Monday, April 8, 2013

Red Mites: Might They Be New Arrivals or Simply Visitors?

 Farmers often learn to expect the unexpected.

While scouting a local San Joaquin Valley almond orchard the other day, something unexpected showed up among the greening trees: European red mites. We did a double-take and checked in with our almond expert, Walt Bentley, a UC IPM emeritus and almond expect.

What emerged is a mystery, something that could use the services of a modern-day Sherlock Holmes. European red mites are typically found further north in the Sacramento Valley. They’re not a common sight in our San Joaquin Valley.

 European red mite is usually seen in the Sacramento Valley.
- UC IPM photo by Jack Kelly Clark
Here’s what UC IPM says about these bugs: “European red mites cause leaf stippling. Prolonged feeding causes leaves to pale and appear bronzed and burned at the tips and margin. Almond trees that are that are not stressed for water or by any other factor can tolerate high infestation levels for extended periods without experiencing leaf drop. If the trees are stressed, however, these levels can cause defoliation. European red mites do not commonly reach damaging levels in almonds.” You can learn more about European red mites at UC IPM online.

Yes, there’s nothing to be alarmed right now. In fact, many growers included a miticide with their dormant season sprays. Overall, there aren’t any major issues with mites. The trees are looking good. The trees have quickly gone from brilliant white and pink blossoms to sparkling green leaves.

Bee boxes like these could have transported red mites here.
Are we going to find more red mites elsewhere? Can we call them simply tourists visiting one of our almond orchards?  One guess is the pests hitched a ride with the bee boxes and landed here as the bees arrive to ply their pollination trade here. We’ll have to do a little more sleuthing. Stay tuned.

From the orchards to the fields:
In alfalfa, some growers have finished the first cutting of the season. The recent rain may dampen the quality of this harvest. On the pest front, we found some blue alfalfa aphids in our sweep net – nothing to be alarmed about at the moment. Even so, it’s important to keep an eye for these bugs.

Some growers have finished the first cutting of alfalfa.
The cut alfalfa being picked up and then loaded into a truck. 

Here is a local field after the first cutting.

A cotton field being worked before planting.

In cotton, the degree day calculations are in and signal a green light for the start of planting. One eager grower already planted his pima cotton. We helped another grower plant a natural habitat of corn, mustard and buck wheat to provide a future home for good and harmful bugs. Yes, the clock is definitely set to ring in the start of the 2013 cotton season.

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