| A unit of Lasting Forests
evolving since March 30, 1999 |
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A Total Forest Management Plan
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History and Distribution
The gypsy moth, Lymantria dispar, is native to European and Asian countries and is currently the major introduced pest of hardwood forests in the eastern United States. The habitat of the gypsy moth encompasses the temperate regions of the world including, central and southern Europe, northern Africa, central and southern Asia, and Japan (Leonard (1981). The gypsy moth was originally introduced to Massachusetts in 1869 by Leopold Trouvelot, a naturalist. Trouvelot attempted to develop a strain of silk moth in an effort to begin a commercial silk industry. Unfortunately, gypsy moth larvae escaped from Trouvelot's home in Medford (Leonard 1981). Surprisingly, it was not until 20 years later that the first outbreak occurred. Despite all control efforts and eradication strategies since its introduction, the gypsy moth has persisted and extended its range. In the United States, the gypsy moth has rapidly moved north to Canada, west to Wisconsin, and south to North Carolina. Gypsy moth caterpillars defoliate millions of trees annually in the United States, eastern Canada, and Europe.
Biology and Ecology
The gypsy moth only has one brook (i.e., is univoltine) and the first instars (the caterpillars) hatch from their egg masses during bud-breaking which usually occurs in mid-spring. Although the larvae are capable of feeding on over 300 tree species and shrubs (Lechowicz and Mauffette 1986), their preferred hosts are largely oaks (Quercus spp.) which often become defoliated during outbreaks. The male and female larvae typically pass through 5 and 6 instars, respectively, before pupating in early to mid-summer. The duration of the pupal stage is approximately 2 weeks and the males emerge one or two days before the females. Adult gypsy moths are sexually dimorphic (different colored / sized); the males are brownish-gray in color, whereas the females are slightly larger in size, white in color, with black markings. Unlike the males, the females are incapable of flight.
Upon hatching from the pupal stage, the females emit a pheromone which attracts males from moderate distances and mating then occurs. Shortly thereafter, the females begin to lay oval-shaped egg masses which are covered with hairs from her abdomen. The buff-colored egg masses contain 100 to 1500 eggs (Carter 1991) and are laid on the underside of tree limbs, bark, rocks, and other structures including buildings, campers, mobile homes, etc.
In areas where the gypsy moth is well-established, population abundance varies. It is high in some areas, low in others. There are 4 distinct population phases: innocuous, release, outbreak, and decline (Campbell and Sloan 1978a). The gypsy moth may remain at low densities (innocuous phase) for many years and for reasons yet unknown, begin to increase rapidly (release phase) toward the outbreak phase. This latter phase is characterized by severe defoliation resulting from fourth instar densities of 250,000 to 2,500,000 larvae per hectare (Carter et al. 1992). In some areas, the densities among populations vary widely and may influence the dynamics of adjacent populations (Campbell and Sloan 1978b). Carter et al. (1992) also reported that larvae develop faster at higher densities than larvae in low density populations. When moth populations are invading new areas, they reach outbreak levels rapidly, within 2 to 3 years. The outbreak phase typically lasts 1 or 2 years; however, they may remain at high densities for several years before declining.
With any given insect population there are a number of factors that affect its dynamics and regulate its size. These factors are typically placed in 2 distinct categories, density dependent or density independent. Density dependent factors are closely coupled to the insect population and exert their effects as the population increases in size. These factors, including, predators, parasites, and pathogens, help to maintain the size of a population at, or near equilibrium. Conversely, density independent factors (e.g., weather) exert their effects at any population size and accordingly, are not closely coupled to the population. The gypsy moth is not immune to population regulation; however, because it is an exotic pest, the normal "checks-and-balances" that are found in its native land are either missing, or, are not in synchrony with its life cycle (Montgomery 1992). While a significant amount of time and resources have been allocated to better understand how North American gypsy moth outbreaks occur, and why they are so extensive and severe in comparison with Europe, recent studies suggest that in Europe, poor synchrony between the host plants and strong delayed density dependent regulation may explain the occurrence of outbreaks at long intervals of time. As a corollary, the greater frequency of outbreaks in North America may be a consequence of a better match up between the gypsy moth and its host plants coupled with weaker density dependent regulation (Montgomery 1992).
