Where to Draw The Line on Home Remedies

On Tuesday Holly posted an extremely interesting article about how Bounce could help control fungus gnats.  Then one of our frequent commenters (and all around great guy) Ray Eckhart pointed out that he has a problem with promulgating an off-label use of a product.  And that got me to thinking.  What household products is it OK for us to suggest that a consumer use for a non-labeled purpose, and what products shouldn’t we suggest?  This is a question that has haunted me for a long time, so with this post I want to give you my line of thinking – I’m not trying to tell you what’s right or wrong – just trying to let you know my thoughts on the topic.

First of all, let’s admit that there are off-label uses of products which most of us hardly think about and simply accept as “generally OK.”  For example, I have never been taken to task for suggesting using a plastic bag for protecting fruit from insects or for suggesting that dish washing detergent may be a good insecticide.  Of course both of these pest control techniques have their drawbacks (it can get hot in the bags in the South, injuring fruit, and insecticidal soap can burn the foliage of sensitive leaves) still, using these products outside of their labeling doesn’t seem to bother people too much.  Likewise, the idea of using alcohol to stunt plant growth, eggshells to stop slugs, or milk to control plant disease doesn’t seem to upset people too badly (whether they work or not being beside the point).

But there are some off-label uses of products which could be considered obviously bad.  For example, controlling weeds by dumping gasoline on them and setting them on fire, or perhaps washing your ripe fruit in a cup of paint thinner.

Then there are the off-label uses of products such as mouthwash for plant disease and tobacco juice for insects.  I see these as neither obviously fine nor obviously terrible.  So where is the line to be drawn?

In my opinion, as an extension educator, I feel that it is my job to tell my audience (That’s you guys!) the facts about different gardening/growing techniques including those that are “off-label.”  I don’t feel that it’s my job to tell you what to do and what not to do (well…maybe with the exception of telling you not to pour gasoline on your weeds and light them on fire or not to soak your food in paint thinner!)  It is up to you to make your own decisions.

Let’s go through a “for-instance” here.  And let’s use one that I’ve written about – using hot peppers as an insecticidal spray.  Hot pepper sprays can work to control certain insects.  Just mix up a few hot peppers with some water, add some dish detergent, put it into a spray bottle, and off you go.  I have used sprays like this myself in small experiments to control mites, and they have worked reasonably well.  I have also read a number of articles showing that these sprays have at least some effect on certain pest insects.  But hot peppers certainly aren’t “labeled” for use against insects, and let me tell you, a little hot pepper in the eyes, or even the skin, and you can be in pain for hours.  Long term damage is unlikely – but not impossible.  So what should I, as an extension educator, do?  In my opinion exactly what I just did – give you the facts and let you make your own decisions.  I feel exactly the same way about Holly’s post about Bounce – she gave you the facts – if you want to try using Bounce to control something then that’s up to you.  Do I recommend Bounce for controlling insects?  No.  But I’m the kind of person who encourages careful experimentation, so I wouldn’t tell you not to use Bounce to try to control insects either – though I would tell you to be very careful and that unintended consequences might arise.

Will cabling a tree’s crown make it stronger?

In a previous column (December 1, 2010) I discussed the problems that wet, heavy snow can cause for trees and shrubs – particularly evergreens.  In response my colleague Terry Ettinger mentioned a cabling technique discussed in the 2nd edition of Arboriculture (1991).  I think it’s worth looking at the science behind this practice and some of the unintended consequences.

Harris’s Arboriculture text is considered the bible for landscape professionals, including certified arborists.  In the late 1990’s, Dick Harris was joined by Jim Clark and Nelda Matheny, two other gifted academics who have crossed over into practical writing.  In the 4th edition of this book (published in 2004), the authors caution about routine use of cables and other support systems for tree crowns.  They state that “evidence for the use of support systems to strengthen tree structure is anecdotal” and based on my reading of the scant scientific literature on the topic I must agree.

