Plant Diagnostic Lab — Page 4 — Plant & Pest Advisory

June 19, 2023 Steven K. Rettke

Landscape Pest Notes for Late June 2023

Azalea Lace Bugs (802-1029 GDD = 3^rd generation): The third generation of this pest will be in full swing for much of NJ by the end of the month. Look for the presence of nymphs (spiny, black), adults (larger, lacy wings), fecal spots (brown, shiny spots) on the underside of leaves, and stippling (feeding damage from nymphs and adults) on the leaves. Remember that the yellow stippling damage persists on the leaves until they are dropped. Look for the presence of actively feeding lace bug nymphs or adults before treating plants.

Azalea lace bug stippling symptoms on Azalea leaves. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

Azalea lace bug frass spots & egg laying

Azalea leaf undersides with frass spots & egg laying along mid-rib. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

When found, use horticultural oil (only if a spray can contact the back of the leaves), or acephate (Orthene) if the shrub is too dense to allow effective use of oil. Imidacloprid (Merit) applied to soils now may require 1-2 weeks before they begin to control this second generation or the beginning of the third generation (longer if soils are dry). Chlorantraniliprole is a reduced-risk insecticide that can be effective against lace bugs. Remember that stressed azaleas in full sun are more prone to lace bugs. Also, & more importantly, predators will be fewer in full-sun locations.

Azalea lace bug adult with oval shaped wings. Lace bug species having oval shaped wings will only feed on broad-leaf evergreens. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

The Landscape Pest Notes for Late June 2023 in addition to the azalea lace bugs also includes information & photographs of oak spider mites, two-spotted spider mites, pine spittlebugs, mimosa webworms, various soft scales, white prunicola scales, red-headed flea beetles & tree species prone to mid-season leaf drop.

June 13, 2023 Richard Buckley

Got leaves?

Have you taken a look at your sycamore lately? Seeing any leaves this spring? Looks like a little problem!

brown, angular leaf spots on plane tree leaves

Classic angular leaf spot and twig blight of sycamore anthracnose. Photo: Richard Buckley, Rutgers PDL

Samples of deciduous shade trees diagnosed with anthracnose have steadily found their way into Rutgers Plant Diagnostic Laboratory this spring. Anthracnose is a common fungal disease of shade trees that results in angular leaf spots, cupping or curling of leaves, and premature defoliation. Green stems and twigs can become infected, causing twigs to dieback and overwintering cankers to form. We’ve had samples of sycamore and London plane tree, but have also had ash, beech, maple and a bunch of oaks.

water-soaked, necrotic spots on distorted ash leaves

Ash anthracnose causes necrotic spots and distorted leaves. Photo: Richard Buckley, Rutgers PDL

The fungi responsible for anthracnose in shade trees are all unique. The fungus that attacks sycamore is not the same as the fungi that cause ash, beech, dogwood, maple, or oak anthracnose. Each tree species has a specific fungus causing its own anthracnose disease, so for example, the beech anthracnose fungus does not infect oaks and the oak anthracnose fungus does not infect maples and so on.

brown, angular spots on silver maple leaves

Marginal necrosis and irregularly-shaped, angular leaf spots on silver maple (Acer saccharinum). Photo: Sabrina Tirpak, Rutgers PDL

Infections by anthracnose causing fungi are favored by cool, wet conditions during the budbreak period in the spring. When the weather favors one of these fungi, it generally favors all of them, so we see the disease to some degree on many different hosts. Anthracnose fungi survive winter in buds, small twig cankers, or fallen leaves depending on which types of trees and fungi are involved. In the spring, the spores are moved by wind and water to newly forming leaves. The longer the weather conditions remain cool and wet, the more damage one can expect. Once the weather becomes dry and the leaves mature, the disease cycle ends and the tree will replace lost leaves with new ones.

