Dogwood Pest?

Discussion in 'Garden Pest Management and Identification' started by dgleadle, Jun 18, 2008.

  1. dgleadle

    dgleadle Member

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    Location:
    Vancouver, Canada
    Please Help Identify Bugs on Dogwood Tree

    I live in Vancouver.

    I have a small dogwood tree. It is about 3 years old, had been growing well until last several weeks when it has been colonized by some sort of pest.

    The surface of the worst leaves have a sticky sap, attractive to bees.

    DSC_3018.jpg

    The underside of the leaves has some sort of pest that I can't identify:

    DSC_3019.jpg
    DSC_3022.jpg
    DSC_3023.jpg

    I would very much appreciate help identifying this pest and advising how to control it?

    Dan Gleadle
    604-648-2977
    dgleadle@telus.net
    dgleadle@tevlingleadle.com
     
    Last edited: Jun 22, 2008
  2. Cakes

    Cakes Member

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    Location:
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    It looks like you have anthracnose. It has been spreading rapidly in the dogwood population these last couple decades.

    the bug i cannot tell. pic three is not uploading for me. the whiteness made me think of moths and also the leaf stickiness. their flatness seemed like scales but they seemed a bit big for that.

    for fungal infections sometimes u have to prune off affected parts. and then control with fungicide. u would actually have to look up the control measures for this specific tree because i do not know. and maybe also try asking ur county extension office for local control schedules. checking state fact sheets can do both for you sometimes.
    list of extension offices:
    http://www.colostate.edu/Depts/CoopExt/4DMG/Links/cool.htm
    county extension offices can often give u a bug ID too. take them some in a jar. maybe call ahead to make sure the right guy is in the office. also plant nurseries might help.

    a few extensive state sites with bug and disease fact sheets/pix/diagnostic tools:
    http://gardening.about.com/od/gardenproblems/a/GardenInsects.htm

    The fungal/anthracnose attack might be partly due to your moist climate/possibly wet soil. and i wonder if u fertilized recently.

    If you did fertilize with a nitrogen rich source and you can remove it or flush it out then you might go ahead and do that. But afterwards try to keep the water source steady. Both drought and drowning manifest themselves as scorched leaf edges in dogwood<so it seems the lack of healthy water flow can help the edges of the leaf tissue be weak where the anthracnose likes to attack.

    This tree does not want poor drainage even though it needs steady water<usually when they say a plant wants good drainage they mean it needs oxygen. if it was a houseplant i would recommend hydrogen peroxide because it adds so much oxygen (it is h2o2 and so loses an oxygen and leaves water); but i haven't actually looked into how if anyone is using it on trees outside yet>it DOES kill bacteria-which prolly grow back the next day but hey idk. up to 3% concentration is okay on plants (same strength as most drugstore bottles) and u can get 35% strength at horticultural supply<watch that stuff because it can burn you and needs diluting down 11 to 1 at the least.

    so re water, maybe try to divert any extra rainfall it gets, like if it drains off the house and you need a gutter. sometimes a worm colony can make tunnels good tunnels. or even drill drainage holes through the hardpan if you have one.

    and re fertilizing, maybe she needs a little calcium. CA deficiency can make curled/scorched looking edges. also spotting. so it may be deficient where you have a disease that attacks edges and makes spots? besides dogwood is a notorious calcium gatherer:
    http://classes.yale.edu/fes_tgs3/fes519/Northmadison/Dogwood/dogwood.html

    she may want a few other minerals like magnesium (def associated with red and leaf curl and often hand in hand with CA use); or the iron that helps soil be acidic. because she does like it acidic and we see interveinal chlorosis on the diseased leaves (an iron symptom). The chlorosis is contrary to a nitrogen surplus but it can happen; we thought we saw rank bubbly green growth in the leaves maybe and u sounded like u were taking care of her and that is why we thought 'lots of N possibly'; lots of N can make tender easily invaded growth<that soft rankness we thought we saw.

    so re the iron-maybe check her pH. of the soil i mean. maybe due to ur courteous cultivation practices and or high rainfall you have left the acidic zone and gotten a bit close to neutral.

    if all this sounds of any sense or if u are just curious and got cash, maybe get a soil test. lots of state offices will do it but not all. you might have to send out to some other state or else go private.
     
