, at least those at higher salinities being Anopheles merus. No larvae were present when salinity surpassed 54% through evaporation, or fell below 13% after rain. The most reliable way to limit or control these pest and vector mosquitoes at Jimbo would be to drain the pond into the sea after rainfall, so that mosquito populations could not increase by breeding sequentially, while salination proceeds.

A programme to control the cassava green mite (CGM), Mononychellus tanajoa, using classical biological control was initiated in 1983 as part of the Africa-wide Biological Control Programme (ABCP). Basic studies on the field ecology and biotic potential of CGM, and surveys of CGM and associated indigenous natural enemies found on cassava throughout Africa are being used to develop ecologically sound release and follow-up strategies. Applied work includes colony maintenance of exotic phytoseiids, development of methodologies for mass producing, transporting and releasing natural enemies, plus experimental releases and post-release surveys. Important parts of the work are being done in collaboration with several institutes and agencies, including foreign exploration and preliminary screening of exotic natural enemies, international quarantine services, regional release and follow-up surveys, taxonomy of CGM and phytoseiids, simulation modelling of CGM in the cassava ecosystem, artificial diets for transporting CGM natural enemies, survey of entomopathogens of CGM and predatory behaviour studies of exotic phytoseiids.

Experiments on artificial infestation of soybean with pod-sucking bugs showed that Riptortus dentipes caused more damage to the plant than did Nezara viridula. The density of four insects per plant used was high enough to significantly damage the plant. The reproductive developmental stages of the plant defined as R3, R4 and R5 were sensitive to the pod-sucking bugs studied. Plots infested with R. dentipes adults suffered 72% pod damage compared to 44% pod damage in plots infested with N. viridula. Riptortus dentipes significantly affected the physiology of the plant and reduced grain yield and grain quality. The results also showed that there is potential for biocontrol of pod-sucking bugs.

Studies were conducted on components of resistance to sorghum midge on four resistant (DJ 6514, AF 28, TAM 2566 and IS 15107) and two susceptible (CSH 1 and Swarna) cultivars. Short floral parts, faster rate of grain development and high tannin content of grain were apparently associated with resistance to sorghum midge, Contarinia sorghicola Coq. Genotypic and phenotypic correlations between the factors associated with resistance to sorghum midge were in the same direction (positive or negative) as their association with resistance to this insect. Glume g2, lemma 12, anther and lodicule length, rate of grain development based on dry weight (except oviposition), and tannin content of mature grain showed correlation and path coefficients (direct effects) in the same direction. These characters can serve as a useful criteria to select for resistance to sorghum midge.

Using D2 and canonical cluster analysis, AF 28 was found to be distinct from other sources of midge resistance. However, based on larvae/100 florets, DJ 6514 was also placed distantly from TAM 2566 and IS 15107. Based on egg numbers, adults emerged and grain damage, DJ 6514 was grouped with TAM 2566 and IS 15107. Susceptible hybrid check, CSH 1 was generally placed distantly from the self pollinated susceptible variety, Swarna. These results indicate that the sources of resistance to sorghum midge are diverse, and there is a distinct possibility of increasing the levels and diversity of resistance to this insect.

This study set out to explore the influence of trap crops designated for the management of Crocidolomia pavonana (Fab.) on two other frequent pests of cabbage: diamondback moth [Plutella xylostella (L.) and cabbage aphid (Brevicoryne brassicae (L.)]. The three pests were offered six hosts in the genus Brassica: kale (B. oleracea var. acephala), cauliflower (B. oleracea var. botrytis), broccoli (B. oleracea var. italica), Chinese cabbage (B. campestris L. ssp. pekinensis), Indian mustard (B. juncea (L.) Czern.), and white cabbage (B. oleracea var. capitata) in multiple (where all the six were offered at the same time) and two-crop trials (where each of the different hosts was paired with cabbage, including a control of cabbage in monoculture) in field trials. Oviposition was considered as a measure of preference for C. pavonana and P. xylostella while colonization and reproduction were measures of preference for B. brassicae. The treatments were arranged in a complete randomized block design with four blocks. The experiment was carried out in the field in 2007 and 2008. The results indicated that C. pavonana oviposition on cabbage was consistently lowered in trap crop treatments when compared with monoculture. The results for P. xylostella and B. brassicae were not as consistent and there was a great deal of variation. It was clear, however, that trap cropping for the control of C. pavonana would not worsen pest problems with the diamondback moth or the cabbage aphid.

