Try not use these spray solutions in winter, when plants are dormant. If you must, however (and it is best to deal with mealies as soon as they are discovered), be sure to keep the plants in a fairly warm place until they dry out.
If you are confronting root mealies, be sure to thoroughly clean the roots, removing infested areas. Discard the soil, and sterilise or discard the container. Standing the roots in insecticidal soap is also helpful, but be sure to rinse them well afterward, and always re-pot in fresh soil.
If the more Environmentally Correct treatments fail, commercial insecticides are necessary. Any of these products should contain a surfactant (wetting agent), which will allow the chemical to penetrate protective honeydew. One grower recommends submerging the pots of infected plants in a solution of water and the powder form of Orthene for 15 minutes. Upper portions of the plants should be sprayed with this solution. Repeat the treatment two more times, at 10-day intervals. Diazinon drenches can also be effective against mealy bugs.
The most fascinating commercial solutions I have come across were in two Roger Brown articles in the newsletter of the Cactus and Succulent Society of America. The first product Mr. Brown discusses is Beuveria bassiana, which contains fungal spores in a spray suspension. This fungus attacks bugs by eating through their skin, then consuming their internal organs. This seems like a wickedly effective solution, and particularly gratifying if you are angry at mealy bugs. The specific products he mentions are Botanigard by Mycotech Corporation, and Naturalis-O by Troy biosciences.
Mr. Brown also mentions another Mycotech product called Cinnamite, which is, yes, cinnamon-based. This product may also be effective as a fungicide. More information can be found at http://www.mycotech.com/horticulture
SCALE
Several types of these sap-sucking insects are a concern, and all are quite prolific. The most common are the oval brown soft scale, which can be all brown, or yellowish with brown spots. Boisduval armoured scale, which are circular and yellow, are also fairly common. They cause wilting, and excrete honeydew. Hand removal is effective against mature scale, because once they are removed they are unable to reattach and so starve. A systemic insecticide applied once a week for a month is effective, as are Orthene, Diazinon, and Schulz.
| Here's the follow-up discussion on this article: | View all related messages |
For a complete listing of article comments, questions, and other discussions related to Leigh SumnerKirk's Cacti & Succulents topic, please visit the Discussions page.