After three years of drought (2007-09) and two wet years (2010-11) — this year is shaping up to be another very dry year. There were two decent rains that somewhat recharged the soil profile, unfortunately they occurred as the 2011 harvest was wrapping up. Those were followed by one rain in November and a shower in December, which provided much of the fall rainfall total (about 45 percent of average). January did not add much more and a good number of vineyards received winter irrigation.
The total rainfall total for the months of October, November and December ended up at 3 inches for the north county and 1.7 inches for the south county. Not since 1976-77 has it been this dry, especially as December was the third driest on record. Dry conditions look to continue and irrigation is probably a good investment right now. Grapes are a low-demand crop for water and nitrogen, compared to most other fruits and nuts, but extremely dry conditions can affect the strength and uniformity of bud push in addition to negatively affecting the final development phases of this year’s fruit buds.
With that in mind, even if you put on a good solid irrigation of 24 to 36 hours or more last month, it would not hurt to put another 24 hours or so, depending on your emitter spacing, size of the emitters, soil type and variety/rootstock. Although this won’t recharge deep soil profiles, we still have a ways to go before the “rainy” season ends and things can turn around very fast. So it’s easy enough to apply some more water at or after bud break, if the drought continues.
Checking out the irrigation system is neither a bad idea nor a waste of time. Checking out the soil profile with an auger or even just a little digging with a shovel may help confirm how well the winter rains and irrigation may have managed your soil profile. Overall it seems there is decent moisture in the top 2 or 3 feet in most vineyards, but that is about it.
Even though January was close to average in total rainfall, seasonal totals are falling behind again. As of the first week in February the north county is at 6.1 inches (44 percent of historical average to date) and the south county is just at 3.2 total inches (approximately 37 percent). Last year at this time there was a total of 13.5 inches of rain in the Lodi area.
The curious weather pattern this winter (besides extreme dryness) is that most daytime maximum temperatures have been slightly above average, while most night time minimums have been well below average; giving the area a summer-like days with winter-like nights.
LBAM continues spread
Chilling hours have been above-average and for a second year in a row, fog has been a more common occurrence as in the ”Good Old” days when the sun often disappeared for three to four weeks at a time. Chilling hours (hours below 45 F) has totaled 1044 hours at this point compared to the long term average of 778 hours (Fruit and Nut Center, UC Davis). ET of winter cover and weeds has been low. Most mornings have seen light to substantial frost, which is a little worrisome for the coming spring. But I better not say any more at this point.
During the last five years there were some scattered frost events in 2011, 2009 and 2008. Just to review last year’s reminder of comparison for soil conditions and cold, to hopefully renew the good luck:
* Firm bare ground, that is wet: +2º F
* Firm bare ground, that is dry: ---
* Freshly disked soil: -2º degrees colder
* High cover crop (24 to 30 inches): -2º to 4º (possibly 6 to 8º colder)
* Low cover crop (less than 24 inches): -1º to 3º degrees colder
* Mowed cover crop: -½º F
As spring and budbreak approach, it appears the European grapevine moth (EGVM) will be determined to be eradicated in San Joaquin County, as there were no other finds last year. Scott Hudson and his staff have done a lot of work and have been helped by all growers to speed the delisting of EGVM. That’s the good news.
The bad news is that light brown apple moth (LBAM), continues to spread and is scattered around the county. It’s still under a quarantine protocol. The other good news is, it’s easy to control. It is a Lepidoptera pest very similar to the OLR and it seems to be susceptible to the same biological control of our native beneficial insect predators and parasites. If you are within a mile of a commercial nursery you probably are in a quarantine zone. If you haven’t been contacted by the Ag Commissioner’s office, you should check.