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

Strawberries

Farm Call: Yellow Leaves in Substrate Raspberries

Part of my work has come to include substrate production of caneberries. Some of these are easy since they are pest management issues which don't vary that much from field problems, but others, like the nutritional situation depicted below, are far more complex.

A couple of things going on in this field, which are raspberries being grown in substrate under macro-tunnels.  First, the very young leaves have a light yellow cast (see photo one below) to them and second the older leaves are seeming to have some difficulty (see second picture below), again becoming a sterner sort of yellow.  I don't worry as much about the older leaves as I do the newer ones, which after all represent the future of the plant.

As you know, I'm not making any call without doing some thorough sampling.  In this case, we took multiple samples of the younger leaves demonstrating the lighter shade of yellow and the same for the older yellowed leaves. To set the baseline, adult normal leaves (those surrounding the yellow leaves in the first picture below) were also sampled in multiple.

An important comment.  We are sampling leaves of 3 different ages, and we should be aware that this is going to distort some of the concentrations.  For example N, P, and K as plant mobile will by default trend higher in younger leaves, and nutrients such as Ca and B are going to trend higher in the older. 

And sure enough in perusing the analysis below, N,P and K are higher in our newest leaves and lowest in the older, with the adult leaves in between.  Likewise, Ca and B are very much higher in the oldest leaves than the other two age leaves, and as a matter of fact in the newest leaves these two nutrients are lower than what one normally would see recommended.  

 Mineral Adult normal leaf  New, yellow  Old, yellow
 N (%)  3.1 3.6   2.3
 P (%)  0.21  0.32  0.20
 K (%)  1.6  2.3  2.1
 Ca (%)  0.9  0.6  1.4
 Mg (%)  0.5  0.4  0.7
 Na (%)  0.02  0.02  0.03
 Fe (ppm)  503  336  1321
 B (ppm)  33 20   78
 Zn (ppm)  23  28  23
Cu (ppm) 4.1 5.8 3.7
Mn (ppm) 343 321 469

Moving on however to the levels of iron things get a bit more interesting.  While it is highly accumulated in the oldest leaves, it is far less so in the youngest at 4x less, and 3x in the normal adult leaves.  Calcium shows a similar pattern of concentration, but the visual symptoms are nothing like what we know calcium deficiency to look like.  Iron deficiency, on the other hand, usually described as chlorosis of one type of another, as a matter of fact does.  In addition, we know that nitrogen can accentuate iron deficiencies because of growth promotion.

The older leaves turning yellow?  It seems to me they are just old leaves, might be some dieback being pushed by high tunnel heat but nothing that excites a lot of attention.

In other words, it looks like the plant is outgrowing its ability to pull up iron for the moment.  Given that we've had (still in October of all things!) some pretty hot plant growth weather, once the weather cools down a lot of this should disappear.

My advice to the grower is watch this one, I'm not sure yet concrete action is merited yet, best to see if once the plant slows down in its growth and nitrogen accumulation these symptoms subside.

Note the contrast of these newer leaves to the midtier leaves around them.  Not an plant mobile nutrient, like NPK, so what could be the issue?
Note the contrast of these newer leaves to the midtier leaves around them. Not an plant mobile nutrient, like NPK, so what could be the issue?

On the other hand, many of the very oldest leaves were showing these symptoms, which look a lot like heat or salt damage.
On the other hand, many of the very oldest leaves were showing these symptoms, which look a lot like heat or salt damage.

Posted on Saturday, November 3, 2018 at 6:22 AM
Tags: iron (3), nitrogen (17), plant nutrition (3), raspberry (24), substrate (1)

You are welcome.

We finally have a label for the insecticide Sequoia. It will be a good one to have in our roster of insecticides in strawberry, not only because it is pretty darn effective in controlling lygus, but also because it can be rotated in with the remaining usable materials we have and keep them effective that much longer.

It does come with the caveat of only being 12 months long, but there always is the possibility of renewal plus the regular Section 3 label is being worked on at the Federal level. Use directions for the Section 18 for Sequoia attached below as a pdf file.

 

The only way to get these labels in California is to have the efficacy from the field to prove that the insecticide actually does what it is supposed to do. This was a job led out of this office of UCCE, and it was a major commitment that stretched over something like 5 years. My colleagues and I get up well before daybreak to beat the wind and do the sprays, are out there week after week to collect the samples, and spend many hours at the microscope counting the lygus, beneficials and other bugs. This was a ton of work over many years and effort put in by some very committed people, in particular Shimat Joseph and Monise Sheehan of UC Cooperative Extension and Hillary Thomas at the time with the CSC, but at the end of the day the effort very much worth it because we got you your Sequioa label for lygus in strawberries.

