McFarland Top Ten Disease and Insect Problems

  1. 1   Bacterial Leaf Scorch
  2. 2   Hemlock Woolly Adelgid
  3. 3   Apple Scab
  4. 4   Scale Insects
  5. 5  Anthracnose
  6. 6   Boring insects
  7. 7   Root Weevils
  8. 8   Mites
  9. 9   Aphids
  10. 10  White Grubs

If trees on your property have any of these tree health problems it is imperative you contact someone and get it dealt with right away. Left untreated these trees could cause serious harm to the landscape and people. Please call us or fill out this form.

#1 Bacterial Leaf Scorch

This is the number one disease that is facing the shade trees of our area and will result in startling losses. This disease is caused by a bacterium and is spread by insects. It affects Red Oak, Pin Oak, Scarlet Oak, Black Oak, American Elm, and Sycamore. Trees that are infected with this disease will decline rapidly and will die without treatment. The host range for this disease continues to grow, and no ‘cure’ exists to date. For more information on this disease please click on the following link.

We are constantly monitoring the latest research on this disease, and when any new advancements are made, we will post them here.

#2 Hemlock Wooly Adelgid

Wooly Adelgid

This insect is the one most commonly encountered by our arborists, and can cause the death of the tree if left untreated. This bug is an example of how the import of pests into our country, in this case from Asia, can have devastating results to our forests and landscapes. Since there are no indigenous predators for this insect, it has spread unchecked throughout our landscapes and is threatening the native stands of Hemlock throughout the northeast. The adelgid itself is a small black insect that attaches to the under- side of hemlock twigs, where it remains and feeds. As the insects develop, they secrete the characteristic white wax that gives the bug its name. A mature infestation of adelgid looks like small cotton balls have been pasted to the underside of the twigs. Fortunately, this insect has proven to be easy to control, and we have had success in reviving trees with significant damage and heavy infestations. We feel that hemlocks are one of the most versatile and beautiful of our native evergreens and their use should not be discouraged because of this insect.

#3 Apple Scab

The overwhelming popularity of crabapples has made this disease one that we encounter regularly. This is a fungal disease that causes spots to form on the leaves of crabapples starting in the spring. The spots enlarge as the season progresses and the leaves begin to drop by mid summer. Often by August, a highly susceptible tree will be almost completely defoliated. In addition, the fruit is affected which will disrupt the fruit display that normally graces a disease free tree in the fall. The disruption of photosynthetic leaf area and premature defoliation of the tree on a yearly basis will reduce the amount of photosynthesis that occurs and result in a weakened tree. We have been very successful in treating this disease with both foliar sprays and injections.

#4 Scale Insects

These are a group of insects that are widespread and notoriously difficult to control. Most trees and shrubs are susceptible to attack from some sort of scale. The most common and obvious scale is the azalea bark scale. This insect appears as a white fuzzy object on the lower stems of azalea plants, somewhat resembling popcorn. This scale is extremely difficult to control as the white waxy covering over the insect prevents insecticides from coming into contact with the insect. We have had excellent success in managing this insect with modern techniques. Another very common scale is called euonymous scale, which attacks all of the euonymous genus as well as Pachysandra. This is a small gray to white, oblong insect that appears on the underside of leafs and coating the stems. The damage inflicted on the plant appears as yellow to white spots on the leaf and a general lack of vigor. This insect can wipe out entire Pachysandra and euonymous plantings. Our company has been successful managing these difficult and destructive insects.

#5 Anthracnose

Anthracnose is a fungal disease that affects a number of deciduous shade and flowering trees. The most serious Anthracnose disease is Dogwood Anthracnose that affects the common flowering dogwood and can be lethal. Dogwood Anthracnose begins as spotting of the foliage in the late spring and summer. The fungus can then move from the leaves into the twigs and eventually into branches. Once the fungus enters larger branches it forms structures called cankers that will enlarge from year to year, eventually girdling and killing the entire branch. Sycamore Anthracnose and Ash Anthracnose are two others that have caused many problems in our region in recent years. We have had excellent success in managing Anthracnose on all trees with either carefully timed foliar sprays or injections.

#6 Borers

These are the most serious and devastating group of insects that we encounter. The adults of these insects lay their eggs in the tree. When the larvae hatch they bore through the wood of the tree and feed on the important conductive tissues. These insects are attracted to trees that are under stress, and serve to exacerbate the stress and usually cause the decline of the tree. With the severity of the recent droughts, many trees are stressed and thus are being attacked by borers. Obviously, the best means of managing borers is to prevent the tree from becoming stressed. When borers do attack, there are a number of options that we can pursue to minimize the damage. The bronze birch borer is the most notorious of the borers, and consistently devastates the white birch. The primary reason for this is that the white birch is not adapted to the hot summers that occur in our region, and thus it consistently comes under stress during heat. People love these trees and refuse to part with them even though they do not belong here. Fortunately, some recent advances have given us a tool to manage the bronze birch borer on a preventative basis.

Most Susceptible Trees

  • Oak
  • Ash
  • Dogwood
  • Maple
  • Beech
  • Pine
  • Spruce
  • Hornbeam
  • Styrax
  • Horsechestnut

#7 Black Vine Weevils

Black Vine Weevil is an insect pest that primarily attacks the ericaceous plants, which include the Rhododendron, Azalea, Pieris, and Mountain Laurel. Because of the overwhelming popularity of these plants, this insect has become a very serious pest. The adult weevils emerge from the mulch layer at the base of the plant at night to feed on the lower leaves of the plants, causing the characteristic notches on the leaf margins. While this damage is unsightly, it is not a serious detriment to the plant. The real damage is caused by the larvae of the weevil, which reside in the soil and feed on the roots of the plant. Root damage causes a serious decline in the vigor of the plant, and allows the plant little tolerance to drought. We have had excellent success in treating for Black Vine Weevil.

#8 Mites

These insects attack a wide array of plants and can seriously affect the look of the plant. The conifers are a group routinely attacked by mites, and due to their evergreen nature, the damage remains evident for a number of years. Winged Euonymous or Burning bush is commonly defoliated in the late summer by the two-spotted spider mite, eliminating the bright red fall display this shrub is planted for. A number of mite species also attack deciduous trees such as maple and pear causing defoliation and weakening of the tree. Timing is critical and multiple applications throughout the season are necessary for control.

#9 Aphids

These insects attack a wide array of plants causing a loss in vigor, leaf yellowing defoliation, and in some instances severe distortion of the foliage. As aphids feed on the plant, they excrete excess sap called honeydew. In cases such as Tuliptree aphid infestations, the honeydew drips out of the tree onto surfaces below the tree. A fungus called sooty mold can then grow on the sugars contained in the honeydew, causing blackening and serious staining. Aphids are generally easy to control with a wide array of materials and techniques.

#10 White Grubs

These insect larvae are notorious for the damage they cause to lawns, but they also will attack landscape plants. Grubs feed on and damage the most critical portion of the plant, the roots. Oriental beetle grubs will attack Rhododendron, Azalea, Pieris and Juniper. Japanese beetle grubs, while generally not a serious pest, will yield adult beetles that are voracious feeders on a large number of plants. We can control grubs with one seasonal application.

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