Loss estimates are needed to develop rational economical control measures and to impress upon administrators and donors for efficient disease management. Losses can be actual and potential, incidental and regular, transitional and structural, primary and secondary. Various measuring principles and development of methods to estimate losses are discussed.

Laboratory studies were carried out in Egypt to examine the effects of treatment of the nymphs of Schistocerca gregaria during the later period of third instar with different dosages of gamma radiation ranging from 1000 to 3000 rad. The data indicate that treatment with a dose of 3000 rad induced complete mortality for all treated nymphs. However, irradiation with a dose of 2000 rad produced fourth instar nymphs which enter a state of suspended development for about 14 days. Exposure to a dose of 1000 rad induced three types of response associated with the endocrine activities. Some of the treated nymphs developed to the fifth instar with soft and thin cuticle without tanning or darkening, these nymphs did not survive more than a few hours after ecdysis. Other treated nymphs became fifth instar with anomalous wings and normal cuticle which survived about 18 days as permanent fifth instar nymphs before dying, while the rest of the treated nymphs moulted to permanent fourth instar which survived more than 1 month and eventually died. Corpora allata (CA) volumes in the permanent nymphs were estimated by planimeter method, revealing a pronounced reduction in their size in comparison with the untreated controls. It reflects a sharp inhibition in their synthetic activity of juvenile hormone (JH).

We deduce that the permanent nymphs may be produced as a result of a direct inhibition on the cerebral neurosecretory cells of the brain, the source of stimulating factors for JH and ecdysone production. Gamma rays prevented the production of the tanning and darkening factor (Bursicon Hormone) in these cells.

Spray distribution in an apple tree canopy using an adapted knapsack mistblower fitted with a spinning disc, with the provision of an induced electrostatic charge on the droplets was studied.

Droplets were sampled using uvitex fluorescent tracer on Kromekote cards positioned in different areas of the canopy.

Droplets were highest on the outer surface and decreased sharply into the canopy. Uncharged spray droplets gave the poorer deposition with better distribution, but by adding an electrostatic charge, droplet deposition was significantly improved in the outer parts of the canopy. An average of 3 ml/tree of spray liquid was used in all applications. The larger variety (Red Victoria) required about 50% more spray liquid, but distribution was still lower than that achieved by the smaller Keswick variety.

Laboratory strain-R of Tribolium castaneum, resistant to lindane and multi-resistant strain-L, having developed resistance to lindane and malathion under field conditions, were compared with the standard susceptible strain-S for the nature of resistance to different groups of insecticides. Lindane resistance in both the strains extended to aldrin, dieldrin, endrin and heptachlor. Unlike laboratory strain-R, resistance did not extend to endosulfan in the field strain-L. Both the strains were found susceptible to p, p′-DDT, methoxychlor and allethrin. Also, lindane resistance did not extend to organophosphorous insecticides, viz., malathion, fenitrothion and dichlorovos. Lindane resistance extended to carbaryl and carbofuran, and only slightly to propoxur in the laboratory strain-R, whereas field strain-L remained susceptible to this group of insecticides. Synergist piperonyl-butoxide was found to overcome cross-resistance to endosulfan and propoxur, but to carbaryl in the lindane resistant strain-R. It is, therefore, indicated that one of the three mechanisms responsible for lindane resistance in the laboratory strain of T. castaneum, was stable in the field strain. Thus, the other two mechanisms showing cross-resistance to endosulfan and carbamates were unstable.

Genetic diversity analysis was conducted on a set of 20 sorghum [Sorghum bicolor (L.) Moench] cultivars having resistance to shootfly (Atherigona seccata Rond.), originating from different geographic regions, and representing different taxonomic groups. The genetic diversity for shootfly resistance was assessed using multivariate analysis (D2 statistic and canonical variate analysis), and geographic/taxonomic divergence. The grouping of cultivars based on genetic divergence was found more accurate and relevant than that based on either geographic or taxonomie divergence. Both D2 and canonical variate analyses gave very similiar clustering patterns over the years analysed. Trichome density contributed mainly toward genetic divergence in shootfly resistance, followed by glossiness. Based on the presence or absence of these traits, the cultivars resistant to shootfly were classified into four major clusters. Resistant cultivars IS 844 and IS 1054 formed separate clusters over the years. Heterosis for shootfly resistance was found associated with genetic divergence but not with geographic or taxonomie divergence.

The collapse of Glossina tachinoides populations, within a 27-month period of weekly sampling by means of unbaited biconical traps, in two peridomestic agroecosystems is described. Consistent removal of parous flies through trapping and low recruitment of young flies into the population, were largely responsible for unabated decline in the apparent density of both G. tachinoides populations. Reduction in the size of the resident pig population to below five pigs/week/agroecosystem triggered the collapse of both tsetse populations. Some ecological implications of these findings and their possible application in tsetse control are discussed.

