Looking at Rain, Bugs and Pest Management This Season

 Will the wet winter meanfarmers will be dealing with fewer pest problems this season?

The answer is yes … and no. 

“My crystal ball is a bit fuzzy,” Dr. Pete Goodell, extension adviser of University of California Statewide Integrated Pest Management Program, told a group of farmers at a recent field day.

Pete explains that in some instances the near-record rains are likely to keep crop-threatening pests at bay, especially overwintering populations. In other instances, it might not have much of an impact.

Other factors come into play such as daily temperatures, including the number of freezing nights.

Here’s Pete’s run down about the possible impact of the rain on pests in alfalfa, cotton and almonds in 2017:

Alfalfa

Weevils. A warm January and February brought out weevils a little early this year.  In the Fresno area, for example, January recorded daytime highs averaging 2 degrees higher than normal, according to the National Weather Service. It even hit 71 degrees on January 8. 

Weevil larvae cause the most damage in alfalfa.

“They are out there,” Pete says about weevils. One grower told the field day gathering that he recorded a count of 20 weevils per sweep of a sweep net in one field.That’s about normal right now, Pete says. If this was harvest time, the grower would want to start cutting the crop to avoid damage to the plants.

According to UC IPM, weevils overwinter as adults in field trash or other hiding places and come out in late winter or early spring.  That’s when adult females start inserting eggs into alfalfa stems. It is the young larvae that feeds on the plants and causes the most damage.

Growers should start monitoring for weevils now. Pest management should be focused before the first cutting.  “Control options are insecticides and early harvest. Biological control is not effective at preventing economic damage in most areas because populations of natural enemies are not sufficient to provide control in the spring.” UC IPM says.

Armyworm: The rains will spur growth for host plants. That means growers are likely to see larger worm populations this season.

Cotton

Lygus bugs expect to be a problem for cotton this season.

Suppliers are reporting an increase in seed orders. That bodes well for the California cotton market. Look for more planted acreage due to anticipated increases in water availability this season.

Lygus – The flip side of the wet winter are weeds such as London rocket should thrive this spring, providing a nice home for lygus. Pete says an extra generation of lygus is likely to emerge in early summer as weeds dry out and the pest looks for a new home such as cotton.“We’re probably going to see some widespread outbreaks of lygus. I have no doubt about it. “Growers should check weeds for the presence of lygus through the end of this month.  This could be a really bad year for them.”

Mites and aphids: Pete says the winter impact on these pests is uncertain. Whitefly tends to increase during a drought. “Ithas to get really cold to freeze some of the overwintering insects out.”

Almonds

Leaf-footed plant bugs can pose a problem in almonds.

 Leaf-footed plant bug – The forecast is unclear. The soggy soil won’t impact this pest because it doesn’t overwinter in the ground. You need really freezing temperatures below 28 degrees to have an effect on the population. “They’re still out there,” Pete says.

Navel orangeworm (NOW) and peach twig borer – the rain has been a positive to reduce the overwintering population. The same goes for mites. “It’s not a nice environment for them,” Pete says. 

We’ll have to wait and see how these predictions play out. Meanwhile, Pete stresses that it is  important for growers to remain vigilant and keep monitoring their fields or orchards for pests.