Forest Insects and Disease Sharon Paul USDA FS Forest Service Lincoln National Forest
High stand density
Horse Thief Basin, Prescott NF, 2002
Pi単on Outbreak in 2002 Pi単on Mortality
East of Flagstaff, AZ
West of Cochiti Lake, NM Near Mesa Verde, CO
Looper, Nepytia janetae. Larva, adult and landscape damage.
Douglas-fir tussock moth, Orgyia pseudotsugata. Larva, larval feeding, tree damage and adults (male on left, female on right is flightless)
Western spruce budworm, Choristoneura occidentalis. Larva, adult, landscape damage and cycles.
Western tent caterpillar, Malacosoma californicum. Larva, adult with egg mass and larva with stand damage.
Symptoms of bark beetles attack • • • •
Crown fading Pitch tubes/streaming Boring dust Woodpecker activity
Roundheaded pine beetle, Dendroctonus adjuntus. Galleries and adult. Flights in the Fall
Western pine beetle, Dendroctonus brevicomis. Larval development in outer bark, woodpecker activity
Ips
WPB
Ips pini in ponderosa pine showing small groups of trees attacked.
Pinyon ips, Ips confusus. Adult, galleries, pitch tubes and landscape damage.
Douglas-fir beetle, Dendroctonus pseudotsugae. Galleries, adult beetle and tree damage.
Blue Stain Fungi
Suppression Treatment of infested trees • • • •
No sprays available for treating infested trees Solarization – infested logs covered w/ plastic Chipping, burning, peeling Removal from site: disposal or sanitation
Prevention of Beetles • Silvicultural strategies to reduce tree density and favor non-host trees
• Must manage thinning slash • Avoid stacking green firewood or infested wood next to standing pine
Preventative watering • Water most valuable trees • Water to 2-3 feet deep once per month during dry months
Drip line Watering zone
Preventative sprays • Preventative sprays are available • Sevin SL, Astro, Permethrin Plus C
• Spray must be applied up entire trunk to 4 inches in diameter • Sprays work about one year
ag.arizona.edu/extension/fh/pdf_files/preventative_spraying.pdf
Dwarf Mistletoe
Dwarf Mistletoe (Arceuthobium) • An obligate parasite- must have a live host. • Leafless. • Always grow on conifers. • Spread by explosive seed. – Distribution in stands is usually “patchy,” due to the means of spread – Rate of lateral spread: 1-2 feet year • All ages and sizes of trees are susceptible
Witches’ Brooms
RMRS photo
RMRS photos
Dwarf Mistletoe Lifecycle Rains wash them onto the twig
July - August
Fruits mature after 2+ more years and the life cycle starts again.
Shoots first appear 2+ years later.
They germinate and infect the twig
A swelling appears in about 2 years.
Note: Life cycle takes a minimum of 6 years. Latent period may be 4 to 10 years !
DM Distribution in the SW Over 1/3 ponderosa pine acres infested
Over 1/2 mixed conifer acres infested
Biotic associates • Birds and squirrels often use witches’ brooms as nesting platforms • Higher snag densities in infested areas provide habitat for some birds • Several insects feed on dm plants; these in turn attract insect-feeding birds • Feeding by birds on dm itself is probably uncommon
Effect on tree growth: DMR 1–3
none
DMR 4
10-20%
DMR 5
20-30%
DMR 6
30-100% (dead tree)
On average, a tree’s DMR increases every 10 years.
Can we control mistletoe? Yes, it is possible to control them silviculturally because: 1) they are obligate parasites and 2) they spread relatively slowly However, controlling them is not easy, because of 1) latent infections and 2) relatively rapid intensification after thinning Releasing the trees releases the “toe”
Sanitation Thinning
Seed-Tree Cut
Shelterwood Cut
Patch Clear-cut/Group selection
Underburning can reduce dwarf mistletoe infection via scorch pruning and mortality of heavily-infected trees
White Pine Blister Rust
White pine blister rust Cronartium ribicola J. C. Fisch. Native to Asia, introduced to North America ~turn of the 20th century In at least 38 states Hosts: SW white pine. Limber pine and bristlecone pine also susceptible. Alternate hosts: Currants and gooseberries (Ribes) spp.
The “Discovery Tree� of white pine blister rust on the LNF in 1990?
White pine blister rust life cycle Infected 5-needle pines, mortality
Aeciospores in the spring
Two obligate hosts
Infected Ribes spp., no mortality Basidiospores in the fall
Effects of White pine blister rust. Powdery urediniospores for cycling
Effects of White pine blister rust. Dead branch “flagging�
Mortality in small trees
Branch flagging and mortality in larger trees