The Monday Report: May 25, 2020

We can still see the remains of low temperature injury from a couple of weeks ago.  Not to worry, the next set of leaves will cover up the desiccated leaves and stems.

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The Crop Protection Guide for Nursery and Landscape Plants (OMAFRA publication 840) contains the crop pest recommendations for nursery and landscape.  Download it onto your phone or computer for easy reference.

DECIDUOUS SHRUBS:

PseudoColdTempSyringaVulgaris Seeing malformed, stunted leaves with brown-black marginal necrosis on container grown lilac (Syringa spp.)?  This is due to a combination of low temperature injury and a weak bacterial pathogen, Pseudomonas syringae. It is quite common on the first flush of leaves of container grown lilac and plants usually grow out of it to put on a more normal-looking second set of leaves.

CornusSeptoriaLeafSpot                 Leaf  spots on deciduous flowering shrubs are showing up everywhere because of the cool, wet conditions we had during leaf emergence.  Leaf spots appear as purplish to brown, with yellow to brown necrotic margins.  Several fungi (Colletotrichum, Septoria etc. ) cause leaf spots on ornamentals. When the second flush of leaves start to emerge in overhead irrigated containers, you may want to protect new growth with a foliar application of fungicide (Banner, Daconil, Dithane, Nova). Once container grown stock is planted in the field, the disease symptoms diminish.

DECIDUOUS TREES:

image0008 Fireblight is a systemic bacterial disease that causes twig and branch dieback and bark cankers on large limbs and the main stem. It infects apple and pear trees through flower or through recent wounding (e.g. pruning). It is a serious disease in juvenile trees.  It is important to watch for late blossoms, called ‘rat tail’ blossoms, which are very susceptible to infection by this bacteria. Click on the risk map for either apple or pear to help you decide what management precautions you need to take to reduce fireblight infection.

WoolyBeech2 WoolyBeech1 WOOLLY BEECH APHID are feeding on beech. These aphids are small and green but they cover themselves with bright white, woolly strands and produce honeydew droplets that cling to the woolly masses. Populations are usually not threatening to tree health but applications of Insecticidal Soap can be very effective at reducing populations of young nymphs, especially when adequate spray coverage on LEAF UNDERSIDES.

Where HONEYLOCUST PLANT BUG was a problem in the past, monitor trees for tiny, green, wingless, nymphs (see above image for plant bug shadows on leaves).  Plant bug nymphs and adults were a problem in many areas last year as these sucking insects caused stunting, malformation, chlorosis and senescence of leaves (see lower image).   Shake new leaves over a white surface to assess populations of plant bug nymphs.  Most contact insecticides work very well against this pest.

DSC_0056 Reducing populations of honeylocust plant bug now is important since multiple generations will be cycling over the next few weeks.

OystSclSyringaCrawlers of Oystershell Scale have hatched in container production and are starting to hatch in the field/landscape (adults shown above).  These crawlers are tiny and brown and very susceptible to insecticides including insecticidal soap and the summer rate of horticultural oil.  This scale species can be found on several deciduous trees including lilac, ash, magnolia, maple, hackberry, willow etc.

EVERGREENS:

JuniperTipBlightClose Brown shoots on juniper may be a symptom of juniper tip blight (Kabatina blight). A small grey band or pinched grey canker with black fruiting structures can be found at the base of the infected shoot, this is where the spores come from. Pruning is not suggested once new growth appears, as it will help spread this disease. Where cankers are found, copper and Dithane are registered to protect emerging new growth this spring and summer.

TaxusScaleMay_15AM          Fletcher scale (Taxus scale) nymphs are actively feeding on Thuja and Taxus and are getting larger.  They have a distinctive white stripe down their backs.  You will probably notice the honeydew first.  This scale is difficult to manage at this size but an application of systemic insecticides may help reduce populations in hot spots.  It will soon be entering its most rapid growth/feeding phase.

<img class="" src="http://dkbdigitaldesigns.com/clm/sites/default/files/imagecache/Image_node/images/CLM-8509_0.jpg&quot; alt="Chionaspis spp. adults on pine.” width=”438″ height=”292″> Crawlers (photo above) and nymphs (photo below) of Pine needle scale can be found on white/mugo/Scots pine at this time.

<img class="" src="http://dkbdigitaldesigns.com/clm/sites/default/files/imagecache/Image_node/images/CLM-8882.jpg&quot; alt="Chionaspis spp. crawlers on pine.” width=”446″ height=”297″> Pine needle scale crawlers and nymphs are susceptible to applications of acephate, carbaryl, dimethoate, horticultural oil, insecticidal soap, malathion.  Good coverage is required to effectively reduce populations of this armored scale insect pest

Pine bark adelgid eggs  have hatched into tiny yellow nymphs (photo above right, Dave Cheung).  Look for small, woolly-white masses with eggs and nymphs underneath.

PineBarkAdelgidLStitt These pine bark adelgid nymphs will be moving to feed on emerging foliage and will cover themselves in a woolly coating soon, making them much less susceptible to contact insecticides.  Avoid using horticultural oil on white pine as it will dull the glaucus sheen to the needles.  Other options include insecticidal soap, acetamiprid, dimethoate, malathion.

neodiprion sertifer damage on scots pineneodiprion sertifer larva on scots pine

Where needles on Mugo/Scots pine are disappearing, look closely for dark headed European pine sawfly larvae (Sawflies have >6 pairs of prolegs) with long stripes down their body.  They can sometimes be found on Eastern white pine.   Young sawfly larvae are susceptible to applications of insecticides such as Success, Pounce/Dragnet, Tristar and Sevin.

<img class="" src="http://dkbdigitaldesigns.com/clm/sites/default/files/imagecache/Image_node/images/CLM-1860.jpg&quot; alt="Pikonema alaskensis (Yellowheaded Spruce Sawfly) adult laying eggs.” width=”527″ height=”349″>                        Yellow headed spruce sawfly adults are emerging and starting to lay eggs on emerging foliage of Colorado and white spruce.

YelHeadSpruceSflyLarvaDamageWatch for needle tips to turn straw-coloured as the first sign of 1st instar larval feeding of yellow headed spruce sawfly in the next week or two. (Remember, “Sawflies have Six or more pairs of prolegs”). The smaller they are, the easier they fall. Effective insecticides include Success and Pounce.  Insecticidal soap can give good suppression if coverage is really good.

Yellow Warbler Identification, All About Birds, Cornell Lab of ...

Are you hearing a new song in the trees?  “Sweet Sweet Sweet Meadow Sweet!” This is the song of the Yellow Warbler (photo above, from the incredible Keenan Yakola ).  Yellow warbler males have song that is a real treat for all of us.  You’ll find them singing from the trees on the edges of lakes and rivers, and your irrigation pond ♥

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About Jen Llewellyn

OMAFRA Nursery and Landscape Specialist @onnurserycrops
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