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Showing papers in "International Journal of Pest Management in 1996"


Journal ArticleDOI
TL;DR: Essential oils of D. tripetela and P. guineense achieved 100% mortality of adults of Callosobruchus maculatus and Sitophilus zeamais in 24 h and cowpea and maize grains treated with seed oils suppressed the e...
Abstract: Seed powders and the essential oils of Dennettia tripetela Baker F., Piper guineense Schum and Thonn, Mondora myristica (Gaerth) Dunal and Xylopia aethiopica Dunal A. Rich were evaluated for their effectiveness in protecting cowpea and maize grains during storage. D. tripetela powder mixed with maize grains, at 1.5 g per 25 g was significantly more effective (P < 0.05) than P. guineense, M. myristica and X. aethiopica in achieving 100% mortality of adults of Sitophilus zeamais in 24 h, and was also as effective as pirimiphosmethyl (10 ppm) in achieving 100% mortality of adult weevil in 24 h, 3 months after treatment at a dose of 3g per 25 g. There was no F1 emergence except in grains treated with M. myristica, X. aethiopica and the untreated controls. Essential oils of D. tripetela and P. guineense achieved 100% mortality of adults of Callosobruchus maculatus and Sitophilus zeamais in 24 h. Except in cowpea treated with X. aethiopica cowpea and maize grains treated with seed oils suppressed the e...

159 citations


Journal ArticleDOI
TL;DR: No evidence could be found to indicate a cause of root necrosis other than brown streak virus, and some varietal differences in response to CBSV were apparent from the survey and at least one variety developed above‐ground symptoms but notRoot necrosis.
Abstract: A survey was conducted in southern Tanzania to determine the relationship between above‐ground symptoms of cassava brown streak virus (CBSV) infection and root necrosis which is often associated with the disease. CBSV symptoms were found in 62 of the 64 fields sampled. Seventy‐nine per cent of plants with above‐ground symptoms of CBS also exhibited root necrosis, compared with only 18% of plants with no visible symptoms of CBSV. No fungi were isolated on acidified water agar from more than half the root samples taken from plants with root necrosis. Where fungi were isolated they represented a range of common soil‐borne fungi, and no single fungus predominated. No evidence could therefore be found to indicate a cause of root necrosis other than brown streak virus. Some varietal differences in response to CBSV were apparent from the survey and at least one variety developed above‐ground symptoms but not root necrosis.

110 citations


Journal ArticleDOI
TL;DR: Ground leaves and essential oil extract provided the greatest protection of maize and sorghum against attack by the insects, and all the plant materials bioassayed evoked higher mortalities in the moth.
Abstract: The bioactivity of materials from the leaves and succulent stems of 0. suave was tested against Sitophilus zeamais (Mots.), Rhyzopertha dominica (Fab.) and Sitotroga cerealella (Oliv.) in maize and sorghum. O. suave applied as dry or ground leaves was not toxic to S. zeamais but as essential oil extract was highly toxic to the weevil. Higher dosages of ground leaves and essential oil extract induced 100% mortality in R. dominica. S. cerealella was most susceptible to O. suave since all the plant materials bioassayed evoked higher mortalities in the moth. The materials also caused significant reduction in progeny produced by the insects. All the plant materials were highly repellent to S. zeamais with ground leaves evoking the highest repellent action. There was, however, considerable variation in the repellency of the materials against R. dominica and S. cerealella. Ground leaves and essential oil extract provided the greatest protection of maize and sorghum against attack by the insects. The pot...

