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

Strawberries

Distinguishing Drosophila Larvae from LBAM Larvae

Sometimes what seems so obvious from the isolated heights of the ivory tower is not so obvious for those working in the field.

In a query which is far from the first time, I had a question submitted over the weekend over whether worms emerging from strawberry fruit were LBAM.  LBAM, which is the acronym for light brown apple moth, is also found in berry fields as is Drosophila, but as a quarantined lepidoperous pest responds to different methods of control as well as carrying a heavy regulatory risk with it.  In short, it's real important to not get the two mixed up!

The picture below of the bell jar where the fruit in question was held shows what was found.  It's not LBAM. The larvae are quite small (probably 1/8" when fully grown), are white, are emerging from inside the fruit and have no webbing.  

The second picture is of an LBAM larva on strawberry. It's green in color, relatively large compared to Drosophila larvae (1/2 inch when fully grown is common), rarely is found inside the fruit and is almost always accompanied by an abundance webbing (as it is in the picture).

As always, really appreciate the input and questions as to what is all going on out there. 

Drosophila larvae emerging from strawberry fruit held under a bell jar.
Drosophila larvae emerging from strawberry fruit held under a bell jar.

LBAM larva in strawberry.  Green larva emerging from under the calyx, note the abundance of webbing to the left of the picture.
LBAM larva in strawberry. Green larva emerging from under the calyx, note the abundance of webbing to the left of the picture.

Posted on Saturday, April 27, 2019 at 11:38 AM

Blowout Beginning for Botrytis Trial

Those of you familiar with my program of research and extension are aware of my rising interest in developing a protocol for consistent treatment separation in Botrytis gray mold fungicide work.  More often that not in the years past, we ended up doing all of the spray and evaluation work just to end up with data with no significant differences, even between the untreated check and the grower standard.  This is a widely known issue in the strawberry researcher community, but so far with little progress on ameliorating it, apparently.

I certainly haven't been idle in this quarter, and have tried larger plot sizes, longer intervals between fruit harvest and even last year putting misters in the plots to soak the flowers and fruit before sunset for the long period of free moisture necessary for development of this disease.  All to no avail, and significant treatment differences were still elusive and rarely found.

On reviewing the literature this past winter, I did find that California Botrytis trials running early in the year, like in March and April, tended to pick up differences in treatment from time to time.  That was the only signal I needed to arm up my spray gear and give it a shot.

As noted in a previous post, my colleagues at PSI and I initiated the first spray application on March 19 before a fairly decent rainstorm (1/2", that counts - CIMIS station # 111 is about 100' away, so it's an accurate number), and proceeded to do the same two more times ahead of subsequent rains and showers (see Slide 1 below,).  The goal of course is to protect the developing fruit and critically the flowers for the periods of free moisture propitious for development of gray mold disease.

Harvest began two weeks ago, and along with picking marketable fruit, cull fruit and evaluating Botrytis in the field, the crew keeps a subset of the marketable fruit for me to take to the lab for clinical evaluation.  The clinical evaluation is done as per the protocol developed by former UCCE plant pathologist Steven Koike, meaning holding the fruit at room temperature and looking for signs of Botrytis infection in the days that follow.

As you can see in slide 2 below, the clinical results are very, very solid.  The untreated control is very much more infected than the grower standard ( 2 applications of Switch, followed by 2 applications of Captan) and the biologicals and a special type of oil are somewhere in between.

Very encouraging results here at the start of the work. I'll reach a bit and think we could be on our way to uncovering the path to a consistent screen of Botrytis fungicides in strawberry.

Slide 1: Rain data from CIMIS station #111 for March and April 2019.  Red arrows mark spray dates.
Slide 1: Rain data from CIMIS station #111 for March and April 2019. Red arrows mark spray dates.

Botrytis clinical evaluation #2 for the 2019 campaign.
Botrytis clinical evaluation #2 for the 2019 campaign.

Botrytis on strawberry.  Note that fruit here is substantially smaller than the fruit in our 2019 study.
Botrytis on strawberry. Note that fruit here is substantially smaller than the fruit in our 2019 study.

Posted on Thursday, April 25, 2019 at 1:08 PM

Don't Like Writing?

If you don't like writing, you are in distinguished company.  This past weekend, I read a most interesting comment from Peggy Noonan, who writes a weekly column for the Wall Street Journal and used to write speeches for Ronald Reagan.  To say the least, she is very gifted at her craft and recognized as such by some of the best in the game.

Yet, she writes this in her column.  "Writing is never pleasurable, at least for any one sane...".  

I really like to write, and am curious what she means by this.  For me, writing is a creative process that lets me get my head around an idea in a way that talking about it, or listening to it, never will.  Rather than consuming an idea undigested in some vaguely understandable form, writing about it allows me to turn an idea over in my mind from many angles, and figure out how I am going to understand it.  I enjoy that.

Maybe I'm not aware of it, but perhaps I am just not sane.

 

 

Posted on Thursday, April 11, 2019 at 4:49 PM

Comparing Phytotoxicity Damage with Zythia

I have a pretty unique opportunity going right now in one my test plots.  The plot has a fairly decent run of Zythia going, at the same time one of the test materials is causing a slight burn on the leaves (it's an unregistered oil), so we have the chance to compare the two.

Those of you have called me concerning Zythia know that I look for the little brown to black spots representing fruiting bodies (thank you Steven Koike!) in the centers of the necrotic areas caused by the fungus to confirm it.  Usually there are concentric rings of growth also, and while these aren't diagnostic they for sure point out that symptom in question is being caused by a living organism.

Contrast that with phytotoxic burn of the leaves and other plant parts.  No fruiting bodies for sure, nor any rings of growth.  Too, if one is familiar with how spray droplets disperse on the leaves, it should be a small matter to trace back areas of burn to where water would gather.  Veins, edges of leaves and low spots on the foliage are common.

Let's go to the pictures to make my point, shall we? 

View from the top, distinct areas of tan colored burns distributed around the most exposed leaves.
View from the top, distinct areas of tan colored burns distributed around the most exposed leaves.

Spray burn close up.  Distinct tan area at leaf edge.
Spray burn close up. Distinct tan area at leaf edge.

Leaf severly infected with Zythia fungus.  Note the abundance of dark colored fruiting bodies towards the center of the spot.
Leaf severly infected with Zythia fungus. Note the abundance of dark colored fruiting bodies towards the center of the spot.

Comparing phyto burn (leaf on the left) with Zythia (leaf on the right).
Comparing phyto burn (leaf on the left) with Zythia (leaf on the right).

Challenge question.  Which one is the phyto?  Spoiler alert - the answer is now in the comments below.
Challenge question. Which one is the phyto? Spoiler alert - the answer is now in the comments below.

Posted on Wednesday, April 10, 2019 at 12:39 PM

Bounty of Big Berries on the Way

Sure enough, just a few days of real summer weather and the strawberry plants are pushing out some seriously high quality fruit.  There's a lot of messed up ones yet in the field that came to fruition during the rains of the past few weeks, but once those are cleared out and all the new ones come in we are up for some big harvests of nice fruit.

Found this beautiful number in my KPAM crop termination plot.  San Andreas variety, almost as big as my hand, easily tops 50 g.
Found this beautiful number in my KPAM crop termination plot. San Andreas variety, almost as big as my hand, easily tops 50 g.

Posted on Wednesday, April 10, 2019 at 12:08 PM

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