Managing MPB After a Wildfire -Sky Stephens, CSFS

Managing Mountain Pine Beetle After a Wildfire

7-9-12

S. Sky Stephens

970-491-7282 or sky.stephens@colostate.edu

Recent wildfires throughout Colorado have raised a number of questions about managing post-fire forests. In this document I hope to address a number of issues that have come up concerning mountain pine beetle (MPB), including the impacts of wildfire on the beetles and which management activities may be appropriate post-fire. Given the diversity of burn severity and the range of impacts on individual trees throughout a burn area, all information provided will be general. Please contact me with specific questions and we at the CSFS will do our very best to assist you in making post-fire management decisions.

Direct Impacts of Recent Fires on Beetles:

• Recent fires have impacted large areas of our forests; however, the area impacted by MPB is much larger.

• Depending on the level of burn severity in an area, the direct impacts on beetle populations are highly varied within the fire area and along its boundaries.

• Some fires (High Park, Hewlett and others) have destroyed numerous trees that harbored this season’s MPB population.

• There are also many unaffected trees within the burn areas which still harbor beetles.

• The increased stress on trees scorched by the fire will increase their susceptibility to MPB.

• Recent fires haven't stopped the MPB outbreak.

Other Beetle Issues:

• Douglas-fir beetle and Ips beetles typically show an increase in activity after a fire.

• Trees with scorched bark have an increased susceptibility to Ips and Douglas-fir beetle.

• We will likely see an increase in these beetles’ activity in and around fire areas.

Impacts on Previously Applied Preventive Products:

• Chemical sprays exposed to high heat or directly to fire will have lost some, if not all, of their effectiveness. - We are not aware of any studies that have looked at the impacts of heat, smoke or fire on chemical preventive products for MPB.

- Most chemicals degrade faster when exposed to heat; depending on levels of heat exposure, some preventive products may have a reduced efficacy after a fire.

- Products applied directly to bark that has now burned have also been burned and are not likely to have any remaining efficacy.

　

• Pheromones exposed to high heat or directly to fire also will have lost some, if not all, of their effectiveness. - We are not aware of any studies that have looked at the impacts of heat, smoke or fire on pheromones.

- Direct impacts of fire and extreme heat may have melted pheromone packets, making them ineffective.

- Pheromones are chemicals, and increased rates of degradation would be expected with exposure to heat; depending on levels of heat exposure, pheromones may have a reduced efficacy after a fire.

　

　

• Considerations for Reapplication of Preventive Products: - Proper application of preventive products will remain key to their effectiveness.

- Some trees impacted by the fire will survive, others will not. This is very difficult to predict and tree loss will not be apparent in many trees until next spring.

- Trees that do not currently show any signs of beetle activity may be suitable for reapplication of a preventive product this year.

- Preventive chemical sprays may adhere less effectively to scorched bark, due to presence of soot/ash/charred bark.

- Pheromone packets can be reapplied without concern other than monetary costs.

- With increased stress on trees in fire areas and fewer host trees available, all preventive products may have a reduced effectiveness.

　

• Future Seasons After a Fire - Post-fire bark beetle impacts will occur and change over several seasons.

- Post-fire survival of trees will be dependent on each tree’s adaptability to fire; for example, ponderosa pine is more fire resilient than lodgepole pine, and the conditions of the seasons following a fire event, including levels of precipitation and changes in soil condition, will vary for each location.

- Management of MPB in forests and on individual trees in post-fire areas will remain important while MPB remains active on those landscapes.

- Management of MPB will be dictated by each landowner’s management objectives.

　

• Final Thoughts - Preventive treatment of remaining trees may be more important than ever over the next few seasons because in fire-impacted areas, the trees remaining represent a smaller selection of hosts and those remaining trees will likely have experienced additional stressors (and may be less success at defending themselves against MPB).

- For 2012, the window of opportunity to reapply preventive products is rapidly closing. No products are currently proven effective in trees already impacted by MPB.

- Efficacy of any preventive product will remain dependent on proper application, adequate coverage, correct dosage and good timing.

Weather Update for the Week From Planalytics

From Agri Business Weather Brief at Planalytics.com: 

THIS WEEK:

An end to record breaking temperatures this week as a more progressive temperature pattern evolves. First, a slow

moving upper low pressure will move into the Plains early in the week and gradually push eastward. A second low pressure moves out into the Plains on Easter Weekend. Look for a slight warming trend ahead of each of these two systems. Timing favors the East with a warming trend for eastern portions of Canada and the Northeast U.S. for the Holiday weekend.

There will be two cooling trends for the central portions of the U.S. and Canada. The first occurs on Tuesday into Wednesday. The second begins on Easter Sunday. Temperatures will warm in these areas between systems. Both of these cool downs will be accompanied by freeze-frost scenarios for the western portions of the Dakotas to southwest KS, including eastern CO and western NE.

