Mighty Mites Protect Sun Valley's Rosehip Crop

In part two of our "Robin Goes to Willow Creek" series, we hear about the mighty mites that protect our rosehip crop.

Our Willow Creek farm is home to one of my favorite crops: rosehips. When I visited two weeks ago, I was overwhelmed by the beauty of the flowering roses and the smell of roses in the wind. But I’m not the only one who favors these plants. Spider mites, tiny crawlies measuring less than a millimeter in size love making their homes on the leaves of these plants. A female spider mite can lay upwards of 20 eggs in a day which will hatch in around three days and begin laying eggs of their own in about five. These mites feed voraciously on the leaves of whose undersides they occupy and can cause big trouble for those who choose to grow plants they favor.

You can almost smell these beauties.

One surprising way to combat these spider mites is with more mites! And that is just what we are doing at our Willow Creek Farm. Last week I got the layman’s rundown on the predatory mites we are using to keep those pesky spider mites at bay. This year we are employing the help of two types of mites; neoseiulus californicus and phytoseiulus persimilis. Like the mites on which they prey, these mites are small in size but big in reproduction!

Our Willow Creek farm is a great place to be a on a sunny day.

The neoseiulus californiucs, as you may have guessed from its name, is native to this area and will lay between two and four eggs a day during its twenty-day lifespan, or 40 to 60 eggs in total. Fortunately for this mite and for us, their development is accelerated when the two spotted spider mites are regularly on the menu. These mites will reach adult stage about three times as fast as the spider mite which means they can consume them faster than the spider mite can reproduce, making them a perfect predator to keep our roses happy long enough to form the gorgeous rosehips we’ve been producing year after year. Another plus of this type of predatory mite being native is that it can survive our winters and will make a comfortable home for itself in the cracks of branches and proliferate the following year.

Unlike the neoseiulus, the phytoseiulus persimilis is not native to this area so it won’t hang around with us through the winter. These guys earn their keep by eating seven spider mites or up two twenty eggs per day and living on average 30 to 36 days. This gives them more than ten days more than our native neoseiulus to feed on those pesky spider mites. Their prolonged healthy appetites help keep our rosehips happy which keeps us happy, too!

Leaf inspection

Before leaving Willow Creek, I recruited team leader Vicente, to help me inspect the undersides of the rosehips for the eggs of the predatory mites that had been released just a few days prior. No luck this time, but I expect to see them during my next visit (how can I resist those gorgeous pink blooms?!)

Pollination is important for rosehips.

By the time the rosehips are ready to ship in the fall, the predatory mites will have devoured the spider mites, the neoseiulus will have evacuated the rosehips for the neighboring trees where they’ll nest for winter and the phytoseiulus will have naturally died out, leaving the rosehip leaves intact and beautiful for you and your customers.

Check out our rosehip Resource Page to learn more.