Weather pattern and disease pressure

[fireaxe]

Having a thought for a few years now that perhaps annual weather patterns have significant impact on what diseases show up. Anybody read research on this? I didn't have much luck web searching.

 

[Tom Dunlap]

Many bugs that carry or transmit diseases are killed by low temperatures. If there is an unseasonably warm winter or two the disease rate will spike.

In the 2000-2004 winters in the Twin Cities there were too many warm winters. There was a HUGE amount of Dutch Elm Disease as a result. The outbreak was very much like the DED epidemic in the '70s. Whole blocks of boulevard elms marked with red paint rings for removal.

 

[fireaxe]

Thanks for the response

I have noticed this type of a trend on many things. The one that has me going today is an evaluation/recommendation consult that I have to perform (just RCA practice). This is a situation from some time ago. The home owner's trees of a particular species have lost most of their leaves due to Actinopelte leaf spot disease in early September. The year in question saw super high rainfall followed by drought. I have to tease out a solution - part of which is going to be advising weather monitoring to determine the need for potential spray applications of fungicides. Typically, in my practice, I would advise nothing - the leaf damage is done for the year on leaves that would be shortly shed anyway. On a disease that typically has little impact, I would normally advise staying away from applications to prevent the problem, but I am in the minority there.

I digress. The cycles that follow particular weather events seem to have some pretty drastic effects. I still haven't found any research to support my position.

 

[Tom Dunlap]

Maybe the minority, but your thoughts are what I have been taught about disease control. If there is vector, like weather conditions, that encourage a pathogen, direct the treatment based on those vectors.

One problem that came up irregularly was anthracnose, especially on silver maples. What I learned was that the treatment needed to be applied close to bud break to reduce the effect of weather conditions that might come up weeks later. If it was dry and warm...on anthracnose. It seemed like the conditions would be 'right' about ever 4-5 years. That meant that 3-4 treatments would be applied for 'no reason'...just a gamble. Is it worth the gamble? I sure couldn't justify it to my clients. They could spend their tree budget on doing things that were 100% effective like pruning, cabling, fertilizing, etc.

Ag and hort production has paid attention to weather for decades. since their 'crop' comes to market quickly they need to be ahead of the game. For amenity trees the 'crop' that we maintain is decades and centuries old. Arbo and forestry haven't looked at short term effects like the other crop industries have.

 

[fireaxe]

The emperor has no clothes.

It is the long term effects of applications that I worry about. I was on a property a number of years ago and I could not find ONE single insect. It was scary! I know that may sound like a peculiar fear. I am old enough to remember love canal :|. The happiest trees that I get to work on have had the least services performed on them .

I would argue against cables and fert almost as much as preventative pesticide treatments. I think of the leg braces we used to put on children as the example. Crutch it or brace it and the supporting tissues will not develop.

I read a study done in the 30's about applying fertilizer to forest crops. The findings were that the resulting fiber was not so useful. I forget what exactly was the reason, I only put the conclusion in my brain.

Tim the anti-salesman :|.

 

[Tom Dunlap]

Ohhh....lets not get side-tracked too far

Take what I said as big picture observations not under the microscope.

One time I was talking with a salesrep from a 'scorched earth' PHC company about treatment thresholds. Like you found, they would put the fear into their clients and kill any organism. Good for the paycheck, I did question how reasonable that was for the environment. Treating lilacs for powdery mildew seems like a waste...except to make money. One year powdery mildew didn't show up...very dry and warm year. A client asked what was wrong with their lilacs because they were too green. they'd gotten used to seeing the white sheen on the leaves and took that to be normal.

 

[fireaxe]

I'll try to stay on point. I will not quote the scorched earth policy . I have to say that I do not employ a spray tech, so I don't have that mouth to feed. The fear tactic for sales just ain't right and is practiced way too much. I always say to clients that if I were to walk into a doctor's office and that doctor tries to scare me into buying a treatment, I will seek another doctor. Tell me the options, the probable outcomes (without lying) and let me decide.

For your example of powdery mildew - tip of the iceberg for most application recommendations. I seriously think the only fungal disease that the typical PHC guy knows is Anthracnose and every tree has it.

The one I am most irritated by is prophylactic borer treatments via injection. I have a few clients with dying trees - girdled at the root collar from multiple years of injections.

 

[RopeShield]

http://www.ipm.ucdavis.edu/WEATHER/ddconcepts.html

Hope this is a good start for you.
There are books available and your local University or Horticulture station will be a good source.

Cheers

 

[oceans]

On this topic, has anyone practiced companion planting, or increasing biodiversity as a measure of preventive care?

 

[fireaxe]

Absolutely! It usually only sells to people that absolutely love me though

. Some of the higher pressure sale spray rig operating guys want to apply stuff to make it better (medicate)

. I feel pretty strongly about the forest community models that I have been taught. You really can't go into a pure stand of much of anything (that I have seen in my travels anyway). There is always a mix and there is always a fairly narrow range of circumstances a particular species is found. We don't harp on these facts often enough.

Can't have a stable community until you get a few trades operating. Need that doctor, trash guy, farmer, tree guy, etc.

The two things I find amazing are how little we understand about those interactions and how little we understand about the natural habitat parameters of the trees that we install.

For example - silver maple is a river tree. Sandy soils. High air requirement for roots (a total guess). Plant in a clay soil - major surface root problem. BUT tollerates wet OR dry VERY well. Grows super fast (a super flood will come along about every 50 years and wipe us out) Combination of factors = tree removal in 40 years if planted around a residence (no river to be found). You may replace silver maple with river birch, sycamore, willow, boxelder (sometimes) in the above sentences.

funny graemlins

love it.