Beech anthracnose. Photo: Sabrina Tirpak, Rutgers PDL

Anthracnose can cause a very visible leaf lesion, and depending on the fungus/tree species dynamic, may defoliate the tree. Sycamore anthracnose causes a very significant defoliation, while beech anthracnose rarely does. Furthermore, it is not uncommon for the causal fungus to kill the buds before they open in the spring. It’s also not uncommon for the fungus to kill new green stems and twigs. Although these diseases often seem severe, they have little long-term impact on overall tree health. Leaves and buds damaged early in the season are often replaced by mid-summer.

Small spots with yellow borders and distorted leaves, caused by oak anthracnose. Photo: Sabrina Tirpak, Rutgers PDL

So, what do we do about anthracnose? Not much, really! Rake and remove fallen leaves. Improve plant vigor with fertilization and irrigation in times of drought, and prune all of the dead and dying limbs. Fungicides can be used to prevent the problem in high-value trees. Begin treatments at budbreak to protect the new growth and repeat the treatments 2-3 times at the label specified intervals. Proper timing and good coverage are essential, which will necessitate a licensed professional applicator to make the applications.

By the way, it is too late for fungicide protection this season!

Fungal diseases in most ornamental plants can be prevented with applications of one or a combination of the following active ingredients: FRAC M3 mancozeb; FRAC M5 chlorothalonil; FRAC 1 thiophanate-methyl; FRAC 3 metconazole, myclobutanil, propiconazole, tebuconazole, triademefon, triflumizole; FRAC 7 boscalid, flutolanil, oxycarboxin; FRAC 11 azoxystrobin, fluoxastrobin, kresoxim-methyl, pyraclostrobin, trifloxystrobin; FRAC 12 fludioxonil; and/or FRAC 19 polyoxin-D. Be sure to follow all label specifications for the host plant, the specific diseases controlled, as well as rates, dilution, and timing.

Filed Under: Landscape, Nursery, & Turf, Plant Diagnostic Lab, Uncategorized Tagged With: anthracnose, Plant Diagnostic Laboratory, shade trees

June 2, 2023 Steven K. Rettke

Landscape Pest Notes for Early June 2023

Boxwood Spider Mite: (GDD =450-700) (PPI = Kousa Dogwood; Cranberry Bush) This spider mite, which attacks all boxwoods, is neither a true cool nor warm season mite species. It is usually most active with intermediate temperatures during late spring & early summer. The adult is yellow-tan in color with long legs. When the boxwood mites are active, they can be found on both the top & bottom of new growth. Eggs are light yellow & overwinter on leaves & twigs. There are several generations per year.

Boxwood spider mite feeding damage results in foliage with yellow to bronze stippling, which may resemble injury caused by thrips. Both of these insects cause distinctive linear stippling streaks. These symptoms can be diagnostic when observed on foliage. With high mite populations, entire leaves may develop yellowish-white streaks; premature defoliation can occur.

Boxwood spider mite feeding symptoms. This mite species creates linear streaks on leaves. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

Boxwood Spider Mite symptoms - more mild

Boxwood spider mite symptoms that are more mild. The distinctive linear streaks are more clearly observed. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

Detected overwintering eggs are treated with dormant oils (2-3%). Although normally unnecessary, summer oils (1-2%) or insecticidal soaps are recommended to control mild mite populations. With high infestations, some reduced-risk materials include spinosad, spiromesifen, acequinocyl, & bifenazate. Examples of other materials include hexythiazoc, abamectin, fluvalinate & acephate. Be aware that fluvalinate is a pyrethroid & can promote spider mite resurgence. Acephate may only provide mite suppression.

The Rutgers Plant & Pest Advisory Blog for Early June 2023 includes some commonly observed insect/mite & disease pests within the landscape during the late weeks of spring & early weeks of summer. In addition to boxwood spider mites, the other insect/mite pests included are juniper scale, bagworm, black vine weevil, bronze birch borer, pear leaf blister mite, & beneficial predacious mite. The disease pathogens included are fire blight, oak leaf blister fungus, black spot of rose, powdery mildew & Verticillium wilt. Some suggested monitoring techniques & variables are listed between the insect/mite & disease pests.

