Field trials were conducted to assess the effectiveness of a parasitic nematode, the DD136 strain of Neoaplectana carpocapsae Weiser in controlling Heliothis zea (Boddie) on naturally infested sweetcorn.

Nematode suspensions at concentrations of 0, 4 × 103, 4 × 104, 4 × 103 (applied twice) and 4 × 104 (applied twice), nematodes/ml respectively, were sprayed on the ears at early silking stage.

Treatments with 4 × 104 nematodes/ml sprayed twice at 3 days interval gave significantly better control (55%) than the rest. The mean number of surviving H. zea larvae was also significantly reduced with increasing concentrations of nematodes. Economic damage was not prevented but damage to treated ears was significantly lower than that of the untreated plots.

Plants express evolutionary adaptations in response to overall environmental stresses (selection pressures), of which insect infestation usually represents only a minor component. The majority of insect-host plant relationships involves adaptations of insect species to existing plants. Over time, plants have evolved a variety of physical and chemical defence mechanisms against environmental stresses. Only some of these are active against insects, and then not against all species. Plants rarely seem to evolve defences specifically against insects. Parameters of plant resistance to parasites are classified as constitutive or inducible. Soybean resistance to agromyzid stem-miners involves both constitutive and inducible components. Expression of such resistance parameters involves controls ranging from single genes (e.g. for trichome traits) to various combinations of genes (e.g. for the metabolic pathway for phenyl-propanoids). Environmental stresses (e.g. high illumination) especially affect the expression of resistance parameters which involve dynamic metabolic pathways. Soybean (Glycine soja) resistance to beanflies is an example of ‘horizontal’ resistance. Thus, the expected stability is long-term. Such stability is attributable to its major parameters being fundamental components of the soybean's primary and secondary growth and differentiation. These kinds of parameters are major products of the soybean's successful evolutionary experience at survival.

The paper reviews advances in our understanding of the vectorial capacity and vector–parasite relationship in Kenyan sandflies since the early 1900s (when sandflies were first reported in Kenya). Of the 38 species of sandflies known to occur in Kenya to date, three (Phlebotomus pedifer, P. martini and P. duboscqi) can naturally carry biochemically and serologically confirmed Leishmania (aethiopica, donovani and major, respectively) and 12 (Phlebotomus rhodhaini, Sergentomyia garnhami, S. squamipleuris, S. africanus, S. kirki, S. ingrami, S. antennatus, S. bedfordi, S. schwetzi, S. affinis, S. graingeri and S. clydei) carry various flagellates of biochemically or serologically unknown character.

Current research on naturally infected wild-caught sandflies indicates that L. aethiopica promastigotes have close association with structures resembling a peritrophic membrane and invade P. pedifer gut cells. Promastigotes invade the malpighian tubules of S. garnhami and S. antennatus.

Studies on laboratory-reared sandflies show that P. martini is susceptible to L. donovani amastigotes and that cultured promastigotes of L. donovani can survive in the guts of S. schwetzi, S. ingrami and S. adleri.

Experimental infection of sandflies with Leishmania is discussed and priorities for laboratory work set.

The midge, Contarinia sorghicola Coquillett, is a major pest of grain sorghum in many areas of Asia, Africa, Australia, Europe and America. Literature documenting the status of research on the biology, behaviour, and field and cage screening techniques is reviewed. Numerous germplasm entries have been evaluated and many resistant sources are identified from various midge screening programmes. A high degree of resistance was found in nine working groups viz., Caudatum, Durra, Caudatum/Nigricans-Zerazera, Caudatum/Kafir (Hegari), Nigricans, Caffrorum-Darso, Durra-Nigricans, Durra-Nandyal and Caudatum-Bicolor. The identified resistant sources and the midge resistant varieties released from the breeding programmes are listed. Studies on the mechanisms of resistance showed predominance of antixenosis for oviposition over adult attraction and variable degrees of antibiosis. The morphological characters and biochemical factors associated with resistance have been explored. Short and compact glumes which remain closed during anthesis conferred resistance. The tannin content in the ripening sorghum grain is related to resistance against the larva. The inheritance of resistance showed quantitative nature. The open and closed glume character expression indicated its dominance and recessiveness, respectively. Short glume character can be used as an useful genetic marker. Pedigree and modified pedigree breeding systems were suggested to transfer high level of midge resistance into agronomically acceptable types for selection and hybridization.

