Agronomy is extremely local—but often a common thread connects one problem to another. I got to help a grower solve a ‘new growth death mystery’ recently, and since the outcome carries lessons that might be useful to all of us, he allowed me to share the story with you.

You have flooded four times this spring: for trash removal, frost protection, and finally a frost/bug flood on May 29-June 1. Your vines had progressed out of dormancy nicely, and new growth on the uprights was right on schedule–but as you lowered your bug flood, you see your new growth has dried up and died in the downwind corner. What happened? How do we recover?

The damage we see is very uniform and very complete. All the new growth in this section has died. Taking some upright samples under the microscop at home, you can see necrotic tissue continues right up to the “scar”, which is the delineation between last year’s growth and this year’s growth. So everything tender died, and everything hardy survived.

The obvious straight line and location of the damaged patch makes us pretty certain that this isn’t an application issue–checking chemical and fertilizer history confirms that.  These Mullica Queens were planted in 2011, and were sanded in 2013, 2014, and 2015—but not since.  

We know a few things before we arrive at the bed. Being under water is stressful for a growing plant. Being too hot is stressful, too, and shallow water warms quickly. This bug flood saw daytime temperatures at 70F with no clouds, which means several degrees warmer in the water.  So we know the vines were stressed by lack of air, and by heat–but why did the majority of the bed come out fine, and the downwind corner die? Was there floating trash during the flood, that also prevented the vines from catching sunlight?

When we got to the bed, we found something fairly dramatic that we hadn’t predicted. When I went to take a root sample—the whole plant came up in my hand with almost no effort. We checked around throughout the area with death, and the healthy area, and we found that the areas with death all came up entirely too easily. In the healthy areas, the roots anchored the vines as usual.

Poking into the soil where the plant had come from, I found several inches of accumulated leaves. It ws easy to understand why the roots didn’t “hold on” to anything–they were basically in a cranberry leaf trash substrate. Amaya phrased it “it’s almost like they were hydroponic”.

Consider the difficulty of growing hydroponic plants—you have to keep a very consistent nutrient supply, temperature, pH, everything. A plant’s root system and its interactions with the soil often work like a buffer when the plant experiences stressful conditions. Even when air temperatures are too hot, a plant can survive without losing yield if it has a strong root system and a cool soil temperature. (Good soil temperature is maintained by a good canopy, good soil moisture, and, ironically enough, SOME residue from prior crops). With no root/soil interaction to buffer for over or under supply, these cranberry plants needed to be spoon fed and maintained in a perfect band.

Diagnosis:

We were stressing the vines in several ways. Being underwater once they’re out of dormancy is a stress. Being hot (and being in standing water on a sunny day gets hot) is a stress. Having sunlight blocked by leaf trash prevents photosynthesis to provide quick energy for sustaining life is a stress. And while the vines throughout most of the bed had strong roots and the ability to withstand a bit more stress—our vines in the trashy corner of the bed, where the roots had no soil to anchor them—couldn’t live to fight another day.

Best path to recovery:

-Improve root growth. I believe the best path to this is sanding, and I would go further into the bed than the crisp line where we saw the damage, since I assume there is more leaf trash than usual throughout the leeward side of the large bed. Sanding the entire bed should be a priority.

-Minimize other stresses to these vines. For herbicide apps the rest of this year, skip the damaged area. I would turn off the 2021 Casoron here. When harvesting, get the water off of that bed as quickly as possible. Also if you can suction off leaves a few times that might be a benefit.

We do have a happy ending—in addition to finding out the cause so we can protect them better in the future, the vines have new growth recovering:

This article was posted in Cranberry and tagged Cranberries, new growth death, stress.