I am very grateful to Dow Chemical, now Corteva Agrisciences, Jean-Mari Peltier who sheparded the application through the CDPR and all the growers who collaborated with us for the tremendous support they gave us over the years to get this label to you.

Growers, this is a Section 18, so as always you have to get it on your restricted use permit.

Questions about efficacy?  Lots of studies on this site, type in lygus or sulfoxaflor in the search box and you'll see plenty of information on it.

You are welcome.

Posted on Tuesday, October 30, 2018 at 1:36 PM
Tags: lygus (11), sulfoxaflor (4)

Use of Soil Applied Fungicides for Reduction of Charcoal Rot caused by Macrophomina in Strawberry

Introduction: The difficulty of controlling Macrophomina, the causal agent in charcoal rot in strawberry, in California has brought about a renewed interest in non-conventional methods for its management.

The following study is an attempt to investigate two soil applied fungicides and their effectiveness in mitigating loss from Macrophomina infection.

Materials and Methods: The trial was done as a randomized complete block design of four replicates of one bed 35 foot long by 4 foot wide per treatment on Monterey variety strawberries in a field known to be infested with Macrophomina in Salinas, California. See the picture below for a demonstration of the disease severity of the disease on one side of the field; the side on which the study was done was unfortunately (for the study, not the grower) not nearly as severe.

Application: Applications of both fungicides were done 3 times in the early part of the year, March 2, April 12 and May 3, 2017. The fungicide Rhyme (which is labeled for soil application for management of charcoal rot), applied at 7 oz/acre and Merivon, applied at 11 oz/acre, were applied in approximately 40 gallons of water per treatment pumped in with a gasoline powered pump hooked up to the double rows of high flow drip tape. Injection consisted priming the irrigation tape, injecting the material and then flushing the lines.

It is important to note that the use pattern deployed here for Merivon is as of this time NOT a labeled application.

Evaluation:

Plant diameters were taken in the early part of the season to gauge any initial differences in plant vigor.   One measurement across the widest part of ten plants was taken in each treatment replicate and reported in cm.

Yield of strawberry fruit was the principle measure of plant performance in this trial. Fruit picking commenced in May with weekly picks, and then continued from June through early September with twice weekly picks. Only marketable fruit was included, and it was weighed and counted from each plot.

Since the work here involved two fungicides, one evaluation of powdery mildew was also done on May 9, 2017 but the amount of mildew was insufficient for a significant evaluation.

Results were tested statistically on ARM version 9 using a multiple comparison procedure (Least Significant Difference at the 95 percent level of significance) to determine whether the means of counts and percentages per treatment were significantly higher or lower from the other treatments.

Results and Discussion:

Results are given in Tables 1 and 2 below. While disease was evident with weakening plants from the beginning of May on, it was not as severe as the outbreak on the other side of the field and no plants were lost in any of the treatments.

Table 1: Plant Diameters on Two Dates (in cm) of Strawberry in Plots of Soil Applied Fungicides Rhyme and Merivon Compared to an Untreated Check1

Treatment

Apr 12

May 3

Untreated

32.2 a

33.1 a

Rhyme

32.7 a

34.7 a

Merivon

32.7 a

35.7 a

 

Table 2: Fruit Yield and Size (in g) of Strawberry in Plots of Soil Applied Fungicides Rhyme and Merivon Compared to an Untreated Check1

Treatment

May totl

May size

June totl

June size

July totl

July size

Untreated

2214a

35.6 a

4408a

28.4 a

5636a

21.0 a

Rhyme

2169a

35.3 a

4720a

28.1 a

5525a

21.9 a

Merivon

2216a

34.6 a

4454a

27.9 a

6064a

22.1 a

 

Treatment

Aug totl

Aug size

Sept total

Sept size

Season total

Size avg

Untreated

3051a

21.2b

849.0a

20.9 b

16157a

24.1 a

Rhyme

2617a

22.2a

784.5a

21.5 ab

15816a

24.8 a

Merivon

2752a

21.9a

1009a

22.3 a

16496a

24.6 a

1Method used to discriminate among means Fisher's least significant difference procedure. Treatments followed by the same letter have no statistically significant differences.

As seen in the tables above, use of the soil applied fungicides in this trial did not result in any significant yield differences between any of the treatments. It is interesting to note however, that average fruit size in the later months of the study, those being August and September, was significantly larger in the treated plots than the untreated.

Many thanks to the grower, BASF and FMC for really great support on getting this trial done.

The use of several pesticides is described in this post.  As always, before using any of these or other pesticides, consult the label and if there are further questions contact your local County Agricultural Commissioner.

Some of the Macrophomina action on the other side of the test field.
Some of the Macrophomina action on the other side of the test field.

