Laboratory mice infected with a Trypanosoma congolense isolate of water-buffalo origin did not respond when treated with diminazene aceturate (Berenil, Hoechst, West Germany) at 3.5 mg/kg and 7 mg/kg body weight (b.wt.) and also isometamidium chloride (Samorin, May & Baker, Dagenham, England) at doses less than 3 mg/kg b.wt. Effective cure was achieved with isometamidium and diminazene at 3 mg/kg and 14 mg/kg b.wt. respectively; doses in excess of those recommended for use in the field to treat animal trypanosomiasis by the manufacturers. Irregular use of the two drugs on infected water-buffaloes while improperly restrained may be one of the factors responsible for the dual drug resistant T. congolense isolate emerging.

The potential egg production and egg viability of the potato tuber moth, Phthorimaea operculella (Zell.) was significantly lowered when moths of either sex were exposed in 250 ml glass jars to vapours of orange peel oil emanating from 160 μ oil. Oviposition and egg hatching was totally inhibited when female moths of both sexes were exposed to 220 μl of the oil.

This paper describes briefly four different locust species that constitute potential widespread danger to agriculture and pasture in the eastern, central and southern Africa region. Particular reference is made to the red locust, Nomadacris septemfasciata Serville which mostly feeds on monocotyledonous plants. Reference is also made to the African migratory locust, Locusta migratoria migratorioides R&F; the brown locust, Locustana pardalina Walker; and the desert locust, Schistocerca gregaria Forskal. There were frequent reports of damage to cereal crops by the red locust during the most recent plague of the 1930's. However, since that time only a few yield loss data are available owing, primarily, to the fact that locust infestations have mostly been irregular and confined within their natural breeding areas, away from crop land. The paper provides general background information that should enable evaluation of locust incidence in the region and assessment of consequent cereal crop production losses.

Detailed cytological survey of the developmental stages of Zonocerus variegatus L. revealed major aberrations like lagging, precocious activity of chromosomes, X-autosome associations, pseudochiasmata, deletions, etc. Chiasmata were found to be largely terminally localized and meiosis commences as early as the third instar stage. Models for autocidal control are proposed based on these findings.

The termite Macrotermes herus builds domed earth mounds with no external openings. The internal structure is described here. There is no specialized ventilation system in the mound, unlike those of other Macrotermes species.

The effect of topical application and oral administration of diflubenzuron on the feeding budget in the fifth instar larva of Papilio demoleus has been studied. The LD50 and LC50 values of diflubenzuron were 13.50 and 9.00 μg/larva/48 hr respectively. Topical application was found more efficacious in producing 50% mortality at a comparatively minimum dose of 9.00 μg. The growth efficiency was reduced by 44.54% in oral administration and 38.19% in topical application at the highest sublethal dose over that of control larvae. Not only the growth of the larvae of P. demoleus was inhibited, but the adults showed morphological deformities.

Sun-dried guava (Psidium guajava L.) and eucalyptus (Eucalyptus globulus L.) leaves were evaluated as repellent and toxic materials against the rice weevil, Sitophilus oryzae L., and the granary weevil, Sitophilus granarius L. under laboratory conditions. LC50 values of sun-dried guava and eucalyptus leaves admixed with rice grains against S. oryzae were 2.251 and 4.140g leaves/100g rice grains, respectively, while they were 2.278 and 4.857 g leaves/100 g rice grains in the case of S. granarius, respectively. Guava leaves were more toxic for both species than eucalyptus leaves. Eucalyptus leaves were more repellent than guava leaves.

Both test materials at 15 g/100 g depressed the progeny development of the test insects.

A nuclear polyhedrosis virus isolated from the Egyptian cotton leafworm, Spodoptera littoralis, was found to infect termite castes of Kalotermes flavicollis. Laboratory studies indicated that no specific trend toward mortality responses among the different individuals of termites was noted. All test castes of termites, young, middle-sized, old and reproductive nymphs, and soldiers, were quite equal in their response to the virus infection, regardless of whether the virus concentration was high or low; a concentration of 6.4 × 108 polyhedra/ml, killed only 64% of the treated individuals, while the dosage of 6.4 × 107 polyhedra/ml produced over 90% mortality. Also, thesame trend of response was recorded with the survivors which received challenge doses of NPV suspension each 9 or 10 days. On the other hand, these results revealed that if the NPV is used to control termites, periodic applications would be more efficacious thanone treatment. Virus symptoms were recorded in all affected insects.

