We are looking for an organic remedy for thrips. So
far everyone suggests that we get rid of these beautiful
specimens. The trees affected are rhododendrons.
Best way of control (should be started early in the 'game' though) is using biological control by releasing predator mites (Amblyseius) which are beneficial organisms feeding on Western Flower Thrip, Onion Thrip and a few others. The Botanic Gardens in Christchurch are using them for their thrip control. They are available through ZONDA Hastings (they use local outlets such as FruitFed etc) ZONDA's phone is 0-6-878 6010. They need to be released several times. Aluminium foil around the base of plants as a reflective mulch will repel them, but more feasible around crops such as onions, cucumbers etc and not larger tree specimens. Pyrethrum will work as well, but it is still a toxic spray even though it is allowable as an 'organic' spray. Use as a last resort, put an protection closing, washable hat, goggles and face mask.
We have found Neem oil excellent and use it combined with detergent. Just spray on at frequent intervals. We also use it on sheep wool as a temporary lice control. Sorry the recipe is rather haphazard as we are still experimenting. Jan