80 citations


Journal ArticleDOI
TL;DR: It is concluded that apparent additions to the host range can, in all of the cases examined, be explained in terms of established behavioural concepts of pre‐adaptation, threshold change resulting from host deprivation, and effects of host deprivation.
Abstract: Many biologists perceive organisms as constantly evolving and therefore consider the host plant ranges of biological control agents as labile. Host plant ranges are thus likely to undergo adaptive change should environmental conditions change, for example following successful biological control. As a consequence, the introduction of biological control agents against weeds is considered by many to be an inherently unsafe practice with non‐target plants at risk of attack. However, despite the introduction of over 600 insect species from one geographic region to another for biological weed control during this century, there are relatively few documented cases of changes in host plant range. Purported instances are discussed in relation to behavioural and genetic concepts. It is concluded that apparent additions to the host range can, in all of the cases examined, be explained in terms of established behavioural concepts of pre‐adaptation, threshold change resulting from host deprivation, and effects...

69 citations


Journal ArticleDOI
TL;DR: Acetolactate synthase (ALS)‐inhibiting imidazolinone and sulphonylurea herbicides have been found to be effective in selectively controlling the pernicious parasitic weeds Orobanche, Striga and Alectra spp.
Abstract: Acetolactate synthase (ALS)‐inhibiting imidazolinone and sulphonylurea herbicides have been found to be effective in selectively controlling the pernicious parasitic weeds Orobanche, Striga and Alectra spp. in some crops. This control could be effected both as whole field applications and as seed dressings. Weeds rapidly evolve resistance to this single‐target, high mutation frequency group of herbicides, which usually exert heavy selection pressure. This type of rapid evolution of resistant populations was previously predicted by models, and later validated in the field in other weed and cropping situations. The selection pressure of this herbicide group may be exceedingly strong with parasitic weeds, as they are controlled by very low dose rates and the doses used are in the ‘overkill’ range. A good management strategy with non‐parasitic weeds was to lower selection pressure, but this may be less effective with parasitic weeds. Many of the areas of the world where parasitic weeds are a problem ...

57 citations


Journal ArticleDOI
TL;DR: Mixed and row intercropping significantly decreased incidence and severity levels of both diseases compared with sole cropping, and cultivars differed significantly in their susceptibility to both diseases.
Abstract: The effect of intercropping bean with maize on bean common bacterial blight and rust was evaluated under three cropping systems: mixed intercropping, row intercropping, and sole cropping of bean using five bean cultivars in a randomized complete block design. Both mixed and row intercropping significantly decreased incidence and severity levels of both diseases compared with sole cropping (P < 0.05). In mixed intercropping, common bacterial blight incidence levels were reduced by an average of 23% and 5% compared with sole cropping and row intercropping, respectively. Similarly, mixed intercropping reduced rust incidence levels on average by 51 % and 25% relative to sole cropping and row intercropping, respectively. The cultivars also differed significantly in their susceptibility to both diseases (P < 0.05). Rust and common bacterial blight incidence assessed at three bean growth stages for each cultivar interact significantly with cropping systems (P < 0.05).

47 citations


Journal ArticleDOI
TL;DR: Undersowing leeks with clover drastically reduced thrips infestations which was reflected in improved quality of leeks at harvest, and the quality of the leek at harvest was also better.
Abstract: Leek (Allium porrum L.) is an Important field vegetable in most of western and central Europe. Infestations of onion thrips (Thrips tabaci Lindeman) cannot be controlled with the range of insecticides now available in The Netherlands. Leek rust (Puccinia allii Rudolph) is now also difficult to control. Experiments in which no insecticides or fungicides were applied, were carried out to assess the effects on thrips populations and infection by leek rust when leek crops were undersown with subterranean clover (Trifolium subterraneum L.). To evaluate the economic aspects of this approach, both the quality and quantity of the leeks produced in the two systems were compared. Undersowing leeks with clover drastically reduced thrips infestations which was reflected in improved quality of leeks at harvest. Leek rust incidence was also reduced slightly by undersowing with clover and the quality of the leeks at harvest was also better. Although the quality of the leeks was improved when the crop was unders...

