Pests and Diseases
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Item The Ecology of Insect Parasites and Predators(1933) Varley, G.C.; Hope Department of Zoology (Entomology), Oxford UniversityThe Study Of parasitic and predatory insects has recently become more urgent because of difficulties in preventing serious crop damage and damage to stored products by insects of various kinds. With the discovery of modern insecticides it was expected by the optimists that problems of pest control were now soluble if not yet solved. Tests had shown the very high toxicity of these substances to insects, few of which could survive insecticide application in the field. The short-term effect was beneficial, with a satisfactory reduction of damage. Some pests, however, like the codling moth on apple trees, remained numerous enough to cause economic damage even when frequent insecticide sprays were used. Other pests, like the red spider mites, seemed in fact to be more serious where insecticide was used than without it.Item Annotated Host List of Uganda Parasitic Fungi and Plant Diseases—Part III.(1937) Hansford, C.G.; Department of Agriculture, Uganda Protectorate.These two further instalments of the author's list of parasitic fungi and plant diseases so far recorded in Uganda are on the same lines as the first [R.A.M., xvi, p. 550], and include hosts belonging to 37 families. Armillaria mellea is stated to cause the most important disease of tea in Uganda [ibid., viii, p. 202]. Cotton wilt (Verticillium albo-atrum) [ibid., xv, p. 150; xvi, p. 455] is now known from most cotton areas south of Lakes Albert and Kioga and is increasing every year. The fungus is distributed all over Uganda in seed obtained from diseased plants, and under present conditions dissemination by this means cannot be prevented. It is probable that V. albo-atrum is locally the chief cause of cotton wilt. The fungus was recently discovered attacking cassava at Bukalasa. Mycosphaerella areola, the ascigerous stage of Cercosporella gossypii (syn. Ramularia areola] [ibid., xiv, p. 629] was recorded in its ascigerous stage on cotton. Gibberella fujikuroi, a common saprophyte on dead cotton plants, causes a disease of cotton seedlings simulating sore shin. Cladosporium album [Erostrotheca multiformis: ibid., xvi, p. 322] is recorded on beans (Phaseolus) (on which it causes little damage) and peas.Item A Contribution to the Biology of the Musophagiformes, the So-Called Plantain-Eaters.(1938) Moreau, R.E.; AMANI(1) The various names indicating plantain (banana) eating, by which these birds have been called, have no foundation whatever in their habits in nature. As the English name, " Turacos " is preferred for the Order as a whole. (2) The growth and habits of T. fischeri and T. persa are described from the age of about one month onwards. Young specimens of Crinifer and Corythmola are described. (3) It is a character of the Order that the young are completely clothed with (neossoptile) down; it is probable, but not proved, that they are all born with it. At the age of about four or five weeks this has been replaced as bodycovering by a dense growth of down-feathers (semi-plumes), but on the head and neck it is more or less completely shed (at the age of about two months) before any other covering is ready to take its place. The ear is, however, specially protected at this stage. The coloured contour feathers only begin to appear about the tenth week. The pre-adult wing and tail are complete about the ninth and twelfth week respectively. Evidence (from captive birds) on the date adult plumage is assumed is hopelessly divergent.Item The Internal Anatomy of Corioxenos Antestiae Blair (Strepsiptera)(1938) Cooper, B.; AMANIThe only other species of Strepsiptera of which the internal anatomy has been studied appear to be Xenos rossii and Stylops melittae (Nassonov, 1892-1893). It will be of interest to summarise the principal points in which the internal anatomy of Corioxenos antestiae resembles, or differs from, these species. The alimentary canal is of similar arrangement in all three species. The presence of the large epithelial cells which project into the lumen of the mesenteron and are later absorbed is of interest. The rectal caeca, which are probably homologous with similar organs described by Nassonov, are only slightly different in Corioxenos; they arise separately in two places and each of them branches, whereas in the other species they arise as three in one row, branching and anastomosing, and later being joined to the proctodaeum by a single canal. The nervous system in Corioxenos is more concentrated than in the other species. The abdominal ganglion is not separated from the sub-oesophageal nerve-mass in the female, and it is only separated by a short cord in the male. The circulatory and respiratory systems appear to be similar in all three species.Item Transmission of Plant Viruses by Insects(1939) Storey, H.H.; AMANIInsects, as a general rule, play an essential part in the survival of the viruses that cause plant disease. It is true that a virus will pass from scion to stock, or the reverse, across a graft in those species of plants where organic union is possible. I t is also true that by vegetative