For WA, OR, NV, and CA look for a warming trend by the weekend. Meanwhile, slight cooling occurs over the Southeast for the weekend, but temperatures will be at or slightly above normal.

A slow moving upper low pressure system will spawn a series of surface lows this week that will result in moderate to heavy rain being focused on the eastern Plains and Mississippi Valley. One of the northern lows will trigger moderate to heavy rain as well as a swath of moderate to heavy snow for portions of MT, ND, and the eastern Canadian Prairies.

Some light to moderate rain will occur across the Deep South and southern New England later in the week, but mainly as debris. Rain and mountain snow shifts north of CA by late week and drier conditions even make it to the Pac Northwest for the weekend.

Wheat Disease Update from Oklahoma

I know that we are in Colorado, but wheat diseases have a history of tracking north as the weather warms.  This is from Dr. Bob Hunger, OK State Wheat Pathologist:

Oklahoma:  Wheat continued rapid development across Oklahoma this past week with yield potentials still looking outstanding. Yesterday I sprayed my foliar fungicide trial (Jagger), which rangedfrom boot (GS 10) to heads nearly fully emerged (GS 10.5).  Overall I would place that trial at GS 10.2 (heads about 1Ž4 emerged).  This is 2-3 weeks earlier than I typically make this application.  It strikes me from calls over this past week, that this is representative of where wheat is at across much of Oklahoma.

                Stripe rust continues to be reported from across southwestern, central, and west central Oklahoma, but not as many reports from the north central and northwestern parts of the state.  However, these reports indicate only scattered/light infections.  With daytime temperatures into the 90s over the weekend (and 80s last week) and night temperatures in the 60s, stripe rust should be “shutting down.”  It could be revived with strikingly cool temperatures and moisture, but I don’t see it being a major factor in most parts of Oklahoma this year.

                Leaf rust also is being reported more frequently, but still in fairly low incidence and at a low severity.  Around Stillwater, I can find pustules on susceptible varieties but mostly in the 10-15% severity range.

                Powdery mildew is still a factor, at least on highly susceptible varieties.  Jagger, which is in my foliar fungicide trial, has a severity of around 40-65% on leaves beneath the flag leaf.  Some scattered powdery mildew pustules were visible on flag leaves.

                Tan spot and Septoria/Stagonospora also can still be found on lower leaves, but are not moving up the canopy.  A couple of wheat samples were received from northeastern (Rogers County) andnorth central OK (Noble County) with symptoms indicative of these leaf spotting diseases, and currently isolations are being made to confirm this diagnosis.

                Over the last week, the Diagnostic Lab also had a sample from Kingfisher County that tested positive for wheat streak mosaic virus and High plains virus (Kingfisher County).  As temperatures warm and wheat develops, these mite-transmitted virus diseaseslikely will become more prevalent.

Update on Wheat Pests

From Dr. Tisserat:

More information on some potential insect/mite problems on wheat. 

Dr. Frank Peairs  indicates that ‘ Brown wheat mite is fairly widespread where it was not limited by extended snow cover.’   Chris Stallman reports that the mite infestations in certain parts of Cheyenne and Kiowa counties are severe.

Frank also mentioned that  ‘ Reports of some army cutworm activity are more frequent than they have been for the past few years.  Russian wheat aphid has been reported from the west slope, but so far does not seem abundant in the east.’ 

Bob Hammon from the Western Slope has also indicated that he is seeing a lot of wheat curl mites now.  And just a reminder that the Diagnostic Clinic is performing wheat virus tests to growers again this year.  If you see mites or aphids, and notice symptoms on your wheat, please send them in to the Clinic for screening. 

Wheat Disease Update

From Dr. Ned Tisserat:

The very warm weather will be speeding up the development of the wheat crop in the state.   Because of the dry March, I don’t expect that there is much disease activity, at least not in dryland wheat.   Some of you may be thinking of applying a fungicide along with the herbicide application at tillering as ‘insurance’ or for other reasons (plant health).   In my opinion, unless you know there is active disease (rust, Septoria, powdery mildew) in the field, a fungicide application at this stage is NOT warranted .  Our research trials have not shown any benefit of these early treatments in the absence of disease.   Remember, every time you make a fungicide application, you are potentially selecting for pathogens that are insensitive to that fungicide, whether the chemical is a strobiluron or triazole.   The risk of shifting the pathogen population to one that is insensitive to the fungicide is small, but real.   For example, we now have fungal pathogens resistant to strobilurons in many crops (sugar beet, apples, soybeans, even wheat in the UK). And once that shift occurs, it appears to be permanent (i.e. there is little or no cost to the pathogen).  Let’s save these fungicides for when we really need them. 