The pest complex of sunflower and its relative abundance and economic importance are discussed. A total of 80 insect species were collected—five of these were recorded on roots, 51 on stems and leaves and 29 on floral parts and developing seed. The major pests of sunflower commonly encountered in all the localities studied were Agrotis segetum Schiff, Agrotis ypsilon Hfn, Plusia orichalcea F., Nezara viridula L. and Heliothis armigera HB.

The predation of the booklouse, Liposcelis entomophila (Enderlein) (Psocoptera; Liposcelidae) by the mite Blattisocius dentriticus (Berlese) (Acari; Ascidae) was studied in a series of laboratory experiments. Known numbers of mites and booklice were placed together in small tubes and counted after various durations. Fewer booklice were found in mite-infested tubes and it was possible to rear the mite on booklice, which supports the view that the mite is a natural predator of L. entomophila. Comparative susceptibility of the mite and booklouse to deltamethrin and fenitrothion was assessed by exposing both arthropod species to deposits of the two insecticides. The mite was found to be very susceptible to both deltamethrin and fenitrothion whereas the booklouse was only susceptible to the latter. The increased prevalence of L. entomophila in tobacco storage and grading buildings in recent years may therefore be attributed, at least in part, to the use of deltamethrin which suppresses its natural enemies.

The biological hypothesis that female parasitoids can adjust their fecundity schedule according to host availability, and tradeoff longevity with fecundity was tested in a thelytokous oophagous parasitoid, Trichogramma brasiliensis Ashmead (Trichogrammatidae: Hymenoptera) parasitising the rice moth, Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae). The tradeoff between early and late reproduction revealed that this wasp was able to exploit practically all available hosts during the first day or first few days of adult life. During spells of host unavailability, it was able to adjust its fecundity schedule accordingly. There was a negative relationship between survival and reproduction. Adult females survived shorter (10 days) when an unlimited supply of hosts was present, but longer (16 days) when no hosts were provided. These observations suggest the potential suitability of T. brasiliensis for inundative releases even in conditions of fluctuating host availability.

Field data of counts of eggs and larvae of Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) in 12 uncultivated plants in Tolima, Colombia, were used to conduct analyses of variance of the relative importance of the 12 for the insect. Analyses were based on the number of eggs and larvae found per terminal and per 5 g of terminal material of each host.

Regardless of the analysis, more eggs and larvae of H. virescens were found on Desmodium tortuosum (Sw) DC (Papilionaceae) than on the other 11 hosts. In general, more eggs were found on pubescent plants, especially those with glandular trichomes.

A relatively high ratio of larvae:eggs for Ipomea triloba L. (Convolvulaceae) was interpreted to mean that larvae of H. virescens migrated to this plant from eggs laid on other hosts.

The removal rate of eggs from seven hosts due to unknown reasons was estimated to differ between the seven.

Varietal differences with respect to yield losses due to whitefly, Bemisia tabaci Genn. attack were observed at the “sooty-mould level” and “economic threshold (ET) level” of infestation. At the peak infestation level leading to sooty-mould development, the losses varied from 21.7 to 31.8% in boll numbers, 10.3 and 23.7% in boll-weight; 25.9 and 48.9% in seed cotton yield; 12.4 and 153% in seed oil and 29.4 and 66.5% in seed germination among the group of promising new cultures viz., LK 861, LPS 141 and L 389 and other group of commonly cultivated varieties viz., JKHY 1, MCU 5 and ADB 10050, respectively. Besides, the fibre qualities like length, strength, fineness and maturity were also found to be adversely affected.

Detailed biology of the sorghum earhead bug, Calocoris angustatus Lethierry was studied at Dharwad, India during 1979–1981. Egg incubation and nymphal developmental period ranged from 5.6–11.0 and 10.0–17.0 days, respectively. The duration of first, second, third, fourth and fifth nymphal instars was 2.2 to 3.4, 2.3 to 3.0, 2.0 to 2.8, 2.0 to 3.0 and 2.0 to 2.7 days, respectively. The males lived for 8.9 to 17.6 days and females for 12.2 to 21.3 days. Fecundity varied from 57.7 to 267.1 eggs per female. Preoviposition, oviposition and post oviposition periods varied from 1.2 to 2.1, from 7.2 to 14.0 and from 5.0 to 15.8 days, respectively. All the developmental stages of the bug are described.

Competition between Corcyra cephalonica (Stainton) and Ephestia cautella (Walker) was studied in broken cocoa beans using the two species alone, introduced one before the other and together. Both species of moths cannot co-exist for an extended period and in competition E. cautella becomes extinct. The results offer an explanation of recent evidence that C. cephalonica is rapidly becoming the most important pest of stored cocoa beans in Ghana today.

