The penetration of adult Sitophilus zeamais Motschulsky through maize grain bulks (0.75 m deep), treated with Protect-It®, a diatomaceous earth (DE) at 0, 0.05, 0.1 and 0.2% (w/w), was determined 12 weeks after weevils were released at the upper surface of the grain. Maize was stored in columns in polyvinyl chloride (PVC) pipes, under controlled conditions of 26 ± 2°C and 70 ± 10% RH. Grain samples were collected from various pre-determined depths and the numbers of S. zeamais adults counted. Differences in insect numbers between treatments and at different depths from which samples were collected were highly significant ( P < 0.001). The bottom 2–3 layers (0.65–0.75 m deep) had significantly more insects than the upper layers for all the DE concentrations. No significant differences in total insect numbers (live + dead) were found between the DE concentrations. Dead S. zeamais weevils were found at the bottom of grain treated with Protect-It ® , indicating that insects can penetrate through DE-treated grain 0.75 m deep but then subsequently die. There was no strong evidence that DEs admixed with bulk grain restrict S. zeamais movement within the grain.

Various parameters of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae), such as ovipositional behaviour, development period, and ability of newly hatched larvae to utilise the host for further growth, are affected by host attributes that could be physical or chemical in nature. These factors were assessed using green- and black-gram (Leguminosae) seed characteristics to explore whether they affected oviposition behaviour, fecundity, and breeding success in C. maculatus, and to determine whether the presence of cysteine proteinase inhibitor (CPI) within the seeds caused inhibition of proteinase activity in C. maculatus. Investigation revealed that green- gram ( Vigna radiata ( L.) Wilczek) varieties differed from black-gram (Vigna mungo (L.) Hepper) varieties by having softer seeds with smoother seed coats. Green-gram NM92 and the control had the heaviest seeds with the largest surface area and medium hardness, black-gram had seeds with medium weight, medium surface area, and maximum hardness, and green- gram NCM209 had the lightest seeds with smallest surface area and minimum hardness. Varieties with smooth seed coats and greater seed weight and surface area were preferred for oviposition. Grain texture was more important as an oviposition stimulus than grain surface area and size for the Islamabad biotype of C. maculatus. The level of CPI in seeds was not, on its own, responsible for the observed differences in insect development period or larval activity. Development period was shorter in green- gram with softer seeds and was prolonged in black-gram with harder seeds. Although C. maculatus did not suffer higher mortality in black-gram seeds, the delay in development alone may lead to a considerable reduction in seed loss during storage, due to the low rate of multiplication and lower population growth.

Sitotroga cerealella (Olivier) is an important pest of stored grains, whose biology has been well-researched, but little is known about its population dynamics under field conditions. This study examined the importance of the moth in relation to other storage insect pests on maize and sorghum under smallholder conditions in Zimbabwe. On sorghum heads, S. cerealella and Rhyzopertha dominica F. were dominant, but Sitophilus spp. were dominant on both maize and sorghum grain bulks. The insects themselves and associated grain damage were mostly confined to the top 30 cm of such bulks. An exception was R. dominica, which occurred in large numbers at lower grain levels. The implications of these findings are discussed with reference to reduced pesticide use through more-targeted grain treatment in tropical small-farm stores.

Exploitation of seed hardness, as a mechanism of host plant resistance, could be a useful component of the integrated control of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae). However, traditional methods of measuring larval development period using bioassays do not provide any information on larval feeding activity within seeds. To overcome this difficulty, a biomonitor was used to investigate feeding in seeds of Vigna spp. of different hardness. Larval weight and activity counts were lower in the hard seeded types. Larvae feeding in soft seeds increased their activity with each stadium, with each stadium separated by periods of inactivity. Conversely, for larvae in hard seeds, activity in the second stadium was prolonged and almost indistinguishable from the third and fourth stadia. It is suggested that associations between seed hardness and bruchid development be investigated as contributors to a better understanding of the mechanisms of host plant resistance.

