California Pistachios: 4 Management “Takeaways” From Bob Beede

From Bob Beede’s December Pistachio Task List:

Takeaway #1: Gather Chill Data

Purchase and install a simple temperature recorder in each orchard to collect real-time weather data on chill accumulation and assessment of freeze events. Accurate, local weather data is the missing item to assist growers in determining their chill portions.

Every grower, large and small, should have at least one in every orchard with a different elevation or micro-climate. Having your own weather data may also prove to be valuable for support of a crop insurance claim.

The CIMIS stations appear to be less reliable in recent years, and several reported erroneous or no data. These stations are also designed for assessment of ET, not chill portions. I know of ranches whose chill portions vary by 20 percent due to elevation.

Remember that December and January are the two most important months physiologically for rest satisfaction in deciduous trees. So, you need to be planning now for chill assessment since we cannot predict winter temperatures and the need to apply diffusion or reflection materials that partially mitigate warm weather in January.

Chill portion accumulation began November 1. As of November 26, we had four to five chill portions. This is less than some past years but not alarmingly low. The past two good chill years had similar values by this time.

For real-time updates on chilling hours by CIMIS station, or snowpack and reservoir conditions, you can find links here. The Department of Water Resources has a new site for the snowpack plots, but my webpage link will get you to it.

Takeaway #2: Understand Fleabane Options

Those of you with fleabane problems really need to understand that there are two germination periods (fall and late winter). The prevention of seed production is a must for successful control.

Late fall applications of expensive pre-emergent herbicides effective against fleabane and horseweed (marestail) fail to control plants having emerged in early October, which do not grow vigorously above ground but do develop a very extensive root system.

So, they appear in mid-February to be newly emerged, but are now very difficult to kill. So, you cannot let fleabane become established, especially in young orchards, because the cost to control it rises with every missed opportunity.

Some growers have resorted to hand weeding, which could make the cost of the expensive herbicides very reasonable. Also, UC Farm Advisor, Kurt Hembree, has lots of helpful pistachio weed information at this website.

Kurt has lots of good advice on the internet for management of difficult weeds such as fleabane and horseweed.

Takeaway #3: Sanitize, Sanitize, Sanitize

Everyone agrees that winter sanitation is the cornerstone of a good NOW management program.

Destruction of residual nuts remaining in the trees and on the ground is critical to breaking the NOW life cycle. If navel orangeworm is a problem in your orchard, I would begin knocking the mummy nuts onto the ground as soon as possible, since you want them exposed to rainfall for decomposition.

That said, pistachios are not easy to clean up. After harvest, we leave plenty in the trees, in the crotches and on the ground.

The difficulty is largely related to the small size of pistachios compared to almonds or walnuts. One pound of pistachios contains about 375 in-shell nuts compared to about 184 in-shell almonds and 50 walnuts.

Pistachios are also harder to destroy. Due to their lighter weight, they resist being sucked up and broken by the flail mower. The high air velocity of some equipment used to blow the tree berms free of trash and overwintering nuts can also deposit some mummies into the adjacent tree row just cleaned.

They also get imbedded into the soil around the base of the tree where the ground cracks loose from shaking.

Depending upon how worn the rubber guards are on the shaker frame, the amount of nuts left during harvest at the base of every tree can range from a few to as much as a couple of handfuls.

Despite these challenges, growers with NOW problems have to do what they can to destroy as many mummies as possible.

As you grumble during this arduous task, just remember that every successfully overwintered NOW female produces up to 85-100 eggs in the spring. That means it does not take very many pistachios left per acre to generate a lot of moths for next year. Sanitation is also a community effort. This may be one reason why some areas are more prone to high damage.

NOW pressure also is likely increasing in the southern San Joaquin Valley due to more acres of almonds, pistachios, walnuts and pomegranates.

Realize that sanitation is supported by both past and current research. During his tenure at Wonderful Farms, Brad Higbee concluded after hundreds of hours of detailed research that winter sanitation remains the cornerstone of effective NOW control. His data from large trials supports this long-standing UC IPM position.

Dr. Joel Siegel also has extensive data to support this practice. So, if you do not want NOW problems, you had best do the sanitation thing to the best of your ability. Dr. Kent Daane, research associate Glenn Yokota, and I found from a three-year study that there was greater and earlier NOW emergence on bare berms and in cover crops.

Disking in the mummies greatly reduced the percent survival. Deep incorporation was no better than regular disking. Brad has data to show NOW larva can even crawl out from beneath the soil.

Takeaway #4: Pistachio Day

Plan on attending the Statewide Pistachio Day on January 22 at the Visalia Convention Center. Please pre-register on line to prevent more expense and wait at the door.

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