Chilli Thrips (Scirtothrips dorsalis) defeated by oils and soaps
I'm happy to report that I've been able to suspend the use of strong insecticides to combat chilli thrips, in favor of horticultural oils and insecticidal soap.
When chilli thrips initially infested my roses and other plants, it felt like an impossible problem. But I've found that consistent (weekly) use of either insecticidal soap or insecticidal oil that works through a physical mechanism (vegetable oils or horticultural mineral oils) is more than sufficient to eliminate the threat if started early in the season, and aggressively at the first sign of problems. Only the new growth and the base of the plant need to be sprayed, greatly reducing the workload and volume of spray needed. The undersides of leaves must be contacted by the spray, but this is relatively easy with the small leaves of new growth. Maintenance can drop the frequency to once every two weeks.
I spray either at night after the leaves have cooled or early in the morning. The base of the plant is sprayed to kill overwintering or otherwise maturing pupae - this is not strictly necessary.
Though multiple other low risk insecticides have proven extremely effective (spinosad and ivermectin), chili thrips are analogous to mites in their ability to quickly develop resistance to insecticides. Imidacloprid and neonicotinoids have well publicized issues, and are simply non-starters for me if there's any alternative. I think we should encourage even the use of low-risk insecticides only as a last resort. Obviously the practicality of using oils and soaps varies according to each person's situation, and this is not meant to be a moral judgement - just empowering information.
This post was edited by greentiger87 on Sat, Aug 17, 13 at 10:41