Different ages of the two spotted spider mite Tetranychus urticae Koch and the predacious mite Amblyseius gossipi El-Badry eggs were exposed to selected concentrations of cypermethrin (500 ppm), flucythrinate (200 ppm), cyfluthrin (100 ppm), fenvalerate (200 ppm), Pyridaphenthion (25 ppm), dicofol (250 ppm), avermectin (10 ppm), and dimilin (50 ppm). Generally, the synthetic pyrethroids were effective on eggs especially those of A. gossipi. Dicofol was rather toxic to T. urticae eggs, while avermectin was only effective on older eggs of both species. Eggs treated with different pesticides at late stages took longer to hatch, particularly in the case of A. gossipi.

Six foliar insecticides were evaluated for efficacy in the control of different stages of Clavigralla tomentosicollis, the most important cowpea coreid in Nigeria.

Monocrotophos was highly effective in controlling adults for up to 16 DAT and was statistically better than cypermethrin + dimethoate (Sherpa Plus(R)), deltamethrin, endosulfan and deltamethrin + endosulfan 8 days after treatment. Comparative overall results were obtained between monocrotophos and the mixture of cypermethrin + chlorpyrifos. The best control of nymphs was obtained with monocrotophos, cypermethrin + dimethoate and endosulfan, while the mixtures of cypermethrin + dimethoate and cypermethrin + chlorpyrifos completely inhibited egg hatch. More than 78% egg hatch was obtained from monocrotophos and deltamethrin, while the water-treated control had 96% hatch.

These findings are discussed in the light of product toxicity, residual action and overall reduction of the pod bug populations.

The efficacy of the powder and volatile oil of Piper guineense Schum & Thonn at protecting cowpea against seed beetle, Callosobruchus maculatus (F.) was tested in the laboratory. At low concentrations the powder significantly reduced oviposition and adult emergence while oviposition was completely suppressed at a higher concentration of 42%. The same concentration provided adequate protection for the same amount of cowpea placed in containers of different volumes. The powder, however, did not show any fumigant effect. Volatile oil at 0.002 and 0.005% significantly reduced oviposition and adult emergence, while oviposition was completely suppressed at 0.02% and above. Weight loss of seeds at 90 days after treatment with volatile oil decreased as concentration of the oil increased. The practical significance of the results in small scale storage of cowpea is discussed.

Management programmes for the use of action thresholds to initiate insecticide treatments for controlling pod-borer, Adisura atkinsoni on field bean were evaluated in comparison with standard sprays on calendar basis. Results of three field experiments revealed that management based on initial spray at peak egg laying on tender pods, followed by sprays to maintain 1.5 flat pod damage/inflorescence realised maximum benefit: cost ratio. This management also resulted in reduced insecticide usage.

During the two years research 1983–1985 on traditional maize granaries in Togo, we studied three methods for loss assessment which are discussed by the FAO: the count and weigh method, the standard volume/weight method and the thousand-grain mass method.

In general, between 80 and 90% of the overall losses were caused by insect feedings. Besides Prostephanus truncatus (Horn), the most important storage pests were Sitophilus zeamais (Motsch.), Tribolium spp. and Cathartus quadricollis (Guèr.). Best results were given by the count and weigh method. The significantly highest losses of dry weight (12–13%) were found after 6 months in stored hybrids. At the same time, local varieties appeared much more adapted to traditional storage methods, exhibiting losses of only 3% under the same conditions. Lowest level of losses (<1%) were observed in regularly smoked granaries in the mountain regions. The mean losses of dry weight during primary season were found to be 6.4% after 6 months, while after a storage period of 4 months during the secondary season, losses were as high as 8%. In Togo, P. truncatus was observed for the first time in spring 1984. Because of the different damage P. truncatus causes on corn, a newly developed sample weight method was examined in an additional test. After 6 months of observation, this dangerous pest caused serious losses up to 30.2%.

The male accessory reproductive glands (ARGs) of the tobacco caterpillar, Spodoptera litura begin development on 6th day of the pupal stage. The synthetic activity of the gland begins from the eighth day pupal stage as shown by 3H-leucine incorporation studies. There is a significant increase (2.4-fold) in the specific activity of 3H-leucine incorporation into TCA precipitable proteins in 10 hr old males when compared to newly emerged males (0 hr), and this synthesis is partially blocked (60%) by cycloheximide (5μg/insect) treatment.

The limit of tolerance to temperature treatments that a developing embryo of Ceratitis capitata is able to withstand without suffering a reduction in hatchability or an increase in late abortions was investigated. Major events during embryogenesis were timed and the observation of the chitinous mouth hook inside unhatched eggs was chosen as a marker of late embryo death. This late abortion production was investigated in three different embryo stages and using two pulse lengths. It was found that an exposure of embryos aged 16 hr after egg laying (right before the beginning of the head involution) to 35°C for a period of 15 hr is close enough but below the limit of tolerance for the strain T (Y-nig+)5038 used in this investigation. Consequently, this exposure is proposed as the discriminating treatment in a screening protocol designed for the isolation of a temperature-sensitive embryonic-lethal mutation.