In experiments to select a character for identifying larval instars in Sesamia calamistis and Eldana saccharina, body length, body width and head capsule width were measured in populations reared on artificial diet. Seven instars were found in S. calamistis and 5 in E. saccharina. For both species, body length was determined to be the best characteristic to distinguish instars because it was easy to measure and had the smallest error.

Seedlings of apple variety, Yarlington mill, were sprayed with different sprays containing 0.1% cypermethrin, and were subjected for 15 min to 65.3 mm artificial rainfall. The effectiveness of deposits after rainfall were tested in the laboratory with neonate codling moth larvae.

Cypermethrin formulations sprayed with each nozzle were more persistent after artificial rain, when small droplets of volume median diameter (VMD = 30–70 μm) were applied by spinning discs (charged or uncharged) compared with larger droplets (VMD* = 90–160 μm) produced by air shear nozzle. No significant difference in effects was obtained between droplets by either charged or uncharged disc.

A method is suggested for estimating sampling biases for male tsetse, based on the assumptions of the classical feeding cycle “model”. Sampling intensity for any particular method is denned as the catch of flies in different segments of the non-feeding phase of their current cycles, expressed as a percentage of the catch of flies that are just entering the feeding phase. Two examples are given, of Glossina palpalis in Nigeria and G. morsitans in Zambia. In both cases, sampling intensity is low just after feeding and increases slowly at first, and then rapidly as flies enter the feeding phase.

Flies in their feeding phase can apparently find and feed on hosts within one day. Feeding rates are inversely related to the fat content of flies entering the feeding phase of their current cycle, whilst rates of fat usage increase with this variable. These results suggest that it is important to distinguish between tsetse flight activity in general, and feeding behaviour in particular. Finally, it is emphasised that the analytical technique proposed depends on our still inadequate understanding of the field behaviour of flies.

Sixty artificially infested grain sorghum genotypes were evaluated for resistance against Busseola fusca. Evaluation of leaf feeding damage indicated levels of resistance ranging from intermediate to susceptible. Genotypes were categorized according to the presence or absence of both antibiotic and tolerant characteristics. Genotypes (17%) exhibited both antibiosis against leaf feeding and tolerance for borer damage. Borer damage resulted in a 4% increase in grain yield of one genotype and a 50% increase in the number of heads of a second genotype. Tolerance and recovery resistance were the most important factors limiting yield loss in grain sorghum genotypes. In this study, the ability of sorghum for tillering (recovery resistance) was separated from the ability to produce heads on infested stems (tolerance). The importance of distinguishing between tolerance and recovery resistance in the evaluation of sorghum germplasm for borer resistance is emphasized.

Three severe outbreaks of cassava mealybug (CM), Phenacoccus manihoti, have occurred in Zaire. Two were associated with droughts. The third occurred in the driest part of the country and ended only when nearly all cassava plants had been killed. Native coccinellid predators sometimes greatly reduced CM populations, but only after the cassava crop had been heavily damaged. The exotic coccinellid Diomus sp. may be an effective biological control agent in Kinshasa, where CM on a hybrid form of cassava remained common during the rainy season. CM populations in Kinshasa declined greatly in the second year after the release of the exotic parasitoid Epidinocarsis lopezi. In one study the number of mummies with E. lopezi increased with host densities up to 20 CM per shoot tip. Since CM populations remained low after the releases of E. lopezi it is tentatively concluded that E. lopezi, despite considerable rates of hyperparasitism, prevents CM outbreaks over the whole area of its distribution (130,000 km2) in western Zaire.

Studies on larval movement, feeding and development of Chilo partellus Swinhoe were carried out at Mbita, Western Kenya. Larval movement away from the plant was observed during the first and third instars. Plants inoculated at the stems recorded greater larval migration compared to those inoculated at the leaf whorls. Larval feeding was greater on IS 18363 than on IS 2146, but growth rate, weight gain and efficiency of conversion into body substances were greater in IS 2146. Thus it seems that varietal susceptibility to damage by C. partellus is different from varietal suitability for growth of the larvae.

