The tropical biodiversity greenhouse has had a year to settle down now and the plant growth has been amazing. Species that had never grown more than a metre or two high are now double their previous size and several have hit the greenhouse roof. We use no fertilizers and no pesticides but try to manage the greenhouse as an ecosystem. Last summer we spent hours mixing compost, loam, grit and Seramis to generate a light water retentive, well aerated and nutrient rich soil. Leaves are allowed to fall and get broken down and an occasional top dressing of stable manure on the more nutrient demanding species has meant the soil has an active fauna of earthworms, beetles and woodlice.
One of the challenges of a managed ecosystem is to prevent pest species getting out of hand. Biological control of spider mites and aphids has worked well this year but our introduction of parasitic wasps to control the mealybug appeared not to have been very successful. Two weeks ago we were provided with a tube of Cryptolaemus montrouzieri beetles by Certis who are collaborating with colleagues Jason Sumner, Jess Guy and Alejandra Perotti in research on biological control of spider mites.
Last week we spotted numerous Cryptolaemus larvae about 4-6mm long feeding on the mealybug masses. The larvae are of similar colour to the mealybugs but much more lively and with longer and coarser projections from the body – they look like tiny albino rastafarian woodlice at first glance. This week they have grown to ca 7-8mm long and the number of mealy bugs is visibly decreasing.