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Sample frame selection and representativeness 7 Profile of districts selected for the survey Vill... more Sample frame selection and representativeness 7 Profile of districts selected for the survey Village selection and methods FOCUSOFTHESTUDY RESULTS AND DISCUSSION 10 Role of Crop Production in Household Food Security Strategies 10 Farmers' Perceptions of the Importance of Maize and Cassava 11 Influence of P. truncatus on Production, Storage and Marketing Outcomes 11 Context Production levels Role of P. truncatus in maize and cassava Harvests Role of P. truncatus in the choice of maize and cassava varieties 13 Role of P. truncatus in duration of storage And volume of sales at farm level
The biological characteristics of adult Prostephanus truncatus (Horn)(Coleoptera: Bostrichidae), ... more The biological characteristics of adult Prostephanus truncatus (Horn)(Coleoptera: Bostrichidae), arriving at pheromone-baited flight traps, were investigated in Ghana in agricultural and non-agricultural habitats of two different agro-climatic zones in three contrasting seasons. This was done to determine whether the risk posed to stored maize by dispersing P. truncatus was likely to vary according to season or the source of beetles. Beetles were trapped live and a record made of sex ratio, weight, longevity and female reproductive potential. Comparisons were made with beetles cultured in the laboratory on maize. Some of the beetles trapped in the wild lived for almost a year, and females continued reproducing for over half a year in the absence of males. This suggests that most beetles were captured very young, that females were already inseminated and that these beetles would certainly live long enough in the wild to have a serious impact in stores. The traps captured a higher pro...
Crop Post-Harvest: Science and Technology, Volume 1
Agricultural and Forest Entomology, 2003
1 Attack by Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) on the maize and cassava sto... more 1 Attack by Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) on the maize and cassava stored by smallholder farmers in Africa is sporadic, varying considerably within and between years. The risk that food in store will become infested is related to the number of beetles dispersing by flight. A means of predicting years with high dispersal rates is needed to warn farmers when to be vigilant. 2 The relationship between climatic variables and pheromone trap catches was observed in a forest-savannah transition zone in Ghana. These observations were used to devise a model using a mix of biological and empirical rules that operate on temperature and humidity data. The predicted and actual trap catch deviated by only þ5% to À1% in years when there were high dispersal rates. 3 The first part of the model estimates the numbers of beetles with potential for dispersal. The second part predicts the proportion likely to disperse. This is based on the apparent effect that those P. truncatus developing under low temperature conditions (about 24 C) have a lowered propensity for flight, a response previously observed in a related species. 4 The model was validated using climate data and trap catches from a woodlandsavannah zone and a short grass steppe zone. With minor adjustment, the model worked well for these two habitats.
Journal of chemical ecology, 2003
Male Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) release an aggregation pheromone consis... more Male Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) release an aggregation pheromone consisting of a blend of two components, dominicalure 1 (D1) and Dominicalure 2 (D2). Pheromone from single insects, in different contexts, was collected and measured to determine if this signal is phenotypically plastic. Release rates were lowered when males were moved from maize grains to groundnut kernels or when moved from solitary occupation of maize grain to grain occupied by seven females. The pheromone release was increased again once these moves were reversed. The release of D1 was more affected than D2: thus, on groundnuts or in the presence of females, less pheromone was released and the proportion of D1 in the blend was lowered. Possible reasons for the modifications of the signal are discussed.
Journal of chemical ecology, 2002
Intermale variation in pheromone signaling has been confirmed and quantified by measurements of p... more Intermale variation in pheromone signaling has been confirmed and quantified by measurements of pheromone produced by single adult male Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae). Males varied in both the amounts of the two components of their aggregation pheromone and the ratio of one component to the other. The mean rates of production of the pheromone components T1 and T2 were 1.9 and 0.5 microg/day, respectively. There were repeatable differences among males in the amounts of T2 produced and the proportion of T1 in the pheromone blend over two weeks. Of the 15 males studied, one released a large burst of pheromone in a short period, while the remainder, if they did release, did so over an extended period. This suggested that there may be two alternative release strategies and the significance of this is discussed.