Soil pests are defined as those in which the damaging stage of the life cycle lives in the soil. In Africa the most important soil insect pests are termites, followed by the larvae of various beetles (particularly scarabs), and by millipedes which are included here as they damage plants in a similar way to some insects.

The most important cereals in Africa are maize, sorghum and millet, with wheat and rice increasing in importance. Attack by soil pests usually begins on the root system and yield losses result from plant mortality, lowered translocation of water and nutrients, increased susceptibility to pathogens, or lodging with subsequent damage to grain on the ground from various vertebrates, invertebrates and saprophytes.

Data have often been presented as ‘percentage of plants damaged’ or ‘infested’ and bear little relationship to yield loss, as this depends on the severity and timing of attack. A succession of soil pests can attack the plants from seedling to maturity. Early season attacks can result in compensatory growth by remaining plants leading to overestimation of yield loss by simple estimates of plants damaged. Direct estimation of yield loss is time-consuming and few such studies have been made. However, methods are presented here for termites and maize which could be adapted for other pests and crops. Indirect estimates using pesticides are more common and, in general, indicate that an integrated pest management approach to soil pests is required.

The seed oils (petroleum ether extract) of three plants, Azadirachta indica, Annona squamosa and Pongamia pinnata were tested against the cyclops, Mesocyclops leuckarti sensu lato. Out of the seed oils tested, oil of Pongamia pinnata produced excellent cyclopicidal action followed by Annona squamosa. There was, however, no activity with Azadirachta indica oil. Further examination of Chromatographic fractions of P. pinnata oil narrowed down activity to one of four fractions.

Experiments were conducted during two consecutive years (1983 and 1984) on irrigated rice, in the Southwest of Burkina Faso, in order to monitor the seasonal incidence of the rice gall midge, Orseolia oryzivora H. et G.

The damage incidence is the same whatever the date of planting within the rainy season. Attacks are low during the early growth phase of the rice plants (0 to 3% of “silver shoot”), and increase gradually to reach spectacular levels (20 to 55% of “silver shoot”) between 70 and 90 days after transplantation, after which there is decreased attack.

Parasitism is an important check on the larval population of the pest; up to 77% of parasitized larvae were observed. However, this parasitism due mainly to microhymenoptera, Platygaster diplosisae Risb. and Tetrastichus pachydiplosisae Risb., gets established late.

These results could contribute significantly in developing an IPM process on irrigated rice in Burkina Faso.

Screening of leishmanial parasites from domestic and wild animals was carried out in Kacheliba, West Pokot District. Spleens and livers of the animals were cultured in NNN diphasic medium. Thin smears of the same tissues were also made and stained with Giemsa stain and examined under microscope. Positive slide smears were obtained from goats and positive cultures obtained in four goats, one rat and two lizards.

Assessment of damage to apparently good quality palm kernels by test insect species under laboratory conditions revealed that all the cultures had other pest species due to hidden infestation. The total damage caused by the insects to palm kernels in the experimental jars ranged from 17.5 to 30.9% at the end of a 1-yr storage period. With the exception of test species, Oryzaephilus mercator (Fauv.) and Tribolium castaneum (Herbst) which were predominant in cultures in which they were formally introduced, the other cultures were found to be dominated by O. mercator, T. castaneum, Lasioderma serricorne (F.) and Cryptolestes ferrugineus (Steph.). Thus the damage reported above was principally due to these four species. Symptoms of damage to palm kernels by O. mercator; T. castaneum and L. serricorne have been given for the first time and the pest status of the beetle pests associated with stored palm kernel assessed relative to damage caused.

Xyleborus ferrugineus (F) was found damaging stored yam tubers, Dioscorea spp. in Nigeria. Infestation starts in November when the tuber moisture is about 62%. The mean developmental period in the tubers was 32 ± 3 days at 30 ± 2°C. Eggs were laid on the tuber surface damaged during harvesting and the first instar larva burrows inside the yam. Storage of undamaged tubers is suggested to prevent losses due to the pest.

The influence of soil moisture and temperature on hatchling weight during the solitary phase of Locusta migratoria migratorioides (Reiche and Fairmaire) was studied. Soil moisture is an important weight determining factor; heavier hatchlings are produced in relatively wetter soils. Temperature has no apparent influence on hatchling weight. Hatchling weight and hatchling survival to the second instar showed a positive significant correlation.