reproduction of a diseased plant the virus is perpetuated in its progeny. But every living plant owes its origin ultimately to sexual reproduction; and the real problem, from a theoretical and a practical point of view, is how a virus can become established in a sexually produced plant. In only a few rare instances is it known that a virus can be transferred through the true seed from one or other of the parents (16, 21, 57, 58). Some form of secondary transfer from plant to plant must be possible. Many viruses, but not all, can be experimentally so transferred by mechanical inoculation of juice. It is doubtful, however, whether such a method of transmission can operate generally without human intervention, although the natural spread of one virus has been explained by juice transfer during the rubbing of leaves in the wind (49). A few viruses can be disseminated, in some manner not certainly known, through the air (70) or soil (90). Nevertheless, so far as our present knowledge goes, we believe that the great majority of viruses are transferred in nature from one plant unit, i.e., from the product of a single true seed, to another only by insects; and without the insect the virus would suffer extinction with the death of the plant that had been its host.Item A Groundnut Wilt Disease on the Coast of Kenya(1939) Humphrey, N.; Kenya ColonyTIn 1931 several varieties were obtained and planted in observation plots. Germination was satisfactory and good growth was made in the early stages. Soon after flowering began it was noted that some plants were wilting and dying off, And it quickly became apparent that this wilting would be the cause of serious loss. It appeared in all the plots and by the end of the season only one variety retained any healthy plants at all. This variety, a creeping type from Nyanza, lost only some 60 per cent of its population, the remainder ripening off normally. WILT DISEASE Specimens of wilted plants were sent to the Senior Plant Pathologist for examination, and he reported that the wilt was associated with Fusarium sp. Characteristically, the first signs of disease in the field are the yellowing of the outer leaflets. In the next stage, the leaflets close together and collapse. The plant may then die off rapidly and completely; sometimes, after shedding much of its foliage near the crown, it may partially recover and set a small crop. This is more likely to occur on plants wilting late in the season, and almost certainly depends to some extent on climatic conditions. If a diseased plant is lifted, the taproot will be found to show signs of rotting. It may be noted that once the disease had been recognized, local inquiries confirmed its presence in native gardens, and it became clear that this was the limiting factor in the development of groundnut cultivation in the coastal areaItem Some Aspects of Insect Parasites And Predators(1946) Kirkpatrick, T.W.; East African Agricultural Research InstituteThis article is intended to be interesting rather than of practical utility. Every farmer knows of the enormous value of entomophagous (i.e., feeding on insects) insects and that, without them, the plant-feeding insects would increase so rapidly that within a very few years nearly all crops and indeed most other vegetation would disappear from the surface of this planet. But probably few realize the diversity of the methods of attack that have been evolved by insects against other species of their order. For it may be remarked in passing that insects, in common with all other animals except Homo sapiens, never wage war against their own species. They may occasionally turn cannibals under the stress of famine, and sometimes they kill each other under the dictates of sex, but it is only the Lord of Creation who indulges in organized destruction of his own kind.Item Notes on a Species of Epipyropidae (Lepidoptera) Parasitic on Metaphaena Species (Hemiptera Fulgoridae) at Amani, Tanganyika(1947) Kirkpatrick, T.WThe first-instar larva is exceedingly active although, like so many migratory first stage parasitic larvae of different orders of insects, it frequently stops walking, erects the anterior part of its body and waves itself from side to side. In the laboratory they only survive for two or three days-a very few for five days-in the absence of a host. Presumably they find a host by random searching. Having found a host, the larva takes up its position on the dorsum of the abdomen with its head directed towards the posterior end of the host.Item New East African Aphids(1953) Eastop, V.F. ; East African Agriculture and Forestry Research OrganizationBody elongates oval, in life brown with darker transverse dorsal abdominal bands and the whole body dusted with greyish powder.Item Pests and Petroleum(1956) Petroleum Press ServiceFarmers throughout the world have waged an age-long fight against insect attacks, plant diseases, and animal pests. Though this battle is now fought with very much more effective weapons than were available in earlier times for combating those grave menaces to the productivity of the land, the loss and destruction is still immense. The total value of agricultural produce lost through these causes alone possibly approaches £5,000 