44 citations


Journal ArticleDOI
TL;DR: Neem extract is an economical and biologically safe bird repellent and that it may be useful in developing nations where neem is indigenous or introduced, and when synthetic pesticides are difficult to obtain or expensive.
Abstract: Neem extract (Azadirachta indica) is effective as an insect antifeedant, and limited evidence suggests that it may be useful as a repellent for birds. The present experiments were designed to test this proposition. In Experiment 1, European Starlings [Sturnus vulgaris) were presented with feed adulterated with a commercially available neem preparation (Nimin®). The results showed that the highest test concentration (1.5% m/m) was avoided. In Experiment 2, starlings were presented with an aqueous extract of neem leaves and serial dilutions of that extract. All extract concentrations were avoided relative to untreated water. We conclude that neem is an economical and biologically safe bird repellent and that it may be useful in developing nations where neem is indigenous or introduced, and when synthetic pesticides are difficult to obtain or expensive.

41 citations


Journal ArticleDOI
TL;DR: High variability in storage methods and structures and in the levels of bruchid and parasitoid attack was observed, and some samples with high levels of egg or larval parasitism showed the potential for natural control, given the right conditions.
Abstract: Stored cowpea was collected from village storage units and from a market in Niger, to study the occurrence of bruchid pests and their parasitoids. High variability in storage methods and structures and in the levels of bruchid and parasitoid attack was observed. The village of origin, the cowpea variety and the type of storage structure all had significant effects on the percentage of beans attacked by bruchids. Damage to beans was highest in the Northern Ouallam region, and parasitism was highest in the South near Say. Bruchid eggs parasitized by Uscana spp. were present in 69% of all samples. Emergence holes and adults of larval parasitoids (Eupelmus spp. and Dinarmus spp.) were found in 92% of all samples. Some samples with high levels of egg or larval parasitism showed the potential for natural control, given the right conditions. Storage units seem to function as isolated units with little dispersal between them. The use of insecticides seems to decrease the impact of parasitoids, leading to...

35 citations


Journal ArticleDOI
TL;DR: Yield improvement by neem was variable and significantly greater yield in comparison with the untreated control was obtained only with cv.
Abstract: We tested aqueous leaf extracts of neem at concentrations of 5 and 10% (w/v) and applied twice and four times during cowpea flowering on two cultivars (IT86D‐715 and IT87D‐941–1) in Kano, Nigeria, in 1993–94 wet season. Extracts were applied with a broom, an indigenous farmers’ practice. Flower infestation by pod borers Maruca testulalis and flower thrips Megalurothrips sjostedti was not reduced by neem application except in 1994 in the 10% neem treatment applied four times. Cv. 715 had consistently less pod damage than cv. 941. On average, neem applications reduced M. testulalis pod damage by 12% in cv. 715 by 16% in cv. 941 compared to the untreated control but not as much as by chemical insecticide (25% and 39% in cv. 715 and 914, respectively). Yield improvement by neem was variable. Significantly greater yield in comparison with the untreated control was obtained only with cv. 715, applied twice at 5% in 1994: 515kg versus 243 kg/ha. Inconsistent yield improvement may have resulted from unev...

32 citations


Journal ArticleDOI
TL;DR: The results indicate that insect pests are the most important biotic constraint to cowpea production in Uganda.
Abstract: Field experiments were conducted during the first and second rainy seasons of 1994 to evaluate the seed yield potential of two commonly grown cowpea varieties and five introduced lines under different pest and disease situations. The highest yields (4654.7 kg/ha, 2083.5 kg/ha and 974.6 kg/ha, respectively) were obtained from the lines IT82D‐522–1, IT85F‐1987 and Katumani‐80, and the least yield was from Icirikukwai, a local line. Between 32.5% to 70.7% yield depression was obtained in plots where pests were not controlled, whereas 9.2% to 16.0% yield depression was attributed to fungal diseases. These results indicate that insect pests are the most important biotic constraint to cowpea production in Uganda.

