Pyrethrins Protect Pyrethrum Leaves Against Attack by Western Flower Thrips, Frankliniella occidentalis

Pyrethrins are active ingredients extracted from pyrethrum flowers (Tanacetum cinerariifolium), and are the most widely used botanical insecticide. However, several thrips species are commonly found on pyrethrum flowers in the field, and are the dominant insects found inside the flowers. Up to 80 % of western flower thrips (WFT, Frankliniella occidentalis) adults died within 3 days of initiating feeding on leaves of pyrethrum, leading us to evaluate the role of pyrethrins in the defense of pyrethrum leaves against WFT. The effects of pyrethrins on WFT survival, feeding behavior, and reproduction were measured both in vitro and in planta (infiltrated leaves). The lethal concentration value (LC50) for pyrethrins against WFT adults was 12.9 mg/ml, and pyrethrins at 0.1 % (w/v) and 1 % (w/v) had significantly negative effects on feeding, embryo development, and oviposition. About 20-70 % of WFT were killed within 2 days when they were fed chrysanthemum leaves containing 0.01-1 % pyrethrins. Chrysanthemum leaves containing 0.1 % or 1 % pyrethrins were significantly deterrent to WFT. In a no-choice assay, the reproduction of WFT was reduced significantly when the insects were fed leaves containing 0.1 % pyrethrins, and no eggs were found in leaves containing 1 % pyrethrins. Our results suggest that the natural concentrations of pyrethrins in the leaves may be responsible for the observed high mortality of WFT on pyrethrum

Evaluation of ethanedinitrile (EDN) as a methyl bromide alternative for eradication of European House Borer (EHB)

European House Borer (EHB) Hylotrupes bajulus Linnaeus, is considered a serious invasive threat because it is a destructive pest of seasoned coniferous timber including pine, fir and spruce. If allowed to become established it can cause major structural damage to buildings. The pest is able to live in a variety of climatic conditions however it prefers temperate habitats. Methyl bromide is widely used for quarantine treatment but it is being phased out due to its listing as an ozone depleting substance. Furthermore, complete control of EHB with methyl bromide in timber at low temperatures and high moisture content is difficult. Currently, there are no known chemical or biological controls for EHB larvae in timber and wood packaging and the obvious way to reduce the quarantine threat posed by EHB is to develop reliable and effective means to disinfest wooden materials at the source. There is an urgent requirement for an alternative effective fumigant for the control of EHB larva in timber and wood. Ethanedinitrile (EDN) is a new fumigant (patented under the chemical name “cyanogen”) and it is known to be highly toxic to insect pests of timber and is fast acting. It is believed to have particular potential as a quarantine treatment for timber. EHB larvae of differing lengths were found to have varying tolerance to both EDN and methyl bromide with the larger EHB found to be more tolerant. In all experimental fumigations with larvae of a range of lengths and at varying exposure times (6 and 24 hours), EDN showed more toxicity than methyl bromide. EDN achieved 100% mortality at 40 mg/L, 25°C and 70% r.h. for 24 hours of exposure with timber blocks artificially infested with EHB. However, under the same experimental conditions, methyl bromide at 48 mg/L only achieved a mortality range of 97.3-100%