In January 2014, here at the International Moringa Germplasm Collection, we have spider mites.
1. You can see the mites themselves. They are tiny red or black dots, often on the leaf undersides. You can see them as red dots in the photos above.
2. Webbing. They are called spider mites because of the cobweb like webbing they leave all over the leaves and terminal stems.
3. Speckled bleaching of the leaves. Mites are sucking insects and pierce the leaves with their mouthparts. Presumably it is this damage that causes mite infested plants to have speckled light patches all over the leaves (see below).
1. Do nothing. Moringas under spider mite attack usually drop their leaves. No leaves, no mites. By the time the plants leaf out, the mite infestation has passed.
2. Water. Spray your plants regularly and savagely with strong jets of water, making sure to get the undersides of the leaves. This often knocks all of the adult mites and their webbing off of the plants. If you do it often enough, say once every week or two, you can often keep the mites in check enough to give the plants a chance.
4. Repot. Unlike most plants, which seem to do best slightly underpotted (in small pots), moringas seem to do best when slightly overpotted (in relatively large pots). I am not sure why, but in the collection here the most severely infested plants are in the smallest pots. Larger pots seems associated with more vigorous growth and better resistance. Just remember to use a nice open potting mix. I use 75% coarse washed pumice and 25% potting soil of whatever kind I can get, preferably peat based but I haven't found any here.
6. Or go for the poisons. Just make sure you get one that kills mites. Insecticides like imidacloprid, which is a wonderful systemic for moringa thrip infections, can actually make mite infestations worse. By killing off the beneficial insects, like the little mite-eating mantis on my plants below, the mites are freer to proliferate than ever. Fortunately there are plenty of miticides like abamectin, bifenazate, or chlorfenapyr.