Many insect repellents are not labeled specifically for use on desert roses. They must be used on a trial-and-error basis on small parts of the plant or applied near (but not on) the plant. Many insecticides also repel future infestations. Does this Spark an idea?
Insecticides
Insecticidal soaps are one of the gentlest insecticides to use on a desert rose. As long as the saponins in the soap remain active (i.e., are not broken down by the sun or washed away), they will deter pests from desert roses. Bacillus thuringiensis (Bt) is a bacteria that kills rose-eating caterpillars. After consuming just a small portion of Bt, caterpillars are deterred from eating more and ultimately die, reports the University of Florida.
No Oils
While oils discourage insect infestation and kill off insect problems, they are not safe to use on desert roses. The fleshy stems of the desert rose cannot abide the oil, which causes burning or suffocation.
Warning
Not all insecticides have been checked for compatibility with desert roses. Those that have are often labeled whether they are safe to use. Desert roses are sensitive to many insecticidal compounds, so one cannot assume that an insecticide is safe to use on a desert rose just because there's no precaution against it, warns the University of Florida Extension Service.
Considerations
One of the best ways to keep insect problems in check is to plant a diverse spread of plants that host beneficial bugs. Desert roses need not be fertilized, as fertilizing can make them more vulnerable to insect attack.
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