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.

Field experiments were conducted to investigate the attractiveness of fish bones to predatory ants in a maize agroecosystem. The fish bones were applied crushed in shallow furrows together with dry maize stalks, or broadcast on the soil surface at 3 application rates: 0, 40 and 80 kg/ha; subsequent reduction in termite attack on maize plants was then assessed. Burying the fish bone powder caused higher ant nesting (10–78 %) than surface broadcasting (12–39 %). Attractiveness of the fish bones and the predatory efficiency of the ants against termites in maize was also highest with a dose of 80 kg/ha (1.0 kg/plot) causing higher nesting of ants (>90 %) and 54 % lower termite damage to maize plants compared to control plots. Dose responses indicated significant relationships between amount of fish bone powder applied and termite activity and also between termite damage and maize yield. The mechanism by which the ants are able to protect maize against termite damage may be twofold: direct kill as a result of their predatory action and termite avoidance of maize plants with ant nests. Further studies are required to assess the potential benefits of an integrated use of this technique with other non-chemical options for termite control in maize, such as intercropping.

The sternal gland in Macrotermes michaelseni is located in the anterior half of the fifth abdominal sternite between the third and fourth abdominal ganglia and overlapped by the fourth sternite. It is found in all castes including newly-swarmed de-alates. The gland is largest in major workers followed by major soldiers, minor soldiers and minor workers and is the only source of trail pheromone. Major workers have the highest potential trail pheromone activity followed by minor workers, male and female de-alates, minor soldiers and major soldiers.

There is a change in trail laying behavior with time and direction of travel, from the culture or from the arena and it can be correlated with the deposition of a light or heavy trail, or no trail at all.

The trail of one major worker leaving the culture is attractive to a significant number of workers for 1 hr 30 min and that of five major workers for 1 hr 45 min. The trail of workers leaving the arena is not as strong, one worker trail is attractive for 1 hr and five worker trails for 1 hr 15 min. The well-established trail is attractive to a significant number of workers for 9 hr. All trails lose attractiveness at a constant rate.

The breeding sites and biology of Phlebotomus pedifer was investigated in the caves of the old focus of cutaneous leishmaniasis in Mt Elgon, Bungoma District, Kenya. Phlebotomus pedifer was found to rest mainly in the poorly lighted areas of the caves, on the roof, the floor of caves under objects, and in cracks and crevices inside the caves. The flies were also found in abundance in cracks and crevices outside the caves where hyraxes were found to rest. Immature stages of P. pedifer were recovered from wet areas of the floor of the caves. The biology of this species was investigated and the mean duration from egg to adult was 37 days.

Recognition of Anopheles mid-gut molecules interacting with the malaria parasite is important as they can potentially be targeted to interrupt the life cycle of the parasite in the mosquito's body. The mid-gut of mosquitoes is covered with the glycocalyx, which is composed of various glycoproteins. Pieces of evidence show that mucin proteins are one of the most frequent ingredients of the glycocalyx. In the present study, we isolated and identified the sequence of mucin from the mid-gut of Anopheles stephensi, Liston and Kazerun strains. Anopheles stephensi mucin (AsMuc) has two central core repeats with the consensus sequence TTTTVAP flanked with a hydrophobic N-terminus and a C-terminus which it seems are both necessary for cell surface expression. To show if this molecule is expressed on the surface of the cell, we cloned AsMuc in a baculovirus vector and tracked the expression of the protein in Sf9 insect cells. Immune assays showed the surface localization of the recombinant mucin. AsMuc expression on the surface of the cell suggests it could be a potential ligand for Plasmodium spp. attachment to the Anopheles mid-gut.

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.

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.

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.

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.

The development time and survival of the castor whitefly, Trialeurodes ricini Misra were measured at four constant temperatures. The duration of the egg stage varied from 15 days at 20°C to 4.6 days at 35°C. No eggs hatched at a constant 40°C. The minimum temperature threshold for egg development was calculated to be 17°C. The total development time from egg to adult ranged from 54.4 days at 20°C to 16.8 days at 30°C. Development of the egg and the first-to fifth-instar larva required 63 and 180 degree-days respectively above the threshold value. Immature survival increased from 64.5% at 20°C to 92.8% at 30°C. Trialeurodes ricini is well adapted to high temperatures and may extend its distribution if mean world temperatures increase as a result of global warming.

Trials using deltamethrin impregnated odour-baited targets for control of tsetse, have been running in Galana Ranch on the coastal hitherland since 1986. In July 1988, a similar trial was started in Lambwe Valley, Western Kenya. Glossina pallidipes is the sole vector in the valley and is present in very high densities.

In Galana Ranch trial, octenol and acetone are used as odours while in Lambwe Valley, natural cow urine is used in addition to acetone and octenol. Tsetse population densities were assessed weekly for 3 weeks, before deployment of targets and thereafter at monthly intervals. A herd of cattle is used to monitor the effect of the control measures on disease incidence.

On Galana Ranch, the block where the initial trial began has remained free of G. pallidipes for a period of 3 years. In a period of 9 months in the second year of the trial, the berenil index in a herd of cattle was 0.07 in the controlled area compared to 2.5 in the uncontrolled area.

In Lambwe Valley a 99.9% reduction in trap catches has been observed in most parts of the park at the end of the first year. The berenil index in the cattle has dropped from 6.3 to 0 and there is a general improvementin the health of the animals. Observations are continuing at both sites.