Pheromone traps were used for monitoring flight activity of peach twig borer, Anarsia lineatella (Zeller), during a 3 year period between 1983–1985 in Iraq at Tarmiya and Madain regions, and cumulative emergence was related to physiological time (degree-days, DDs). Data of moth catches indicated the presence of two generations per year and perhaps a partial third generation. Flight in both regions peaked from April to mid-May and from early June to mid-June. First capture of peach twig male ranged from 16 to 29 March and corresponded to a mean DD accumulation from 1 March of 138 in Tarmiya and 127 in Madain. Such results are very important for managing this pest.

By employing histological techniques, it was possible to identify 11 stages of oocyte development in adult female Sarcophaga tibialis (Diptera: Sarcophagidae). Stages 1–4 were represented by the differentiation of the oocyte and the acquisition of the follicular envelope. Stages 5–9 were characterized by a considerable growth of the oocyte which occurred due to an enormous deposition of yolk in the cytoplasm, while the follicle cells were typified by large intercellular spaces. Descriptions are given of the follicle cell degeneration during stages 10 and 11, which end with membrane formation around the mature egg.

Calmodulin is a ubiquitous endogenous calcium receptor in eukaryotic cells and is involved in many different physiological functions. The presence of calmodulins in protozoa has been reported for Tetrahymena and Paramecium. Calmodulin purified from T. pyriformis is composed of 147 amino acids and the amino-terminal is acetylated.Compared to bovine brain calmodulin, there are 11 substitutions and 1 deletion of amino acid residue(s). Besides such structural specificity, Tetrahymena calmodulin (T-CaM) is highly unique in that it has a potential ability to activate the pellicle-bound guanylate cyclase in a calcium-dependent manner. This stimulatory effect is also observed in Paramecium calmodulin (P-CaM). Bovine brain calmodulin represses the T-CaM-dependent activation of guanylate cyclase, indicating that bovine brain CaM exerts its inhibitory influence by interfering with the calmodulin-binding site of this enzyme. The 14S and 30S dyneins extracted from demembranated cilia with EDTA contai ATPase activities which are potentiated by addition of calmodulin. Taken together with its location in cilia, T-CaM appears to regulate the ciliary movement. Moreover, evidence has been provided that calmodulin may be implicated in the glycoprotein biosynthesis. The phosphorylated derivatives of the long chain polyisoprenoid alcohols (dolichol phosphates) are known to act as coenzymes, and the microsomal enzyme involving dolichol phosphorylation is calcium-requiring CTP-dependent and activated by calmodulin. A role for calmodulin in the control of cell growth is postulated by the concerted fluctuations of calmodulin contentand guanylate cyclase activity during the cell cycle in synchronized Tetrahymena cells. In addition, some other possible functions for calmodulin can be considered in protozoa.

Four groups of scientists were invited to participate in this Symposium, including those who have systematically studied or are still studying the relatively new problems of protozoal viruses of protozoa as inactivators of viruses and on protozoa as potential reservoirs of mammalian viruses would have presented itself.

Unfortunately, not all of the invited scientists could come to Nairobi. The most recent results of the Spanish group on protozoa as inactivators of viruses were not discussed (but see Programme and Abstracts of the Congress).

When the compound eye of the adult of the planthopper, Myndus crudus, is light-adapted, pigments are condensed in a zone proximal to the crystalline cones. Viewed externally, the eye is straw-colored. When dark-adapted, pigments migrate distally into the region of the crystalline cones and thus are closer to the cuticle. Viewed externally, the dark-adapted eye is maroon-colored. The eyes of most adult M. crudus observed during daylight hours were light-adapted. Eyes of males and females changed from the light to the dark-adapted condition between sunset and ½hr after sunset. When planthoppers with light-adapted eyes were placed abruptly into darkness at a temperature of 25–27°C, the eyes became dark-adapted within 15–30 min. When planthoppers with dark-adapted eyes were placed abruptly into light, the eyes became light-adapted within 30–60 min. At 8°C the planthoppers were immobile, and light-adapted eyes had not changed to the dark-adapted condition within 45 min. Eyes of M. crudus nymphs, which live in the root zones of grasses, are dark red and do not change color in response to changes in light. Field samples showed that adult M. crudus were active in coconut palms during the day and night, but higher numbers were caught during the day (P < 0.01).

