Blue Diamond Almond Facts March-April 2021

IN YOUR ORCHARD If an acre-inch of water containing 10 ppm nitrate-N will be used in the fertigation set, then 32 gallons less UN32 can be applied. The N in the irrigation water makes up the difference. However, if there is only 1 ppm nitrate in the irrigation water, that works out to a savings of less than a gallon of UN32 and that reduction is hard to measure when setting out 500 gallons of UN32. Reduce N and K inputs if you have reduced water availability as yield should be reduced. Excess nitrogen increases hull rot damage and the potential for nitrate leaching. When nitrate leaches, valuable cations (calcium, potassium, magnesium) go with it. Pest Management: By March 1, mummies should be shredded using a flail mower at slow ground speed. If mummies are not broken up by the mower, navel orangeworm (NOW) may survive, increasing the population of that damaging pest in your orchard. A second pass is a good idea if some mummy nuts are intact after the first pass. Monitoring traps for NOW (for moths and/or eggs) and peach twig borer (PTB) should be up by March 15. Given the warm weather for much of this winter and spring, early pest activity is a good bet. Check traps several times per week until biofix (first consistent trap catch) occurs and then shift to once a week monitoring. In areas with low NOW populations, Dr. Frank Zalom, UC Davis Department of Entomology, suggests using the first egg “catch” date as biofix, even if the weather cools off and the trap activity stops for a week or more. Experience suggests the first egg catch date is a better indication of the start of NOW activity than later dates. Consult with your PCA regarding NOW control strategies for the remainder of the season. Look for leaf footed bug (LFB), early, as alternative hosts may dry up sooner than usual in a low water year. Information o monitoring and control practices for leaf footed bugs are available at: ipm.ucanr.edu/agriculture/ almond/leaffooted-bug/. If trees are water stressed, look for webspinning mites before the usual May start for scouting for this regular pest. Check for beneficial insects and mites at the same time. The up and down temperatures of spring time can help six-spotted thrips and/or predacious mites keep spider mite populations under control heading into summer. Mite scouting information and data sheets are available at: www2.ipm.ucanr.edu/agriculture/almond/webspinning- spider-mites/. If you haven’t already, consider marking your calendar to work on ant monitoring/control starting in June (and/or call your PCA to talk about ant control ahead of harvest). Ant damage at harvest can be costly, especially when slow drying conditions extend the time between shaking and pickup. Different ant baits deliver different control patterns over time. Use of a quick knockdown bait maybe the best approach for a one-harvest, self-fertile block, while a Nonpareil/Monterey orchard might benefit from a long acting product such Clinch ® or Esteem ® . Check with your PCA regarding strategies, materials and timing for ant management. Wild fires and valley smoke may again be an issue this summer, increasing the need to pay attention to pests (rust, scab, anthracnose, alternaria, and mites) that can increase leaf drop at harvest and further slow nut drying. Spraying before it rains gives much better disease control compared to after a rain. Consult with your PCA regarding material selection and rates. 4 2 A L M O N D F A C T S