The Gypsy Moth in the Forest
Hosts, Defoliation, and Susceptible Trees
Many studies have been conducted of the types of tree hosts preferred by the gypsy moth and these are summarized in Table 1. In addition, other studies have examined the susceptibility of these trees and how they respond to defoliation. Carter et al. (1992) reported that the level of defoliation is determined largely by the density of the larval population, species composition of forest stands, and leaf biomass. While most deciduous trees can withstand 1 or 2 years of defoliation before serious decline occurs, conifers will die after 1 complete defoliation (Johnson and Lyon 1988).
Gansner and Herrick (1982) reported that many factors influence the susceptibility of trees to the gypsy moth and these include: timber stand size composition, average tree diameter, timber stocking, stand age, species composition, crown position, crown condition, site index, land capability, elevation, aspect, slope, and position on slope. From these studies, they reported that the most susceptible trees are white oaks, particularly those trees with poor crowns. Gansner and Herrick (1982) classified trees with poor crowns as those having 50 percent or more of the branches dead, when foliage density size, or coloration was of subnormal quality, or when epicormic sprouting was heavy. Using the above variables, Gansner and Herrick (1982) combined the use of various statistical methods (correlation and stepwise regression models) to select the best factors for predicting gypsy moth outbreaks. Their goal was to select those factors that were easy to measure and would explain the most variance within their model (provide the best decision aid). The results of their study suggested that the most important factors involved in tree defoliation were 1) basal area per acre of tree species that gypsy moths tend to avoid 2) percent of basal area in trees that are 3.0 to 4.9 inches dbh, and 3) percent of basal area in trees with poor crowns. Within this study they found that trees with greater stocking in species avoided by the gypsy moth were usually attacked less severely and had a lower mortality rate and a higher growth value. Gansner and Herrick (1982) also reported that trees within a 3.0 to 4.9 dbh class had little or no value for timber products, but those that survived gypsy moth attacks soon grew into merchantable size and had high-value growth rates.
The goal of the current IPM practices for the gypsy moth (and numerous other pests) is to reduce damage or pests to an acceptable level while considering the safety of workers and other people, animals and plants, and controlling cost as well as preserving the stability of the landscape ecosystem (Harris 1992). The concept of current IPM practices also necessitates an emphasis on the real, measured, significant, financial, social, and ecological changes associated with the "pest." Rather than simple "pest control", it is believed that for long-term durations, an emphasis on damage control will benefit the area and its people. There is a considerable distinction between physical change (e.g., leaves being consumed) and injury or damage (e.g., severe loss of trees). Accordingly, damage is not only physical injury but includes associated real financial or measurable esthetic loss. The literature rarely makes the distinction between physical change and real damage.
How the Forest is Changed
Gansner et al. (1982) reported that most forest stands survive gypsy moth outbreaks with little or no damage, while others suffer heavy damage. Gansner et al. (1993a) also reported that impacts on oak forests in Pennsylvania were highly variable. The range of oak mortality and growth in their study plots included, all of the oaks dying, none of the oaks dying, and, all of the oaks tripling in volume. Chestnut and white oak accounted for approximately three-fourths of all oak mortality and was significantly higher than the mortality of northern red oak. While the mortality of oaks in the above studies was variable, the other trees fared better than oaks.
