Preventing Lewis mite damage in poinsettias

2016 turned out to be a bad year for Lewis mite (Eotetranychus lewisi) in poinsettia. Although it’s too early to say how 2017 is going to go, you should be considering possible preventative measures This week for Lewis mite, especially if you have a history of Lewis mite with your cuttings. Treatment of this pest is more difficult later in the crop (though not impossible). Keep reading for biological and chemical control options for this pest.

Left: A new left just showing the characteristic stippling and chlorosis from Lewis mite feeding. Right: Older leaves showing heaving Lewis mite damage. Photos courtesy of Judy Colley, Plant Products.

Lewis mite, a species of spider mite, are exclusively a pest of poinsettia crops in the greenhouse (unless you’re also growing papaya or citrus in there.) Early detection is difficult, since the symptoms are rather subtle at first: faint speckling and chlorosis (see picture below), which can resemble nitrogen deficiency. Additionally, the mite is almost impossible to see without a microscope.

Often, Lewis mite populations go undetected until October, when populations build up enough to start causing noticeable damage: the upper foliage will turn brown and the mites will form unsightly webbing. (Although last year we saw damage as early as Aug/Sept).

Given that they are difficult to detect, but end up causing a lot of damage, a preventive strategy is the easiest solution. However, WHICH preventative strategy you pick is up to you. As with many pests, there are many possible solutions, each with their pros and cons.

Click here to see the proposed options to prevent damage in poinsettias on onfloriculture.com