 

[oceans]

Thanks for the post, Tim. I've been away from the buzz for a few days now, and was glad to see your reply. I've been reading a bunch on the subject of Permaculture and will soon be helping with an installation at my apartment. The interrelationships are quite something to read about, though much can be learned through observation over time.

 

[UrbanForester]

A TRUE PHC program is not about "scorched earth" spraying OR guessing about weather patterns. Its about being on the clients property often enough to be able to treat if insect/disease issues are LIKELY to occur. PHC is about prevention through monitoring. If you wait until the "weather patterns" are right for a given pest issue, you will be too late. Most fungicides, for example are protectants. While some have systemic ability, very few have kickback on active fungus. The idea is sell your program based on monitoring and the implementation of IPM techniques to keep pests below threshold levels. Of course keeping in mind there are 2 VERY different levels, aesthetic and economic. This all needs to be discussed with the client, so THEY understand. I have 2500 PHC clients and renew at a 97% rate yearly.

 

[fireaxe]

[ QUOTE ]
A TRUE PHC program is not about "scorched earth" spraying OR guessing about weather patterns. Its about being on the clients property often enough to be able to treat if insect/disease issues are LIKELY to occur. PHC is about prevention through monitoring. If you wait until the "weather patterns" are right for a given pest issue, you will be too late. Most fungicides, for example are protectants. While some have systemic ability, very few have kickback on active fungus. The idea is sell your program based on monitoring and the implementation of IPM techniques to keep pests below threshold levels. Of course keeping in mind there are 2 VERY different levels, aesthetic and economic. This all needs to be discussed with the client, so THEY understand. I have 2500 PHC clients and renew at a 97% rate yearly.

[/ QUOTE ]

I read the manual.

I am with you on monitoring and making informed choices about the threshold levels. I am sure you have integrity when it comes to applications though many firms see PHC as a profit center and treatments as sales.

By our state's law - prophylactic treatments aren't permitted. If you apply, you are supposed to have evidence of a target. This is not enforced at all.

Do you take tylenol before you get the headache? How about applying calamine lotion BEFORE you get the poison ivy? Get your flu shot this year? Personally, I take the tylenol IF the headache is debilitating AND I can't get the underlying cause corrected (looking up all the time). I use gloves and long sleeve clothing around poison ivy and DO NOT TOUCH my face with my gloved hand. Flu shot - seriously? The fire department has been pushing that on me every year - can't say for sure I have ever even had the flu.

Sidetrack thought: Do trees have a proactive immune system? Sounds like a good thread.

I do not understand all of the mechanisms involved with all fungicides - but MOST of the labels state therapeutic and not curative and work on actively growing cells. I may be wrong, remembering only the take home lessons from micro class, but most fungi reproduce by spores which are nearly impossible to eradicate and found EVERYWHERE. Most fungi are saprophytic in nature with their place in life cycles not understood well. Admittedly, I may not be the most current PHC guy around. I do listen when I am at conferences typically several times a year. Most of my thought processes on the matter are anecdotal in nature which is why I asked if anyone knew of pertinent research.

What I was getting at in the original post was whether it has been recognized that a particularly wet spring leads to a high prevalence of this or that fungi. Sort of a rain-day calendar.

If we were to have 2500 PHC clients, a few spray techs and a few application units, we would know for certain where we were in the degree-day calendar and we would be able to demonstrate to a client the indicators for applications. Absolutely no fert would be applied without a indicative soil test. I do not believe AT ALL that we have this going on as standard practice in MOST companies, even if the company, on paper, has these policies. I have a good example I will give privately if you wish.

As it stands now, for me, I do not do these things. Most of the time problems seem to resolve themselves while I watch/monitor and try to get the environment that the tree is growing in as close as I can to the tree's natural habitat. Sometimes companion plantings are helpful.

 

[UrbanForester]

PHC IS a profit center. I am in the business to make money, as most businessmen are. We are a full service tree company that runs 4 pruning crews as well as lawn care and PHC. A 1-man PHC truck produces more than a 3-man pruning crew every day. Dollars, profit, quality and ethics do not HAVE to be mutually exclusive terms. I have 34 employees that depend on me, so yes I do make money doing this. My thoughts on HOW to do this are based on 25 years of experience. Waiting for the right conditions, or waiting to see lesions of Apple Scab, Diplodia Tip Blight, Dothistroma Needle Blight, Rhizospherea Needlecast means controlling it just got much more difficult. Disease prevention is critical. Once a paticular pathogen gets a "foothold' in your plants control is marginal. Loss of leaf/needle tissue means reduced photosynthesis, then reduced sugar/carb storage, so increased stress. That translates to reduced innate defense mechanisms in the tree, the first thing thats shut down when a tree goes into stress. Now, have I ever seen a crabapple die from Apple Scab, of course not, BUT is a mature crab that defoliates for multiple growing seasons more likely to become pre-disposed to nectria canker, etc. absolutley. With regards to fungicides I've sprayed everything from benelate in the 80's to propiconizole now and have yet see any tree improve, once infected past ANY stage but minor. What they claim on a label is based on controlled testing in controlled environments, not real world urban forestry. Finally you mentioned environment/humdity for pathogen activity, the answer to that is a resounding yes. While GDD can't be applied to pathogens, humidity plays a monster role. For example Apple Scab becomes active after 72 hours of rain in 55 degree weather. Most diseases have temp/humidity activity characteristics. However then you also have to take into account the tree. Diplodia Tip Blight infects at candle break. When does that occur? Here in Michigan that can vary by 3 weeks. There are too many varibles involved in disease control to provide exact timing thats why prevention by anticipating environmental conditions is crucial. I didn't mean to be negative towards your methods or approach OR insult your intelligence. I hope this insight into my approach is helpful.