Tomato is an important vegetable crop that is cultivated for the domestic market in Kenya and other East African countries. Thrips are one of the key pests hampering the production of tomato, both by direct damage to the crop and as vectors of tospoviruses. Field experiments were carried out over two planting times to evaluate the use of sticky traps for monitoring thrips infesting tomato in East Africa. Blue, yellow, and clear sticky traps with and without a thrips lure (Lurem-TR) were tested. Field observations for thrips catches on the sticky traps were made weekly until crop senescence. Sticky traps were replaced with new ones at each observation time. Additionally, both destructive and non-destructive samplings for thrips were done at each observation. Frankliniella schultzei (Trybom) and Ceratothripoides brunneus (Bagnall) were more attracted to blue than yellow traps. Frankliniella occidentalis (Pergande) attraction to blue and yellow traps was not distinctive. The addition of Lurem-TR on traps increased captures of F. schultzei and F. occidentalis but not of C. brunneus. Blue traps with Lurem-TR captures had the highest correlation with absolute estimate of thrips density on the plants. Rainfall had significant negative correlation with thrips population on the crops. Our results show that blue traps and Lurem-TR have strong potential for improving monitoring and management of thrips on tomato.

New data on bat ectoparasites from Mindoro Island, Philippines are reported. Eighty-three individuals of ectoparasitic insects representing seven species of Nycteribiidae and five species of Streblidae (both Diptera), and one species of Ischnopsyllidae (Siphonaptera) were recorded from 11 bat species captured in Naujan Lake National Park, Mindoro Oriental Province, Philippines. Raymondia pagodarum is a new record for the country. Eight species are also newly recorded for Mindoro Island, including Cyclopodia garrula, Leptocyclopodia ferrarii mabuhai, Megastrebla parvior, Brachytarsina amboinensis, B. werneri, R. pagodarum, R. pseudopagodarum and Thaumapsylla longiforceps. Five species are newly documented on various hosts: C. horsfieldi on Pteropus pumilus, M. parvior on Macroglossus minimus, B. amboinensis on Hipposideros diadema, B. werneri on Rhinolophus arcuatus and R. pagodarum on Hipposideros bicolor.

Plant protease inhibitors (PI) constitute a major class of defence proteins being selected as an important strategy towards insect herbivory. With the objective of assessing the effect of PI towards larval growth and development, an artificial diet bioassay using partially purified PI obtained from peas was performed on the melon fruit fly Bactrocera cucurbitae (Coquillett). Larval growth and developmental parameters were assessed at different concentrations (namely 12.5, 25, 50, 100, 200 and 400 μg/ml) on the second-instar larvae of B. cucurbitae. Growth and survival responses determined the anti-insect potential of this PI even in its partially purified state. Larval and total development periods were found to be significantly prolonged for the larvae fed on an artificial diet incorporated with pea PI when compared with those fed with a control diet. Furthermore, when compared with the effect of the control diet (no inhibitor), the partially purified pea PI in the diet reduced larval weight gain, mean larval growth rate and food assimilated with respect to the control of the second-instar larvae tested at the same range of concentrations. The relative effectiveness of pea PI on these parameters is in agreement with the results obtained for percentage of pupation and percentage of adult emergence, as these parameters were significantly affected by the increase in the PI concentration in the artificial diet. Feeding the second-instar larvae a diet containing a range of concentrations (50, 100, 200 and 400 μg/ml) of partially purified pea PI significantly reduced the activities of digestive enzymes (trypsin, chymotrypsin, elastase and leucine aminopeptidase) and significantly affected the activities of other non-digestive enzymes (esterase, acid and alkaline phosphatases, glutathione S-transferase, superoxide dismutase and catalase).

Studies on different parameters of antibiosis to simultaneously compare diverse genotypes with different resistance levels are lacking. Such studies are necessary to identify the genetic variability among resistant genotypes, which, ultimately, can lead to the identification of resistance genes with diverse mechanisms. The current study was undertaken to quantify antibiosis levels in nine rice genotypes against the brown planthopper (BPH), Nilaparvata lugens (Stål), under glasshouse conditions using nine parameters. Among these genotypes, RP2068-18-3-5 and Ptb33 displayed significantly better performance as compared to other genotypes in most of the parameters studied and did not differ from each other. Rathu Heenati was the best in unfertilised eggs laid and similar to the above two genotypes regarding percent of nymphal survival. All the test genotypes performed significantly better than the susceptible check TN1, though INRC3021 did not differentiate from the former in some tests. The overall damage score was positively and significantly correlated with the amount of honeydew excretion, percent nymphal survival and emergence, the proportion of brachypterous females, female population, and growth index, and were negatively and significantly correlated with percent unfertilised eggs laid and nymphal development period. Regression analysis revealed a significant linear relationship between damage score and nymphal emergence, nymphal survival percentage, and proportion of brachypterous females. RP2068-18-3-5 is the new source of BPH resistance identified through this study, which breeders can further use in resistance breeding.