Older articles and texts tend to provide how-to instructions and diagrams on various cabling and bracing techniques, but little to no evidence supporting the practice. More recently, studies have provided evidence that drilling holes for cables, wires, bolts etc. increase the likelihood of introducing disease into otherwise sound wood.  As the tree continues to grow and change over time, even the best of these systems may need to be modified or replaced.  In fact, the systems should be inspected and maintained annually.  Crown cabling is not a permanent, one-time fix – and sometimes it isn’t even a fix.  Failures still occur, often just above the point of attachment of bolts and cables.  In fact, many arborists believe cabling should be the choice of last resort.

Some current research is exploring noninvasive methods of securing crowns, such as belt systems, that provide support without creating additional problems. As with any new technology, long terms studies are pending. Given the potential risks and lack of reliable benefit, I would not recommend cabling or bracing unless there were no other choices for saving the crown of a tree.

Bounce – it’s not just a fabric softening sheet…

…it’s an Integrated Pest Management tool!

[Note added after-the-fact: this was a  tongue-in-cheek bit of  hyperbole – kind of like “it’s not just a Job, it’s an Adventure.” Did not mean to imply that it actually IS an IPM tool. Very badly worded. Hence the beating I took in the comments. Live and learn.]

Fungus gnats (Bradysia spp.) are a pain in the bottom for commercial greenhouse growers. The adults are more of a nuisance than anything else –it just looks bad when a customer picks up your 6” pot of pansies and a bunch of little black gnats take flight.  It’s the larvae that are problematic. Adult females lay the eggs in especially damp growing media, and the newly-hatched larvae feed on the roots. There’s both direct damage and also speculation of easier infection of root-borne pathogens, of which there are plenty. 

 
Fungus gnat larvae, just making a living…

Standard control measures include insecticide drenches, biological controls including a specific strain of Bt (Bacillus thuringiensis – sold as GnatrolTM), nematodes, etc.  One of the easiest control measures is the one I teach my students: to not over-water, i.e. “grow dry”. But that can be difficult in a big greenhouse range with many different-sized containers, all which drain/dry out at different rates. Propagation houses also have high humidity levels and have to stay moist for rooting/germination purposes and are thus favored by fungus gnats.

Entomologist Dr. Raymond Cloyd of Kansas State University and his group were intrigued by Master Gardener anecdotes of dryer sheets repelling mosquitoes, though no research had been done. Could your common Bounce sheet also repel other pests? And, to take it a step further, what, exactly, repels them?  The answers are “yes” and “lots of volatile compounds.”

Their study was published last month in the journal HortScience. Honestly, I’ve never seen descriptors like “controls static cling” and “gives clothes a fresh scent” in a Horticulture journal. Hee! Plus the researchers made it clear this experiment specifically used Bounce Original Outdoor FreshTM. Still kind of humorous, but really good science and the part that’s usually overlooked in the translation to a News Story. Do NOT extrapolate results to include Bounce Spring Fresh, Fresh Linen, and certainly not Downy or Snuggle brands. 

The study had a simple design, releasing lab gnats (ha!) into a  many-chambered container and observing to which chamber the gnats gravitated to (or away from).  There were five different variations on this theme, including an alluringly soggy media sample; when the sample of fabric softener sheet was introduced, they stayed away in droves. All five experiments showed a fairly drastic aversion to the sheet. To determine what was fending off the gnats, they did a steam extraction on sheet samples and ran the condensate through a gas chromatograph – mass spectrometer to measure the volatiles.



Figure from Bounce® Fabric Softener Dryer Sheets Repel Fungus Gnat, Bradysia sp. nr. coprophila (Diptera: Sciaridae), Adults. Raymond A. Cloyd, Karen A. Marley, Richard A. Larson, and Bari Arieli, HortScience Dec 1 2010: 1830–1833

Well, there you have it. Linalool is a monoterpene alcohol found in lavender, basil, and coriander, and is known to be toxic to mites and insects.  Citronello is another monoterpene and lends lemony-freshness to lemon balm, pennyroyal, and rose geranium and has short-term “repellent activity against mosquitoes.”  Benzyl acetate, though not specifically mentioned in the results, is another natural fragrance compound, found in jasmine – and is also an industrial-strength solvent. One man’s solvent is another man’s perfume. Or fabric softener. I bet their lab smelled GREAT, by the way.

