Plant Health Care in Colorado

Tussock Moth

Douglas-fir tussock moth native species

Orgyia pseudotsugata, moths that defoliate Engelmann spruce, douglas-fir, true fir trees and sometimes blue spruce. Douglas fir is the preferred host. Defoliation doesn’t always cause death, but repeated infestations can cause trees to be weakened and to be susceptible to bark beetles. Signs of infestation are defoliated trees that begin at the top and progresses downwards. Improving tree health can help to mitigate the effects of infestations by improving ability to survive defoliation. Thinning out of host species and selecting for non host species may also help by limiting the amount of food for the larvae.  

MOUNTAIN PINE BEETLE (MPB)

Mountain pine beetle, Dendroctonus ponderosae, is .25 inches long and brown to black cylindrically-shaped. They are highly aggressive and can successfully colonize most species of pine including: lodgepole, ponderosa and limber pines. Damage is done when they tunnel through inner bark layers and harm the vascular tissue. The vascular tissue can also be infected by Blue Stain Fungi, a fungus that the beetles often carry spores of, which only speeds up the death of the tree by blocking water and sugar transport in the tree.

IPS Beetle

Ips engraver beetles, Ips spp, are less than a quarter inch long, dark red-brown to black cylindrically shaped beetles. They attack all species of pines and some species of spruces. Signs include yellow to reddish-brown boring dust at entry sites or around the base of the tree. Y or H shaped galleries can be found under the bark where the adult has laid eggs. The larval stage then tunnels around the sapwood and causes dieback or discoloration in the upper parts of the tree. 

Spruce Beetle

Spruce beetle, Dendroctonus rufipennis, is dark brown to black with reddish brown wing covers and .25 inches long that rarely attacks below 9,000 feet.The beetle infests spruce trees with Engelmann spruce being its main host but will also attack blue spruces. They prefer downed spruce trees and trees larger than 16 inches in diameter and forests that are above 9,000 ft. Signs of infestation are yellow-green that fades to gray over a couple of years. Light reddish brown dust can be found around the tree from new borers entering and streams of resin flowing down the trunk that resembles candle wax.

LILAC ASH BORER: native species

Lilac ash borer, Podosesia syringae, is a clearwing borer that attacks ash trees and lilacs. It looks like a wasp in the adult form, but is actually a moth and not harmful to humans. Damage from the larval stage causes tree decline and death in stressed trees while healthy, well established trees are usually not as likely to die. Exit holes are round and usually seen in the lower trunk of the tree and on lower limbs.

EMERALD ASH BORER (EAB): invasive species

Emerald ash borer, Agrilus planipennis, is a flat-headed borer that attacks all true ash trees, this does not include mountain ash. It is emerald green in color and half an inch long. Infestations appear as defoliation in the upper canopy of the tree that progresses downwards as the larvae look for more vasculature to feed on. The larvae cause the most damage to the tree by cutting off transport of water and nutrients. Trees that are healthy and stressed are equally attacked by the beetle so improving tree health does little to stop progression of decline.

GROWTH REGULATORS

Growth regulators are chemicals that can be used to control growth of plants for 2-3 years. By changing the balance of hormones the tree focuses more energy into fibrous root growth rather than branch and stem growth. This allows for better nutrient and water uptake which in turn help mitigate tree stress from drought, nutrient deficiency or damage from pests or the environment.