Response of the onion pests Thrips tabaci (Lind.) (Insecta: Thysanoptera: Thripidae) and Aspergillus niger (van Tieghem) (Fungi: Hyphomycetes) to controlled atmospheres

The effects on onion thrips (Thrips tabaci) of controlled atmospheres (CAs) containing 15, 30, 45 and 60% carbon dioxide in air were determined by measuring the metabolic heat rates (MHRs) using microcalorimetry and compared with previous conventional trials. Black mould (Aspergillus niger), cultured in several different ways, was exposed to the same CAs with the effects being determined by microcalorimetry and colony-growth measurements. The effect of temperature on the MHR of black mould was measured from 5 to 45 °C. These results show CAs high in carbon dioxide are a promising treatment for the postharvest control of thrips but are ineffective for the control of black mould at ambient temperatures. Temperatures above 35 °C, in combination with CAs, may be an effective treatment for black mould if onions are not damaged by these conditions.