Journal ArticleDOI
TL;DR: To assess the impact of cropping techniques on the sustainability of agricultural production systems, suggestions are made for the monitoring of selected physical, chemical and biotic characteristics of agro-ecosystems.
Abstract: In developing countries, agriculture is being intensified to produce more food and agricultural products. In most agricultural development strategies, the order of priorities is on: (i) increasing yields, (ii) crop protection, and (iii) human health, environmental and social aspects. This sequential rather than integrated approach contributes to many problems related to sustainability in agriculture. Examples of increased problems with soil erosion, secondary salinization and waterlogging, soil nutrient depletion, increased pest problems, public health hazards and environmental pollution illustrate this phenomenon. To improve the present situation, agricultural development strategies should be based on an integration of factors determining the agricultural production potential of a particular zone: the biophysical environment, the land reclamation level, and external input use. Integrated Crop Management and systems analyses can help to put these factors in the best perspective, and to set the priorities for agricultural research and development accordingly. Techniques aimed at sustainability are listed, and their use is discussed in areas with different production potentials. To assess the impact of cropping techniques on the sustainability of agricultural production systems, suggestions are made for the monitoring of selected physical, chemical and biotic characteristics of agro-ecosystems.

Journal ArticleDOI
TL;DR: The infestation by the insect on the plants resulted in the compensatory production of tillers which developed in response to the gall midge damage but the compensation was not sufficient to ma...
Abstract: The African rice gall midge, Orseolia oryzivora Harris and Gagne (Diptera: Cecidomyiidae), is an important pest of rice, Oryza sativa, in Burkina Faso as well as other countries in West and East Africa. In spite of its importance, little is known regarding the relationship between gall midge populations and grain yield losses. To determine yield losses the gall midge was reared in cages and adult midges were placed on caged plants of the rice variety ITA 123 at different population levels. The seven treatments consisted of different numbers of insects infested on the plants; 0 insect pairs (non‐infested check), and 1, 5, 10, 15, 20 or 25 midge pairs/cage. The loss in yield in relation to the non‐infested control was highly positively correlated (R2 = 0.81) with the percentage of gall midge damaged tillers. The infestation by the insect on the plants resulted in the compensatory production of tillers which developed in response to the gall midge damage but the compensation was not sufficient to ma...

Journal ArticleDOI
TL;DR: Fumigation failure and low milling degree of the rice stock were confirmed as important factors encouraging rapid and substantial psocid population growth while fungal infection rates, routine spraying of store and bag stack and variations in ambient climatic conditions made no obvious contribution to observed fluctuations in Psocid numbers.
Abstract: Psocids (Liposcelis spp.) are often abundant in tropical storage systems where very large populations can develop relatively soon after fumigation treatments. In order to improve pest management strategies against these pest some factors governing the potential of psocid populations to increase under tropical conditions were investigated in a large‐scale milled rice store and in the laboratory. The factors studied included the success of pest control, rice milling degree, fungal growth and variations in ambient temperature and humidity. Fumigation failure and low milling degree of the rice stock were confirmed as important factors encouraging rapid and substantial psocid population growth while fungal infection rates, routine spraying of store and bag stack and variations in ambient climatic conditions made no obvious contribution to observed fluctuations in psocid numbers. Suggestions are made for improved pest management strategies that need to be tested under operational conditions.

Journal ArticleDOI
TL;DR: More care in processing rice seeds for germplasm exchange is needed to prevent weed seed contamination and spread, and pathogenic seedborne fungi such as Bipolaris oryzae and Fusarium moniliforme were detected from IRRI field‐collected Echinochloa spp.
Abstract: The Seed Health Unit of the International Rice Research Institute (IRRI) conducts seed quarantine tests of incoming and outgoing rice seeds. Forty‐eight percent of the incoming shipments did not carry the necessary phytosanitary certificate from the point of origin. Fifteen percent of the incoming rice seed shipments and 0.3% of the outgoing rice seed shipments were contaminated with weed seeds. Twenty weed species were identified as rice seed contaminants. Echinochloa spp. were the most frequent, with as many as 436 seeds per seed‐lot. Storage fungi Penicillium spp., Aspergillus sp. and Rhizopus sp. were detected in incoming Echinochloa spp. weed seeds. Pathogenic seedborne fungi such as Bipolaris oryzae and Fusarium moniliforme were detected from IRRI field‐collected Echinochloa spp. seeds. More care in processing rice seeds for germplasm exchange is needed to prevent weed seed contamination and spread.

