March 30, 2015

This report covers conditions and observations made between Monday March 16 and Sunday, March 29, 2015. The next report is scheduled for Monday, May 4, 2015. However, in the event of any significant occurrences prior to that date, this site will be updated as soon as possible.

Our photos for the northern region show a few of the typical spring time orchard operations observed over the past few weeks; trails of fertilizer spread down the row and sprinkler irrigation in the Chico area of Butte County, followed by a close-up view of drip irrigation in the Arbuckle area of Colusa County. Our feature image shows a flail mower reducing the vegetation within an orchard near Arbuckle.

Temperatures rose to unseasonably warm values during the latter half of March, providing everyone in the region with a taste of summer during the first days of spring. Taking on a roller coaster-like cyclic pattern, daily maximum temperatures reported in the low to mid 60’s as the period began quickly rose into the low to mid 80’s. Readings then cycled back into the mid 60’s on the 23rd and 24th of the month before rising back into mid 80’s in the period’s closing days. Morning minimum temperatures also exhibited quite a bit of variation, ranging between the lower 40’s to upper 50’s throughout the period.

Observers are reporting rapid growth rates within the region’s orchards as the warm temperatures push nut development ahead aggressively. Nuts have moved through the initial differentiation stage wherein smaller nuts that were not fertilized drop from the trees and are entering the second phase of shedding wherein nuts that the trees are unable to support to harvest are being shed. As is normally the case, varieties shed to different degrees, with Nonpareil typically retaining a greater percentage of its nuts while several California type varieties along with the Butte and Padre shed more aggressively. Growers and observers alike are reporting generally good crop sets, with the greatest variability observed within the Nonpareil, Winters and Aldrich varieties. While all growers in the region would rather have received a good amount of rain since the completion of the bloom, the overwhelmingly dry conditions have resulted in very low disease pressure, with morning dew providing the only form of moisture on the foliage. As a result, orchards throughout the region are virtually free of fungal diseases and in generally good condition.

Rising temperatures have inspired growers to begin the irrigation season, drawing water from their wells and from early releases from local districts.  Growers who normally receive water from the federal Central Valley Project already know that they will not receive any water this year, while those drawing water from the State Water Project are expecting 25% of their contracted allocation. Observers have reported that final allocations have not yet been announced by local districts, and growers in those areas are expecting word within the next few weeks. In any event, the dry winter will force growers to rely heavily on their own resources to provide the water needed to support their crops.

In addition to irrigating, growers throughout the region have been working to complete the wide range of tasks required to support the developing crop. Fertilizers are being applied, both in dry and liquid forms and growers have been sending tractor drawn flail mowers into the orchards to control vegetation in an effort to reduce water consumption.  Native plants growing within the orchards aid water penetration and act as a nursery sight for beneficial insects. However, plant growth also consumes precious water, forcing growers to make difficult decisions on how to manage their orchard floors. Some will simply mow the growth to reduce the amount of foliage while others may opt to eliminate it entirely.

Growers are also monitoring insect populations within their orchards. Observers have noted Navel Orange Worm, NOW, larvae found within mummy nuts remaining in the trees and Pest Control Advisors have set out pheromone traps designed to attract male NOW moths and egg traps to monitor egg laying by females.  Growers are also watching for signs of Leaf-Footed Plant Bugs moving in from grassland areas as they dry out and for indications of web-spinning spider mites. With all that in mind, concerns of water will dominate grower decisions during the current growing season.

Current weather at the National Weather Service
Dennis Meinberg and Ryan Christy
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