June 1, 2015

This report covers conditions and observations made between Monday, May 4 and Sunday, May 31, 2015. The next report is scheduled for Monday, June 29, 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 central region present three options for irrigation growers typically employ. First, an orchard under drip irrigation in the Newman area of Stanislaus County, followed by a fanjet system and a mini-sprinkler system in the Ripon area of San Joaquin County. Growers select the system that best meets the needs of their soil characteristics and the micro-climate of their location.

Relatively mild conditions reign over the central region during May, giving both the orchards and the growers a bit of a break. Daily maximum temperatures ranged from the upper 60’s to the upper 80’s for nearly all of the month, with readings rising into the mid 90’s in the final days of the period. Meanwhile morning low readings were reported uniformly between the mid 40’s and lower 50’s throughout the month. Clouds moved over the region on several days during the period, approaching from the east, over the Sierra Nevada Mountains, rather than from the Pacific, as is normally the case. In addition to providing accent to the sky, the cloudy skies also brought rain to the region on May 7th and 14th, with total accumulations varying from just a trace to as much as one-half inch from several heavy downpours.

Crop development continues in the central region, aided slightly by the relatively cool temperatures experienced over the past few weeks. The lower temperatures experienced during May provided a bit of a respite by reducing the orchards moisture demands, allowing growers to delay and/or shorten irrigations. Rainfall in those area receiving the greatest amounts provided a “good news/bad news” situation, helping to reduce the potential populations of web spinning mites that may have been accumulating, while also increasing the potential for Scab and Rust in plantings that may not have received treatments to prevent the development of summertime foliar fungal infections. As a result, growers were evaluating the potetial for infection duirng the latter portion of the period, with some opting to begin treatments in order to prevent the spread of infection during the coming weeks.

While some growers were also evaluating populations of Leaf-Footed Plant Bugs remaining in their orchards, all in the region remaing acutely focused on the availability of water needed to bring their crop to harvest. Many with reduced supplies of “surface water” from their local irrigation districts have been forced to rely increasingly on ground water from their own wells and from ground water supplied by their district. Impacts in areas of the region drawing poor quality ground water have begun to manifest themselves. Orchards receiving water with elevated pH levels are displaying a yellowish cast while those receiving water with excessive salinity levels are displaying characteristic “burned” leaves and premature defoliation. Fortunately, these symptoms are confined to a relatively small area of the region, mostly along the I-5 corridor.
Observers are reporting notable variation in apparent crop yields, with some plantings bearing visually heavily laden trees while other plantings, in some cases adjacent to each other displaying much weaker apparent yields. The variation in apparent crop yield complicates growers’ fertility programs, with orchards bearing heavier crops requiring additional consideration.

While still almost two months from harvest, growers spent much of the period working to maintain the floor of the orchards. Those with established plantings have been mowing vegetation to reduce the amount of residue remaining on the surface at harvest. Those younger plantings that will be harvested for the first time are also scraping and smoothing the floor of their orchards to ensure that they will be able to pickup all of the nuts during the harvest.

Current weather at the National Weather Service
Mel Machado
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