Effect of Interspecific Competition among Whiteflies (Homoptera: Aleyrodidae) on crops and ornamental plants in Southwestern Nigeria

Whiteflies that are pests of many crops and ornamental plants produce migratory forms during dense populations with different species sharing the same host plant. Fields surveys of these pests were conducted from 8 sampling sites within the five states (Lagos, Oyo, Osun, Ekiti and Ondo states) of Southwestern Nigeria during 2016 and 2019 to investigate the effects of interspecific competition among whiteflies on plants in the region. This survey was carried out in both wet and dry seasons. Whiteflies were collected on crops and ornamental plants in the sampling sites within the mangrove forest, rainforest and the derived savannah zones in the region. Interspecific competition was observed between four species Aleurodicus dispersus , A cocois, Aleurocanthus woglumi and Bemisia tabaci . The species population of whiteflies was analyzed using the Paleontological statistics software package (PAST) and nonparametric t-test was conducted to analyse the sharing of the host surface among species. The results obtained showed that the interspecific competition among species of whiteflies in the region is most during early rain season and yielded less whiteflies infestation and abundance at underside of plant leaves, and as well supported high number of the pest on upper leaf surfaces. The integrative analysis of the consequences of interspecific competition could provide justification for predicting species exclusion resulting into whitefly invasions of upper leaf surfaces as their new ecological niche

Some thermo-physical properties of yam cuts of two geometries

The effects of variation of temperature (-18 to 33°C) and geometries (slab and cylinder) on some thermo-physical properties of white yam were investigated. The measured parameters were density, specific heat, and thermal diffusivity at constant moisture level of 72.7% ± 0.69 (wet basis) using transient heat transfer method. Both the density and specific heat of the sample increased with increase in temperature to maximum levels after which further increase led to a reduction of the values of these parameters; however, they were independent of sample’s geometry. The rate of heat diffusion per second for the yam as measured was between 2.365 to 11.86 x 10-8 m2 and 2.676 to 8.062 x 10-8 m2 for slab and cylinder respectively. The thermal diffusivity and computed thermal conductivity were found to increase with increase in temperature. Conclusively, these thermo-physical properties were correlated with temperature using polynomials of the third order empirical model