May 17, 2023 Tim Waller

Application for Cost-Share Grant Funding for Installation of Deer Fencing on UNPRESERVED Farmland – Out NOW

“The NJDA Deer Fencing Program makes cost-sharing funding available for the installation of deer fencing on unpreserved farms. The program is conducted in accordance with N.J.S.A 4:40-6.1.”

Please click here for the full application, eligibility, and other important information

Timing is important if considering this program. NJDA began accepting applications on 5/15/23.

Filed Under: Blueberry, Christmas Trees, Commercial Ag Updates, Cranberry, Disease Forecasting, Field, Forage & Livestock, Food Safety, Fruit, Landscape, Nursery, & Turf, Nursery, Organic Production, pesticide credits, Plant Diagnostic Lab, Strawberry, Tree Fruit, Turf, Uncategorized, Vegetable Crops, Wine Grape Tagged With: cost-share, deer, fencing, grants, NJDA

May 15, 2023 Steven K. Rettke

Landscape Pest Notes for Late May 2023

Artillery Fungus (Sphaerobolus): This wood decomposer is found in mulched areas and has probably caused the most concern to landscapers and potentially poses some economic concern to their clients. This fungus produces fruiting structures that resemble tiny cream or orange-brown cups that hold a spore mass resembling a tiny black egg (0.1 inches in diameter). When enough water accumulates, the spores are shot high into the air up to several yards. The dark-colored spores resemble small tar spots and will stick to house siding, downspouts, cars, leaf surfaces, and any nearby structure. The artillery fungus is strongly phototrophic & will shoot its spores toward light sources or white-colored surfaces. The spores have extreme adhesive qualities & are difficult to remove, even with high-pressure sprayers.

Artillery fungus spores stuck on leaf undersides

The black colored spores of Artillery Fungus can also be mistaken for pests (e.g., scales) when stuck on the undersides of plant leaves. (Photo Credit: Tim Waller, Rutgers Coop. Ext.)

Artillery fungus spores stuck on white colored house siding.

Artillery Fungus black spores can mare the surface of white siding on houses. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

The Landscape Pest Notes Blog for Late May 2023 reviews a dozen insect & disease pests that are commonly observed during the second half of May within NJ landscapes & nurseries. The insect pests highlighted include the elongate hemlock scale, pine needle scale, Euonymus scale, Taxus mealybug, four-lined plant bug, & aphids. In addition to the artillery fungus, the other fungal organisms included are black sooty mold, Volutella blight, cedar rust diseases, Cytospora canker, & Botrytis.

May 1, 2023 Steven K. Rettke

Landscape Pest Notes for Early May 2023

Fungal Leaf Spots: Commonly found on the foliage of many plants, fungal leaf spots are largely cosmetic diseases. Most do not interfere with the normal growth & development of the plant. Therefore, within the landscape, fungicides are not normally recommended. Years that have relatively dry spring weather will experience fewer leaf spot infections.

Many fungal leaf spot infections will demonstrate typical symptoms. Surrounding the initial infected spot will be alternating light-dark-colored concentric rings. The darker areas contain plant-defensive chemicals that the plant uses in an attempt to compartmentalize the invading fungus. If the fungus is virulent enough it may have the ability to move past the barrier & infect the tissue outside of it. The plant will respond again & form a new barrier surrounding the infected area. Sometimes these light-dark discolorations can continue until a target appearance forms. Many times, black fruiting bodies can be seen within the center of the light-colored bull’s eye site where the infection originated.

A dark colored halo will often surround the central fungus infection site. The black fruiting bodies can be observed within the central tan area. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

Alternating light-dark colored concentric rings. The dark rings are composed of plant defensive chemicals the plant uses in the attempt to wall-off the invading fungus. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

The Landscape Pest Notes Blog for Early May 2023 is listed below & is composed of some commonly observed insect/mite & disease pests occurring within landscape & nursery plants. The insect/mite pests included are andromeda lace bug, lilac borer, boxwood leafminer, spruce spider mite, & horned/gouty oak galls. The disease pathogen pests included in addition to fungal leaf spots are black knot, sycamore anthracnose, Diplodia tip blight, & apple scab fungus.