Table 1. Feeding preference classes of gypsy moth caterpillars (Mason 1987)
Class 1: Species that are preferred for all life stages
Overstory: apple, basswood, bigtooth aspen, quaking aspen, birches, boxelder, larch, American mountain ash, oaks, sweetgum, and willow
Understory: alder, hawthorn, hazelnut, eastern hophornbeam, serviceberry, sumacs, witch hazel
Class 2: Preferred tree species for 4th instars and older
Overstory: chestnut, eastern hemlock, pines, spruces
Class 3: Nonpreferred tree species for 4th instars and older
Overstory: American beech, black and yellow birch, tupelo, Ohio and yellow buckeye, butternut, sweet and black cherry, eastern cottonwood, cucumbertree, American and slippery elm, hackberry, hickories, Norway, red, silver, and sugar maples, pear, silver poplar, sassafras, black walnut
Understory: blueberries, pin and choke cherries, American hornbeam, paw paw, persimmon, redbud, sourwood, sweetfern
Class 4: Nonpreferred species that are rarely consumed
Overstory: ash, bald cypress, Catalpa, eastern redcedar, balsam and Fraser fir, American holly, horsechestnut, Kentucky coffee tree, black and honey locust, mulberry, sycamore, tulip tree
Understory: azaleas, dogwood, elderberry, grape, greenbrier, juniper, mountain and striped maple, Rhododendron, brambles (Rubus species), sheep and mountain laurel, spicebush, sarsaparilla, viburnums
Between 1965 and 1989 the total volume of growth in the Pocono Mountains increased from 865 to 1,385 ft3 / acre. This increase in volume was attributed to the growth of red maple, sweet birch, white ash, black gum, and other hardwood species which are of low vulnerability to the gypsy moth. Gansner et al. (1993a) reported that oaks accounted for over 500 ft3 / acre; the highest volume recorded since the 1950's and it comprised 43 percent of the total inventory. In addition, the authors also reported that gains were made by northern red oak, a favorite timber species.
During that same year, Gansner et al. (1993b) developed methods for predicting gypsy moth defoliation potential; they combined susceptibility ratings with maps depicting defoliation potential. These were developed in order to provide resource and pest managers an understanding of what to expect from the gypsy moth when it enters a forested area. [While methods for predicting and estimating damage within the forest environment have been established, similar studies with regard to gypsy moth damage within the urban/suburban environment have not been conducted.]
History of Gypsy Moth Management
The first attempts at eradicating of the gypsy moth began in 1891, in Massachusetts. Several methods were attempted including the application of creosote or acid to egg masses, burning infested trees and shrubs, and spraying with insecticide (Kirkland 1905, Burgess 1930). Paris green was the first insecticide used, followed by lead arsenate. Other control efforts were productive and provided a great deal of baseline data for today's researchers. Between 1891 and 1900, the eradication efforts were so successful that the Massachusetts Legislature chose to abandon this project; however, this was a tragic mistake as the gypsy moth began to increase and spread again.
From 1900 to 1905 gypsy moth infestations increased and spread from Massachusetts to neighboring Rhode Island, New Hampshire, Connecticut, and Vermont. Then, in 1906, the Federal Government began to experiment with natural enemies of the gypsy moth, which were imported from several European countries and Japan (McManus and Mclntyre 1981, Brown and Sheals 1944). The gypsy moth continued spreading and in 1912 quarantines were established in an effort to help reduce the spread and prevent new infestations of other areas. A barrier zone was established from Canada to Long Island, NY, in 1923; however, the barrier zone eventually became infested in 1939. Additional attempts at gypsy moth eradication in the 1940's included the use of the insecticides cryolite and DDT. Pennsylvania was the first state to receive experimental aerial applications of DDT, and, despite some success, several undetected infestations remained and the gypsy moth continued to defoliate forests and increase its distribution in other states.
In the 1950's, DDT was the insecticide of choice; however, a national concern arose in 1957 about the persistent residues of DDT and other chlorinated hydrocarbon insecticides, and in 1958, DDT began to be slowly replaced with the insecticide, carbaryl (Sevin). A shift from chemical use to microbial pathogens began in the 1960's with studies on Bacillus thuringiensis (BT) and nucleopolyhedrosis virus (NPV). Sterile-male techniques and the synthetic pheromone gyplure were also developed and evaluated at this time. However, the amount of defoliation caused by the gypsy moth increased and the gypsy moth continued its spread in many states.