Microscopic examination of stem tissues damaged during larval feeding revealed that feeding was mainly restricted to the pith and that the vascular bundles were hardly affected.

A comparison was made of the EAG responses of repleted males and females of Glossina palpalis gambiensis Vanderplank, G. tachinoides Westwood, G. fuscipes fuscipes Newstead, G. morsitans morsitans Westwood and G. austeni Newstead to the odour of various concentrations of acetone, 4-heptanone, 3-nonanone and l-octen-3-ol. The stimulatory effectiveness of these substances increased in the order: acetone < 4-heptanone < 3-nonanone < l-octen-3-ol. Amounts of acetone 103–104 times greater and of 4-heptanone and 3-nonanone 10–100 times greater than those of l-octen-3-ol were required to obtain similar EAG responses. These results are discussed in relation to the behavioural effects of the odours of these substances on tsetse in wind tunnel experiments in the laboratory and catching experiments in the field. In G. m. morsitans and G. tachinoides, the EAG responses of males were somewhat higher than those of females. In G. austeni, G. f. fuscipes and G. palpalis gambiensis, however, the reverse occurred. All species were equally tuned to the four odour substances, which indicates that these odours do not determine host specificity.

Since the introduction of irrigation in the early 1950s major changes in the crop regime have taken place in Israel. These changes had greatly influenced the populations of the four species of corn borers found in Israel. Chilo agamemnon, which was the main pest during the 1960s decreased and the numbers of Sesamia nonagrioides increased. The reduction in the sorghum acreage, caused a decrease in the numbers of Sesamia cretica. In 1981 an increase in the numbers of the European corn borer, Ostrinia nubilalis, was observed. At present S. nonagrioides and O. nubilalis are the main corn pests in Israel.

Chilo agamemnon was first recorded in Israel in 1959 near the Gaza strip. In the course of 2–3 years it became a very serious pest in the southern parts of the country. Later, the spread of the pest continued throughout the country. Since 1973 a drastic decrease in the populations of C. agamemnon was recorded. The probable reasons for the decrease in the populations of this pest in Israel are:

(1) The relative increase of the areas of sweet corn, which is not its preferable host plant.

(2) Rice and sugar-cane, which are very important host plants in Egypt, are not grown in Israel.

Field experiments against C. agamemnon, carried out when populations were high, showed that dust applications were more effective than sprays.

Non-parametric statistics were used to describe the spatial distribution of eggs laid by Zabrotes subfasciatus Boh. (Coleoptera, Bruchidae) inside pods of wild Phaseolus lunatus and cultivated P. vulgaris. Eggs tended to be uniformly distributed among seeds inside the pods of P. lunatus whereas egg distribution patterns were random or aggregative inside P. vulgaris pods. These differences were explained in terms of the internal pod morphology of the two host plants. It was concluded that this bruchid normally oviposits uniformly among accessible seeds inside the pods of its host plants in the wild.

Juvenile hormone analogues (JHAs), JHA I (6,7′-epoxy-3′,7′-dimethyl-dec-2′-enyl 6-ethyl-3-pyridyl ether), JHA II (3′,7′-dimethyl-undec-2,6′-dinyl 6-ethyl-3-pyridyl ether), MV-678 (2-methoxy-9-[4-isopropyl phenyl]-2, 6-dimethylnonane), and R-20458 (4-ethylphenyl-6, 7′-epoxy-geranyl ether) in acetone solution were applied to insect diets at 10ppm (v/v), and their effects on four species of stored products beetles observed. The larvae of the flour beetles, Tribolium confusum Jacquelin duVal, and Tribolium castaneum (Herbst), reared in media treated with JHAs I and II failed to pupate. At the end of the 6-week observation period, these larvae had not yet pupated. MV-678 and R-20458 produced ecdysial failures, lethal morphological abnormalities and larval/pupal and pupal/adult intermediates. Only a few apparently normal adult flour beetles emerged from these treatments. The lesser borer grain beetle, Rhizopertha dominica (Fabricus), completely failed to reproduce in a medium treated with JHA I. JHA II, MV-678 and R-20458 affected the reproduction of the two grain beetles, R. dominica and Sitophilus oryzae (L.), to varying extent, with MV-678 being the least potent JHA.