I had a conversation quite recently with Doug Shaw, UC plant breeder, concerning the concept of chill in the day neutral varieties and the desire of some Central Coast growers to reduce the recommended amounts significantly, even all the way down to zero days of chill:

In the way of review, please recall that chill requirement in strawberry in California is made up of two essential parts.  One part is what the plant accumulates in the field before being harvested, and the other is accumulation of chill after harvest and the plant is in storage.  There is a big difference between the two and one does not supplant the other.  In-field chill takes place when the plant is still in the soil, out in the open and still has all its leaves.   Supplemental chill takes place after harvest of the plant and occurs in a constant near freezing temperature, in the dark and the plant has none to very few leaves left (Figure 1 below).

Accumulation of chill, especially supplemental chill, in the strawberry transplant makes it stronger and better able to survive the stress of plant harvest, transplant and the growing season beyond.  

As some of the chill sensitivity has been bred out of the modern UC day neutral varieties such as Albion, Monterey and especially San Andreas, it is indeed possible to grow these varieties with less than the recommended amounts (10-18 days) of supplemental chill.   However, those who choose to reduce chill below these amounts should recognize the amount of risk they are taking and that this is not an exercise for those still using training wheels.   Should growing conditions take a turn for the worse, these underchilled plants do not have the vigor to help them pull through and will suffer more than those adequately chilled.  Moreover, while UC day neutral strawberry plants chilled significantly less than the recommended 10-18 days can produce fruit earlier than others (probably owing to the earlier planting date), these plants quite likely will not perform optimally in terms of overall yield and quality along with showing a tendency to produce smaller fruit later on in the season.

The only case where one would want to go short on supplemental chilling time would be if the plant harvest was so late that a minimum chill time of 10 days would result in a planting date so late that it would compromise plant growth and establishment.

Other than that, it is still recommended to give the UC day neutral varieties 10-18 days of supplemental chill.

A response to the question posed to us concerning how soon one should be applying water to Chateau (flumioxazin) sprayed in the furrows for weed control in strawberry.  The label says that this herbicide can be applied at a minimum of 30 days before transplant of strawberries, but it doesn’t seem to specify how soon to apply the water after application.

Probably the sooner you apply water to furrows the better, but in a study run by Oleg in Ventura County, Chateau was applied to furrows about a month before sprinklers were turned on and the herbicide was effective against several broadleaf weed species, including wind-dispersed weed seed that landed in furrows after application.

Chateau does not degrade and just remains on soil surface, provided furrows stay dry during that time. If the furrows get wetted enough to germinate weeds the herbicide will be sufficiently activated as well.

The residual efficacy of Chateau is diminished over time, but you can reapply it to furrows if needed – there is no co-distillation, so as long as there is no drift, strawberry plants should be safe. You can extend the control by reapplying it with shielded sprayer in-season as long as the strawberry plants do not have flowers and fruit (which is soon in Southern California but quite a bit later here in Watsonville and Salinas) and you do not intentionally overspray the beds (first photo below) .

Also, thinking about traffic going through the field after application, specifically the wheels of tractors moving through the furrows, it does create some breaks in the barrier that the initial application of Chateau has formed.   It might be interesting to do a little experiment with different levels of disturbance post-application to see how much efficacy really is affected.  However, remember that Chateau can be reapplied later on in December and January in the furrows in order to get better control since it will be catching multiple flushes and cohorts of weeds from both the seed bank and wind dispersal. 

UC IPM guidelines for Chateau in strawberry are available at:

www.ipm.ucdavis.edu/PMG/r734700411.html

The use of flumioxazin (Chateau) is extensively written about in this article.  Before this or any other product, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.

This is simply a summary of one year of biological fungicide work in strawberries in 2012-2013 and should not be understood as a recommendation to use any of these products.  This investigation is will continue into 2013-2014 and will serve to confirm and adjust the work here.

Introduction: A number of biological fungicides registered for use in strawberries have not been thoroughly tested through empirical studies to give guidance to growers on their efficacy and use.

Materials and Methods:

Table 1 below is an outline of materials tested in 2012-2013.

The field involved in the study was organically farmed and had a tested infestation of Verticillium at the average level of 25 microsclerotia per treatment replicate.  Grower standard was managed as per grower practice, that is to say normal irrigation, fertility and pest management practices were applied.  This grower standard did not include any sort of biological fungicide either by dip or injection through the drip tape during the season.

Plot was replicated three times and each replicate consisted of at one bed of 180 feet in length. 

Application of the materials took place as indicated in the table below:

Table 1. List of treatments.