In the 1970's it appeared that the attempted eradication of the gypsy moth was futile. Accordingly, the eradication philosophy began to be replaced with one of management. During this time, research was accelerating in the areas of population dynamics and correspondingly, newer population monitoring techniques were developed. This change then, involved a variety of techniques including, defoliation surveys and the sampling of egg masses, larvae, and pupae. In addition, the development of disparlure, a synthetic attractant for male gypsy moths, led to its use in pheromone-baited traps for their capture. Also developed at this time was the insect growth regulator Dimilin, a chitin synthesis inhibitor. Research was also conducted on the natural enemies (e.g., insect and other predators, parasitoids, etc.) of the gypsy moth in conjunction with the newly developed chemical and microbial insecticides. This philosophy, which coupled control methods, population monitoring, and other environmental practices, was the forerunner of a more encompassing system now known as Integrated Pest Management (IPM).
Current Gypsy Moth Management Practices
General Surveillance Techniques
A variety of survey methods are available for sampling gypsy moth populations as well as estimating and predicting their environmental impact. However, 2 of these are commonly employed; 1) pheromone-baited traps and 2) egg-mass counts. Pheromone-baited traps contain 500 ug (+) disparlure, and, are usually arranged in a 2 or 3 km grid in forested and rural areas (Carter et al. 1994). In areas of special concern, however, traps are placed in a finer, much smaller grid. These traps are placed in the spring and are usually checked twice a year (Fleischer et al. 1992).
Egg mass counts are probably the most reliable method of determining the amount of defoliation to be expected by a gypsy moth population. This is largely based on the relationship between the number of egg masses and the percent of defoliation in an area. Etter (1979) established action (treatment) thresholds consisting of 250, 500, and 1,000 egg masses/acre, (618, 1,236, and 2,471 egg masses/hectare) respectively, and several current sampling methods use these thresholds. These include, timed walks, fixed and variable radius plots, and a variety of sequential and binomial sampling plans. Currently, egg mass density is the primary criterion used to make gypsy moth control decisions (Ravlin et al. 1987).
Although pheromone-baited traps are perhaps the best method used to delineate gypsy moth populations (Ravlin et al. 1987), the relationship between the number of males captured and population density has not been precisely established for 2 reasons: 1) trap efficiency changes as the traps fill (Elkinton 1987) and, 2) they become saturated (Bellinger et al. 1990). In the first case, particularly in those areas with high moth populations, the traps are filled with moths from adjacent populations, and, these traps do not have the capacity for additional male moths. In the second case, usually in areas with low egg mass density, migrant male moths fill the traps from distant areas. In both of these scenarios, the relationship between the number of male moths and moth egg density remains uncertain. Many factors effect the relationship between egg mass density and population density; these are very complex relations and additional research on alternative strategies are necessary.
Suburban and Urban Surveillance Techniques
The determination of gypsy moth population densities outside the forest environment requires different sampling strategies than those presented above. Suburban and urban habitats are not the same as the forest environment. This is largely due to the presence of humans, their dwellings, and other objects that contribute to changes in the spatial distribution of gypsy moth egg masses. The spatial distribution of egg masses within suburban and urban habitats has been shown to be influenced by artificial objects as well as the forest edge, and, differs from the continuously forested habitats (Campbell et al. 1976). Bellinger et al. (1989) reported that egg mass densities were 2.4 times higher in forest edge trees than interior trees. They also reported that the edge side of edge trees had approximately 3.2 times the egg masses of the edge side of interior trees and about 4.8 times more egg masses than the interior side of these same trees. Bellinger et al. (1989) concluded that sampling along the forest edge tends to overestimate population levels, or, increases the probability of populations being over the action thresholds. However, the authors cautioned that the avoidance of edge sampling would underestimate populations. Further, the authors suggested that egg-mass sampling, involving timed walks be conducted perpendicular, rather than parallel to the forest edge.
Typical Federal and State cooperative suppression programs use an action threshold of 618 egg masses / hectare (250 egg masses / acre) and require that there be at least 1 house per 62 hectare in a spray area. Within urban areas, Thorpe and Ridgeway (1992) determined that 0.01 hectare egg mass surveys were the most efficient method and that 70 percent of egg masses were found on trees. However, because of the uniqueness of the suburban and urban environments, the sampling plans used within the forest are probably not appropriate (Thorpe and Ridgeway 1992).
