| There are between 2-2½ million acres of trees
and forests in Iowa representing about 6% of the total land area. About 92% of
Iowa's forests and trees are in private ownership. Iowa's forests contribute
significantly the agricultural based economy by protecting water quality,
creating wildlife habitat, and providing a variety of recreational
Wood industries in Iowa employ over 7,000 people, producing lumber and high quality wood products. Trees in our small and large communities or "urban forests" increase property values and conserve cooling and heating energy.
Forest health monitoring is a cooperative effort among various agencies: DNR, USDA Forest Service, USDA APHIS, Iowa Department of Agriculture Land Stewardship State Entomologist, Iowa State University, private and public foresters, and private landowners. This cooperative effort encourages efficient monitoring and fosters communication amongst all the interested parties involved in Iowa's forests and their future health.
|Monitoring Efforts for
Estimates of insect, disease, and severe weather impacts, were determined by aerial surveys of over 282,000 acres of major river valleys of Iowa: Des Moines River, Cedar River, Iowa River, Mississippi River and the Upper Iowa River. About 142,500 acres of upland forests and 139,500 acres of bottomland or floodplain forests were surveyed. Surveys by DNR foresters along with trained master woodland managers and community tree stewards ground checked forest health problems at various locations. The gypsy moth, Lymantria dispar, a potentially serious exotic defoliator of Iowa's native trees and shrubs was monitored through a partnership with IDALS State Entomologist, USDA APHIS and the DNR Forests and Prairies, by placing approximately 5,805 pheromone survey traps across the state. The purpose of the trap setting was to determine possible infestations and locate potential sites in need of eradication. The DNR coordinated gypsy moth survey efforts of 38 western Iowa counties (750 traps), Yellow River State Forest (50 traps over 8,000 acres) and a statewide volunteer monitoring effort with over 400 trained community tree stewards.
Iowa sustained record amounts snow from the end of December 2000 to the first part of March 2001. A wet spring along with severe weather caused a record 78 tornadoes, with three F3 tornadoes causing two deaths and significant damage to trees in Agency, Blue Grass and Manchester. Wet and humid conditions caused a noticeable incidence of anthracnose disease caused by Gnomonia sp. and Gloeosporium sp. and other leaf blights on urban trees across the state.
The wet spring caused delays in tree planting right up to the first of July, with parts of northeastern and southern Iowa receiving excessive amounts of precipitation resulting in flooding. The DNR estimates 245 acres of forest along the Cedar, Iowa, Turkey and Missouri Rivers were damaged by flooding.
There was limited tree seed and fruit production across the state. There was a noticeable lack of acorns and walnuts noted across the state.
|Tree Disease Issues
The oak wilt fungus, Ceratocystis fagacearum, invades water conducting tissues (xylem) and causes the foliage to wilt and kill infected oaks. DNR foresters reported 429 new acres of oak wilt infections. Although all species of oaks are susceptible, the red oak group, especially black oak, Quercus veluntina, northern red oak, Quercus rubra, and pin oak, Quercus ellipsoidalis, often die within weeks of infection. Bur oaks, Quercus marcocarpa, were also infected. Oak wilt is spread via root grafts and sap-feeding nitidulid (picnic) beetles. Although there is no cure for oak wilt, control strategies such as preventing tree wounds during high infection periods (March 1 to June 1), disease containment by cutting or killing roots of infected trees, and killing oak trees surrounding the infected trees all appear to have some use in management and prevention. Sanitation of dying and dead oaks before oak wilt fruiting bodies appear the following spring reduces the risk of overland spread. This year in the Des Moines metro area, oak wilt was confirmed in late August and early September on bur, pin and red oaks. High-valued oaks may be protected through high cost systematic injections of the fungicide, propoconizol.