The efficacy and persistence of two commercially available enhanced diatomaceous earth (DE) products (Dryacide® and Protect-It®) against four common tropical storage pests (Prostephanus truncatus, Sitophilus zeamais, Callosobruchus maculatus and Acanthoscelides obtectus) were studied when admixed with typical host commodities at different application rates and relative humidities. Persistence of the enhanced DE treatments was considered after 3 and 6 months storage by assessment of both adult mortality and F1 progeny emergence. Both DEs usually increased parental mortality and reduced progeny emergence of all four insect species in comparison with the untreated control at both 50% and 60% r.h., and at all storage periods. However, efficacy was inversely related to duration of storage and over time the host commodity also became less suitable for insect development. Each insect species differed in its susceptibility to the DE treatments, highlighting the need for field application rates to be based upon the entire spectrum of pest species likely to be present during storage.

Farmers repeated prioritisation of the need for improved methods of controlling insect damage to stored commodities in Zimbabwe led to the search for alternative grain protectants to the locally available organ ophosphate-based pesticides. In field trials the diatomaceous earth (DE) products, Protect-It(R) and Dryacide(R), gave good protection to threshed maize, sorghum and cowpea from insect attack during 8 months storage, enabling households to increase both their food security and control over grain sales. However the initial trials, although on-farm, were researcher-managed and only evaluated by farmers at the end of the storage period. No information existed on how effective DEs were under real farmer management.At the start of the 1999/2000 storage season, farmers in Buhera and Binga districts set up trials in their own granaries using their own maize and sorghum grain, respectively. During a 7 months storage period they evaluated the application of 0.1% w/w Protect-It(R) compared to their typical grain protection methods. At 5 and 7 months storage, farmers compared the treatments using the parameters they view as important such as insect damage, expected 'sadza' yield and quality and sale price. The DE treatments outscored other practices for all parameters and farmers were keen to purchase DEs to protect their future harvests. Grain samples from the same trial were also analysed in the laboratory at 5 and 7 months for insect populations, damage and moisture content. Although grain damage and insect numbers were higher in the typical grain protection treatment than the DE treatment, the differences were not statistically significant. (C) 2002 Elsevier Science Ltd. All rights reserved.

Farmers and grain traders in sub-Saharan Africa are forced to sell stored produce prematurely because of deterioration due mostly to insect damage. Producers expressed a need for a relatively cheap and safe method of insect control. Diatomaceous earths (DE) offer safer alternatives to synthetic chemicals, but information on their efficacy under tropical small-scale farming conditions is lacking. Two commercially available DE products, Protect-It® and Dryacide®, were tested against the major post-harvest insect pests of grains and pulses. On-farm field trials in Zimbabwe showed that both inert dusts gave significant protection against insect damage when admixed with farm stored maize, sorghum and cowpeas for periods of 40 weeks. However, efficacy of these DEs is closely linked to the application rates and differs between commodities, locations and insect pests. An admixture application rate of 0.1% w/w of Protect-It® or Dryacide® can be recommended to protect both maize and cowpea grain that is to be stored for 4 months or longer in Zimbabwe. However, Dryacide® was not effective in preventing damage to sorghum grain by the bostrichid Rhyzopertha dominica unless applied at a higher rate of 0.2% w/w.

Small-scale traders operating in the Tamale market store grain for up to 5 months. Individual traders may store as much as 30-40 t in sacks. Storage facilities and their conditions are very poor. Sheds are constructed with walls of ill-fitting timber planks, roofs of rusty, holed corrugated metal sheets and invariably broken concrete floors. Stores are frequently shared by several traders, which makes good commodity management extremely difficult to implement. These conditions, together with a lack of appropriate knowledge or training, have resulted in traders suffering large losses in both weight and quality of stored grain, mainly as a result of insect infestation, including that by the Khapra beetle, Trogoderma granarium. Trials were conducted to assess both conventional insecticide application and novel methods of protection, including: applying inert dusts; covering stacks with treated cotton or polythene sheeting; and PH3 fumigation. A system was developed allowing an integrated approach to grain protection to be introduced, which included improvements to store hygiene, albeit at a minimal level. Furthermore, a small fumigation centre was constructed adjacent to the market, which enabled centralised disinfestation of commodities before storage. This centre, constructed for US$ 15,000, together with the IPM system, could provide a practical template for traders in other African countries.