Carter et al. (1994) recently developed a sequential sampling plan for urban / suburban environments which employed Wald's (1947) sequential probability ratio test. Carter et al. (1994) suggested that this method could be used for any urban / suburban habitat where the housing density ranged from 0.247 to 12.35 houses per hectare. Based on their results, the authors were able to reduce the number of egg masses sampled by 31-49 percent, a substantial savings of both time and resources.
Silvicultural Practices
Silviculture can be used to change the susceptibility and vulnerability of tree stands to the gypsy moth (Gottschalk 1992). Silvicultural practices include a variety of techniques which reduce competitive stress among trees and create stand conditions that do not favor gypsy moths. While silvicultural practices have not been successful at preventing outbreaks, they can minimize and prevent stand losses. The advantages of silvicultural treatments include: 1) they are usually inexpensive, 2) they treat the cause of the problem instead of the symptoms, by creating healthy mixed forests, 3) they can be used in high priority areas where they will be most effective, and, 4) they are ecologically preferable to using chemical insecticides. The limitations and/or disadvantages of silvicultural practices include: 1) they can only be applied to a limited acreage per year, 2) it takes a long time to have a major effect on the pest habitat, 3) they will not prevent outbreaks of many pests, and, 4) they cannot be used in areas where tree removal is not allowed (Gottschalk 1992).
General IPM Strategies
A variety of techniques are currently used in gypsy moth IPM programs and using these requires the combined efforts of private property owners and public agencies; however, they have the common goal of keeping gypsy moth damage at an acceptable level (Davis 1992). The following are among the most commonly-used techniques.
1) Plant resistant plants - because some trees are less preferred by the gypsy moth than other trees, tree selection should be based largely on the desired landscape function (Table 1),
2) Keep plants healthy - trees that are stressed are more vulnerable to the effects of defoliation. Attempts to minimize stress would include adequate water, aeration, and nutrients.
3) Destroy egg masses - before spring, egg masses should be removed from trees and other locations where they are found. In midspring, hiding places for females seeking pupation or egg-laying sites should be reduced or eliminated.
4) Band trees - burlap bands are placed on trees and surround the entire trunk. As the larvae migrate down the tree, they seek refuge within the band. This band is checked every day or two, and the larvae are destroyed. Barrier bands are bands coated with a sticky material that are also placed around the trunks of trees. Larvae either starve below the band or are trapped on the sticky surface.
5) Disrupt mating and trap males - mating disruption is a technique which uses small pieces of confetti-like material that are impregnated with the female sex attractant. When used in a small area, the males cannot find the females. Pheromone-baited traps (discussed above) also remove males from a population but are more commonly used to estimate population sizes. Some evidence suggests that only 30 percent of male gypsy moth populations are trapped using this method (F. W. Ravlin, pers. Comm.).
6) Use insecticides - a variety of insecticides are registered for use against the gypsy moth. The choice of insecticides will largely depend on the type of environment in which they are used. Probably two of the most commonly used insecticides in gypsy moth suppression programs throughout Virginia are BT and Dimilin. BT kills only caterpillars and is generally effective; however, it must be sprayed on tree foliage when caterpillars are in their 2nd or 3rd instar. Dimilin is 90 percent effective against gypsy moth caterpillars, has excellent residual properties, and has little effect on predators or parasitoids (Davis 1992). Sometimes the spraying of trees is not desirable and systemic insecticides such as BidrinR (dicrotophos) are injected into tree trunks; these chemicals are eventually translocated to the leaves and kill caterpillars for at least a month. A major disadvantage of using this method is that it can disfigure the tree with unsightly wounds (F. W. Ravlin, pers. comm.).
History of Gypsy Moth Management in Virginia
In Virginia, the gypsy moth has received significant attention beginning in 1987 with a supplemental appropriation from Congress. It was then that the Forest Service initiated the Appalachian Integrated Pest Management (AIPM) Gypsy Moth Demonstration Project. As with most IPM strategies, this project attempted to slow the spread and minimize the impact of the gypsy moth along the Allegheny Mountains in Virginia and West Virginia (Carroll and Ravlin 1991). A secondary objective of this program was that, if successful, it would serve as a model IPM program for large geographic areas, and would implement a variety of management methods in an environmentally sound manner.