<
6

New Year’s Prediction: Invasive Fire Continues to Burn

Happy New Year!  I hope everyone had restful and enjoyable holidays.  In addition to looking back over the year that just past, a common New Year’s tradition is to make predictions for the coming year.  Without going too far out on a limb, one of my predictions for the upcoming year is that the debate over invasive plants will continue to intensify, especially as it relates to Landscape Horticulture.  Along these lines, a couple of recent articles by Gregorio Gavier-Pizarro and his colleagues at the University of Wisconsin and the USDA Forest Service caught my eye.

 

In both studies; “Housing is positively associated with invasive exotic plant species richness in New England, USA” (Ecological Applications 20:7, 1913-1925) and “Rural housing is related to plant invasions in forests of southern Wisconsin, USA” (Landscape Ecology 25:10, 1505-1518), the investigators conducted on-ground assessments of species richness and density of commonly listed invasive plants  (e.g., Japanese barberry, Autumn olive, Honeysuckle, Common buckthorn, Multiflora rose) in conjunction with spatial analysis of remote sensing data to examine patterns of invasive spread in the urban/wildland interface.  As one would expect, the presence and species richness of the invasives increased with development.  An important ‘take home’ message, however, is that disturbance associated with rural housing development and the creation of edges appears to be the biggest driver of invasive species encroachment.  That is, land clearing, road-building and other development activities create habitats that are more susceptible colonization – a condition referred to as ‘invasibility’.  So whether a particular homeowner plants natives or non-invasive exotics they may still contribute to the expansion of invasive exotic plants in their region by increasing its invisibility.

 

The other thing that makes this work and related studies significant is that I think we will see a continued shift in the efforts to curtail the expansion of invasive exotic plants.  In particular, rural housing development and associated landscape practices will become and increasingly intense front-line in the invasive battle.

</d

Friday puzzle uprooted!

Wow, we had some very creative answers on this one – and all of them made sense!  Peter, however, was spot on with his identification of roots (of a Thanksgiving cactus) growing in water (in an antique graduated cylinder).  I made it tricker by turning the photo upside down on Friday.  Here it is right side up:

What I love about this photo is that the various parts of actively growing roots are clear (more or less):  starting from the bottom you can begin to see the root tip and the hairless zone of elongation, followed by the zone of maturation with fuzzy root hairs, followed at the top by the area where lateral roots develop.</d

Last puzzle of 2010

I had a few weeks’ hiatus while scrambling around for the holidays – but have one last teaser for you before the close of 2010.  This photo is reminiscent of what Christmas trees will start looking like in the next few weeks. Can you figure out what it is? 

Ignore the parallel horizontal lines – they will be explained on Monday.  And yes, the photo quality’s not great, but the reason for that will be clear on Monday as well.

Have a very happy new year, and be sure to keep reading us in 2011!

One To Go!

Just one more little holiday to go over holiday week (A week during which faculty at UMN were put on furlough — in other words unpaid vacation), but for many of you I’m sure it’s a big one: New Years.  I’ve never been one for New Years resolutions.  It’s always just seemed kind of artificial to me.  Still, some people find real motivation with the passing of a new year.  What about you?  Any great New Year’s resolutions out there related to gardening?

Annual reporting – and you can help!

As many of you know, we Garden Professors justify our existence as faculty members every year through annual reporting.  Blogging is one of the newer educational opportunities that most university systems haven’t quite figured out how to measure and evaluate.

So we’re taking matters into our own hands. I’ve created a short survey to assess our effectiveness in outreach education in the blogosphere. 

The more feedback we get, the easier it is for us to make the case for continuing this effort.  (And feel free to suggest other questions or metrics we should include.  This is a first attempt on my part to create this feedback tool.)

Thank you all for a great year!