Blue Diamond Almond Facts March-April 2022

over one big one). A best management guideline for nitrogen was recently published and can be found at: almond-industry/orchard-management/soil-health-and-nutrients/nutrient-management. Peach Twig Borer (PTB) pheromone traps should be placed in orchards, one per 20 acres by March 20 in the southern San Joaquin Valley (SJV) and by April 1st in the Sacramento and northern SJV. Hang traps six to seven feet high in the northern quadrant of the tree, one to three feet from the outer canopy. Monitor twice a week; replace pheromone caps at the interval recommended by the manufacturer and trap bottoms after 100 moths have been counted and removed. If shoot strike monitoring indicates treatment is necessary, use trap catches and degree days to time a May spray. Optimum timing for first generation larvae (the May spray) is between 400 and 500 degree-days after the first male is trapped in April when using spinosad (Entrust, Success), spinetoram (Delegate), or the organophosphates. When using insect growth regulators (IGRs) like Intrepid, make the application at 300–400 degree-days. Accumulate degree-days for peach twig borer using a lower threshold of 50°F and an upper threshold of 88°F. See calculating degree days at looking under almond and then peach twig borer. Do not allow weeds to exceed four to five inches in height before treating or mowing. Mowing down winter weeds early can increase orchard temperatures. Weeds are more difficult to control chemically when more debris is left on the orchard floor. There are documented reports of weed resistance developing to certain herbicides. The UCIPM website has charts that show which weeds are controlled by what herbicides, and an excellent weed photo gallery includes many weed species commonly found in California for easy reference

Stay Safe and Good Luck!

Brent Holtz, Ph.D., Orchard Systems Advisor, University of California Cooperative Extension in San Joaquin County

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