I’ve been continuing to track some of the reports of injury to conifers associated with the new herbicide, Imprelis. Interest in the problem is likely to escalate given a front page article in the Sunday’s Detroit FreePress. http://www.freep.com/article/20110710/NEWS06/107100467/New-lawn-chemical-chief-suspect-mysterious-deaths-trees
I visited about ten sites last week with an applicator that had used Imprelis this spring. The landscaper was a certified applicator with about 15 years of experience with herbicides, insecticides and fungicides, who was knowledgeable about his chemicals and plants. We saw bout 50 trees, mostly pines and spruces with varying levels of injury. The typical symptoms were brown or off-color needles, and stunted or twisted shoots. Damage was mostly limited to the current flush of growth, resulting in a distinctive pattern of growth. In many cases, there was evidence of spiral movement up the trunk of the tree. The most rapid growing points (usually terminal leaders) were most severely affected. Based on my experience with other forms of herbicide injury and other types of environmental damage, I suspect all but the most severely injured trees would recover is given enough time and some corrective pruning. The problem, of course, is that most homeowners don’t want to wait around while the tree in their yard tries to rally.
Some photographic ‘highlights’
The $64 question now becomes, “What happened?” In order to receive registration from the US EPA, each new herbicide has to go through extensive testing. According to DuPont, over 400 tests were conducted with Imprelis. Despite some claims elsewhere on the internet, this testing included independent university trials on spruces and pines at up to 4x the labeled rate. The key to unlocking the mystery of Imprelis injury will probably lie in understanding how conditions in actual application conditions differed from the testing.
Today I was sent a link to a posting on “droopy leaves.” Essentially, it suggests that droopy leaves are a means to conserve water on hot days and that watering these plants causes more problems than it solves because the roots don’t get enough oxygen. A link to the science of transpiration is provided. The advice is to wait until the evening and if the plants perk back up, then they didn’t need water after all.
This is one of those maddening articles that has enough science in it to make it sound reasonable, but is ultimately incorrect in its assumptions and advice. It’s worth looking at the topic in a little more detail.
Some plants are adept at conserving water in hot weather. Their leaves tend to be small, thick, with a heavy layer of waxes protecting the surface. Leaves can also move to limit their sun exposure and thus reduce the heat load. But wilting is not a method of conserving water. Instead, it’s a sign that water loss (evapotranspiration through the leaves) exceeds water uptake from the roots. And if you ignore wilt, you do so at your own peril. Once terminal wilt is reached, it’s all over for that part of the plant.
Wilt. Sorry it’s a fuzzy photo.
Large, thin leaves, common in many of ornamental, annual and vegetable species, do not conserve water. Tomatoes, zucchini and black-eyed susans, the plants specifically mentioned in this article, are not water conservers. Chronic wilting of these and other can eventually cause leaf tip and margin necrosis (or tissue death). It also reduces growth, so that your yield of tomatoes, zucchini and black-eyed susans will be decreased.
Leaf tip and marginal necrosis from chronic drought stress
So yes, do water your plants if they are wilting in the midday heat! Use mulches to conserve water! (You’ll notice in the photograph on the linked site that the plants are in bare soil.) Fine root systems are generally near the soil surface, and keeping these hydrated keeps them alive. You won’t see an instantaneous response to watering if plants are already wilting, but they will recover – much better than if you don’t water them at all.
Sorry about the long wait in discussing the weekend’s post! (Technical troubles with access here in BlogVille.) In any case, many of you zeroed in on the defunct lime kiln as a possible pH adjuster. It would have been really interesting during those years to see how materials were processed – for instance, was there a lot of lime dust that settled over the area? Where did the limestone come from – was it carted in by train or was it local? Were chlorosis problems visible then?
In any case, my educated guess is that a lot of limestone chunks brought to the area for processing were left scattered around the site and were eventually buried over time. Plants recolonized the area, but where these chunks of limestone are sited we have pockets of chlorosis. The only way to tell for sure would be to test the soil pH, and I did not have pH strips in my backpack.
An artifact from the old settlement, long since covered by the forest.
It’s high season at our blueberry farm. Each morning, the yard fills with cars (at 7:00 a.m. – aargh) and eager blueberry pickers hit our four acres of Northern Highbush berries. No late freezes, lots of hard work by our honey bees, and good rainfall have added up to a blockbuster crop. Certainly helps with the mortgage.
Running a you-pick ( U-Pick makes me itch) farm is an …interesting experience. Upside – you do the picking, we weigh the buckets, we take the money – $2.40/lb + tax. Very reasonable for big, fat berries. Our average sale is right around 10 lbs. I’d (theoretically) invite 90% of our customers to stick around for dinner – they’re that nice. Downside, besides hot, grumpy children, bee stings, and porta-potties: some people literally eat their way across the field. We absolutely expect pickers to taste a few as they go. That’s part of the you-pick experience. But I have witnessed some remarkable acts of blatant face-stuffing. Kids, I can kind of understand, but adults? I mean, do you eat your way through the produce section of the grocery store? The truly noble customer recognizes this and offers an extra dollar or two (“Gosh, I may have eaten a lot”). But the clueless #%$& who eats with both hands for an hour and then pays for a pound makes us a bit queasy. We get reports all the time from concerned customers i.e. “See that guy in the brown hat? He’s eating more than he’s picking.” One incident that comes to mind is a lady that completely denuded a 6′ plant; encouraging her daughter to eat the whole time, and then paid for less than a pound.
We try not to sweat it – maybe it’s a compliment as to how good our blueberries are – but it still puzzles me. What am I missing here? Why is this acceptable? Taking a tip from another local farm, we put out a jar near the register last week. They call it a “sin jar” but that’s a little too judgmental for us. We call it “munch money” and note that the contents of the jar goes to our local woefully-underfunded animal rescue and shelter. We make a donation yearly anyway; now it’s more fun (and satisfying), served up as a gentle nudge – we raised $120 for the shelter over the 4th of July weekend alone!
Today my family took our annual 4th of July weekend hike. We ended up on a fairly new trail through the Robe Canyon Historic Park. It was a gorgeous day and we saw all manner of plants and animals. The highlight of this trail is an old lime kiln; bricks and other remnants of early settlers are scattered around the area. The kiln closed in the 1930’s. (The hot link embedded in the park name leads to a 2004 article about the trail and the history of the site.)
Ever on the lookout for interesting plants or plant problems, I found many of our native species with definite signs of interveinal chlorosis. This is indicative of a foliar deficiency of iron or manganese. These forest soils are rarely deficient in either nutrient, and they also tend to be acidic (meaning that it’s easy to take up iron and managanese; alkaline soils inhibit uptake).
So why are these native plants, naturally growing on native soils, showing iron and/or manganese deficiency?Answer on Monday!