First record of a specialist folivore of Chromolaena odorata (Asteraceae) in Togo, and indices of its range expansion in Nigeria: implications for biological control

ABSTRACTPareuchaetes pseudoinsulata is reported for the first time in Togo and widespread in south-western Nigeria, albeit in low densities and difficult to detect. Country-wide surveys are warranted in both countries, with the intention of renewing efforts in the biological control of Chromolaena odorata in western Africa, where the socio-ecological impact of the weed is significant

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

Host stage preference and performance of Dolichogenidea gelechiidivoris (Hymenoptera: Braconidae), a candidate for classical biological control of Tuta absoluta in Africa

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is native to South America but has invaded the Afro-Eurasian supercontinent where it is currently the most devastating invasive arthropod pest of tomato. As a part of the first classical biological control programme against T. absoluta in Africa, a larval parasitoid, Dolichogenidea gelechiidivoris Marsh. (Syn.: Apanteles gelechiidivoris Marsh) (Hymenoptera: Braconidae), of T. absoluta was imported from Peru into the quarantine facility of the International Centre of Insect Physiology and Ecology, Kenya. We report on the host larval preference of D. gelechiidivoris and the host suitability, and the parasitoid’s reproductive strategy, including lifetime fecundity and egg maturation dynamics. Dolichogenidea gelechiidivoris females preferentially oviposited in early (1st and 2nd) larval instars of T. absoluta but parasitized and completed development in all four instars of the host. Host instar did not affect D. gelechiidivoris sex-ratio but females reared on the first instar had significantly fewer eggs than when reared in late larval instars (3rd and 4th). Females of the parasitoid emerged with a high mature egg load which peaked 2 d post eclosion. The females of D. gelechiidivoris survived 8.51 ± 0.65 d and produced 103 ± 8 offspring per female at 26 ± 4 °C (range: 24 to 29 °C) and 50–70% relative humidity (RH) with males present and fed honey-water (80% honey). Increasing maternal age decreased the proportion of female offspring. Under the aforementioned laboratory conditions, the Gross and Net reproductive rates were 72 and 39.5 respectively, while the mean generation time was 20 d. The potential intrinsic rate of natural increase was 0.18. This study shows that D. gelechiidivoris is a potential biological control agent of T. absoluta and should be considered for release in Kenya and across Africa following host specificity testing and risk assessments