The leaf miner Coelaenomenodera lameensis Berti & Mariau (Coleoptera: Chrysomelidae: Hispinae) is the most serious pest of oil palm in West Africa. A study of mortality factors was carried out at 19 sites located in seven plantations of 3000–7000 ha, over a 2–4-year period in the early 1980s throughout the forest zone of Côte d'Ivoire, West Africa. All life history stages of C. lameensis were found to be attacked by natural enemies. Fluctuations in numbers of egg parasitoids were related to climatic factors and host population dynamics and parasitism rates varied substantially among sites. High egg mortality in C. lameensis, related to parasitism, was directly linked to climatic factors, mainly relative humidity. Fluctuations in egg mortality not linked to parasitism were similar among plantations. There was also a negative correlation between beetle fecundity and egg mortality; climatic conditions favourable to an increase in fecundity also disfavoured egg mortality. This can be a major cause of population increase of larval C. lameensis. Different species of larval and pupal parasitoids and predators were observed. In addition, viruses, isolated from dead larvae in galleries, killed 55–60% of the larvae, probably playing an important role in limiting populations. The destruction of mines by several species of ants also eliminated about 25% of beetle larvae. Parasitoids played a smaller role (less than 10% of larval mortality is due to parasitoids). Mortality in larvae and pupae can exceed 90%, but varied widely from one plantation to another. Examples of mortality tables are given for clearly characterized situations and they help to explain the stability of populations and the occurrence of outbreaks on a plantation or sites scale. Mortality rates lower than 98.6% can lead to population instability and an outbreak in an area.

Laboratory and field studies were undertaken to establish the efficacy of some selected botanicals in the control of the tea red spider mite, Oligonychus coffeae Nietner, a major pest of tea. Bioassays were performed to evaluate the dose-mortality response of adults and eggs of O. coffeae to aqueous plant extracts. The order of adulticidal toxicity based on LC50 and slope values was Sapindus mukorossi L. > Nyctanthes arbor-tristis L. > Phlogacanthus thyrsiformis Nees. The order of ovicidal activity was reversed and was P. thyrsiformis > N. arbor-tristis > S. mukorossi. In addition, different concentrations of the aqueous extract of these plants exhibited repellent properties against adult mites and also significantly decreased the deposition of eggs by the mites on treated tea leaf surfaces. In field conditions, the extracts significantly reduced O. coffeae populations compared to propargite, a synthetic acaricide. There was no phytotoxic effect and the quality of tea was not adversely affected by the treatments. Further, the plant extracts caused no mortality or decrease in the predation efficacy of the adults and fourth instar larvae of Stethorus aptus Kapur, a natural predator of O. coffeae. Using the procedure adopted in this study, tea growers can easily formulate these low-cost eco-friendly botanicals for O. coffeae management in tea plantations.

Data on 2n-numbers of 55 species, belonging to six families of Ghanaian shield-bugs, collected in Southern Ghana, West Africa, are presented. Micrographs and tracings of karyotypes observed for each species are reproduced as figures. Histograms of chromosome numbers of the various families have been constructed and these results, together with the existing information in the literature, are analysed and discussed.

In all, 217 species of Pentatomoidea were found to be known cytologically in the literature. With the present work, the total number of species of shield-bugs where the karyotypes are now known stands at 266.

The following karyotype groups appear to emerge from the study: 14 and 12. Under group 14 is the family Pentatomidae, whilst the families Scutelleridae, Cydnidae and Plataspidae fall under the karyotype group 12. No basic chromosome number can however be cited for the other families of Pentatomoidea, namely the Dinidoridae, Tessaratomidae, Acanthosomatidae and Urostylidae, because the cytological data for each of these are too scanty for any such conclusions to be arrived at. The interrelation of various groups in the superfamily Pentatomoidea is discussed, and the present investigations tend to support the work and conclusions arrived at by morpho-taxonomical studies.

Observation of the damage caused by Mussidia nigrivenella (Pyralidae) on corn cobs and cotton bolls begun in Togo in 1988 was continued in 1990 and 1991. The study was conducted at IRCT's Anié-Mono station at the Dalanda, Notsé and Kouvé test and on small holdings in the Notsé region. M. nigrivenella is the main pest on corn (over 90% of the caterpillars observed). Its larvae populations were higher in 1991 than in the previous year, owing to favourable climatic and cropping conditions.