Dutch elm disease (DED) caused by the fungus Ophiostoma umli/novo-ulmi affected approximately 164 acres of American elms, Ulmus americana, across the state. DED occurred in small and scattered drainages in rural areas and in isolated urban trees. Continued lack of sanitation contributes to spread of the disease overland by providing breeding grounds for disease carrying bark beetles.
|Tree Species Decline Issues
DNR field foresters continue to observe scattered dieback and decline of native white and green ash Fraxiness americana and F. pennsylvanica . Ash decline was reported in 35 counties in central and eastern Iowa. Although the exact cause of this dieback and decline of native trees is still under investigation, DNR field foresters are recommending early removal of white ash during commercial and pre-commercial thinning and by increasing species diversity in urban areas.
Non-native Scotch pine, Pinus sylvestris, is one of the most commonly planted conifers for wildlife habitat, windbreaks and ornamental trees in Iowa. Over the past 3 years there has been an increase in reports of sudden browning and mortality of Scotch pine. Both the DNR and Iowa State University believe that Scotch pine decline is due to attacks by the bark beetle Ips grandicollis, and the pine wood nematode, Bursaphelenchus xylophilus. Drought also contributes to Scotch pine decline, but there is still not enough information for a definitive cause and effect. The loss of Scotch pine occurs most often in stagnate and dense plantings on heavy clay soils, when the trees are 20-30+ years of age. Scotch pine decline has also been reported in Christmas tree plantations. DNR foresters documented 430+ acres of Scotch pine were lost in 73 out of Iowa's 99 counties.
|Tree Species Insect Issues The gypsy moth, Lymantria
dispar, is a potentially serious, exotic defoliator of Iowa's native
deciduous trees and shrubs. Originally brought to the US in the 1860's from
Europe to establish a silkworm industry, it escaped and has spread throughout
forests of the northeast, and is now established in Michigan and Wisconsin.
IDALS and USDA treated 10 acres of a nursery where moths were
DNR foresters placed and monitored 750 traps in 38 western counties, and the Yellow River State Forest in NE Iowa costing $22,000 in staff and related expenses. Remaining GM traps were placed by IDALS and APHIS, with the DNR coordinating 400 volunteer trappers as well.
During the 2001 gypsy moth trapping season (May 1st to September 1st) a total of 26 male moths were caught in 13 Iowa counties. This is a drop from the 46 male moths caught in 2000 and the 135 moths caught in 1999.
| Japanese beetle, Popillia japonica, is spreading into Iowa.
During 2001, visual reports and traps determined severe infestations in
Dubuque, Linn and Scott counties, with modest infestations in 10 other eastern
and central Iowa counties. The adult beetle is a pest of turf and perennial
plants such as roses, but it has been reported defoliating native and
non-native lindens, Tilia spp. Misuse of over-the-counter beetle traps
has been reported which is attracting beetles to an area rather than killing
them. It is expected this pest will move across the state in the next 10+
|Other Tree Health Concerns
Severe winter conditions during the winter and early spring of 2001 contributed to an increase in wildlife damage to ornamental, plantation and forest trees. DNR foresters, along with Iowa Christmas tree growers and others reported widespread browse damage from white-tailed deer. Approximately 1,800 acres of browse damage was observed in 92 out of Iowa's 99 counties.
Deep snows also allowed deer to climb over fences and other obstacles in search of forage. Eastern cottontail damage was also reported to be severe throughout the state. Rabbits aided by deep snows, girdled young trees and plants in urban and rural settings.
Invasive Species Efforts Established
State agencies and universities are beginning efforts to increase awareness of invasive animal and plant issues related to urban and rural forest areas. A working group is leading the effort to conduct workshops and training sessions for natural resource professionals. An initial "Invasive Species Tour" was held in central Iowa in 2001. The DNR is in the initial stages of producing an invasive species poster and other materials for distribution statewide.
|For more information contact:|
IA Dept. of Natural Resources
Forest and Prairies Division
Wallace State Office Building
Des Moines, IA 50319-0034
|Forest Health Protection
State & Private Forestry
USDA Forest Service
1992 Folwell Avenue
St. Paul, MN 55108
|Updated: January 2002.......|
|Iowa Forest Health Highlight 2001, PDF|
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