Stripe rust has been reported in Kansas ( Manhattan and Wichita) and Oklahoma, but not in any regions closer to Colorado (see Kansas report below).   It is still advisable to keep a close watch on the developing crop for stripe rust.

The following is from Erick DeWolf, Extension Specialist, Kansas State University.

The wheat crop in Kansas ranges between the jointing to boot stage of growth.  I suspect some wheat in Southeast Kansas is already be heading.  This is 2 or 3 weeks ahead of normal crop development.  Weather forecast for the next 3 days indicates that temperatures will remain warmer than normal with high temperatures consistently in the 80's and low temperatures in the 50's for much of KS. Weather forecast for the next 3 days indicates that temperatures will remain warmer than normal with high temperatures consistently in the 80's and low temperatures in the 50's for much of KS.

Stripe rust was observed in Sedgwick County (South Central, KS) yesterday (March 28).  Gary Cramer, Extension Agent for Kansas State University, reported the find.  Gary indicates that low levels of stripe rust in the mid canopy of a production field west of Wichita.  The wheat in this field was near flag leaf emergence at the time stripe rust was detected.  The grower indicated that this field was planted with the variety "Everest".  Everest was considered moderately resistant to stripe rust in 2010 when KS experienced a severe epidemic.   My discussion with Bob Bowden, USDA wheat rust specialist here in Manhattan, suggests that Everest often develops some symptoms of stripe rust but the reaction type has been moderately resistant in previous years.  I will do additional scouting and checking for infections this next week.

Leaf rust was  detected in research plots near Manhattan (Northeast, KS) today (March 29th).  The incidence of leaf rust was very low (<1%) in these plots. The wheat in this field was at flag leaf emergence and leaf rust was found in the mid-canopy.  The infection was on an older variety "2137" that is known to be susceptible to leaf rust. 

 No reports of stem rust to date in Kansas.

 Severe tan spot was reported in Riley county( Northeast, KS), and powdery mildew continues to increase in many areas.

Aphids are present at considerable numbers in Southeast Kansas and have also been observed near Manhattan.

Insecticidal Soaps

This past week in the Diagnostic Clinic, we received some photos of a Japanese Maple whose younger leaves were exhibiting curling at the edges.  No insects were found and so the search began for the cause of the damage.  As more information was forthcoming, it was also noted that the new buds on some of the blue spruces were turning brown as well.  We also learned that a nearby plum tree had recently been sprayed with an insecticidal soap.  Since the symptoms on the Japanese Maple and the Spruce were associated with new growth, not the older growth and no insects were found, it appeared that there was most likely an abiotic issue.  So we did some research and discovered that insecticidal soaps can cause phytotoxicity damage to certain plants if sprayed at the wrong time, and that newer growth on Japanese Maple is extremely susceptible to damage from insecticidal soaps.  An excellent fact sheet from Cornell University provided the information that we based our diagnosis on, which also indicated that if the insecticidal soap was applied when temperatures were above 90F, it could increase the incidence of phytotoxicity damage.  The link for the fact sheet can be found at http://ccesuffolk.org/assets/Horticulture-Leaflets/Using-Insecticidal-Soap-In-Your-Home-Garden-Or-Landscape.pdf. 

The take-home message from all this is that reading the label is important to make sure your plants won't be unnecessarily harmed by the use of any product.

Update from the Clinic...........

This year we have seen a variety of diseases that usually don't happen frequently in Colorado.  We have confirmed anthracnose on Ash from Aurora, and just this morning, found anthracnose on Oak here at the CSU campus. http://www.ext.colostate.edu/pubs/garden/02930.html is a link to the fact sheet on Sycamore Anthracnose, but control measures would be similar for Ash and Oak.  

We are also seeing samples of Oak Leaf Blister on a regular basis this year.  http://www.umassgreeninfo.org/fact_sheets/diseases/oak_leaf_blister.pdf is a fact sheet from U of Mass on oak leaf blister that shows some really nice pictures of the blisters on oak leaves. Older blisters can often be confused with anthracnose. 

We are also still seeing effects of the prolonged fall/winter (2010-11) drought on trees and shrubs.  Winter watering is critical in our area for survival of trees and shrubs.  http://www.ext.colostate.edu/pubs/garden/02926.html is a fact sheet that talks about healthy trees and tree roots and provides insight on what can affect the growth of a tree via the roots.     

There may be some residual effect of the cool temperatures in May and June on vegetable production in the home garden.  The coolness has pushed back fruit set on a lot of the warmer season vegetables, so be patient with your plants.   

Lastly, there are a lot of aphids out there.  A blog post from Gardening After Five has some recommendations on control, http://gardeningafterfive.wordpress.com/2011/07/08/year-of-the-aphid/.