  3. dgleadle

    dgleadle Member

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    Location:
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    Re: Dogwood Pest? (Cottony Maple Leaf Scale)

    In researching this further, I am fairly certain this is Cottony Maple Leaf Scale). Before realizing this, thinking it might be aphids, I applied Neem Oil yesterday on the advice of someone at Art Knapps.

    Yesterday, I noticed also that the scale had moved to 4 nearby maples, that have less of the problem.

    I also sprayed Neem Oil on the maples.

    Web surfing has suggested I should try Orthene and/or Malation, adding a horticultural oil as a surfactant.

    Others have suggested a good spraying down of the infected plants would help.

    My current plan is to leave the Neem Oil work for a week or so, then spray the plants with a garden hose (trees are 8 to 10 ft high) and then, after consulting with a garden shop or two, either reapply the Neem Oil or try Orthene, Malation.

    Am I on the right track?
     
  4. chimera

    chimera Well-Known Member 10 Years

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    Location:
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    Re: Dogwood Pest? (Cottony Maple Leaf Scale)

    Interesting, would think you are if the neem oil works on this scale. Good digging.
     
  5. dgleadle

    dgleadle Member

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    Re: Dogwood Pest? Wolly Maple Leaf Scale - Neem Oil

    My online research suggests Neem Oil works on scale.

    Time will tell.
     
  6. Cakes

    Cakes Member

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    Location:
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    great catch figuring out what bug it was!

    Neem seems like it might work if it is applied at exactly the right time of year or if a soil drench will allow it to be taken into the tree's sap. Because, since the adults sit there protected by their scaly selves and suck sap, they are not affected by foliar sprays of neem<this is well proven in many gov texts. You have to hit them while they are in the vulnerable crawler stage or else u have to put the neem in the sap.

    The time to spray in your area for crawlers is info your county extension office or state fact sheets can help with. Correct timing is an issue for MANY sprays/bugs. The window of opportunity for scale crawlers may be only 10 days long once a year.

    one good way to get the right fact sheet is to search with your state, the bug and the words "fact sheet".

    how to find your closest extension office:
    http://www.csrees.usda.gov/Extension/index.html

    NEEM comes from the Neem Tree. so does lots of horticultural oils.

    Really/ well that makes sense if the pesticide were watery enough. In organic gardening, oil is the main killing agent and soap is used as it's surfactant.

    smothering>the way oil works on bugs. it's mechanical nature is hard for bugs to evolve against and that is why it is the best organic control we have. Dust/ashes is another one for the same reason but idk that it would apply here.

    Winter dormant oil sprays are sometimes recommended as a control for scale. so it might be that it works. The reason that dormant oils are not recommended in the summer is sunburn, the action of sunlight on the oil. But that is old traditional knowledge and modern organic texts say you CAN spray in the leafy season if your weather permits (the 140 Rule).

    Oil is also a solvent (like linseed oil for paint?). And using a solvent (isopropyl alcohol*) is what is recommended to wipe scale away. Oil is also recommended to get out bubblegum>maybe it would help cleanse off the honeydew secretions on the leaves.

    *don't use methanol or ethanol..i think it might have been ethanol i forget. it's in an orchid link at the bottom of the post. Cinnamon they also use in orchid culture, to combat fungi. Cinnamon cannot be combined with alcohol tho.

    oil as a solvent and how to do the 140 rule:
    http://www.stonepages.com/forum/index.php?showtopic=811

    with water? that is for aphids. and works. but the aphids crawl back up again the next day. Also at certain times of the year, aphids are flyers.

