The savage heat of the past few weeks has really wreaked havoc on our blackberries. Normally thought of as being fairly stalwart sorts of plants, relatively easy to grow with few disease and insect issues, blackberries seem to be revealing themselves as a bit sensitive to high temperatures.
Not only are we seeing many, many cases of white druplet and subsequent necrosis (first photo), but also leaves of plants, especially at the margins (second photo), are being burned. Close readers of this space will know that white druplet is caused by intense ultraviolet radiation, and that the marginal burn of leaves probably means that the plant is not keeping up in moving sufficient water to its extremities.
Most galling however has been the large amount of red druplet disorder, better known as reversion. As one can see from the third photo below, reversion is a nuanced reddening of pretty well the whole fruit (as opposed to the starkly demarcated reddening caused by redberry mite - see elsewhere in this blog). This occurs post-harvest, meaning the fruit looks just fine at harvest and only reddens when it's been in the cooler for a bit.
It's almost certain that this fruit reddening is being caused by rapid and large changes in temperature. Research has shown that fruit with an internal temperature of over 72.5o F followed by a fairly rapid drop to cold is most likely to experience red druplet disorder. Given that in our pronounced heat spell over the past few weeks, with temperatures in production tunnels up to and even exceeding 110o F (see photo below), and movement of fruit from that environment to the mid 30's of the cooler (a drop of more than 70o F) being the embodiment of a large, rapid change in temperature, then perhaps having a huge amount of reversion shouldn't be so much of a surprise.
Ways to avoid this problem during high ambient temperatures are to avoid getting fruit that hot into the box in the first place. To whatever extent possible, early picking and quick transport to the cooler are clearly best. The other, which has been explored by researchers and may be in effect in some areas, is a staged cooling which gradually brings down the temperature to avoid the rapid shock of what forced air at 35o F imposes.
Perfectly formulated exposition on one of the advantages of writing. Don't get me wrong, I like to write anyway, but I too have found myself with a much better understanding of a topic once I've gone through the process of writing about it. Writing about something forces me to wrestle with it, to research parts about it and nail down in my mind how all the parts fit together. The net result of course is that I have much richer understanding of the topic than before I started to write about it.
Adding on to this thought, I remember reading in Erica Jong's seventies bestseller "Fear of Flying" about one of the protagonist's high school boyfriends who could just wind a piece of paper into a typewriter and pound out a multi-page paper on medieval history. No forethought, no editing, just straight through and done. While at the time I was pretty impressed with the massive amount of knowledge it would take to actually do this, in my maturity I'm actually thinking those papers weren't that good - undoubtedly the raw facts of that subject were there, but I just can't see how anyone could piece all of them together in a coherent form in one go. Good writing just doesn't work that way, and I am made to wonder if a strong, reflective writer like Jong wasn't making that statement too.
There have been some reports of a small black wasp (photos 1& 3 below) associated with hollowed out raspberry laterals and some lateral death this past summer. What confounded us was actually getting a live sample, but we finally had a good one submitted (thanks Jaime!) and could make an identification that these are sphecid wasps of the genus Pemphedron.
According to the High Plains Integrated Management Website, sphecid wasps of the genus Pemphedron are aphid hunters. This is good, but the more interesting part for us on this is that these wasps actually excavate chambers out of the pith of plant branches (see second example photo below). Critically, the wasps gain entrance to the branch by any vertical break - pruning, tipping or branch breakage. Since neither the xylem nor the phloem elements of the plant are concentrated in the pith, one would not expect a lot plant damage coming from this activity. That said, the grower who has been communicating with me on this has indeed reported a correlation with some dead laterals and Pemphedron wasp excavation.
To answer the inevitable question, this is a "C" rated pest, meaning it's not invasive and not going to generate unwanted regulatory attention. I would leave it alone, but things change all the time and so it still it bears watching given the ability to cause plant problems.
Thanks to Jaime Lopez from Reiter Affiliated Companies, Pamela Cassar from the Santa Cruz County Agricultural Commissioner and of course Kevin Williams who did the ID for us at the CDFA. Great teamwork once again to get to the right answer and keep us in the know.
This just out of Growing Produce magazine:
"While berries as a whole have been on a strong upward trend for some time, organic growth continues to be at a faster pace than its conventional counterparts."
Year over year sales in organic berries have surged 22% in dollar value and 16% in volume.
The last paragraph of the article is probably the most informative, as it quotes retailers stating that the biggest hurdle to growing sales in organic is cost, indeed finding the "sweet spot" between convenience and fair pricing (is the implication that pricing is currently NOT fair!?) will be the key to future growth in this space.
I've had this forwarded to me a bunch of times over the past few days, and finally did have a chance to read the whole thing. Although I trend more towards the meat and potatoes fare of the Wall Street Journal, it's always a pleasure to read the beautiful mastery of English on tap at the New Yorker magazine.
I wouldn't say the title is quite congruent with the content, since the UC program plays a huge role in the story as well.
Final comment without getting into too much detail, is that while the author did a really good job of writing, some of the opinions shared with her (yes, opinions) don't agree with what I believe.