Numerous growers are reporting increased populations of Spider mites in almond orchards again this year. UC Cooperative Extension Pomology Advisor for Merced County David Doll noted high temperatures and water stress related to heat likely contributed to mite pressures.
Doll explained the reasons why growers see mite flare-ups, “one, they can be tied to pyrethroid usage within the field, but the second is making abamectin applications too early in the season.”
Applying miticide as a preventative measure in late April and early May can create additional problems later in the season. “What we actually do is remove all the food source for the beneficials and therefore the beneficials cannot establish,” Doll stated.
Abamectin and other miticides can reduce or eliminate beneficials such as western predatory mites and sixspotted thrips. Killing off the food source for natural defenses creates an absence of predators in the field, “and the mites have free reign once the conditions turn hot,” said Doll.
Research has shown that natural defenses can be extremely effective in combatting mite populations. Doll noted that “we’ve been able to successfully manage orchards in Kern County with just beneficial insects and proper selection of miticides, with a single miticide application.”
Some fields have remained clean and are not experiencing the same mite pressure felt in other areas. Heavy populations have mostly developed along dusty roads and in orchards that are downwind from fields with mite issues. Some growers were forced to resort to a third miticide application before shaking the trees. “To hear that people are struggling, especially in the north part of the San Joaquin Valley, it suggests that most likely these applications are being made at the improper time,” said Doll.
Listen to the interview below.