    I see by my limited looking at pesticide texts that good research would be best if u were picking out a serious agent to use. Some work this way and some are all around general this and that except for certain so and so's..u cannot trust what anyone tells u on forums like this when it comes to such things. folks here often have knowledge limited to their own experiences or if they were schooled or have done the research previously, their info may be dated.

    some pesticides cannot be cleaned out of your applicator device. Like if you buy one of those little tubs that attach to your water hose (proportioner, $5 USD) or whatever type sprayer<the tub and applicating equipment are no good for anything else>you cannot rinse them and then use them to apply fertilizer the next time.

    not only pesticide knowledge evolves, but also biological controls. like they are always discovering or offering for sale a new parasitic wasp or beneficial nematode or something. English sparrows are said to be very good for cottony maple scales and lady bugs are good against the crawler stage.

    Lots of folks kill sparrows due to how they nest in house eaves and make messy droppings. Some folks used to make houses for them, but in the US they are not native and have done so well that many think we should not make houses for them anymore. I think if i was you tho, i might try to attract some. <they are contraindicated at times u plan to spray a serious poison.

    Establishing beneficial habitat can keep good birds and bugs around. <what kind depends on what/who you want to hang around. There are lots of texts on this if u search beneficial(s) habitat and maybe even add the name of your desired guest or unwanted pest. One tip i have is carrots<their fine foliage when they flower and seed is what many good bugs like. if u buy the carrots with the green tops, they root real easy. Also if u get ladybugs, then put the sprinkler on before release so they will not go flying off looking for a drink after their long captivity. also, do not let ur praying mantis egg case thaw out in ur house, heh heh. praying mantis are contraindicated around baby birds/houses* (a mantis can also take a mouse).

    *do not build bird houses from cedar. the (moth repelling) fumes are toxic and make brain damage on baby birds.

    Scale doesn't often kill a tree but it can. it can cause die back of the shoots and tips/ also leaf fall. The sticky excretions provide an environment for sooty mold. <<it might be that i am seeing that die back and or mold damage when i said in my last post that i think the tree has anthracnose. but the wilt pattern on the tips of your leaves looks EXACTLY like some images i see of anthracnose. This year seems to be a huge one for anthracnose/wilt type stuff in the States. due to the humidity level i think.

    separating these diseases and bugs is often hard to do. like there are two kinds of maple scale that have cottony stuff but their crawlers have different schedules/are vulnerable at different times of the year. Now i have been reading a few of these scale texts today and i have found that they follow the same pattern that other scientific texts do>>they are mixed up. At one site they will be attributing characteristics to a certain scale that the last site just told you belonged to the other.

    re mold and fungi type disease in general, i often recommend baking soda/bicarbonate. It needs to be applied many times though, at least three times (with three day intervals). It's severe alkalinity may be contraindicated during times of neem use due to how neem can be deactivated by alkaline things. that alkalinity also needs to be considered if allowing it to drip more than a little into certain soils (like turn it off unless u are directly spraying the tree).

    a less caustic treatment is vinegar. vinegar would be number 1 choice for sure if ur plant had nice flowers u did not want to be withered up. same deal about repeat treatments tho. Molds and fungi come back easily as long as the environment is favorable. if u read the combat texts for them u will see written that once the disease has a foothold, not much hope exists. the sprays just kill the top layer. and then it resprouts from cracks and crevices and neighborhood vegetation. to make it worse, the tree wood can be colonized maybe, like resprout from there whenever conditions permit. this is why house beams get sanded or replaced during mold retrofits-the painting on of poisons just won't do it.


    http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note37/note37.html
    http://www.neemamerica.org/research/neem15.html
    http://www.hort.wisc.edu/mastergardener/Features/insects/cms/CottonyMapleScale.pdf
    http://scarab.msu.montana.edu/YardGarden/docs/neem-insect.htm
    good detection method and avoiding pesticide resistance:
    http://nathist.sdstate.edu/orchids/pests/scales.htm

    biological control explained:
    http://www.nysaes.cornell.edu/ent/biocontrol/info/biocont.html
     
    Last edited: Jul 3, 2008

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