Journal ArticleDOI
TL;DR: The first instar nymphs were found to be the most efficient transmitters compared with the second to fourth instars and adults and adults, and the transmission efficiency in brachypterous females and males was 47% and 27% respectively.
Abstract: Sorghum stripe virus (SStV), an isolate of maize stripe tenuivirus on sorghum, is transmitted by a delphacid planthopper (Peregrinus maidis) in a persistent manner throughout its life with intermittent transmission in some individuals. The efficiency of virus transmission by the vector was 42% when individual viruliferous vectors were used per test seedling and 100% with five viruliferous insects. The minimum acquisition and inoculation feeding periods were 4 h and 1 h respectively. Vectors became viruliferous and able to transmit the virus within an 8 days’ incubation period after acquisition of virus from the source plant. The first instar nymphs were found to be the most efficient transmitters (64%) compared with the second to fourth instars (50%) and adults (33%). Fifty‐three percent and 35% of macropterous females and males respectively transmitted the virus, whereas in brachypterous females and males the transmission efficiency was 47% and 27% respectively. Of 595 nymphs obtained from the e...

Journal ArticleDOI
TL;DR: Under field conditions, impatiens necrotic spot (INSV) and tomato spotted wilt tospoviruses (TSWV) were detected by the dot blot technique in chrysanthemum (Dendranthema grandiflora Tzvelev cv. Polaris) plants from Villa Guerrero and Coatepec de Harinas, State of Mexico.
Abstract: Under field conditions, impatiens necrotic spot (INSV) and tomato spotted wilt tospoviruses (TSWV) were detected by the dot blot technique in chrysanthemum (Dendranthema grandiflora Tzvelev cv. Polaris) plants having concentric rings and line patterns, from Villa Guerrero and Coatepec de Harinas, State of Mexico. There were 15 species of thrips associated with chrysanthemum in the region, 10 already known and five being described as new species. The known species were: Frankliniella adadusta, F. aurea, F. helianthi, F. inutilis, F. minuta, F. simplex celata, F. occidentalis brunnescens, F. occidentalis dubia, F. occidentalis and Thrips tabaci. From among the aforementioned species, only the last two have been recognized as vectors of tospovirus. Twenty‐six species of weeds were found associated with chrysanthemum, of which, 16 were positive for the TSWV and none for the INSV.

Journal ArticleDOI
TL;DR: Mulching decreased the rate of parasitization by Aleochara bilineata (Staphylinidae), resulting in a higher number ofhealthy pupae per plant in grass‐mulched plots, and these healthy pupae were heavier.
Abstract: The effects of mulching with organic materials on yield and damage by brassica root maggots (Delia floralis and D. radicum) in cauliflower, were studied in field experiments for 3 years. Mulching with grass‐clippings consistently resulted in increased yield and reduced damage by root maggots, as measured by wilting symptoms and root damage. During one of these years, the effects of mulching with grass‐clippings on root fly population dynamics was also studied. Mulching did not reduce egg‐laying but resulted in increased egg‐predation. The number of D. floralis pupae per plant was not reduced by mulching, probably because of higher larval mortality owing to competition in unmulched plots. Mulching decreased the rate of parasitization by Aleochara bilineata (Staphylinidae), resulting in a higher number of healthy pupae per plant in grass‐mulched plots, and these healthy pupae were heavier. All these effects were most pronounced when the mulch material completely covered the ground, even close to th...