Since it was first reported in Tanzania in 1981 the Larger Grain Borer (LGB) has spread from a small area in the northwest of the country to 17 of the 20 regions. Only in the extreme south, along the Mozambique border, has the pest not been found. It has also become established in Kenya, Burundi, Togo and Benin.

LGB can cause very high weight loss in farm stored maize and dried cassava, commodities on which it is able to breed. After 5 months storage during the dry season in western Tanzania, mean losses of 9% were found, a much higher level than losses of less than 1% which would be expected in LGB-free areas in East/Central Africa.

Application of 0.5% permethrin dust at 2.8 ppm provides excellent protection against LGB when applied to loose maize grain for 1 year. However, the storage of shelled maize predisposes towards the development of Sitophilus species which can result in high losses being sustained. A “cocktail” of permethrin and pirimiphos-methyl, applied at 3.3 and 17.7 ppm respectively, successfully controls all storage pests and is currently being used in an extensive control campaign in Tanzania.

A multi-donor funded control and containment campaign, co-ordinated by FAO, has been in operation in Tanzania since 1984. The programme is comprised of a training element for agricultural staff and several field extension campaigns which assist with insecticide distribution and with dissemination of information to farmers. The primary objectives of the programme are to reduce farm storage losses and to contain LGB within the areas it is now found. In some regions, where LGB is relatively isolated, attempts are being made to eradicate it.

The circadian flight activity of mosquitoes breeding in septic tanks in Jos, central Nigeria, was studied using exit and entry traps. The pattern of peak activity in Culex quinquefasciatus, Culex horridus and Culex cinereus leaving septic tanks was the same between males and females. Aedes aegypti left the tanks earlier than any of the Culex species. There was a difference in time and pattern of peak activity between sexes in this species. Also, a significant difference in peak activity between females of different physiological states was noted in Cx. quinquefasciatus.

Larva of fifth instar silkworm, Bombyx mori L. (Lepidoptera: Bombycidae), parasitized by uji-fly, Exorista sorbillans (Weidemann) (Diptera: Tachinidae), consumed less food and egested less faecal matter than unparasitized one in the instar period. Uji-fly infested worm showed increased digestibility in the last 2 days while the unparasitized larva ingested excessive amounts of food than needed during these days. A reduction of 18.1% in the mean weight of parasitized worm at pupation was recorded. Further, parasitization resulted in 50.7% reduction in the mean cocoon weight and 51.12% reduction in the mean shell weight. Parasitized worms started spinning a day earlier than the healthy ones and the cocoon spun by the former was abnormal.

The toxicity of dursban, reldan and abate were tested against the larvae of Culex pipiens L. and Aedes aegypti (L.), in addition to evaluating effect of two bacterial toxins (Bacillus thuringiensis H-14, and B. sphaericus 1593) against C. pipiens larvae.

The synergistic effects of bacterial toxin-insecticide combinations were calculated and the new LCp-lines were determined by using a sublethal toxin dose of B. thuringiensis and B. sphaericus in combination with the three tested insecticides against Culex pipiens larvae, which was the most tolerant mosquito species.

Bacterial toxins potentiated the three used insecticides at different levels of potentiation, depending on the chemical structure of the insecticide used.

Several insects attack the groundnut, which is a major crop in Senegal. Sporadic attacks of Heliothis ( = Helicoverpa) armigera Hbn. and other insects have been recently noted. In order to reduce the pest attack, neem cake extract (1 and 3%) was compared with cypermethrin and a mixture of dimethoate and deltamethrin and gave satisfactory results. However, yield was not significantly increased.

Experiments carried out in a coffee plantation to determine the developmental period of Icerya paltersoni (Newst.) showed that the female and male scales lasted 157 and 129 days on average, respectively. The different stages of I. pattersoni females were found to be recognizable by the number of antennal segments. The antenna of the stage I nymphal instar is six segmented, stage II is nine segmented and stage III is eleven segmented. The antenna of adult males is eighteen segmented. Females are neotenic but the males possess a pair of grey wings and atrophied mouthparts. In the field the I. pattersoni pest population size is highest in the heavy rainfall months of April and May.

Storage method encompasses the patterns and periods of storage as well as particular storage techniques. Storage management is therefore a major determinant of post-harvest losses in stored cereals: affecting the magnitude of losses and their susceptibility to reduction. Key issues are the location and scale of grain storage which, in most developing countries, involves both rural domestic storage and larger seal “buffer” storage at district centres, commonly near towns.

Various storage techniques are described and discussed against the background of available informatio on storage losses and with regard to the common patterns and periods of storage in Africa at the farr level and in “centralized” storage. The importance of long-term development planning for cereal crop production and utilization is stressed as a major factor in storage pest management and the reduction of storage losses.

The handling of imported food grains is discussed with regard to storage management problems arising from moisture content/relative humidity equilibria as affected by grain temperature.