Feeding damage by spider mites to almond leaves.
The combination of the presence/absence of mite monitoring techniques and newer selective miticides has changed the picture of spider mite management in almonds in recent years. This was the message entomology farm advisor David Haviland took to growers and PCAs at The Almond Conference last December. Haviland, with Kern County UC Extension, said these newer reduced-risk, selective miticides are effective in controlling spider mites while at the same time allowing beneficials to survive. In addition, they have different modes of action, allowing for an effective resistance management program.
Almond growers may still be making early-season applications with broad-spectrum products to stay ahead of mites and prevent flare-ups later in the season, but this may lead to more problems later.
Beneficial Thrips
Beneficials such as six-spotted thrips
are very effective at providing biological control of spider mites; however, early-
season miticide applications with
products such as abamectin reduce the food source for these natural predators. Moreover, abamectin is known to kill six-spotted thrips. Pyrethroids and other broad-spectrum insecticides should be avoided as well, and saved for hullsplit
timing, unless they are necessary for leaffooted bug or other pests for which
there are no alternatives.
Six-spotted thrips are the most effective predator of spider mites, but there are others: minute pirate bugs, lacewings and predatory mites. A season-long IPM program should include monitoring for the presence/absence of both spider mites and natural predators.
Monitoring
Weekly monitoring should begin in the middle of March in the southern
San Joaquin Valley and by early May farther north. About fifteen leaf samples should be taken from each of at least five trees in representative areas within the orchards. Early-season spider mites will typically be found near the crotches of trees at the base of the scaffolds, and will move out into the canopy as the season progresses.
As a general rule, Haviland said
that growers should treat with a selective miticide if one-third of the leaves sampled have mites and some beneficials are found. If no predators are found, that threshold drops to 25% of leaves with the presence of mites.
Information on miticide products and how best to use them can be found
on the UC IPM website. A form for presence/ absence sampling is also available.
The Almond Board of California is holding a series of themed workshops as part of its California Almond Sustainability Program (CASP). A series on Pest Monitoring and Decision Making will
be announced soon. Go to the CASP website for a list of dates and locations.