Journal ArticleDOI
TL;DR: A low temperature‐captan or benlate combination involving the dipping of harvested potato tubers in 300 ppm captan or Benlate and storing at 10°C proved very effective against the rot incited by the pathogen.
Abstract: Solutions of six fungicides, Benlate, Dithane M 45, Captan, Cupravit, Brestan and Borax, were tested for control of soft rot in potato caused by Rhizopus oryzae. Low temperatures in isolation or in combination with the fungicides as well as storage In open laboratory, farm barn, and well drained soil pits were also separately evaluated against natural infections of the tubers by the fungus. Captan, benlate and cupravit at 400–500 ppm were consistently effective against spore germination, mycelial growth and rot development by the rot‐causing organism. Low temperatures (0–5°C) completely inhibited the spore germination and rot development by the pathogen. A low temperature‐captan or benlate combination involving the dipping of harvested potato tubers in 300 ppm captan or benlate and storing at 10°C proved very effective against the rot incited by the pathogen. Storage of potato in well drained soil pits particularly in open sites significantly reduced natural infection of the tubers by the fungus.

Journal ArticleDOI
TL;DR: The soil pest problems encountered in smallholder farming systems in sub‐Saharan Africa are discussed, including host ranges, interactions and environmental factors affecting the major weed, insect and disease pests in the region.
Abstract: In this, the first of two review papers, we discuss the soil pest problems encountered in smallholder farming systems in sub‐Saharan Africa. Host ranges, interactions and environmental factors affecting the major weed, insect and disease pests in the region are discussed as well as the effects of cultivation practices on pest occurrence.

Journal ArticleDOI
TL;DR: An individual-based, process-oriented simulation model was designed to investigate the effects of Bacillus thuringiensis var.
Abstract: An individual-based, process-oriented simulation model was designed to investigate the effects of Bacillus thuringiensis var. kurstaki (Bt) sprays on populations of spruce budworm. The model shows that the diameter of Bt droplets is the single most important determinant of efficacy. Fine sprays (numerous small droplets) are predicted to cause a considerable amount of larval feeding inhibition and subsequent protection of foliage. Post-spray temperatures are predicted to have an important impact on the level of final mortality. When susceptibility to Bt is assumed to be constant between instars, the model predicts that spraying late (instar V or VI) should kill more larvae and lead to somewhat lower defoliation, compared with spraying early (instar IV). Conversely, when susceptibility is assumed to be proportional to body weight, optimal spray timing in terms of foliage protection and budworm kill occurs during instar IV. Efficacy predictions were highly sensitive to some questionable assumptions regarding the expression of ingested doses of Bt. This underscores the need for more basic research into the mode of action of Bt. Full model validation could not be performed because of insufficient input information from field trials. Nevertheless, two comparisons of predicted and observed efficacy were attempted with more complete spray-trial data sets from Ontario, although in both cases estimates of several important model parameters were lacking. In the first comparison, model predictions were commensurate and consistent with observations. In the second, predicted efficacy grossly underestimated observed efficacy. Model responses to major input parameters and alternatives to critical assumptions are discussed.

Journal ArticleDOI
TL;DR: The characteristic features of these sources of resistance are described, and two genotypes showed high level of resistance to late leaf spot, but were only moderately resistant to rust.
Abstract: A total of 979 germplasm accessions was screened for resistance to rust and late leaf spot in preliminary field trials at ICRISAT Center, Patancheru, India during 1989–1990. Selected genotypes were further evaluated in separate advanced screening trials conducted with erect bunch [Spanish (var. vulgaris) and Valencia (var. fastigiata)], spreading bunch [Virginia bunch (var. hypogaea)], and runner [Virginia runner (var. hypogaea)] types during 1991–1993. Thirty‐eight genotypes (21 erect bunch, 5 spreading bunch, and 12 runner) were identified as resistant to rust, and seven (five erect bunch and two runner) to late leaf spot. Four genotypes (ICG Nos 6843, 10890,11567, and 12112) showed resistance to both rust and late leaf spot; ICG 10881 and ICG 11567 belong to the Spanish bunch group. Two genotypes [BPZ 691 and 259–2 (Red)] showed high level of resistance to late leaf spot, but were only moderately resistant to rust. The characteristic features of these sources of resistance are described, and t...