Plant dips were made by suspending the requested rate of fungicide in approximately twenty gallons of water and submerging and soaking about a half a box of strawberry transplants (about 500 plants) thoroughly and then distributing to planting crews for transplant.  Note that in the case of the two Actinovate treatments, plants were held for one night to prior to transplant, ostensibly to establish the organism on the plant roots.

Drip applications were made with a portable pump injecting each fungicide.  Each application normally was preceded by filling the drip tape with clear water, injecting the mix and then further pumping in clear water to make sure the fungicide had moved well out of the drip tape.

Application dates:

Preplant application – 11/3/2012

            Dazitol

            Terra Clean 5.0

            Terraclean 5.0 + Serenade Soil

            Tainio Spectrum + Pepzyme C

            Biotam

Root dip + one overnight hold – 11/7/2012 (planted November 8)

            Actinovate rate 1

            Actinovate rate 2

Root dip and immediate planting – 11/8/2012

            Double Nickel 55

            Soilguard

            Biogenesis + Pepzyme C

10 days post – plant – 11/20/2012

            Serenade 4 qt

            Serenade 2 qt

Monthly applications (12/11/2012, 1/16/2013, 2/26/2013, 3/27/2013, 4/30/2013,  and 6/13/2013)

Terra Clean 5.0

Terraclean 5.0 + Serenade Soil

Tainio Spectrum + Pepzyme C

Serenade 4 qt

Serendade 2 qt

Actinovate rate 1

Actinovate rate 2

Double Nickel 55

Biotam applied 2/26/2013; Serenade 4 qt per acre applied other dates in treatment

Soilguard

Several dying plants from different areas of the test plots were sampled in July to confirm that Verticillium was the cause of plant death.

As a gauge of plant vigor from each treatment, strawberry plant diameters were measured February 13, and April 13.  Measurements were in centimeters and from twenty plants in each plot.

With the beginning of fruit ripening, fruit harvest was done weekly in each treatment replicate.   On each pick date, fruit from each plot was weighed and counted.

Results:

Means followed by same letter do not significantly differ (P=.05, Student-Newman-Keuls)

Means followed by same letter do not significantly differ (P=.05, Student-Newman-Keuls)

Plant diameters measured on February 13, 2013, were significantly larger in the low rate of Actinovate than the other treatments with the exception of the high rate of Actinovate, Tainio and Double Nickel 55.

Both rates of Actinovate realized higher fruit yield than all other treatments except for the Dazitol, in cumulative fruit yield, which included six weekly harvests, up to May 14, 2013.  No further differences were realized between May and August.

As noted above, this field has a very high infestation of Verticillium and all plots began to experience pronounced plant dieback in June, with some 60-80% remaining alive or declining and by end of July, nearly all plants in all replicate plots had died.   There was a trend for plants which had produced larger amounts of fruit in April and May to experience lesser fruit production lesser vigor and earlier dieback as the season progressed.

Conclusion

The results of this trial are encouraging.  In the early part of the season up through the middle of May, several treatments had significantly higher amounts of fruits harvested than the grower standard.  Nonetheless, none of the treatments provided sufficient protection to the plants to prevent an almost complete die out of the plants by August, effectively ending the season.

It’s not easy for a farmer who is used to selling direct at farmers markets, a roadside stand, or to a processor to make the big step into selling boxed and labeled product to wholesale and other buyers. Yet these buyers really want to meet small farmers so they can serve the rapidly expanding market for locally grown food. The University of California Cooperative Extension offices in Santa Cruz and Santa Clara Counties, along with the Agricultural Sustainability Institute at UC Davis are planning to connect these farmers and buyers from the San Francisco Bay Area during a bus tour on Tuesday, November 5.

Farmers who want to join the bus tour need to pre-register by contacting UC Cooperative Extension Santa Cruz County at telephone (831) 763-8040; email cesantacruz@ucdavis.edu or by stopping by the office at 1432 Freedom Blvd in Watsonville.  There is a $20 registration fee, which is fully refundable upon boarding the bus.

The day long tour will leave UC Cooperative Extension in Watsonville at dawn, pick up more growers in San Martin on the way to San Francisco, then tour the San Francisco Produce Market and see different kinds of buyers in the area. The farmers will also visit an independent retailer who buys direct as well as a foodservice or restaurant buyer. The tour will be a “workshop on wheels” where participants will learn about food safety requirements and credit and loan opportunities. Farm Credit banks, which have provided support for the tours, will have a representative on board to discuss financing options.         

Link to further information and registration is provided here:

http://cesantacruz.ucanr.edu/files/174315.pdf