Environ. Horticulture, Pears, Cherries, and Viticulture
University of California
Environ. Horticulture, Pears, Cherries, and Viticulture

Strawberries

Nice Article on Leak Rots for Progressive Crop Consultant

My colleague Steve Koike over at Trical Diagnostics and I wrote a really good article on leak rots caused by Mucor and Rhizopus for the last edition of Progressive Crop Consultant.  The impetus for writing the article, as you will see when you read it, is that even though these pathogens cause a great deal of fruit loss in the berries, almost no work has been done on them by researchers.   Well, get ready to hear more as we endeavor to mitigate this issue together.

The article is an overview of the pathogens, their biology, epidemilogy and lastly what (meager) tools we currently have in the way of management.

It's a good read for the weekend - enjoy!

Posted on Friday, September 27, 2019 at 11:22 AM
Tags: leak rots (1), Mucor (3), Rhizopus (2)

Remarkably Large Blackberries

Just a few shots below of some unusually large blackberries we are taking out of study looking at fertility modification and tunnel plastic management to reduce "reversion" in this crop (more to follow - it's an interesting study).  Variety is PrimeArk 45 and most of the big ones are coming out of one treatment.

One of the larger exemplars we picked yesterday, this one weighed 14 grams. And yes it was quite tasty.
One of the larger exemplars we picked yesterday, this one weighed 14 grams. And yes it was quite tasty.

Ten more of these bad boys and we complete a clamshell.
Ten more of these bad boys and we complete a clamshell.

Posted on Wednesday, September 18, 2019 at 1:34 PM

Use of the Lignin Surfactant Shadow to Minimize Flower Abortion in Strawberry

Introduction: An interesting phenomenon that I've been called out to a number of strawberry ranches starting about five years ago has been the appearance of aborted flowers, also known by growers as duds, in noticeable numbers right around and after the longest day of summer - June 21, the equinox.  As shown in Figures 1 and 2 below, the duds would present themselves as browned out centers of the flowers with no fruit forming subsequently.

With the idea that these duds may be caused by an excess exposure to ultraviolet (UV) radiation brought about by the longer days, I worked with a Salinas grower in 2018 and 2019 to apply a protective layer with a liquid surfactant called Shadow, (a lignin material designed specifically to reduce sunlight reaching the plant) over the plant and flower in an attempt to reduce this problem.

Materials and Methods: In 2018, a total of four applications (June 21, July 3, August 24 and October 19) of Shadow at the rate of 1 gal per acre as part of the regular tank mix were made to two very large areas of the field divided by areas where it was not applied.  This was repeated in 2019, with a total of three applications (the first two prior to June 21, the last being June 24) of Shadow again at the rate of 1 gal per acre as part of the tank mix made to three very large areas of the field divided by large strips were it was not applied. 

Strawberry variety was proprietary, and known to be very susceptible to producing a large number of duds.

The duds were counted by two people over three minutes in at least four different treated areas of the field (twice in one large treated area, and again twice in another), and again in at least four different untreated areas of the field.  Additionally, to evaluate possible effects on fruit size of this protective spray, fruit was gathered by two professional pickers, for a total of six clamshells out of the treated area and six clamshells out of the untreated area.

In both years, statistical differences of dud number and fruit size were tested by the TTEST function on Microsoft Excel by date at the 95 % level of confidence.

Results and Discussion:

Shadow significantly reduced the number of duds in 2018 (see Table 1 below).  Fruit size was apparently not affected, with no significant differences in average size recorded between the treated and untreated in either 2018 or 2019.

Table 1: Number of duds (aborted flowers) per 3 minutes of searching with 2 people.

Date      Untreated average duds Treated average duds
6/21/2018 7.7 4.8
7/3/2018 27.0* 18.2*
8/24/2018 6.2* 1.3*
10/19/2018 5.2 4.5
6/27/2019 3.3 4.2
7/4/2019 4.2 2.5

* Significantly different at the 95% level of confidence.