On immature cotton bolls, C. leucotreta remains the dominant species. However, the extent of M. nigrivenella activity on mature bolls was revealed for the first time. In certain locations, over 90% of the caterpillars and chrysalids observed in attacked mature bolls belong to this species. Hence, cotton plants which are not destroyed after harvests can act as reservoirs for pyralid pests.

A survey was conducted in the four regions of Tanga, Morogoro, Coast and Dar es Salaam in eastern Tanzania to determine the distribution and species composition of cereal stemborers and their natural enemies. A total of 22 fields were sampled in Tanga, 28 in Morogoro, 17 in Coast and one in Dar es Salaam. Chilo partellus was found to be the predominant species, accounting for 80 % of all stemborers collected. Busseola fusca, Sesamia calamistis and Chilo orichalcociliellus made up 15,4 and less than 1 % of the stemborers collected respectively. Infestation levels varied with the age of the plants, whereby younger plants were more severely infested (infestation ranging from 20–40 %) than mature plants (infestation ranging from 5–15 %). Two larval parasitoids, Cotesia sesamiae and Cotesia flavipes, were the main natural enemies collected. However, the levels of parasitism of the stemborers were very low. The exotic natural enemy Co. flavipes may have spread from the Kenya coast (where it is established) into eastern Tanzania.

The immature stages, preferred oviposition sites, hatching patterns and egg morphology of two important rice pest species, Leptocorisa oratorius (Fabricius) and L. acuta (Thunberg) (Heteroptera: Alydidae) were described. Species specific differences were found in all these features. These differences may be useful for identification in fields where these pests occur together.

Termite damage to annual crops on smallscale farms was surveyed in eight areas in southern Malawi during 1989/90 to 1991/92. The most frequently grown crop was maize, followed by pigeonpeas, Phaseolus beans, cotton, cowpea and groundnuts. Twenty-seven species of termites were found attacking crops. The most numerous and widely distributed were several species of the Macrotermitinae, including Ancistrotermes latinotus, four species of Macrotermes, four species of Microtermes, three species of Odontotermes and Pseudacanthotermes militaris. All species damaged maize but only a few damaged bambara, cassava and banana. The damage appeared to be more frequent in dry areas than in wet ones.

The agroecosystem is the basic unit of consideration in the integrated pest management approach. The target crop within this ecological system and its level of susceptibility to insect pest species is of fundamental importance, and can be altered genetically through breeding for pest resistance. The relative level of pest resistance as influenced by pest density, demands a knowledge of pest density and plant damage (yield) relationships. An understanding of these relationships leads to the determination of economic injury levels and subsequently to the establishment of dynamic economic threshold levels. Comparing the economic injury level of insect resistant cultivars to that of susceptible cultivars defines the resistance level and provides the base-line data on which to quantify the effects of other direct control tactics and natural pest density suppressing agents.

Insect resistant sorghums are used as a model to examine the unique values of this tactic as a component in an integrated pest management strategy; the role they play, and how they influence other direct control and support tactics.

Viruses have been identified in a large number of insect species and many have been shown to have a regulating effect on natural populations of insects. Increasing dissatisfaction with the use of chemical pesticides has resulted in a search for biological control agents such as viruses. A number of insect viruses, primarily the occluded viruses (baculoviruses and cytoplasmic polyhedrosis viruses) have been used effectively to control pest species of insects. This review describes the major groups of viruses which infect insects and the areas of research that are being pursued.

There are five caterpillar instars in the life cycle of Spodoptera exempta (Walk.) when they feed upon star grass, Cynodon dactylon (L.) Pers., maize, Zea mais L. and Kikuyu grass, Pennisetum clandestinum Chiov. at 25–30°C. When the temperature is 18°C, however, there was an additional instar in the cycle. Similarly extra instars are formed on Guinea grass, Panicum maximum Jacq., Setaria plicatilis (Hochst.) Hack, and a sedge, Cyperus maranguensis K. Schm. even when the temperature appears to be sufficiently high for normal development. Occasionally the additional sixth instar is also too small to pupate, in which case a seventh instar is formed. It appears that caterpillars on nutritionally inadequate host plants or those at low temperatures are being partially starved and must continue moulting until the appropriate size is attained or exceeded. Measurements of the head capsule widths or distances between the frontal clypeal setae suggest that only individuals reaching or exceeding a species specific threshold size pupate. Extra moults appear to be an adaptation to environmental fluctuations obtaining within the range of occurrence of S. exempta.

The advantages and disadvantages of host plant resistance in crop protection are considered. The role of plant resistance as a primary tactic in integrated pest management and its interactions with other tactics, i.e. biological, chemical and cultural are discussed.

