In early July, the nut fill in the pistachio orchards of the southern San Joaquin Valley was progressing well, reports veteran pistachio grower and consultant Carl Fanucchi, Fanucchi Diversified Management, Inc., Bakersfield, Calif.
Like the grapes and almonds in this region, the pistachio crops are maturing about 10 to 14 days earlier than usual.
In fact, kernels began filling as early as June 15, notes Bob Beede, University of California Cooperative Extension Farm Advisor, Emeritus, in the July-August issue of his newsletter, Pistachio Task List.
However, the start of nut fill in a particular orchard varied greatly from one location to another. Beede attributes that to high ambient temperatures in January, which reduced the number of chilling hours (temperatures below 45º F) in some areas needed to release trees from dormancy and provide for normal tree growth and nut development. University of California researchers estimate this threshold is about 750 hours for Kerman and, possibly, as much as 850 hours for Peters, Beede says.
“Orchards on the Valley floor more likely received sufficient rest to leaf out and bloom normally,” Beede writes. “However, orchards at even slightly higher elevations were reported as having significant delays.”
The very protracted bloom period due to the low chilling hours doesn’t seemed to have caused any unusual increase in the number of blank nuts this season, Fanucchi adds.
Meanwhile, the dry winter weather appears to have kept insect pest pressure low. Still, he recommends continuing to keep an eye out for leaffooted plant bugs and stink bugs. They’re harder to spot once the shells of pistachio nuts harden than earlier in the season. Then, the softer shells develop brown lesions where these bugs damaged the nuts while feeding. At this point in season, all that’s evident is a tiny, clear bead of sap on the hull where the insect’s stylet penetrated.
Inside the nut, however, the feeding causes the nutmeat to darken, often developing a sunken necrotic area and an off-flavor.
As described in the UC IPM Online website (www.ipm.ucdavis.edu), leaffooted plant bugs typically damage entire clusters, while stink bugs can transmit some pistachio diseases, such as Stigmatomycosis and panicle and shoot blight.
Also, of course, the navel orangeworm is another continuing threat in pistachio orchards. “This pest doesn’t seem to care how dry winter was,” Fanucchi says. “We still must keep the pressure on navel orangeworm.”
In his latest newsletter, Beede refers to research showing the critical times for evaluating the need to treat for NOW are 1,700, 2,200, and 2,700 Degree Days from Jan. 1. That’s when NOW activity increases.
As for the size of this year’s California pistachio crop, the jury’s still out.
“Growers on the east and west sides of the Valley, where chilling was the poorest, are not optimistic about their yields,” Fanucchi says. “Some are saying they won’t know how many nuts filled until the latter part of July. Other growers just don’t have a lot of good, full nut clusters on their trees. My early-July guess is that we will break 500 million pounds. The question is, by how much?”
Regardless of how many nuts growers harvest this year, he expects an increasing number of them will choose to shake their trees twice. Once considered the exception, this practice is now becoming more of the norm, Fanucchi notes.
“This will be a good year for a double harvest,” he says. “Considering the penalties for insect damage and the bonuses paid for clean nuts, it makes sense to harvest the nuts early to get the bulk of the crop. Then, you come back in 10 to 14 days to glean the rest of the crop after it matures. This way, the early nuts don’t deteriorate and become insect-infested while hanging on the tree as you wait for the later bloom to mature.”
Meanwhile, he adds, growers are enjoying record-high prices for their pistachios. And, despite the drought, this is helping to push the demand for land to plant new pistachio orchards to very high levels.
Still, such developments are being over-shadowed by the limited supplies of water to irrigate the orchards.
“Groundwater pumping levels in this area of the Valley continue to drop rapidly,” Fanucchi says. “In many areas, the quality of that water is deteriorating. It’s tolerable for pistachios, but it’s wreaking havoc in almonds, cherries, blueberries and other crops.”