Central California – May 26, 2014

This report covers conditions and observations made between Monday, April 28 and Sunday, May 25, 2014. The next report is scheduled for Monday, June 30, 2014. However, in the event of any significant occurrences prior to that date, this site will be updated as soon as possible.

Taken along the west side of Stanislaus County, our photos for this report show a grower mowing the vegetation in a new planting near Vernalis, followed by a close-up of the Fritz variety under deficit irrigation and two plantings near Newman along the Delta-Mendota Canal. Note the lack of new growth in the second photo, a sign that the trees are under stress. In our third photo, the near orchard is receiving enough water to support the trees, while the far orchard has been abandoned due to the lack of an adequate water supply, even though it’s planted literally on the banks of the Delta-Mendota.

Temperatures in the central region followed a wave-like pattern during May, with readings rising above and falling below seasonal normal levels throughout the period. Daily maximum temperatures peaked three times during the period, reaching into lower 90’s in the first days of May, the mid and upper 90’s at mid-month and the lower 90’s in the period’s closing days. In between the short-lived pulses of heat, readings reached only into the lower 70’s as weakening low -pressure systems passed over the state. Meanwhile, morning low temperatures followed a vaguely similar trend, with readings varying between the low and upper 40’s.

While conditions during the period were predominately dry, the weak low pressure systems spiraling over the region delivered trace amounts of rainfall on the 6th and 21st in the San Joaquin and Stanislaus County areas. Greater influence was exerted by the winds that blew through the region on quite a few days during the period, with speeds ranging from 10 to 20 mph.

Growers throughout the central region spent the month focused on water management as they worked mete out the season’s supply of water. Several windy days during the period have magnified moisture requirements, particularly along the west side of the region, where winds are typically a bit stronger. Data from the California Irrigation Management Information System, CIMIS, showed typical pan evapo-transpiration, (ETp) rates in the range of 0.20 to 0.27 inch per day. However, ETp rates climbed to as high as 0.41 inch on the windiest days.

Casual observation of the region’s orchards indicates that the orchards are in good to very good condition. However, closer examination from within the orchards reveals increasing water stress, particularly along the west side of the region. As shown in the second of this report’s photos, lack of spur growth is the most typical sign of water stress. While not necessarily playing a role in the current crop, this new growth is required to sustain subsequent crops and is an indicator of potential impacts on the developing nuts now in the trees. Some west side orchards are also showing increasing levels of salt injury resulting from the use of poor quality ground water from privately owned wells. While nearly all orchards in the region are receiving some amount degree of irrigation, there are a few plantings that have been abandoned due to a total lack of water.

While water worries have dominated discussion among the region’s growers, the normal growing season activities cannot be ignored. Weed control and fertilization of the developing crop played a major role in the grower’s daily schedule of activities during the period and quite a few spray rigs could also be observed crawling through the region’s orchards as growers timed treatments to the susceptible stages of Navel Orange Worm and Peach Twig Borer. While there have been some reports of increasing populations of web spinning mites, wide spread infestations have not made an appearance.  And finally, while some growers were forced to treat infestations of Leaf-Footed Plant Bugs earlier in the season, the natural progression of the crop has hardened the shells in the most preferred varieties, reducing the insect’s ability to penetrate into the kernel, thus allowing growers to forego additional treatments.

Observers are reporting that kernel development is progressing normally and slightly ahead of last year. While the first fully solid Nonpareil kernel was found on May 10th in the Westley area of Stanislaus County two days ahead of last year, solid kernels of several pollenizer varieties were also discovered a few days later. At the time this report was being prepared, kernels of the later harvesting varieties along the Highway 99 corridor such as the Butte, Padre, Monterey and Fritz were also nearly completely solid. Growers and their advisors will be monitoring the Nonpareil variety for the first signs of hull split, which could begin as early as the last week of June.

Current weather at the National Weather Service
Photos: Mel Machado, 5/26/14
Click an image to enlarge it.

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