In a survey carried out in 1979–1982 in Sudan, 5830 tick immature stages were collected from cattle, sheep and camels and identified. Hyalomma anatolicum anatolicum, Rhipicephalus evertsi and Amblyomma lepidum immatures were feeding on cattle and sheep. Amblyomma variegatum immatures were collected from cattle. H. impeltatum nymphs were found, for the first time, to feed on camels and sheep, while H. dromedarii nymphs were recorded from camels.

Feeding H. a. anatolicum larvae on rabbits, 53.4% of the ticks behaved as three-host feeding cycle.

Experiments were carried out to study the effect of sublethal doses of gamma radiation (10–100 krad) on fecundity, longevity and sterility of adults of Silotroga cerealella. The results indicate that fecundity of females decreased as the dosage increased from 10–90 krad. At 100 krad no eggs were deposited. Raising the dose to 100 krad resulted in shortening the longevity to about half the longevity of the untreated moths. When irradiated females mated with similarly irradiated males, a dosage of 20 krad caused 97.17% sterility. A dose of 28 krad induced 96.69% sterility when normal females were mated with irradiated males, while 94.14% sterility resulted when normal males were mated with irradiated females.

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.

Studies were carried out to elucidate the parental (vertical) transmission of Nosema marucae Odindo and Jura, in infected females of Chilo partellus Swinhoe. Results indicated that only infected females of C. partellus could pass infection to the offspring. Infection also lowered both the total number of eggs laid per female and egg hatchability- Some adults which developed from the sublethally infected fifth instar larvae of C. partellus had deformed wings while some pharate adults failed to free themselves from the pupal cases. The significance of these deformities to the ecological survival of C. partellus is discussed.

In 1996, many swarms of red locust, Nomadacris septemfasciata (Serville), formed in the Buzi-Gorongosa outbreak area in Mozambique. Some of these swarms migrated and crossed international boundaries, on a scale not seen since the last plague of 1929–1944.

The swarms did not breed in countries that they invaded, namely, Zimbabwe, Zambia, Botswana and South Africa. On the other hand, in Malawi, successful breeding by the swarms resulted in hopper bands. Filial generation outbreaks continued into 1997 in the breeding area, but at a reduced scale.

An analysis is made of the possible causes of the upsurges of 1996 and the likely implications to the preventive control strategy that has been the principle for red locust plague prevention.

There is need for a further comprehensive study of the Buzi-Gorongosa plains so as to understand better the factors that contribute to its high potential as an outbreak area.

The distribution and existing control measures for three important Chilo spp. (C. partellus, C. orichalcocilliellus and C. sacchariphagus) to cereal crop production in 10 east African countries and their neighbouring Indian Ocean Islands are reviewed. Various cultural, biological, host-plant resistance/tolerance and chemical control methods developed in the past 30 years of cereal research programmes are discussed. Cultural methods are very effective on Chilo spp. control, but are not widely practised. Although several effective natural enemies have been identified for Chilo spp., very few systematic programmes of their utilization have been effected. Several resistant/tolerant maize and sorghum lines have been reported, but they are not yet fully used. Chemical control though effective, has proved rather unsuccessful in traditional agriculture. Suggestions to incorporate these control methods in Integrated Pest Management (IPM) programmes for Chilo spp. in different places in the region are given.

The International Red Locust Control Service (IRLCS) was formally established in 1949 with the primary objective of controlling locusts in their outbreak areas, thereby preventing the recurrence of plagues. The name of IRLCS was subsequently changed in 1970 to the International Red Locust Control Organisation for Central and Southern Africa (IRLCO-CSA), but retained the same objectives. Over the years, IRLCO-CSA has experienced changes in membership and locations of its Headquarters and operational centres. Its principle mandate has remained the same even though it has been modified and rationalised from time to time. The organisation carried out investigations that led to the identification of the red locust outbreak areas and the development of various control technologies. Control methods developed from the original physical ones which were laborious and inefficient; to insecticide dusting and baiting; to the spraying by aircraft. In its history of locust control programmes, IRLCO-CSA has used arsenic compounds, BHC, DNOC, dieldrin and fenitrothion as insecticides. The success that IRLCO-CSA has enjoyed in its 50 years history has been thanks to the cooperation of countries in eastern, central and southern Africa which are vulnerable to attack by the red locust, and the international community.

Oviposition and development of Evania appendigaster and Tetrastichus hagenowii in live P. americana oothecae ranging in age from 0–44 days was investigated. E. appendigaster oviposited in oothecae of all ages but developed only in 0–28 days old oothecae. T. hagenowii oviposited only in oothecae 0–34 days old, but developed only in 0–28 days old oothecae. Oothecae parasitized by E. appendigaster were superparasitized only during the first 4 days after the initial parasitization. A single parasite emerged from each such oothecae, indicating that only one of the two ovipositions was successful. Oothecae superparasitized by T. hagenowii during the first 8 days of the initial parasitization, resulted in ca. 90 parasites from both ovipositions. Oothecae parasitized by each species of parasite were subjected to multiple parasitism by the other species. Oviposition of E. appendigaster in 0–25 days old oothecae, parasitized by T. hagenowii was ineffective as it resulted in the emergence of T. hagenowii only. Reparasitization of 0–36 days old E. appendigaster-parasitized oothecae by T. hagenowii within 0–32 days resulted in the development of T. hagenowii, but reparasitization thereafter was ineffective as only E. appendigaster emerged. Even though T. hagenowii is more efficient than E. appendigaster, in parasitizing and developing in different types of P. americana oothecae, under field conditions the two species of parasites contribute equally towards the natural control of P. americana.

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.