Sample frame selection and representativeness 7 Profile of districts selected for the survey Vill... more Sample frame selection and representativeness 7 Profile of districts selected for the survey Village selection and methods FOCUSOFTHESTUDY RESULTS AND DISCUSSION 10 Role of Crop Production in Household Food Security Strategies 10 Farmers' Perceptions of the Importance of Maize and Cassava 11 Influence of P. truncatus on Production, Storage and Marketing Outcomes 11 Context Production levels Role of P. truncatus in maize and cassava Harvests Role of P. truncatus in the choice of maize and cassava varieties 13 Role of P. truncatus in duration of storage And volume of sales at farm level
The biological characteristics of adult Prostephanus truncatus (Horn)(Coleoptera: Bostrichidae), ... more The biological characteristics of adult Prostephanus truncatus (Horn)(Coleoptera: Bostrichidae), arriving at pheromone-baited flight traps, were investigated in Ghana in agricultural and non-agricultural habitats of two different agro-climatic zones in three contrasting seasons. This was done to determine whether the risk posed to stored maize by dispersing P. truncatus was likely to vary according to season or the source of beetles. Beetles were trapped live and a record made of sex ratio, weight, longevity and female reproductive potential. Comparisons were made with beetles cultured in the laboratory on maize. Some of the beetles trapped in the wild lived for almost a year, and females continued reproducing for over half a year in the absence of males. This suggests that most beetles were captured very young, that females were already inseminated and that these beetles would certainly live long enough in the wild to have a serious impact in stores. The traps captured a higher pro...
Crop Post-Harvest: Science and Technology, Volume 1
Agricultural and Forest Entomology, 2003
1 Attack by Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) on the maize and cassava sto... more 1 Attack by Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) on the maize and cassava stored by smallholder farmers in Africa is sporadic, varying considerably within and between years. The risk that food in store will become infested is related to the number of beetles dispersing by flight. A means of predicting years with high dispersal rates is needed to warn farmers when to be vigilant. 2 The relationship between climatic variables and pheromone trap catches was observed in a forest-savannah transition zone in Ghana. These observations were used to devise a model using a mix of biological and empirical rules that operate on temperature and humidity data. The predicted and actual trap catch deviated by only þ5% to À1% in years when there were high dispersal rates. 3 The first part of the model estimates the numbers of beetles with potential for dispersal. The second part predicts the proportion likely to disperse. This is based on the apparent effect that those P. truncatus developing under low temperature conditions (about 24 C) have a lowered propensity for flight, a response previously observed in a related species. 4 The model was validated using climate data and trap catches from a woodlandsavannah zone and a short grass steppe zone. With minor adjustment, the model worked well for these two habitats.
Journal of chemical ecology, 2003
Male Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) release an aggregation pheromone consis... more Male Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) release an aggregation pheromone consisting of a blend of two components, dominicalure 1 (D1) and Dominicalure 2 (D2). Pheromone from single insects, in different contexts, was collected and measured to determine if this signal is phenotypically plastic. Release rates were lowered when males were moved from maize grains to groundnut kernels or when moved from solitary occupation of maize grain to grain occupied by seven females. The pheromone release was increased again once these moves were reversed. The release of D1 was more affected than D2: thus, on groundnuts or in the presence of females, less pheromone was released and the proportion of D1 in the blend was lowered. Possible reasons for the modifications of the signal are discussed.
Journal of chemical ecology, 2002
Intermale variation in pheromone signaling has been confirmed and quantified by measurements of p... more Intermale variation in pheromone signaling has been confirmed and quantified by measurements of pheromone produced by single adult male Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae). Males varied in both the amounts of the two components of their aggregation pheromone and the ratio of one component to the other. The mean rates of production of the pheromone components T1 and T2 were 1.9 and 0.5 microg/day, respectively. There were repeatable differences among males in the amounts of T2 produced and the proportion of T1 in the pheromone blend over two weeks. Of the 15 males studied, one released a large burst of pheromone in a short period, while the remainder, if they did release, did so over an extended period. This suggested that there may be two alternative release strategies and the significance of this is discussed.