 

 Table 2: Average fruit size - weight per fruit in g 

Date      Untreated average fruit size Treated average fruit size
6/21/2018 25.9 28.9
7/3/2018 30.9 31.7
8/24/2018 23.8 22.5
10/19/2018 20.9 20.6
6/27/2019 31.6 29.1
7/4/2019 30.4 25.8

 

It is interesting to note that in both years the number of duds in the plots treated with Shadow were lower (significantly so in 2018 and close to significantly lower (p=0.07) on July 4, 2019), only after the longest day of the equinox had passed, which does indicate some activity in minimizing flower abortion in strawberry associated with lengthy exposure to solar radiation on the part of this material.

Figure 1: Close up of strawberry flower dud.  Note brown color which indicates the fruit will not make.
Figure 1: Close up of strawberry flower dud. Note brown color which indicates the fruit will not make.

Figure 2: A wide sample of flower duds.
Figure 2: A wide sample of flower duds.

Posted on Wednesday, September 11, 2019 at 12:09 PM

New Book About the California Strawberry Industry

And this one is sure to make a splash.

Just bought it on Amazon, and I'll set aside my current read (Plato's Gorgias) to wade into this one.  It's supposed to arrive on Friday, so I can start into it already this weekend.  From the reviews I see it does tilt in a certain direction, and indeed I've spoken with Julie on several occasions (and have some of my work referenced there apparently), so there is some anticipation of what is to come.

Then again, it's good to know what is being written about my vocation and my friends.

Comments to follow later on when I finish.

wilted
wilted

Posted on Wednesday, August 14, 2019 at 7:53 PM

ISCA Hook Bait and Kill for Management of SWD in Blackberry

Some questions have been coming up concerning "what's new" in SWD management in berries, so I thought I would share this work that I've presented at some of the meetings during the winter cycle.

This study concerns the use of a bait and kill approach with a bait designed specifically for SWD, that is to say Drosophila suzukii, rather than using baits like GF120 which is designed for true fruit flies (NOT vinegar flies) and subsequently have activity on SWD that is so so.  The method is attractive in theory, since it avoids contact with beneficials like honeybees and predators, at the same time that it delivers the active ingredient (in this case spinosyn) straight into the gut of the target.

The work was funded by the USDA IR4 program, which facilitates pesticide registrations in minor crops.

 

The trial consisted of 3 treatments, those being an untreated check, one treatment of ISCA HOOK applied once a week and another of ISCA HOOK applied every other week, and was executed as follows:

  • Weekly applications of ISCA HOOK bait and kill made on September 6, 13, 20 and 26. 
  • Biweekly applications of ISCA HOOK made September 6 and September 20.
  • Both application schedules at the rate of 1.5 L material per acre.
  • Large replicate plots at 15,750 ft2 each.
  • Material distributed with a whisk broom at the base of the hedgerow.
  • Two commercial insecticide applications made during the duration of the study, once 9/8/2018 and then again on 9/22/2018.

Going to slides 3 and 4 toward the bottom we can see that numbers of larvae found per fruit were significantly lower than the untreated check in both biweekly and weekly application treatments a little bit less than a month after initiation, and numbers of adults were significantly lower in the biweekly application treatments a little bit less than a month after initiation, and then significantly lower in both treatments five weeks after initiation of the trial.

Bottom line is that this bait does work in reducing numbers of SWD in blackberry, look forward to seeing it registered and available to growers.

As always, there is a pesticide reviewed in this post, and growers should always refer to pesticide labels before making an application and refer questions to the local Agricultural Commissioner or Cooperative Extension office. 

 

 

Freshly applied ISCA HOOK.  Mark Bolda, UCCE.
Freshly applied ISCA HOOK. Mark Bolda, UCCE.

Condition of ISCA HOOK Oct 10, several weeks after last application.  Mark Bolda, UCCE.
Condition of ISCA HOOK Oct 10, several weeks after last application. Mark Bolda, UCCE.

Number of SWD larvae per 5 blackberry fruit.
Number of SWD larvae per 5 blackberry fruit.

Number of SWD adults per 18' of row (one side).
Number of SWD adults per 18' of row (one side).

Posted on Friday, August 9, 2019 at 1:57 PM

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