Insect and Disease PestsIn Delaware’s Forests

Envirothon TrainingUpdated October 2007

Glenn (Dode) Gladders

Symptoms vs. Signs

• Symptoms Changes in the

plant’s appearance that indicate something is happening. Ex: crown dieback, wilting, cankers.

• Signs Indications of the

insect or disease itself. Ex: frass, pitch tubes, fungal fruiting bodies.

THE ENVIROTHON SEVEN!

• Know these:1. Emerald Ash Borer2. Asian Longhorned

Beetle3. Southern Pine Beetle4. Gypsy Moth5. Sirex Wood Wasp6. Bacterial Leaf Scorch7. Sudden Oak Death

• For each, know:1. Native/non-native

2. Present in Delaware?

3. Host species

4. Symptoms & Signs

5. Type of damage

6. Control measures

INSECTS

Emerald Ash Borer (EAB)

• Non-native• Has not been found in Delaware, but present in Maryland• A threat to ash trees only• Larvae create galleries in the cambium of infested trees,

girdling the trees

Adults are bright green and easy to identify.

Emerald Ash Borer (EAB)

Galleries D-shaped exit hole, splitting bark

Crown dieback

Woodpeckers feeding

• Control in our area = ERADICATION (Remember, it has not been detected yet in

Delaware)

• Cut all ash trees in the area of new infestations. Chip the trunks and branches to a small size.

Emerald Ash Borer (EAB)

Asian Longhorned Beetle (ALB)• From China• Has been detected in New York, New Jersey, not DE• Threatens numerous types of trees, particularly the

maples.

Asian Longhorned Beetle (ALB)• The beetle develops within the

xylem (wood) and then bores its way out. Eventually the many exit holes will destroy the cambium and kill the tree. The weakened wood can also cause structural failure (tree breaks in half).

Asian Longhorned Beetle (ALB)

• Large exit holes are conspicuous signs of ALB infestation.

Asian Longhorned Beetle (ALB)

Infested trees must be removed,

and chipped to destroy all beetles.

Asian Longhorned Beetle (ALB)

Packing materials are inspected at ports of entry.

Southern Pine Beetle (SPB)

• Native• Present mainly in southern DE• Hosts are hard pines (all

except white pine)• Chews galleries which can

girdle trees. Also introduces a harmful fungus.

• Delaware is at the northern end of its range. A more serious pest in the South.

Southern Pine Beetle (SPB)• Infested stands

can be detected with aerial surveys. Infested pines display brown foliage.

Southern Pine Beetle (SPB)

Small round holes

S-shapedgalleriesPitch tube

Southern Pine Beetle (SPB)

Infested trees can be cut and burned, chipped, or sprayed.

Control

Gypsy Moth

• Non-native

• Introduced into Massachusetts in 1869. Since then it has spread throughout the northeast, including Delaware.

Gypsy Moth

• Larvae feed on the leaves of many broadleaved species, particularly the oaks.

• Host trees are damaged through defoliation.

Gypsy Moth

• When severe defoliation occurs several years in a row, widespread mortality can result.

Gypsy Moth

Defoliation can be seen from the air during June survey flights

Egg masses

Gypsy Moth

• Egg masses are easily seen in the fall. These methods can determine the need for a control program the following spring.

• Control = chemical sprays.

• Non-native

• Has not been found in Delaware

• Threatens loblolly and other pines

• Forms galleries that injure trees

• Carries a fungus that causes more damage

Sirex Wood Wasp

Sirex Wood Wasp

Round exit holes

Resin beads

Symptoms / Signs

Wilting and discoloration

Sirex Wood WaspControl

• Control measures unknown (new pest)

• Biological controls have been successful in other parts of the world

• Early detection surveys in DE using trap trees

Red pine trap tree at White

Clay Creek SP

DISEASES

Control:

• Native to the United States

• Present throughout Delaware

• Hosts = red oaks and other trees

• Mainly northern red, pin, black, and scarlet oaks

• Symptoms = Marginal leaf scorching in late summer and fall, dieback

Bacterial Leaf Scorch (BLS)

• The bacteria are spread (vectored) by insects that feed on the xylem

• Bacteria reproduce and physically clog the xylem

• Simply a “plumbing” problem. Not enough water can move through the xylem to branches and leaves, so living tissues dessicate and die.

Bacterial Leaf Scorch (BLS)

Bacteria clogging

xylem

Symptoms

Bacterial Leaf Scorch (BLS)

Marginal leaf scorch

Dieback

Control

Bacterial Leaf Scorch (BLS)

• No proven prevention

• No proven cure

• Treatment trials ongoing in Delaware and elsewhere

• Do not plant northern red oak or pin oak

• Non-native

• Has never been found in Delaware

• Threatens oaks and other trees, as well as viburnums and other understory plants

• Two types of symptoms:

Sudden Oak Death (SOD)

• Understory plants

• Foliar scorching

• Twig dieback

• Overstory trees

• Bleeding stem cankers

• Dieback+

Understory plants

Dieback

Twig dieback

Foliar symptoms

Overstory Trees

Bleeding canker

Sudden Oak Death (SOD)

Control:

• No control in generally infested areas such as California

• Control in other areas is quick response after detection. Cut, pile, and burn is an accepted prescription in new detection areas.

• Quarantines are in place to prevent new introductions.

Sudden Oak Death (SOD)