Effect of seed collection times and pretreatment methods on germination of Terminalia sericea Burch. ex DC

A nursery experiment was conducted to study the effects of seed collection times and pretreatment methods on the germination of Terminalia sericea Burch. ex DC. (Combretaceae). T. sericea is amultipurpose tree species occurring in the miombo woodlands whose seedling production is hampered by very low seed germination rate. Seeds were subjected to four treatment methods each at fourdifferent duration of exposure; soaking in hot water, immersion in concentrated sulphuric acid (95%), nicking and soaking in cold water and fire scorching. First collection was done when 60% of the fruitswere deep-green to brown while second collection was done when all fruits were purple-brown to pinkpurple. Nicking and soaking in cold water for 12 h gave the highest cumulative germination percentage(51%) for the first collection and appears to be the most feasible and suitable pretreatment method for small scale farmers than use of sulphuric acid. Soaking in hot water for 15 and 20 min and immersion inconcentrated sulphuric acid (95%) for 3 and 4 h gave poorest germination (0%). However, in the second collection, use of concentrated sulphuric acid for 2 h gave highest germination (14%) followed by nicking and soaking in cold water for 24 h (12%). Sulphuric acid is expensive, requires proper handling techniques; therefore nicking and soaking in cold water for 12 h is being recommended as a cheaper and less hazardous pretreatment method to improve germination in T. sericea

Population dynamics of Thaumastocoris peregrinus in Eucalyptus plantations of South Africa

Thaumastocoris peregrinus is a sap-sucking insect that infests non-native Eucalyptus plantations in Africa, New Zealand, South America and parts of Southern Europe, in addition to street trees in parts of its native range of Australia. In South Africa, pronounced fluctuations in the population densities have been observed. To characterise spatiotemporal variability in T. peregrinus abundance and the factors that might influence it, we monitored adult population densities at six sites in the main eucalypt growing regions of South Africa. At each site, twenty yellow sticky traps were monitored weekly for 30 months, together with climatic data. We also characterised the influence of temperature on growth and survival experimentally and used this to model how temperature may influence population dynamics. T. peregrinus was present throughout the year at all sites, with annual site-specific peaks in abundance. Peaks occurred during autumn (February–April) for the Pretoria site, summer (November–January) for the Zululand site and spring (August–October) for the Tzaneen, Sabie and Piet Retief monitoring sites. Temperature (both experimental and field-collected), humidity and rainfall were mostly weakly, or not at all, associated with population fluctuations. It is clear that a complex interaction of these and other factors (e.g. host quality) influence population fluctuations in an annual, site specific cycle. The results obtained not only provide insights into the biology of T. peregrinus, but will also be important for future planning of monitoring and control programs using semiochemicals, chemical insecticides or biological control agents