In Zambia, termites have been recognized as pests of agricultural crops, plantation trees, structural timber, manufactured wooden goods as well as paper. This makes their control imperative. In line with the concept of pest management, appropriate control measures of termites must take into account their taxonomy, biology and ecology, as well the assessment of crop damage and yield losses. This paper discusses some of the problems inherent in developing such a scheme in Zambia and provides alternative solutions.

Field trials were carried out for two seasons on the effect of insecticides on insect pests, damage and yield of three cowpea cultivars.

During the first season, the preflowering stage of crop growth was found to be infested by Aphis spp, Empoasca spp, Ootheca spp and Epilachna spp, the flowering stage by Megalurothrips sjostedti, Heliothis armigera, Astylus atromaculatus, Coryna kersteni and Mylabris amplectens and the postflowering stage by H. armigera and a number of coreid and pentatomid bugs. Fenthion gave the least protection against pod damage by H. armigera. There were significant increases in the number of harvestable pods per plant with insecticides. There were no significant differences in hull weight and shelling percentage. Grain yield was increased by 96.2 and 109.4% after treatment with dichlorvos and cypermethrin, respectively.

In the second season, cypermethrin and monocrotophos were most effective. Cypermethrin reduced the number of pod-sucking bugs by 58%, H. armigera by 93%, while monocrotophos reduced Empoasca spp by 39% and M. sjostedti by 79%. Cypermethrin reduced damage by pod-sucking bugs by 28%, and by H. armigera by 95%. Monocrotophos reduced damage by pod-sucking bugs by 14%, and by H. armigera by 80%. Significant increases in the number of harvestable pods per plant were obtained with monocrotophos and cypermethrin treatments. There were no significant differences between the number of seeds per pod, and the weight of 1000 seed-grains. Grain yield was increased by 55.4% after both cypermethrin and monocrotophos treatment. The application of these insecticides were financially beneficial but the gain was reduced when six sprays were applied. Cypermethrin and monocrotophos are promising insecticides for controlling insect pests on cowpeas.

Increasing anthropogenic disturbance in tropical rainforests is a major challenge to biodiversity conservation. The responses of herbivorous insect communities to habitat changes are not well understood. In this study, we investigated the resilience of galling insect communities associated with Neoboutonia macrocalyx (Euphorbiaceae) trees to logging in Kibale National Park, Uganda. Resilience was measured by comparing the species density, abundance and community structure of gallers in nine differently aged successional forests with those in adjacent primary forests. Insect galls were sampled from the canopy of 10 randomly selected trees in each successional stage, five times in a 10-month period. A total of 7219 individuals representing five galler species were recorded. No significant differences were found in the species density and overall density of gallers between the regenerating and primary forests. The mean tree height was positively correlated with the overall density of gallers. The community structure of gallers differed significantly among the successional stages, but exhibited no clear directional recovery trend. In addition, remarkable seasonal variations were observed in galler communities, with peak abundance being found in the wettest months. The results of the preset study indicate that specialist galling insects whose hosts are pioneer trees can recolonize successional sites rapidly and are resilient to the effects of selective and clear-cut logging in case primary or secondary forests with an established population of Neoboutonia host trees (source populations) are close by. Thus, recovering tropical forests can provide important habitats for galling insect biodiversity, highlighting the need to include them in management and conservation priority plans.

Environmental characteristics (for example, temperature, photoperiod) as seasonal cues can affect the offspring sex ratio and reproductive tactics of many hymenopteran insects. Leptocybe invasa Fisher & La Salle is the most critical invasive insect pest of Eucalyptus spp. in the world and displays thelytokous reproduction. In the current study, we studied the effects of temperature and photoperiod on offspring sex ratio and reproductive tactics in L. invasa. Results show that sex ratio (female: male) of L. invasa was under 15, 25 and 35 °C with both L 12: D 12 and L 16: D 8, and cold and thermal acclimation were 74.5:1, 71.0:1, 59.0:0, 17.3:1, 53.0:0, 64.0:0, 47.0:1 and 56.0:0, respectively, which was highly significantly female biased and with no significant difference due to temperature or photoperiod. Offspring virgin females oviposited and induced the bump-shaped galls on plants under the same conditions as described above. Constant temperature, photoperiod and their interaction, and cold and thermal acclimation had no significant effect on the infestation rates of Eucalyptus branches induced by offspring virgin females. Thus, temperature, photoperiod and cold and thermal acclimation did not influence female-biased sex ratio and tactics with thelytokous reproduction of offspring females in L. invasa.