million a year for the world as a whole. American statisticians put the U.S.A.'s own losses from insects and plants pests as high as 8,000 million dollars (nearly £2,900 million), while crop losses through weeds add another 5,000 million dollars to that already frightening figure. It has been estimated that the total quantities of the world's grain crop destroyed by insects of all kinds would be sufficient to feed some ISO million people. The latter figure represents about 6 per cent of the world population, now standing at nearly 2,500 million people.Item Control of insects attacking maize on the cob in crib stores(1958) Kockum, S.; Department of Maize and Produce Control, KenyaThe climatic conditions in Kenya normally prevent maize from drying out sufficiently in the field to allow immediate shelling. At harvest time the husk is removed and the maize on the cobs is stored in cribs until dry enough for shelling and delivery. For this and various other reasons the harvested crop is often kept in this manner for six to eight months or even longer. During this storage time on the farm before any control methods were introduced, ideal conditions existed for many pests to increase to large numbers causing considerable losses in weight and quality. In 1952 the Agricultural Department of Kenya made an investigation (unpublished) of losses in crib storage. Six untreated farm cribs in different districts were shelled out after four months, and six further untreated cribs were shelled out after six months. After correction for changes in moisture content the average weight loss during storage was found to be 9.6 per cent after four months and 23.1 percent after six months. Calandra oryzae L. and sitotroga cerealella Olivo attack the growing crop, but build up mainly in the stores. From the cribs and stores these pests may spread to adjoining maize fields and to other grain crops such as wheat, barley and sorghum. The importance of reducing these enormous losses and preventing the pests from contaminating the growing crops has long been realizedItem The Insect Pests of Agriculture in the Coast Province of Kenya II - Cashew(1960/1961) Wheadey, P.E.There are four main insect pests of cashew and many minor ones. Cashew does not yield a large return per acre and therefore expensive spray programmes are out of the question. Helopeltis can be controlled to a large extent by insecticides, but this is unlikely to prove economic in the case of the peasant farmer and no general recommendation for its control can be made. Cashew-nut weevil and cashew-nut girdler are both increasing in importance on the Kenya coast. They can be adequately controlled by cultural measures, and it is very important that these measures are actively encouraged by the staff of the Agricultural Department; there is no doubt that the effort entailed will be amply rewarded. Pselldoaonidia is potentially a very serious pest, although it is of little importance in areas where cashew densities are fairly low. Control can only be achieved by spraying. and whether this is likely to prove economically sound is at present doubtful. The minor pests of cashew do not normally cause serious damage and no action is recommended against them.Item Centre for Overseas Pest Research(I C I P E, 1961-1962) Johnstone, D.R.; Overseas Development AdministrationIn keeping with the general policy of streamlining Government Departments and in order to strengthen and improve certain aspects of British aid to agricultural research and development overseas it has been decided that certain scientific units of the Overseas Development administration, which are primarily engaged in the entomological fields, should be merged into a single organisation. The units involved are the Anti-Locust Hese8lch Centre, the Tropical Pesticides Research Unit, the Tropical Pesticide, Research Head quarters and Information Unit and the Termite Research Unit.Item spray distribution from a piper pawnee 235 aircraft fitted with boom and nozze equipments(Kenya Agricultural Research Institute, 1964) Park, P.; Lee, W.; Burnett, G.F.; Kenya Agricultural Research InstituteThe results are given of assessments of the distribution and deposit of insecticide emulsion sprays applied using conventional booms and nozzles fitted to a Piper Pawnee 235 aircraft.-J.L.M.Item A Note on the Incidence of American Bollworm Heliothis Armigera (Hub.) (Noctuidae) in Sorghum(1964) Doggett, H.; East African Agriculture and Forestry Research Organization, SerereThe American bollworm, a troublesome pest of cotton in Africa, feeds on a wide range of plants. Maize is an important host, and often serves as a source of Heliothis adults which lay eggs on the cotton crop. At silking time, the moth may be attracted away from cotton to oviposit on the maize silks. The relative planting time of the maize determines whether it is harmful or beneficial to the cotton crop. Pearson (1958) has reviewed the literature on this. The sorghum crop in East Africa can also carry large American bollworm populations (Peat et al. 1955, Saville et al. 1958), and a high incidence of Heliothis larvae in types with compact panicles has been reported (Valentine 1954, Peat et al. 1955). The very similar New World bollworm