Alkyl-substituted gamma - and delta -lactones as feeding deterrents for aphids

摘要

An effect of alkyl-substituted gamma - and delta -lactones on the settling behaviour of the green peach aphid Myzus persicae was studied. The choice test (the 'half-leaf test') showed that the following lactones had deterrent properties: 5-(1-bromo-2-methylpropyl)-4,4-dimethyl-dihydrofuran-2-one, 5-bromo-6-isopropyl-4,4-dimethyl-tetrahydro-2H-piran-2-one, 5-(1-iodo-3,3-dimethylbutyl)-4,4-dimethyl-dihydrofuran-2-one, and 5-(3,3-dimethylbutylidene)-4,4-dimethyl-dihydrofuran-2-one. The last one had the most durable effects: the number of aphids settled on the treated half of the leaf remained reduced until the end of the experiment, i.e. 24 h after application. The other three named lactones lost their deterrent properties after 1-2 h. The aphid behaviour during settling was affected mainly by 5-(3,3-dimethyl-butylidene)-4,4-dimethyl-dihydrofuran-2-one. Although the total time of probing was not affected, the probes on the treated leaves were nearly twice as short as the probes on the control leaves and lasted less than 4 minutes. It may be assumed that the deterrent effect was active within leaf epidermis and/or mesophyll. The reduction of penetration time may appear important in the case of non-persistent virus transmission by the aphids..