The distribution and abundance of the stem-galling fly, Cecidochares connexa (Macquart)(Diptera: Tephritidae), a biological control agent of Chromolaena odorata (L.)(Asteraceae), in Ghana

Chromolaena or Siam weed is one of the worst invasive weeds in West Africa and a serious threat to food security. The stem-galling fly was released in the Ivory Coast in 2003 and first detected in Ghana in 2014. Its distribution and abundance in Ghana was determined by country-wide surveys in 2015 and 2016. Galls were found at varying densities across Ghana and also in Togo in low numbers. The gall fly has dispersed about 1000 km in ten years and, while there is some evidence that the gall fly is still moving eastwards, its range and densities could be limited by the dry climatic conditions. Actively redistributing the agent over this dry corridor to the more humid and higher rainfall areas of Nigeria, may result in its spread through the rest of West and Central Africa, thereby aiding the control of chromolaena in the region

Substrates most preferred for black soldier fly Hermetia illucens (L.) oviposition are not the most suitable for their larval development

Larvae of black soldier fly (BSF), Hermetia illucens (L.1758) (Diptera: Stratiomyidae), are increasingly being used as animal feed ingredients. Larvae are usually produced by placing eggs, obtained from adult rearing on growing substrates but can also be obtained by exposing substrates to naturally occurring BSF females. In the latter system, the substrate needs not only to be nutritious for the larvae but also attractive to the females for oviposition. The ‘preference-performance principle’ suggests that female insects prefer to oviposit in substrates that maximise offspring fitness. In this study conducted in Ghana, six organic substrates known to be suitable for BSF production were evaluated for their suitability as oviposition attractants and larval development: pito mash (waste from a locally brewed sorghum drink), millet porridge mash, pig manure, chicken manure, fruit waste, and waste from roots and tubers. These were first exposed outdoors to measure the quantity of eggs laid on them by naturally occurring BSF females. In a second experiment, the quality of the substrates as larval rearing media was tested by placing a standard amount of young larvae to measure the individual and total weights of prepupae obtained, their number, and their development time. The nutritional profiles of both the prepupae and the substrates were determined. The substrate used significantly influenced the quantity of eggs laid and the development of the resulting prepupae, but the substrates most favourable for larval development were not the most favoured by gravid BSF for oviposition. In the oviposition tests, millet porridge mash was the most attractive substrate, whereas only a few eggs were recovered from the other substrates. All substrates allowed the successful development of larvae but pig manure was more productive than the others