H. zea (Boddie) is a sorghum pest in the U.S.A. (Quinby and Gaines 1942, Randolph 1959). The data reported here were collected at Ukiriguru, Tanganyika, in 1954-55.Item Spray Application Problems: LXXVII Insecticide Spraying Trials in Willow Beds Using a Shoulder-Mounted Mistblower(1965) Mapother, H. R.; Stott, K. G.; Long Ashton Agricultural Horticultural Research StationThe following is virtually the authors' summary. The performance of a shoulder-mounted mistblower fitted with a double nozzle was examined in south-western England for applying insecticides on basket willows. An operator can spray 10 acres per day, applying 3 gal. spray per acre, by walking at 2-3 miles per hour through each tenth row. Dilute sprays containing a mixture of 0.0216 % γ BHC and 0.025 % DDT and concentrated ones containing 0.108 and 0.125%, respectively, gave moderate control of aphids, of which the principal species on willow are Aphis farinosa Gmel., Cavariella pastinacae (L.) and Pterocomma pilosum Buckt. Control of the willow leaf beetle (Pyrrhalta (Galerucelld) lineola (F.)) was satisfactory at both concentrations if the spray was applied more than once. A single spray applied at the beginning of July gave control for about three weeks. It is essential that the beetle should be controlled at the beginning of the infestation, and the results suggest that two sprays a fortnight apart may provide adequate protection. The proportion of clean straight rods in the sprayed blocks was double that in the unsprayed one.Item Spray Application Problems: LXXV the Production of Small Spray Droplets with Experimental High Speed Air-Shear Equipment.(1966) Morgan, N.G.; Russell. J.H.; Long Ashton Research StationAn important aspect of crop protection spraying, particularly with small volumes of liquid, is the size of the spray droplets used and therefore the number available for distribution on the crop. This number increases rapidly with reduction of the diameter of the droplets from a given volume of liquid. Therefore a method is required for breaking the spray into the smallest droplets that can be deposited on the crop in sufficient number to provide effective cover.Item Transfer of resistance to the Streak Virus into East African Maize(1967) Audrie, K.H. ; Storey, H.H.; E.A.A.F.R.O., Kikuyu, KenyaStreak disease is caused by infection with a virus that is prevalent in maize and some grasses in many parts of Africa. It has been frequently described (eg Storey, 1925; McClean, 1947); typically it results in leaves developing with a nearly uniform pattern of chlorotic and green areas; in its most severe form some half or more of the total leaf area may be chlorotic, and in this form the disease causes a marked reduction in the growth and productivity of the plant. Because the virus is transmissible only by a specific insect vector of the genus Cicadulina (Storey, loc. cit.) and by no other known means, prevalence of the disease in the field is dependent not only on the presence of the virus but also on the frequency with which the vector occurs. In consequence, outbreaks of streak disease may vary from season to season and from place to place. Nevertheless, in aggregate the disease can cause large losses in productivity of maize; and a search for resistant maize types is justified. Glasshouse studies of streak resistance in maize have been prosecuted over a number of years at EAAFRO That this resistance existed had been recognized in the early thirties in South Africa, but owing to difficulties inherent in studies of this problem under field conditions, research workers there had been unable to arrive at any hypothesis for the manner in which resistance was inherited (Rose 1938; Gorter, 1959). The purpose of the work at EAAFRO was to see whether a genetic hypothesis would emerge from studies carried out under the more exact, more reliable and more rapid conditions provided byItem The Effects the Two Spotted Spider Mite, Tetranychus Urticae, of Dicofol Concentration and Deposit Distribution on the Leaf Surface(1968) Fisher, R. W.; Morgan, N. G.; Research Station, Canada Department of Agriculture, Department of Entomology, Long Ashton Research Station University of BristolDicofol was applied to bean leaf discs in various ways. The number of drops per disc, the concentration of dicofol in each drop, and the size of the drops were related to egg laying and mortality of adult female mites placed on the discs. Under the conditions of the experiment, an increase in concentration above normal field strength (0.046% active ingredient) had little effect, even though the deposits were discontinuous and similar to those expected from low volume spraying. Repellency of dicofol to mites was reaffirmed and toxicity effects were significant were about one-quarter of the leaf surface was covered by deposit.Item Charops Sp. (Hymenoptera: Ichneumonidae) A larval parasite of Orgyia Mixta Snell(1970) Migunda, J.; East African Agricultural and Forestry Research Organization, Muguga, KenyaCharops sp. is probably an important parasite 10 the natural control of O. mixta. The parasite attacks O. mixta during the early larval stages from the last instar larvae. The larval, cocoon, and adult stages of the parasite are described.
