Valley Alfalfa Growers: Building a Natural Habitat for Bugs

We all know about Habitat for Humanity – the charity that gathers community members to build homes for the less fortunate.

Did you know San Joaquin Valley alfalfa growers boast their own version? Call it Habitat for Entomology. Yes, these growers “build” homes for a diversity of good bugs and crop-damaging pests.

Leaving a strip of uncut alfalfa  can keep pests out of nearby cotton fields.

Of course, we’re not talking about brick and mortar or hammer and nail type of homes. We’re looking speaking of 8- to 12-feet wide, hundreds of feet long swaths of fresh alfalfa.

In farmer parlance, it’s called strip cutting. And this time of year, we’re joining University of California extension advisors in spreading the word to alfalfa growers to start making plans for leaving uncut strips of alfalfa as habit to attract natural predators as well as pests, including the dreaded lygus.

Alfalfa harvesting disrupts  the homes for pests.

Dr. Pete Goodell, a UC Integrated Pest Management advisor and cotton expert, says the first fruit, or square, on the young cotton plants are starting to emerge. Pests living in the alfalfa fields will flee to nearby cotton fields as the crop is cut and harvested.

Let’s put it another way. If you lose your home to fire or an earthquake, the first thing you do is find another house to live in. Well, that’s the same thing pests such as mites and lygus do when their home – i.e. alfalfa field – is cut down every few weeks through the fall. Mites and lygus – which are rather fond of alfalfa – are troublesome pests to cotton. (Check out Dr. Goodell’s blog for more information about lygus.)

So we remind alfalfa growers to leave a “home,” or strips of uncut alfalfa as a habitat to attract natural predators such as green lacewings and parasitic bugs and provide a place for lygus to stay until the alfalfa grows back. Right now, growers are in their second cutting of the season for alfalfa. They haven’t been leaving strips so far – some may figure pests fleeing the alfalfa haven’t been a threat yet to cotton.

Some cotton plants have developed the first square.
- Photo by Mississippi State extension

But field scout Carlos Silva and Dr. Goodell visited some cotton fields last week and found most plants were at five to six nodes and a few even have developed the first square, which signals the plant is entering an important growing stage that ultimately determines yield potential. The young plants are looking good and are about five to six inches tall.

Young cotton plans are developing nicely in the Valley.

As growers move into the second cutting of alfalfa, Carlos reports no significant pest issues at the moment. Alfalfa aphids have pretty much gone away. Some have weevils. He’ll starting looking for other pests soon such as beet armyworms.

Almond field scout Jenna Horine says she has found some orchard locations with nuts damaged by leaffooted bugs. As we mentioned previously, leaffooted and green stick bugs will leave a gummy substance on the outside of the nuts. But day-night temperature swings can affect nuts and result in similar gumming as well. To determine pest damage, you have to cut the nut in half.

Jenna says the pest damage is rather spotty and doesn’t appear to be a major problem overall. Check out UC IPM online to learn about controls for the leaffooted bug.

Irrigation could be affecting ant colonies.

  In the meantime, Jenna reports a rather large number of ants crawling around orchard floors. This is the time for growers to check their orchards for ant colonies to determine if there is a need for treatment. It’s best to tackle ant problems now to limit damage and crop loss after shaking this summer. In the northern San Joaquin Valley, growers should survey for ants two to three days after irrigation around this time and in June. You can learn more about monitoring and treatment decisions for ants from UC IPM.