An important aspect of fruit fly management is accurate information on the species and their host spectrum. Studies were conducted between October 2011 and September 2013 to determine the host range and species diversity of pest fruit flies in the northern savannah ecology of Ghana. Fruit samples from 80 potential host plants (wild and cultivated) were collected and incubated for fly emergence; 65 (81.5%) of the plant species were positive to fruit flies. From records in Africa, 11 plant species were reported to be new hosts to the African invader fly, Bactrocera invadens (Drew, Tsuruta and White, 2005). This study documented the first records of Dacus ciliatus (Loew) and Trirhithrum nigerrimum (Bezzi) in northern Ghana although both species have been previously reported in other parts of the country. Infestation by B. invadens was higher in the cultivated fruits; Ceratitis cosyra dominated in most wild fruits. Cucurbitaceae were mainly infested by three species of Dacus and Bactroceracucurbitae, a specialized cucurbit feeder. Among the commercial fruit species, the highest infestations were observed in mango, tomato, sweet pepper and watermelon, whereas marula plum, soursop, tropical almond, sycamore fig, African peach, shea nut, persimmon, icacina and albarillo dominated the wild host flora. The widespread availability of host plants and the incidence of diverse fly species in the ecology call for particular attention to their impact on commercial fruits and the development of sustainable management strategies against these economically important pests in Ghana.

The control of stored-product moths in bagged commodities is difficult because the developmental stages of the moths are protected by the bagging material from control measures such as the application of contact insecticides. Studies were carried out to assess the ability of Hymenopteran parasitoids to locate their hosts inside jute bags in the laboratory. The ability of different parasitoids to penetrate jute bags containing rice was investigated in a controlled climate chamber. Few Habrobracon hebetor (Say) (Hymenoptera: Braconidae) passed through the jute material while a high percentage of Lariophagus distinguendus (Förster), Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae), Theocolax elegans (Westwood) (Hymenoptera: Pteromalidae) and Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) were able to enter the Petri-dishes. Significantly more L. distinguendus and T. elegans entered compared to H. hebetor. There was significant difference in the mean percentage parasitoids invading depending on species. Head capsules and/or thorax widths were measured in order to determine whether the opening in the jute material would be large enough for entry of the parasitoids. These morphometric data differed depending on parasitoid species and sex. The parasitoid Venturia canescens (Gravenhorst) (Hymenoptera: Ichneumonidae) did not enter the bags, but located host larvae inside the jute bags and parasitized rice moths Corcyra cephalonica larvae by stinging through the jute material. Venturia canescens significantly reduced the number of C. cephalonica adults emerging from the bagged rice; therefore, it could be released in storage rooms containing bagged rice for biological control of C. cephalonica. The use of parasitoids to suppress stored-product insect pests in bagged commodities could become a valuable supplement to the use of synthetic pesticides.

Adult male Tribolium castaneum (Herbst) secrete an aggregation pheromone that is attractive to both sexes. The responses of T. castaneum to different pheromone concentrations (0.5, 1.0, 2.0, 4.0 and 8.0 mg/septa) were tested in the laboratory. In general, pheromone-baited pitfall and probe traps were over 50% more effective than unbaited traps. A curvilinear relationship between numbers trapped and pheromone concentration indicated that 2.0 mg of pheromone per trap elicited an optimum response. The proportion of marked beetles released in 2.5 m × 0.3 m × 0.4 m trough, filled with wheat and caught by unbaited probe traps, declined with distance from release point, whereas pheromone traps captured a similar proportion up to 2.0 m from the traps. Tracks of T. castaneum responding to different pheromone concentrations in still and moving air in a 2.5 m × 0.4 m olfactometer indicated that the aggregation pheromone stimulated the beetles to walk faster at higher concentrations, to increase the frequency and magnitude of turning and to decrease track reversal distances and distances between turns. The behavioural responses of the beetles to the pheromone in still and moving air were similar, indicating chemotaxis as the major orientation mechanism used by T. castaneum to locate an odour source. The beetles showed greater orientation efficiency within a discrete pheromone plume than a diffuse plume.

The bioactivity of materials from the leaves of Ocimum kilimandscharicum was tested against Sitophilus zeamais Mots chulsky (Coleoptera: Curculionidae), Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) and Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae) in maize and sorghum grains in the laboratory. Exposure of adults of the three insect species to dried ground leaves and essential oil extract of O. kilimandscharicum induced 100% mortality after 48 h. Fresh and dried whole leaves were not toxic to Sitophilus zeamais or R. dominica. Grains treated with dried ground leaves and essential oil extract caused significant reductions in the number of progeny and survival rate of all three pest species tested. There was no adult survival or progeny production in grains treated separately with each of the two materials at doses of 25.0 g (dried ground leaves) and 0.3 g (essential oil) per 250 g of grain, respectively. Unlike R. dominica and Sitotroga cerealella, grains treated with fresh leaves enhanced the feeding activity of Sitophilus zeamais. Ground leaves and the essential oil, however, protected the grains against feeding by all three species, resulting in lower weight loss and number of damaged seeds compared with untreated grains. All the plant materials were repellent to S. zeamais with the essential oil extract applied at 0.3 g/250 g of grain evoking the highest repellent action. There was, however, considerable variation in the repellency of the materials against R. dominica and Sitotroga cerealella. The results are discussed in terms of the efficacy of O. kilimandscharicum for protection against loss due to insects in traditional grain storage in developing countries.

