Happy Cows Will Mean a Good Season for Alfalfa Growers

It’s not an exciting crop. It’s not a higher end crop like almonds. But it covers a lot of acreage and plays a vital role as food for California’s giant $6 billion-a-year dairy industry.

Alfalfa is the prime food source for the dairy industry.

Yes happy cows love alfalfa. And a successful alfalfa season will keep them happy. There’s a lot that goes into a good year for growers. Moreover, it takes a lot of work.

 Growers harvest the crop about six or seven times during the year, irrigating between cuttings. As the season progresses, the alfalfa quality diminishes and brings in a lower price than the crop cut earlier in the season.

Blue alfalfa aphids cover a stem of alfalfa.

During the five-year drought when water was like liquid gold, some alfalfa growers stopped irrigating in early summer and diverted the precious supplies to more profitable crops.

 This year, the USDA National Agricultural Statistical Services predicts alfalfa hay acreage in California will dip to 1.07 million acres, down slightly from 1.1 million acres in 2017. Two years ago, alfalfa acreage stood at 1.22 million acres.

With margins supermarket-thin, it’s important for alfalfa growers to operate as efficiently as possible and protect against disease and pest damage throughout season.  That’s really important as the weather starts heating up in the Valley.

 Aphids are especially worrisome when the weather gets hot, says field scout Damien Jelen. 

 UC Integrated Pest Management notes that four type of aphids cause damage in alfalfa: Cowpea aphid – the only black aphid found in the crop – pea aphid, blue aphid and spotted alfalfa aphid.

Examples of blue alfalfa damage. (Oklahoma State photo)

A few years ago, a blue alfalfa aphid outbreak impacted local growers. The pest feeds on alfalfa stems and can lead to wilting and stunted growth.  The blue alfalfa aphid was first found in alfalfa near Bakersfield in 1974. The following year, this invasive pest from eastern and southwestern Asia was discovered throughout Southern California. Today, this aphid can be found as far east as Kansas and Oklahoma. 

During the Valley outbreak, pest control advisors found that treatments weren’t totally effective against the blue alfalfa aphid, which meant a loss of revenue for some growers.

For the most part, aphids in alfalfa have many natural enemies such as lady beetles, parasitic wasps and minute pirate bugs. The good bugs can quickly reduce infestations. UC IPM offers a list of natural enemies. 

Minute pirate bugs are a natural enemy of aphids.

Farm advisers recommend checking every two to three days to determine if natural enemies are effectively keeping aphid populations in check.

 According to UC IPM, here’s the best way to take pest samples:

• Randomly choosefive stems from each of four areas per field, noting if the average plant height is less than 10 inches, 10 to 20 inches, or more than 20 inches.
• Bend each stem sample over a white pan and tap; dislodged aphids will fall in. The stem can also be shaken into a sweep net if a pan is not available.
• Take sweep net samples for lady beetle adults and larvae, fungal-killed aphids, parasitized aphid mummies, and the presence of other predators such as syrphidflies and lacewing larvae.
• Record results on a monitoring form. A pesticide application may be warranted if natural enemies fail to keep the aphid numbers in check.

In the meantime, growers are irrigating their alfalfa fields as they prepare for the second cutting of the season in a few weeks. We’re sure growers are hoping an uneventful spring and summer.