The olfactory response of the parasitoid Aphidius colemani (Viereck) (Hymenoptera: Braconidae) to odours in a tritrophic system involving three cultivars of common cabbage, Brassica oleracea var capitata, characterized by different levels of susceptibility to Myzus persicae (Sulzer) (Hemiptera: Aphididae) was studied in a four-way olfactometer. Odours influenced A. colemani response in the olfactometer to varying degrees. The magnitude of parasitoid response to odours of uninfested cabbage depended on cultivar, with Derby Day [green-leaved, susceptible to M. persicae and the crucifer specialist, Brevicoryne brassicae (Linnaeus) (Hemiptera: Aphididae)] and Minicole (green-leaved, partially resistant with known antibiosis factors for B. brassicae) preferred over Ruby Ball (red-leaved with antixenosis factors for M. persicae and B. brassicae). The odour of the cabbage cultivar on which the parasitoid had been reared was preferred over the other cultivars. However, when provided with a choice between odours of infested plants, parasitoids did not show a significant preference for the cultivar on which they were reared. Results from the study show that parasitioids differentiated between odour of the three cultivars in dependence of their rearing history when the plant is uninfested.

The influence of cultivars of common cabbage, Brassica oleracea var. capitata with varying levels of resistance to Brevicoryne brassicae (L.) and Myzus persicae (Sulzer) on key biological characteristics of Aphidius colemani (Viereck) was investigated under laboratory conditions. The total development time for female parasitoids reared on M. persicae did not differ significantly between Minicole (green-leaved, partially resistant with antibiosis factors for B. brassicae) and Derby Day (green-leaved, susceptible to both aphid species); but development was significantly faster (ca 10%) on Ruby Ball (red-leaved, partially resistant with antixenosis factors for B. brassicae). Total development time for females reared on B. brassicae was slightly shorter on Ruby Ball than on Minicole. Males reared on M. persicae developed into adults significantly faster (ca 10%) on Ruby Ball than on Minicole. However, when B. brassicae was the host, no significant variations in development time were observed. Sex ratios, size and longevity of both male and female parasitoids on either host were not significantly influenced by cultivar. The results are discussed in relation to the compatible utilisation of host-plant resistance and biological control in the integrated management of aphids.

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A survey was conducted in Tororo, Bugiri and Kapchorwa districts in eastern and northeastern Uganda on farmers' perceptions of constraints in maize production. Farmers in Tororo and Bugiri consistently ranked stemborers and striga as the major production constraints in maize growing, while those in Kapchorwa ranked stemborers and lack of capital as the most important. Approximately 35 and 40% of the farmers in Tororo and Bugiri, respectively, identified stemborers as the 'caterpillar' that destroys their maize. In Kapchorwa, 50% of the farmers identified stemborers. Pesticide application was the most common control measure while the use of indigenous and cultural control measures was limited. Less than 50% of the farmers were aware of the existence of alternative plants/grasses on which stemborers feed. This study identified the need for creating farmers' awareness on the biology and ecology of stemborers. Empowering farmers by letting them learn and experiment will facilitate the development of innovative control measures.Résumé. Une enquête a été conduite dans les districts de Tororo, Bugiri et Kapchorwa dans l'est et le nord est de l'Ouganda afin d'évaluer la perception qu'ont les fermiers des principales contraintes de production du maïs. Les fermiers des districts de Tororo et Bugiri considèrent les foreurs et le striga comme les contraintes majeures de production du maïs alors que ceux de Kapchorwa considèrent que les foreurs et le manque d'argent sont plus importants. Environ 35 et 40% des fermiers de Tororo et Bugiri respectivement ont établit le lien entre les foreurs et les chenilles qui attaquent leur maïs; à Kapchorwa ils sont près de 50%. La pulvérisation d'insecticide est la méthode de contrôle la plus communément utilisée alors que les méthodes culturales et traditionnelles sont peu appliquées. Moins de 50% des fermiers connaissent l'existence de plantes alternatives sur lesquelles se nourrissent les foreurs. Cette étude a permis de souligner le besoin d'informer les fermiers sur la biologie et l'écologie des foreurs. Donner la possibilité aux fermiers d'apprendre et de tester par euxmêmes devrait faciliter le développement de mesures de contrôles novatrices.