A major feature of the currently-operating Virginia AIPM program is that management strategies are directed by a program manager within each county, using current state-of-the-art technologies. The program managers take into account the unique features (e.g., percent defoliation, percent forested land, percent urbanized land, type of forest, land use, etc.) of their respective counties and therefore, each county would appear to have different intervention strategies. However, the strategies employed are directly proportional to the level of gypsy moth infestation and are determined by a central plan. [For an in-depth review of county-by-county strategies, refer to Carroll and Ravlin (1991).]
Proposed Intervention Strategies for the Gypsy Moth
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| Figure 1. A proposed sampling gird for gypsy moth egg mass collection for the Indian Head Naval Ordnance Station. Property boundary and roads are shown. Samples are typically taken near the center of each grid (but intersection corners may also be used). |
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| Figure 2. Road locators and associated zones around them where danger of gypsy moth incidence is greatest. |
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| Fig 3. Forested areas potentially affected by gypsy moth. Combinations of cell (Fig. 1), roads (Fig. 2), and forested areas (as shown here) can lead to an effective control and monitoring program. |
Using the map layers now in the GIS, we produced Figures 1, 2, and 3. These illustrate the discrimination and managerial directions now possible with the present data base and will be discussed below.
After evaluating these results and discussing their relevance to current conditions on the base, managers may initiate an intensive program that includes:
An extensive GIS has been developed . The map layers to be studied after data collection and entry to the system are:
c). The Station will then be divided into a series of cells (Figure 1) and priority will be assigned to each of these (Table 2). Treatment thresholds may be mapped to define the egg mass density at which treatment is recommended to prevent tree defoliation and tree mortality from reaching specified levels.
d). Egg-mass data will be collected after the leaves fall from the trees in autumn, or early winter. Egg masses are typically viable between September and April, and the following procedure takes into account those egg masses that were laid the previous year and have hatched, or, are no longer viable. Egg mass data will be collected using the recommended thresholds of 618 egg masses/hectare (250 egg masses/acre) suggested by Fleischer et al. (1992; Table 3.). Using the procedures of Kolodny-Hirsch (1986), Fleischer et al. (1991), and Liebhold et al. (1991), 1/40th acre (0.01 hectare) circles (radius 18.6 ft.) are drawn on the map, usually the center of each or the node (line intercepts) of a number of specified cells (Figure 1). Within these circles, the trees are examined from all sides, the egg masses are counted, and binoculars are used to search the higher portions of the boles and crowns. Loose bark and rocks are also overturned within the circle. This sampling method (sequential sampling) requires that the sampler take at least six (1/40th acre) samples; the egg mass counts are summed. The sum is then compared to the range of values shown in Table 3, and based on it, sampling either stops or continues. The plan will recommend either to stop or to continue sampling. If the count indicates that sampling should be stopped, then the sampler moves to the next sample grid cell. If the procedure indicates additional sampling, then sampling is continued until it is recommended that sampling be stopped, or, the maximum sample number (9) is reached.
e). Pheromone-baited traps containing 500 ug (+) disparlure, may be placed in the spring and checked in mid-summer. These may be placed in the road zone shown in Figure 2. Because of the historical importance of the large trees at the headquarters, at least two traps will be placed within each 1 km cell on these streets. In the forested (wooded) areas of the base, however, traps will usually be placed in the standard every-other-cell or 3 km grid (Carter et al. 1994). The target area for a trap will be within the road zone (Figure 2) and within the grid center. These are minimum sampling intensities. Proximity of roads and ease of access may allow a more dense and low-cost grid (more traps rather than more time spent in precise placement.) Pheromone-baited traps will serve as sentinel traps, and the information obtained from these will be used by the program manager for management decisions. Where feasible, the same numbers and locations should be compared.