Posted on Friday, October 26, 2018 at 11:40 AM

The Use of Esteem, Oberon and Prevam for the Control of Greenhouse Whitefly in Strawberries

A couple of months ago, I had a meaningful conversation with my colleague Gerald Holmes at the CalPoly Strawberry Institute concerning extension of our research results.  It dawned on me that over time I have accumulated quite a bit of information that could be pretty useful, but haven't really distributed it all that widely, just because like many of you I like doing stuff outside with my hands and also get distracted by more immediate needs. 

Anyway, I'll try and get some of these things out to this blog as we go along.   The following is a nice piece of work I did together with Plant Sciences in 2005 testing a variety of chemistries on whitefly in strawberry.

Introduction: Greenhouse whitefly, Trialeurodes vaporariorum, has been a pest of strawberries for many years in the Monterey Bay growing region.  In addition to the weakening of plants, whitefly feeding deposits honeydew on leaves and fruits and has been implicated in the dispersal of several viruses in strawberries.

This trial was designed to test the efficacy of the insecticides Esteem, Oberon and Prevam in controlling greenhouse whitefly in strawberries grown on the Central Coast of California.

Materials and Methods: The trial was done as a randomized complete block design of four replicates of three 30 foot long by 4 foot wide beds per treatment on PS592 variety strawberries in a field in Salinas, California. 

Application:  An application of all materials and mixes was made on August 11, 2005.  Subsequent applications of certain materials were made on August 21, August 31 and September 9, 2005.   See Table 1 below for timing of each pesticide treatment.

Experimental applications were made at the rate of water carrier of 150 gallons per acre at 150 psi pressure. Applications were made with a motorized backpack sprayer with a hand held boom consisting of 10 8001 flat fan nozzles.

 

Table 1. Treatments, Rates and Timing

 

Product 1,2

 

Rate (Product / Acre)

No. of Appls.

Application Interval

1. PrevAm

0.4 % v/v (= 51.2 ozs. / 100 gals)

3

10 days

2. Esteem 0.86EC

10 fl ozs / acre

2

30 days

3. PrevAm +

     Esteem 0.86EC   

     (tank-mix)

0.4 % v/v (= 51.2 ozs. / 100 gals) + 10 fl ozs / acre

2

30 days

4. Oberon

16 fl ozs / acre

2

30 days

5. PrevAm +

     Oberon (tank-mix)

0.4 % v/v (= 51.2 ozs. / 100 gals) + 16 fl ozs / acre

2

30 days

6. Brigade WSB

32 ozs / acre

2

10 days

7. Pyganic 1.4EC

64 fl ozs / acre

3

10 days

8. UTC

(untreated control)

-----

-----

-----

 

Evaluation:

Counts of adult whitefly were made by randomly sampling and turning over, without detaching from the plant, 40 medium-aged strawberry leaflets per replicate plot and counting the number of adults present.  Adult whitefly counts were be made from all of the treatments at the following intervals:  0-day (just prior to first application), 1-day after each application, and 10-days and 20-days following the final application of treatments 2 and 3. 

In addition to the adult counts, separate counts of whitefly eggs and whitefly nymphs were made using a random sample of at least 10 medium-aged leaflets per replicate plot, taken at each evaluation interval specified above for the adult evaluations. 

Results were tested statistically using a multiple comparison procedure (Least Significant Difference at the 95 percent level of significance) to determine whether the means of counts and percentages per treatment were significantly higher or lower from the other treatments.  The graphs below give a pictorial presentation of the results.

Conclusion: Treatments of Prevam and Brigade limited numbers of whitefly eggs, nymphs and adults to levels significantly lower than the untreated control on many evaluation dates. Esteem and Oberon mixed with either Prevam or Kinetic gave exceptional control, with consistent and significant control over other treatments of whitefly eggs, nymphs and adults over the course of the study.

 

Greenhouse whitefly adults with waxy exudate.
Greenhouse whitefly adults with waxy exudate.

Greenhouse whitefly eggs.
Greenhouse whitefly eggs.

Control of greenhouse whitefly eggs with various materials.
Control of greenhouse whitefly eggs with various materials.

Control of greenhouse whitefly nymphs with various insecticides.
Control of greenhouse whitefly nymphs with various insecticides.

Control of greenhouse whitefly adults with various insecticides.
Control of greenhouse whitefly adults with various insecticides.

Posted on Thursday, October 11, 2018 at 1:31 PM

Extension Meeting: Management of Gophers and Groundsquirrels

To be held at our office at 1430 Freedom Blvd, Suite E in Watsonville on October 24.  Sign in starts at 730 am and the meeting goes to noon.

Get here early, looks to be a pretty heavily subscribed event.  Agenda below.

Posted on Monday, October 8, 2018 at 12:17 PM

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