Maples continue as top selling shade tree but are leafhoppers bringing you down?

Every year, starting in May/June, the American red maples suffer from potato leafhopper damage.  The curled and twisted tip growth is all too familiar to most nursery managers.  In dry years the damage is usually heavier. Since we are still in drought conditions growers can probably expected leafhopper damage to be fairly heavy this year. Or course, now that I made this prediction, I will be proved wrong. Hope for your benefit that I am wrong. Just in case, let’s look at what you can do for dealing with potato leafhopper.

First off, where do potato leafhoppers come from? Generally, the potato leafhopper (Empoasca fabae) cannot overwinter in the North because of sensitivity of eggs to the cold. On occasion, the leafhopper has been found overwintering in the southern, eastern shore of Maryland. With such a mild winter, it may be possible that this year some of the eggs could have overwintered in other parts of Maryland but this has not been confirmed.  The potato leafhopper is found year round in the Gulf of Mexico. In May and June when the prevailing northern winds carry the leafhoppers into the Jet streams and drops them out in states such as Maryland.

The females will deposit eggs in slits in veins on the undersides of maple leaves or in petioles. You really would find it difficult to detect the eggs. The nymphs hatch in about 7 –14 days after laying. The nymphs go through 5 instars (shed their skin 5 times). Up to 6 generations per summer have been recorded in Maryland. The potato leafhopper feeds in the vascular tissue, primarily in the phloem. As the stylet probes the plant tissue, internal cells are lacerated and plants cells fragmented. Salivary toxins injected into tissues cause the cells to distorted and collapse. When vascular tissue is damaged in shoots, the tip tissue to distort with curling and twisting tip growth. The multiple generations keep damaging new flushing tip growth on the maples.

Solutions

Plant breeders at the National Arboretum have released 3 red maples (Acer rubrum) that have excellent resistance to leafhopper damage. Acer rubrum ‘Somerset’ and “Sun Valley’ were released to the nursery trade in 1994. “Sun Valley’ is hardy in zone 4 –7. ‘Somerset’ is hardy to Zone 8. Both cultivars have excellent fall color that is long lasting and significant tolerance to leafhopper injury. ‘Somerset’ at 12 years old are 23 ft tall with an 11 foot crown. ‘Sun Valley’ at 10 years of age is 21 feet tall, and 10 feet.  wide. ‘Brandywine was also released in 1994 and has similar resistance to leafhopper damage. The fall color on this red maple is a brilliant red-purple. All three selections roots from softwood cuttings under mist, 1000-3000 ppm IBA.

Chemical options

We are conducting trials at Ruppert Nursery in Laytonsville to evaluate imidacloprid (marathon) applied as a soil injection. We will be seeing if we can obtain season long control. The present cost is approximately $800.00 to treat an acre of trees. Orthene applied to foliage will give about 2 weeks of foliar protection. 

Pest monitoring

Early activity of potato leafhopper in Maryland will be posted on the pest monitoring site when it's available.

Stanton Gill is a regional specialist for commercial horticulture at the Central Maryland Research and Education Center, University of Maryland, in Ellicott City, MD.