SEM and TEM investigations carried out on a model dental casting alloy containing 0.4% C, 30% Cr, 5% Mo and the rest Co, and a similar alloy also containing 1% Nb which is suitable for blending with ceramic material, have shown that the apparently two phase microstructure observed under the optical light microscope is in fact much more complex that at first thought. From the energy filtered TEM pictures it was able to show that in both alloys, in addition to a block shaped a-phase, an extremely fine eutectic also exists which consists of a Co-rich solid solution together with M23C6 and M6C carbides. In addition, also arranged within the eutectic, the niobium containing alloy also contains extremely fine niobium carbonitrides. As a result of discovery of this extremely fine ternary eutectic, it is now possible to explain the extremely good casting properties of these two alloys.

A novel, quite flexible strategy for the surface pre-treatment of graphite anodes for lithium ion cells has been developed. The treatment involves a high temperature cleaning step in inert Ar atmosphere before treatment with gaseous reactants such as CO2 or O2. The effects of surface modification on the formation of the solid electrolyte interphase (SEI) and the corresponding irreversible charge losses are discussed by way of several examples. Morphology changes due to burn-off of carbon are particularly highlighted.

Six plant species (Cassia sophera, Chamaecrista nigricans, Mitragyna inermis, Ocimum americanum, Securidaca longepedunculata and Synedrella nodiflora) traditionally used in Ghana to control insect pests of stored grain and legumes were screened in the laboratory at three concentrations (0.5, 1 and 5%, w/w) against four common storage pests (Rhyzopertha dominica, Callosobruchus maculatus, Sitophilus zeamais and Prostephanus truncatus). All the plants showed some ability to control all or some of the test insect species. Levels of efficacy varied according to test concentration with the highest concentration tested providing the best control. The S. longepedunculata plant induced the highest percent mortality and was the best at reducing emergence of the F(1) generation. The six plants were also incorporated into standard rat diet at two concentrations (1 and 5%, w/w) and fed to rats over a 6-week period to assess potential deleterious effects against vertebrates. None of the plants demonstrated any neurotoxicological or neurobehavioural effects to the rats over the course of the trial. However, S. longepedunculata and C. nigricans caused a significant reduction in rat growth rate when incorporated at 5% in the diet, induced cell hyperplasia in the liver, and reduced the mean weight of the liver and kidneys, compared to the control group of rats. Kidney pathology was affected only by the 5% concentration of S. longepedunculata which caused a reduced accumulation of alpha2mu-globulin. The implications of these results are discussed in the context of farmer usage of insecticidal plants for stored product protection.

Metal grain tanks, as constructed in Swaziland, were demonstrated to be extremely effective structures for fumigation on a small scale; phosphine gas concentrations were maintained well above the recommended minimum concentration of 150 p.p.m. throughout the minimum seven days exposure period. Current methods of sealing the tanks were shown to be inadequate but were improved by sealing the tank inlet and outlet using plastic sheeting and adhesive tape. Application rates of 3·33 g of phosphine per tonne of grain (as currently recommended in Swaziland) were more than adequate, provided the tanks were well sealed. “Tiny Bags” (produced by Degesch GmbH) were slightly slower in releasing phosphine when compared to conventional tablet formulations. However, the pattern of gas release and subsequent decay in concentrations were similar for “Tiny Bags” and tablets. As a result of the high degree of gas tightness which can be achieved using metal grain tanks, the recommended application rates for phosphine could be reduced.