All sorts of things can be blamed on this prolonged drought. And here's another one – avocado brown mite. These arachnids love water stressed trees that are covered with dust. You can see them in most orchards along picking rows, most years. The dust covers the leaves and slows and prevents the natural predators of doing their thing. Instead, the predatory mites spend lots of time cleaning their joints so that they can rush around attacking the pest mites. If you see mites running around on avocado leaves, it most likely is a predatory mite or tydeids (tidy mites), the later eat pollen, fungi and other mites. When they are cleaning, they are not eating, and brown mites get out of control.
Brown mites are leaf surface feeders and when their populations get large enough, trees can defoliate. This is especially noticeable late summer, also when persea mites start building their populations. In most years, rain washes off the leaves and along the coast, fog is also important in cleaning the leaves. This water keeps the leaves and predators clean so they can do their thing.
In years when abamectin is sprayed to control persea mite, it's also controlling brown mite. When persea is not a problem and brown mite has gotten out of hand, it may be important to spot treat the orchard with horticultural oil. This is usually along tree rows and those areas that show water stress. If the trees are showing water stress, make sure they are adequately watered before spraying or the oil itself can defoliate the trees.
Avocado Brown Mite
Avocado Brown Mite Damage
Tydeid Mite
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