Like many landscapes here in Hawaii, my home has a Chinese red hibiscus hedge (Hibiscus rosa-sinensis). And, like many such hedges, mine is infected by a little mite, aptly called the “leaf-crunching mite,” a.k.a., the Hibiscus Erineum Mite, a.k.a., A. hibisci (for those of you who prefer the latin-based names). The only name it doesn’t have yet, (that I’m aware of), is a Hawaiian name, and that’s only because it hasn’t been here very long.
A. hibisci didn’t attract official notice until 1989, or 21 years ago, in Oahu (where most bugs, like most tourists, tend to land first). But this little guy made itself at home quickly, and is now spread throughout all the islands and, as far as I can tell, all the Hibiscus hedges–at least, the ones with red flowers.
You can tell if you have A. hibisci, by the combination of deformed bumpiness that it inflicts on stems, leaves, twigs, and flowers. There may be galls on the insides of unopened flowers, and you will also see “corky” tissue on the stems. If damage is strong, leaves will drop, and then other pests will move in as well. The mites themselves are so tiny that it takes a microscope to see them clearly. The other bugs you may find on the galls that are clearly visible are only opportunistic tenants.
My horticultural friends, Derrick and Arlene Salomon, suggested that I treat the hedge with compost. Their argument is that healthy, well-fed plants will resist the pests, or at least most of them, and they pointed out that the soil around my house had probably not been “fed” with compost and mulch for the last five years (and, indeed, the gardener had been spraying pesticides and using chemical fertilizers, to which hibiscus plants are especially sensitive). Sure enough, after I paid for a small truckload or organic compost and spread it around the base of the plants, the hedge responded enthusiastically. Now, two years later, it’s looking like a teen with a bad case of acne, and I know it’s time to feed it again (with organic compost).
Interestingly, every plant on my property that I fed with compost became less pest-infested–whether the problem was white fly, mites, or sooty mold from aphids. This underscores the importance of keeping the micro-organisms happy (they are the ones who really feed the plants), and it shows that natural, organic methods can work, with fairly long-lasting effects. Now that I’ve seen how well the hedges (even red ones) can respond when properly fed, I’ll switch to an annual feeding. We may never be rid of the mites, but perhaps we can live in greater harmony.
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