The onset of oviposition, incubation period, instar duration and polymorphism in the first progeny of Macrotermes michaeheni were investigated. Most incipient colonies have their first batch of eggs within the first week following establishment of the colonies. The incubation period for these eggs was 36.2 days. Three male and female larval instars, minor and major workers, and minor soldiers were found in the first progeny. Neither fourth instar larvae, which subsequently moult into major soldiers, nor nymphs, which develop into reproductives, were detected.

The duration of each larval instar was determined. The longest duration was that of third instar larvae developing into both minor and major workers. The first neuter terminal castes which appeared in the colonies were minor workers, followed by major workers and, soon after, by minor soldiers in the majority of cases.

Population trends of Chilo suppressalis during the past 20–35 years in Japan, Korea and Taiwan were compared in terms of light trap records and the area infested by Chilo. In all three countries, Chilo showed a declining population trend, first observed in the late 1950s in Japan, followed by the same pattern in Taiwan and Korea, successively. Among the contributing factors, the early planting of rice was suggested as one common factor. This early planting of rice is also followed by, or associated with, various agronomic practices, e.g. the use of varieties with a larger number of tillers, more intensive pesticide control, early harvesting, the mechanization of agricultural practices, etc. An integrated technology system based on early planting was considered the primary factor responsible for the recent decrease in Chilo. The increased utilization of machinery in rice production will encourage a further decline in Chilo in this region. Local and small scale outbreaks of Chilo were observed in all three countries, due to the widespread use of straw for the culture of special crops. However, so long as the current production system remains the same, there is no scope for Chilo's revival.

A 2-year study in a vegetable-growing area (Tori, Hla Avamé) in Benin has shown that the invasive aphid parasitoid Lysiphlebus testaceipes (Cresson) was attacked by three species of native hyperparasitoids. On several occasions, hyperparasitoids emerged from more than 90% of the mummies collected. The dominating hyperparasitoid was Syrphophagus africanus (Gahan). Two species in the genera Pachyneuron (Pteromalidae) and Aphanogmus (Ceraphronidae), respectively, were also recorded as hyperparasitoids. Charipinae hyperparasitoids were lacking. The only aphid host present at Hla Avamé was Aphis gossypii Glover, a dominating species in vegetable agroecosystems in Benin.

A morphological diversity study was conducted on African rice gall midge Orseolia oryzivora Harris & Gagné and two other African species, Orseolia bonzii Harris and Orseolia nwanzei Harris & Nwilene, sp. n. Morphological differences between adult and immature stages of the three species are slight and mainly evident in pupal characters. Due to limited differences in morphological characters, genomic DNA fingerprinting of these three insect species was carried out using random amplified polymorphic DNA (RAPD) and sequence-characterized amplified region (SCAR) methods. Out of 90 operon primers, 15 showed polymorphism among the three species tested, generating 86 bands, 60 (70%) of which were polymorphic. Primer OPV6 produced three RAPD markers that distinguished the three Orseolia species. These markers were cloned and sequenced. Their sequence was then used to design six SCAR primer pairs. Each SCAR primer pair amplified and distinguished the three Orseolia species at genomic DNA level. Both SCAR and RAPD genomic DNA fingerprinting revealed that O. oryzivora and O. bonzii are most closely related and O. nwanzei is distinct. Each of the six SCAR primer pairs produced a specific DNA fragment size specific for O. nwanzei, O. oryzivora and O. bonzii. The DNA fingerprints will be useful for entomological survey, identification of new species and differentiating aggressive from non-aggressive species, aimed at the effective development of rice cultivars with durable resistance to African rice gall midge.

In North Africa, the potato tubermoth Phthorimaea operculella (Zeller) is an important pest in traditional, non-refrigerated potato stores. A collaborative research programme of the Institut National de la Recherche Agronomique de Tunisie (INRAT) and the International Potato Center (CIP) investigates the relationships between, (a) the dynamics of the field populations, (b) the harvest date, (c) the economic damage in the field, and (d) the subsequent damage in stores under Tunisian conditions. Emphasis was given to the identification of cultural practices that allowed reduction of pesticide applications and to the replacement of the commonly used parathion with less toxic products.

Potato tubermoth control was achieved by applying a synthetic pyrethroid (permethrin) or Bacillus thuringiensis at the beginning of the storage period. The latter, however, seemed to be less effective on tubers with a high initial infestation (over 20%). The studies showed that tuber damage could be avoided by an early harvest and insecticide applications in the field were not indicated.

An integrated control approach including an early harvest date (to reduce initial tuber infestation), and the application of B. thuringiensis or a synthetic pyrethroid is being developed.