Gypsy moth is a Federal and State quarantined leaf-eating insect that is a serious threat to forest and urban trees, as well as ornamental plants. This pest is not native to North America and has the potential to defoliate trees year after year causing significant environmental, economic, and quality-of-life issues.
You may be wondering why do we treat for gypsy moth, and why is it such a concern for Iowa? Gypsy moth is not part of the natural ecosystem, and doing nothing is not the same as letting nature take its course.
Gypsy moth has no significant enemies to keep the pest population in check. A single gypsy moth caterpillar can consume as much as one square foot of leaves per day, and large pest outbreaks can devastate entire forest and urban areas, leaving a bleak winter-like appearance in mid-summer. Infestations of this pest are taken very seriously for the following reasons.
- Consistent or repeated defoliation over several years can have devastating effects, often leading to large areas of tree mortality, which can lead to liability concerns as dead and dying trees may damage property or cause injury to people.
- The costs to remove and replace dead and dying trees in urban landscapes would be funded completely at the local level and often by property owners. The loss of mature trees would have a direct negative effect on property values.
- Caterpillars invade outdoor living areas and homes in mass migrations. Hairs from the insect may cause allergic reactions in some people, which may cause difficulties with skin, eyes, and respiratory systems.
- Fecal pellets from the feeding caterpillars rain upon people’s yards and public areas making it difficult to enjoy the outdoors. And like any other nutrient, droppings will get washed into sensitive watersheds causing additional problems, especially for trout and other aquatic organisms.
- Gypsy moth is easily moved to new areas by unsuspecting human activities, and can be moved long distances by hitch-hiking on any outdoor article that is transported by people. We have a responsibility to other communities to limit the spread of this pest.
- Millions of dollars have been spent to lessen the impact of gypsy moth in other states. History has shown that it will cost 3 times less to deal with small pest infestations, than to react to large, well established populations. The longer we can keep gypsy moth out of Iowa, and also manage the pest population when it does become established, the less the long term economic impact will be from a local and statewide perspective.
Eastern Iowa is considered to be in the transition zone of gypsy moth advancement. Small pockets of infestation are becoming more common in northeastern Iowa, as would be noticed from the natural advancement of this pest. The established 'western' front for gypsy moth is now considered to be 35 miles east of the Mississippi River.
As the gypsy moth continues to advance, and as more small pockets of gypsy moth infestation become common ahead of the front, the management strategy has been to "slow the spread" of the pest. The best way to control low populations of gypsy moth over a large area is to use mating disruption. This strategy uses the pheromone attractant of the female gypsy moth to confuse the male moth in finding a mate, which in turn limits or controls natural reproduction of the pest. This strategy is especially effective when the pest density per area is low to moderate in size.
Determining Treatment Locations
Iowa is currently included in the Gypsy Moth Slow the Spread Foundation (STS). STS provides the framework for states to determine the areas that need to be managed for gypsy moth. This program focuses on early detection of low level gypsy moth populations, and then disrupts the normal build-up and spread of gypsy moth in those locations.
- Gypsy moth detection traps are first placed throughout the management area using a precise topographical grid. Iowa’s gypsy moth detection trap program started in 1970 and has been done annually each year. It is the first step to determine areas that need to be managed for gypsy moth. The traps are a simple design that contain the same gypsy moth pheromone used in mating disruption treatments. Male moths are lured to the trap where they are stuck in glue. Additional traps are placed in areas where trap catches are higher to find the extent or to 'delimit' a gypsy moth infestation.
- A computer uses a mathematical formula to analyze each year's trap data, and provides recommendations for project boundaries, delimitation, and treatment. A trap catch above a certain threshold of male moths, triggers a more intensive trapping effort the following year to find the extent of that localized infestation.
- Some measure of control may be taken in the third year to "slow the spread" in those locations if data suggests that action is necessary. As the gypsy moth population builds in a new location, the strategy gradually moves from slowing the spread of the pest to suppression of large outbreaks.
What to Expect on Treatment Day
- Disrupt® II is a pheromone flake product that uses an inert sticker similar to Elmer’s® glue to adhere the flake to tree foliage. The flakes are very small and not easily found from the ground after the application is done. The application rate ranges from ½ oz. to 6 oz. of product per acre. Less than ½ cup of flakes are typically used for 1 acre of land.
- Splat GM is another pheromone product that looks similar to hand cream and forms a waxy flake when dry. The product is applied in very fine droplets when released from the airplane, and is designed to stick to tree foliage. The application rate of the product ranges from less than 1 oz. to 1 cup per acre.
Aircraft typically begin early in the day and will continue until done depending on weather conditions. The airplane will fly over the treatment area by making several passes and will be noticeably loud. An area of 1 square mile will take about 30 minutes to complete.