Thursday, December 01, 2011
Back in March when I noticed the spiraling leaves on the pomegranate tree I searched the internet and print sources for information on what might be causing the deformed leaves. I found nothing definitive; also not anybody else wondering about the problem. Said it looks like insect damage, and shelved the question.
A little while passed, the leaves were still spiraling, and I finally found a reference to Aceria granati, the (apparently if this is indeed the culprit) aptly named pomegranate leafroll mite. I meant to post this update but didn't get a round to it.
A fellow pomegranate grower here in So Cal inquired the other day about the twisted leaves, since they too have the same thing on their punica granatum. And so I am given the impetus to post this update on the pomegranate. It still has spiral leaves; about 1/2 of the remaining (some has seasonally dropped) foliage is spiraled. The tree produced few flowers this year and only one fruit; bear in mind this is a p. granatum nana and so doesn't bear a lot of fruits. Still, I will say there was a definite reduction in productivity. My plan is to prune off the affected leaves now before they drop; allow the tree to further defoliate for winter; watch for infestation early spring; and treat with neem or insecticidal soap if there is mite sign. Chemical use against mites often gives a bad result because the pesticide kills off predators that would otherwise feed on the mites; also mites can become resistant to chemicals.
University of California IPM guidelines for spider mites (different but possibly similarly controlled organism) suggests that water stress and dust can set up a plant for mite infestations. So I will probably supplement water the pom in spring and spray off the leaves if there is sign of trouble with aceria granati.