Almond Facts, May-June 2021

Bait should go out early (four to eight weeks ahead of shaking, depending on the material) as it takes time for the product to reduce ant activity. Altrevin is a short PHI material that provides rapid knock down of ant activity but provided fewer weeks of ant control than Clinch in UC research conducted by David Haviland, UCCE Entomology Advisor in Kern County. • Efficacy of ant bait materials is also impacted by how they are used. Ant bait materials work because ants are attracted by the soybean oil in the bait. Rancid soybean oil does not attract ants. Bags open a week or so may have rancid oil and reduced efficacy. Buy new material and use it quickly. Regardless of the material used, wet bait is less effective than dry material. Spread bait several days ahead of irrigation, especially sprinkler irrigation, or wait a day or two after irrigation for best results. 3. Hull split sprays: Properly timed and applied hull split sprays reduced nut damage from navel orangeworm (NOW) and peach twig borer (PTB) by about 50%. Check with your PCA about materials and timings. Poorly timed and applied sprays will cost nearly as much as properly timed sprays (material and labor) but the results may be far less — especially in a high pressure year. The first spray should go out when the first nuts in the interior orchard trees (usually in the upper, southwest edge of the canopy) reach 2C stage of hull split (see photo) and the entire orchard sprayed within a week. If you are going to make one worm spray this year, this is the one to do according to David Haviland, UCCE Entomology advisor in Kern County. If a second spray is planned, the recommended timing is for later in July when residue of the first spray is fading, pollinizers are beginning to split and the start of 3rd generation NOW egg laying is approaching. Spraying when relative humidity levels are over 40% and temperatures below 80 o F helps reduce evaporation spray loss. Many growers have moved to late evening through mid-morning spray timings. See extensive discussion of hull split spraying in the Time to Consider column in the May/June, 2020 issue of Almond Facts . Other pest considerations this time of year include spider mites, summer diseases and rodents. With drought conditions up and down the state, mite pressure should be up this year. Beneficial insects, particularly six-spotted thrips, and predatory mites can help control spider mites during these months ahead of harvest dry down. Knowing the balance of mites to predators in an orchard is key to limiting costs while avoiding leaf damage and crop reduction. Monitor for spider mites and predators through May and June. There is no need to count mite numbers on a leaf, just note if there are spider mites and/or predators on each of 15 leaves per tree from five trees. Details on mite monitoring, including a printable, sampling form to record pest and predator levels is available at: ipm.ucanr.edu/ PMG/C003/m003fcspdmites02.html. Information on the biology of mites along with options for control materials is available at: www2.ipm.ucanr.edu/agriculture/almond/ webspinning-spider-mites. There is no rain in the forecast as I write this, but disease infections following sudden late spring and/or summer storms are an annual concern. In particular, rust infections can produce leaf loss at harvest and extend nut drying Night spraying. Photo credit: Franz Niederholzer 5 1 M A Y – J U N E 2 0 2 1