We may be in the midst of springtime, but the Central Valley continues to deal with the challenges of a cold, wet winter that left our rivers swollen, our fields flooded, and many producers out of work.
The winter weather also impacted our pest populations. One notable example is California red scale, one of the most common pests of California citrus. Typically, the first male flight of California red scale occurs in early March. This year, experts in Kern County didn’t see the area’s first biofix until April 9, roughly five weeks later than usual. Citrus growers in other areas can expect even longer delays. “In Tulare, Fresno, and Madera counties, things happen 10 to 14 days after what we see in Kern County,” says Sandipa Gautam, the Area Citrus Integrated Pest Management (IPM) Advisor at the University of California. “That means the first generation, which would usually come by the first week of May, is going to come later this year.”
Why is California red scale’s schedule so different this year? Generally, the infestation process begins during the winter. This year’s winter was unseasonably cold, though, which killed off much of the overwintering immature population of CRS. That means that the season is now beginning with a mostly adult population. Since the first biofix in Kern County was seen so much later this year than in warmer years, producers should update their pest management plans accordingly.
Gautam advises growers to take stock of their citrus and, if needed, wait several weeks before applying insecticide. “Especially the growers who were planning on spraying the fields early in May, targeting that first generation, they might want to go and walk the fields and see what’s happening with the population,” she advises. “Because unlike previous years,” she adds, “this year everything is going to be delayed in terms of red scale seasonal phrenology.”
Longtime growers know that the management of California Red Scale has changed throughout the years. Decades ago, orchardists worked to control populations of California red and yellow scale using organophosphates and carbamates. Many scale populations in the San Joaquin Valley became resistant to those chemicals in the 1990s, however, leading to a more widespread adoption of integrated pest management approaches. Natural predators like parasitic wasps and lady beetles are a safe and effective part of those IPM approaches, but so are conventional pesticides.
In 2022, Gautam’s team at the Lindcove Research and Extension Center studied the efficiency of several different insecticide treatments on California red scale. They found Movento to be the most effective treatment for reducing the amount of fruit infested with CRS. Three other insecticides — Centaur, Senstar, and Sivanto — also significantly reduced infestation. To find the right insecticide for your fruit trees, visit an FGS full-service retail store!
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