Males of Tribolium castaneum (Herbst), T. confusum (Duval) (Tenebrionidae), Rhyzopertha dominica (Fabricius) and Prostephanus truncatus (Horn) (Bostrichidae) secrete aggregation pheromones attractive to both sexes. Responses of the four species to synthetic aggregation pheromones were investigated in relation to age, habituation, time of day, sex and previous mating experience in an olfactometer in which odour gradients were set up in moving air. Habituation reduced pheromone response in all the species tested but all recovered to pre-habituation levels after 48 h except Tribolium spp. males. Both sexes of T. castaneum and T. confusum were responsive to pheromone immediately upon eclosion, males reaching maximum response after 19 and 21 days and females after 21 and 16 days, respectively. Pheromone response was linearly related to age of the Tribolium spp. and T. castaneum males showed a greater response than the females. Sex or having mated did not affect the responses of T. confusum, P. truncatus and R. dominica. All the pheromones evoked periodicity of response, peaking between 10.00 and 18.00 h.

The abundance and distribution of Ceratitis capitata (Wiedemann) in Late Valencia citrus orchards and other alternative host crops was investigated using trimedlure-baited traps at the University of Ghana's Agricultural Research Centre in the Eastern region of Ghana. The effect of some climatic factors on the population dynamics of the pest was also studied. The population of C. capitata increased from September to October 2006 and from February to March 2007, when Late Valencia citrus fruits were ripening or ripened. The fruit fly population was the lowest from November 2006 to January 2007 when citrus fruits were in the immature green stage. Ceratitis capitata was not trapped in mango, pawpaw and pepper fields and did not emerge from fruits of these crops. Multiple regression analyses also revealed that rainfall and temperature significantly influenced the pest population. The results of this study have important implications on the decision-making process for the safe, effective monitoring and management of C. capitata in Late Valencia citrus orchards in the study area in Ghana and probably in other areas as well.

Cocoa (Theobroma cacao L.) is an important foreign exchange earner for Ghana. However, production is constrained by a high incidence of pests and diseases. Based on farmers' needs, this study focused on the control of capsids, mainly Sahlbergella singularis Haglund and Distantiella theobroma (Distant) (both Hemiptera: Miridae). Annual crop loss caused by capsids is estimated at 25–30%. To control capsids, formal research recommends application of synthetic insecticides four times between August and December. However, farmers hardly adopt this recommendation, which they consider unsuitable for their conditions and context. Three alternative control methods were tested with farmers: mass trapping, using sex pheromones; applying crude aqueous neem Azadirachta indica A. Juss. (Meliaceae) seed extract (ANSE) and using the predatory ant Oecophylla longinoda Latreille (Hymenoptera: Formicidae) as a biological control agent. Contrary to most previous reports, studies on temporal distribution of cocoa capsids indicated that the population peaked in March. ANSE was effective against capsids and other cocoa insect pests and did not affect the predatory ant. When O. longinoda occurred in high numbers, capsid incidence was low. Shade did not influence ant or capsid abundance significantly. ANSE caused 100% mortality of capsids in cage and 79–88% in field experiments. The sex pheromone was as effective as ANSE or ants in suppressing capsids. All the three methods were effective and compatible; hence, they can be used in an integrated pest management strategy for cocoa, including organic production in Ghana.

The sweet potato whitefly Bemisia tabaci (Gennadius) is a pest of diverse agricultural systems worldwide, owing to its capacity to transmit viruses, both intraspecific and host-associated variations. In Ghana, it is the only known arthropod vector for cassava-infecting begomoviruses (Geminiviridae). Two genetic variants of B. tabaci, previously characterized by RAPD–PCR and subsequently reared on cassava and okra, were allowed access to five weed species in order to examine host preference and suitability: Amaranthus retroflexus, Chromolaena odorata, Desmodium tortuosum, Euphorbia heterophylla and Malvastrum coromandelianum. Overall, the duration of the life cycle ranged between 16.5 and 26.3 days and survival rates were 0–27.5%. The population from field-infested okra reproduced and developed to maturity on C. odorata, D. tortuosum and E. heterophylla. Both populations produced male and female progeny. Amaranthus retroflexus and M. coromandelianum were considered poor hosts for both populations, due to the low fecundity and survival of eggs, pupae and adults. The rearing host did not significantly (P>0.05) influence survival on subsequent hosts in either case. The host-restriction of the population collected from cassava was not corroborated here, based on the demonstrated ability of the Ghanaian cassava population to complete its life cycle on D. tortuosum and E. heterophylla. It was estimated that B. tabaci could achieve 13–22 generations per year in Ghana. Removal of C. odorata, D. tortuosum and E. heterophylla from the vicinity of susceptible crops is recommended.