The ultrastructural changes in the ejaculatory duct epithelium in Glossina morsitans morsitans Westwood was examined for special features related to spermatophore formation; special attention was paid to the cytoplasmic organelles and the plasma membrane specializations (apical infoldings and space formation). Internally, the transportation system is characterized by a cuticle-lined lumen bordered by cuboidal cells. The endoplasmic reticulum is scarce, while mitochondria are distributed throughout the cytoplasm. At the cuticular surface of the cells, extensive apical infoldings are associated with numerous mitochondria. Glycogen granules are found only in the cytoplasm of teneral flies. Apically, adjacent cells are tightly apposed; however, prominent intercellular spaces develop (1 to 7 days), permeate most of the epithelium and connect to the basal surface of the cells. These are features characteristic of transporting cells believed to have an absorptive function. As the adult fly ages, the ultrastructural characteristics of the epithelium change and are typified by the disappearance of glycogen granules and the formation of intercellular spaces. The features of the ejaculatory duct are discussed briefly in terms of their role in spermatophore formation.

The methods for and the problems of recognizing bird and rodent damage are described. For birds the methodology for assessing the damage, and the necessary statistics for determining sample design and sample size exist. Damage is measured either by visual estimation of the percentage loss (sorghum, maize, millet) or by weighing/comparing of damaged/undamaged spikes/panicles (wheat/rice). Sampling usually involves randomly selected transects. A system is also available for assessing bird damage over large areas of District, Regional or even countrywide levels involving aerial surveys of crop hectarage and ground teams sampling damage levels at randomly selected points.

For rodents, the methodology is less well established but damage in the field is usually quantified in terms of the percentage of rows of cereals destroyed at germination (maize) or by the number of cut stems compared to uncut stems in sample quadrats (wheat, barley).

Manpower and resources for bird control do not often extend beyond control operation to damage assessments. As a result the necessity for and success of bird control has to be evaluated in terms of diminishing farmer complaints or expressions of farmer gratitude rather than objectively in terms of crop saved or cost-effectiveness. It is suggested that in the long run, emphasis must inevitably switch to damage assessments as the economic pressures on Africa continue to increase.

The actions of diisopropylfluorophosphate (DFP), an irreversible anticholinestrase (Anti-ChE) agent, were studied on the glutamatergic neuromuscular synapse of insects. The present study reveals that DFP interacts with pre- and post-synaptic regions, also it gives alternative explanations of the symptoms of organophosphate poisoning in insects. Exposure of the metathoracic flexor tibialis muscle of Locusta migratoria to DFP (0.5 mM), at physiological solution, contained normal external calcium concentration (2 mM), increased spontaneous neurotransmitter release which was large enough to trigger action potentials (APs) and endplate potentials (EPPs). A cyclic pattern of APs and EPPs burses and silence periods were recorded. The spontaneous firing of APs and EPPs was calcium-dependent. Reduction of external calcium concentration abolished this phenomenon, suggesting a pre-synaptic site of action of DFP. A transient pre-synaptic depolarization, caused by the agent, could explain the spontaneous transmitter release and repetitive EPPs firing. The spontaneous activity, induced by DFP, was blocked by a sodium channel blocker such as tetrodotoxin. Exposure to α-bungarotoxin, α-Naja-toxin or atropine did not affect the spontaneous release of the transmitter induced by OP agent. Coupled with the pre-synaptic effect, a decrease in the peak amplitude of endplate current (EPC) and shortening of the decay time constant (τEPC) recorded after exposure to the flexor muscle to 1 mM DFP. Both the pre- and post-synaptic effects of DFP were reversible upon washing the preparation. The present findings shift the focus of the occasioners of hyperexcitation of insects treated with OPs from indirect effects of these compounds on the central nervous system (CNS) to direct effects on neuromuscular junctions and indirect effects on CNS.

Inheritance of resistance to sorghum midge, Contarinia sorghicola Coq. was studied on a set of 21 diallel crosses involving four midge-resistant and three susceptible sorghum, Sorghum bicolor (L.) Moench cultivars under natural midge infestation at Dharwad during the late rainy season (August to November) 1983. Both additive and nonadditive genetic variances were important for midge resistance. The parents, DJ 6514 and TAM 2566, proved as better general combiners. Mean performance of the parents and their general combining ability (GCA) effects were strongly correlated. Crosses with positive specific combining ability (SCA) effects in both F1 and F2 generations had at least one parent with high GCA effects and better per se midge resistance. Midge-resistant parents, DJ 6514 and TAM 2566, with high per se resistance and GCA effects should be utilized in breeding for midge resistance.

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.