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.
|Adult normal leaf
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.
Here's one that I've never seen before. True spiders with webbing so heavy that it could interfere with the growing point of raspberry.
On approaching the field, once notices a lot of the very top of many raspberry plants in this field under tunnels with those leaves rolled up. Of course this sets off alarm bells that it could be LBAM, but closer inspection reveals a far heavier webbing than is customary for a leafroller. And... lots and lots of spiders.
What would the call be to do about this? Hard to say, readers if you have experience and/or suggestions what to do, write in and I'll post your answer.
Pics taken today of the situation posted below.
A couple of pictures below from a farm call concerning unusual damage on the tips of growing raspberry. Some of the leaves are affected as in Photo #1, but others are pretty well aborted and not growing at all. Incidence wasn't more than 5%, but still this is disconcerting and I was over at the grower field within 15 minutes to take stock of the situation. No flowers or fruit yet on the plants.
No signs of frass or webbing that would be associated with leafrollers (some like to feed at the nitrogen rich tips), and I've checked this sort of thing in caneberries before and haven't found that viruses or nutrients are at cause either.
But we did find lygus and Photo #2 explains that we may have identified the cause. While some lygus were to be found wandering around on leaves, others were nestled in the growing point of the plant, which on the very young leaf can show up as a lot of damage later on when it fully expands. It's quite possible that this insect activity could be causing the tip to die entirely in a situation reminiscent of "black flagging" in cotton, which is the death of terminals in cotton caused by lygus feeding.
I was called out last week to evaluate the following situation, which I am sure is not at all unfamiliar to any of you who spend time working with raspberries under tunnels. Symptoms, as shown in the pictures below, consist of very obvious yellowing, sometimes half the leaf, sometimes less, sometimes more, started a few days after the tunnels went up and a run of hot days.
Consistent with the work we have done on this issue in the past, it's fairly clear that the leaves are dying from the high temperatures in the newly erected tunnels. The elements nitrogen, phosphorous and potassium are being remobilized from the yellow leaves to newer leaves on the plant, while others, markedly calcium, are left behind or continue to accumulate (look at the large differences between iron and boron in healthy green leaves as compared to yellow leaves). Curiously, copper trends high in both – usually I see that around 2 or 3 parts per million.
Recommendation to the grower last week when I took the samples was to vent the tunnels by moving the plastic up a bit, and happily he reports an improvement in the plants already.
Excellent Powerpoint given by UC Davis' Marita Cantwell at Oleg Daugovish's caneberry meeting this past April. Probably the best you are going to find anywhere concerning post harvest handling of these delicate fruits: