Postharvest insect pest control for western flower thrips, Frankliniella occidentalis, in exported cut Proteaceae flowers

A seriously limiting factor to the Proteaceae cut flower export industry of South Africa is the presence of entomofauna within export consignments, which leads to rejection of consignments when exporting to strict international markets. This study aimed to assess the efficacy of two potential postharvest pest disinfestation techniques, controlled atmosphere and temperature treatment systems (CATTS) technology, which is a heated controlled atmosphere treatment, and ethyl formate (EF) fumigation treatment. The post-treatment flower quality was evaluated with two Leucadendron cultivars, ‘Safari Sunset’ and ‘Jade Pearl’, as well as with the Chamelaucium cultivar ‘Ofir’. A small and cryptic insect pest, that can be present in high numbers after harvest, is thrips. Both CATTS and EF treatments were assessed for their efficacy against the western flower thrips (WFT), Frankliniella occidentalis. In the CATTS treatments the temperature was increased from 23 to 40°C at 30°C h or 35°C h, under a controlled atmosphere of 1% O2, 15% CO2 in N2. EF fumigation treatments were carried out at room temperature with EF concentrations of 10 or 20 g m for 1 and 2 h. Untreated control and treated flowers were stored at air- and ship-freight simulated conditions, after which flower quality and vase-life were determined. CATTS treatments yielded the best results, as the flower quality and their vase-life matched untreated controls across all commodities and treatments, with no reduction in either of them, following simulated air- or ship-freighting (3 or 21 days, respectively, at 2°C). However, EF treatments resulted in a rapid flower deterioration and unacceptable quality soon after treatment. Both CATTS and EF were highly effective in controlling the WFT mortality, as 100% mortality was achieved across all treatments within 24 h of treatment. The results suggest that for the cultivars tested here, CATTS technology holds a great promise as a postharvest treatment against the WFT, as their flower quality was maintained under treatment conditions that effectively controlled the insect pest.