Journal ArticleDOI
TL;DR: The relationship between planting dates and damage by the legume pod‐borer, Maruca testulalis (Geyer) was investigated in successively planted cowpea during July and August, 1993 and 1994.
Abstract: The relationship between planting dates and damage by the legume pod‐borer, Maruca testulalis (Geyer) was investigated in successively planted cowpea during July and August, 1993 and 1994. The population tended to build up in the course of the sowing periods in both years. The number of flowers and pods infested were more in cowpea planted in August than in July in both years. Grain yield also decreased significantly in late‐planted than in early‐planted cowpea. Planting cowpea within the first and second week of July would reduce damage by the pod‐borer.

Journal ArticleDOI
TL;DR: The challenges of providing recommendations for managing a range of pests in complex cropping systems are identified and objectives for future research into soil pest problems of smallholder farmers are identified.
Abstract: In this, the second of two review papers, we discuss potential management strategies for the soil pest problems encountered by smallholder farmers in sub‐Saharan Africa, and analyse the potential role for IPM in smallholder agriculture. Adopting a farming systems approach is seen as essential, given the resource constraints on smallholders: this ensures that adequate attention is given to both the agronomic and socio‐economic characteristics of different farming systems. The challenges of providing recommendations for managing a range of pests in complex cropping systems are identified together with objectives for future research into soil pest problems of smallholder farmers.

Journal ArticleDOI
TL;DR: Breeding activity of all species was mainly restricted to the grain surface and top grain layers during the months of November and December, although some insects were found at all depths in varying numbers.
Abstract: The distribution of insects in a wheat‐filled large concrete silo was studied by drawing grain samples from the whole vertical depth by means of a special probe. The major insect species found were: Trogoderma granarium (Khapra beetle), Rhyzopertha dominica (Lesser grain borer), and Tribolium castaneum (Red flour beetle). Maximum activity of all species was found on the grain surface although some insects were found at all depths in varying numbers. Breeding activity of major insect pests was detected by incubating grain samples and then counting the number of emerged insects. Maximum emergence of T. granarium and R. dominica was observed in nearly all grain depths in October to November and July to November, respectively. Maximum emergence of T. castaneum was noted in almost all grain depths during August. Breeding activity of all species was mainly restricted to the grain surface and top grain layers during the months of November and December.

Journal ArticleDOI
TL;DR: It is concluded that managing crop residues by placing the old stems horizontally on the ground, exposing them to the sun and heat, is suitable for both commercial and subsistence farmers because of the low input of labour and money.
Abstract: Stubble and old stems of maize and sorghum constitute an important reservoir for infestation of lepidopterous stemborers. Therefore, a number of experiments were conducted to assess the feasibility of managing crop residues in order to reduce aestivating populations within a complex consisting of two pyralids, Chilo partellus and C. orichalcociliellus and one noctuid, Sesamia calamistis. The survival of stemborer larvae and pupae in old stems placed horizontally on the ground was compared with survival in stems left in their vertical position after harvest. In those experiments where the post‐harvest weather was dry and hot, a significantly higher proportion of larvae and pupae died in horizontal stalks compared with stalks left in their vertical position. It is concluded that managing crop residues by placing the old stems horizontally on the ground, exposing them to the sun and heat, is suitable for both commercial and subsistence farmers because of the low input of labour and money.

Journal ArticleDOI
TL;DR: There were significant decreases in the numbers of maggots as drying time increased, suggesting a practical possibility for the protection of dried catfish against maggo...
Abstract: Studies involving a survey of infestation of the African catfish, Clarias gariepinus (dried for 4 days and stored for more than 30 days), obtained from the fish market in Maiduguri, northeastern Nigeria, as well as the direct exposure of freshly caught catfish to three sun‐drying regimes, i.e. 1 day, 7 days and 14 days (stored for further 30 days under laboratory conditions) were carried out over a 5‐month period. Variations in weather conditions during the period were: daytime temperatures, 32–39.9°C; night temperatures, 23.1–27.7°C; and relatively humidity, 40–69%. There was a preponderance of dermestid larvae over adults and calliphorid maggots in fish samples dried for 4 days, 7 days and 14 days. Catfish dried for 1 day harboured significantly higher numbers of maggots compared with the numbers of dermestid larvae and adults. There were significant decreases in the numbers of maggots as drying time increased, suggesting a practical possibility for the protection of dried catfish against maggo...

Journal ArticleDOI
TL;DR: Trapping of medfly in a box thorn hedge of the oasis of Tozeur, Tunisia, indicates that despite this plant being largely neglected by medfly later in the year, it is a principal early‐spring host of the pest.
Abstract: In the Mediterranean region, from November to early June, Mediterranean fruit fly or medfly (Ceratitis capitata Wiedemann) populations decrease drastically and in some places disappear. For area‐wide control or eradication programmes, it is important to know on which wild hosts a medfly population can establish itself and subsequently cause later in the season important losses in commercial crops. Trapping of medfly in a box thorn (Lycium europaeum L.) hedge of the oasis of Tozeur, Tunisia, indicates that despite this plant being largely neglected by medfly later in the year, it is a principal early‐spring host of the pest. Fruit infestation rate in May was c. 292 pupae/kg of fresh fruits and an average of two larvae per infested fruit. The trap capture rate was c. 26 flies/trap/h. The importance of this non‐commercial key‐host in the development and distribution of medfly population during the early season when no other host is available is discussed. The diurnal bimodal flight activity rhythm o...

Journal ArticleDOI
TL;DR: Applying a dose of 13 000 spores per locust to adult Locusta migratoria migratorioides in 10 ppm cypermethrin inhibited feeding by 50% on day 1 after treatment and advanced the onset of locust mortality from the fungus by 48 h.
Abstract: A problem in the use of the fungus Metarhizium flavoviride Gams & Rozsypal to control locusts is that the locust continues eating for the first few days after the fungus has been applied. Applying a dose of 13 000 spores per locust to adult Locusta migratoria migratorioides (Reiche & Fairmaire) in 10 ppm cypermethrin (approximately LC10, even 7 days after dosing) inhibited feeding by 50% on day 1 after treatment and advanced the onset of locust mortality from the fungus by 48 h. A similar inhibition of feeding from the cypermethrin also occurred in combination with doses of fungus as low as 375 spores per locust, but the earlier locust mortality was not then observed. It was also determined that cypermethrin was not toxic to M. flavoviride in in vitro tests.

Journal ArticleDOI
TL;DR: Mild infection of downy mildew increased the fresh weight of the shoot and the number of basal and nodal tillers, but severe and systemic infection reduced all of them, and plant height and test weight were inversely related to the infection.
Abstract: To estimate the loss caused by downy mildew, two separate experiments were conducted on pearl millet cv. HB 3. Mild infection of downy mildew increased the fresh weight of the shoot and the number of basal and nodal tillers, but severe and systemic infection reduced all of them. Dry matter (%) increased with infection. Plant height and test weight were inversely related to the infection. Reduction in grain yield in categories 5, 4, 3 and 2 plants was of the order of 97, 65, 26 and 9% respectively over the category 1 (healthy plants). Based on the incidence level of 62%, the estimated yield loss was 34% over the healthy crop. The yield reduction was 57% when the yield of the unprotected crop was compared with the yield of the protected crop.