| Table 2. Priority for treating parcels of land (Fleischer et al. 1992a) | |
|---|---|
| Priority | Definition |
| 1 | Forested recreational/educational areas: including parks, picnic areas, valuable scenic areas and trails, golf courses, forested areas around public water supplies, and trees of historical importance. |
| 2 | Forested residential, high density (>5 dwellings/10 hectare). |
| 3 | Forested residential, medium density (>1 and less than 5 dwellings/10 hectare) |
| 4 | Rare forested habitat (including rare, threatened, and endangered species). |
| 5 | Uninhabited forest land (includes pastures, fields with few or no trees near historical structures), and trees of no particular aesthetic or commercial value. |
| Table 3. Sequential sampling decision chart for egg mass management thresholds (Fleischer et al. 1992b) | ||||
|---|---|---|---|---|
| Cumulative egg mass counts | ||||
| Threshold ( eggmasses/ac) |
Sample 1/40 ac |
Stop Sampling (below threshold) |
Continue Sampling |
Stop Sampling (above threshold) |
| 250 | 6 | 0-3 | 4-71 | >71 |
| 7 | 0-9 | 10-77 | >77 | |
| 8 | 0-15 | 16-83 | >83 | |
| 9 | 0-21 | 22-89 | >;89 | |
| 10 | 0-27 | 28-95 | >95 | |
| 11 | 0-33 | 34-101 | >101 | |
| 12 | 0-39 | 40-107 | >107 | |
| 13 | 0-45 | 46-113 | >113 | |
| 14 | 0-51 | 52-119 | >119 | |
| 15 | 0-57 | 58-125 | >125 | |
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| Figure. 4 Primary sampling centers based on the grid of Figure 2. used each year to aid in making comparisons and analyzing trends |
g). Once intervention is indicated, but not before, the forested trees on the base will be treated with BT when 2nd or 3rd larval instars become apparent. These areas will be sprayed using either rotary or fixed-wing aircraft. The headquarter trees may be sprayed with Dimilin using a high-pressure, hydraulic hose.
h). A volunteer program on the Station that may enlist the help and support of servicemembers, residents, and schoolchildren. These volunteer can be taught:
BT and Dimlin
The following budget/contract information is based on a phone conversation with Gary L. McAnich, the Gypsy Moth Coordinator, Office of Plant Protection, Richmond, VA.
Previous Contracts (Suggesting Scope of Work and Costs)
Contract #1 -- helicopter for 40,000 acre use in Fairfax and Arlington counties and Alexandria, Virginia. BT $13.49/acre, 24 BIU (billions of International units); Dimilin $13.56/acre, 1/4 oz insecticide/acre
Contract #2 -- fixed wind for Prince William, Fauqier, Culpepper, and Stafford counties, Virginia. BT $5.71/acre; Dimilin $4.59/acre
Contract #3 -- fixed wing for Shenandoah valley, 35,000 acres. BT $8.61; Dimilin $7.49/acre
Contract #4 -- ground treatment (Dimilin or BT) with hydraulic hose for 4 acres, Bartlett and/or Davey $10.00/acre (acre or tree equivalents)
Phermone Traps
1) Milk-carton traps trap/each $3.25; case of lure (100), $135.00, case of lure (25) $37.50; case of vapor tape (52), $52.00
2) Multipher traps traps/each complete $12.00, single traps w/o lure and tape, $8.95; 24 traps w/o lure and tape, $182.50
Environmental Concerns
Most of the above intervention techniques for use against the gypsy moth have been taken from the ongoing Virginia AIPM program and are in agreement with the Final Environmental Impact Statement for the AIPM program (USDA Forest Service Management Bulletin R8-MB 33, 1989).
Literature Cited
Bellinger, R.G., F. W. Ravlin, and M. L. McManus. 1989. Forest edge effects and their influence on gypsy moth (Lepidoptera: Lymantriidae) egg mass distribution. Environmental Entomology. 18: 840-843.
Bellinger, R. G., F. W. Ravlin, and M. L. McManus. 1990. Predicting egg mass density and fecundity in field populations of the gypsy moth (Lepidoptera: Lymantriidae) using male moth wing length. Environmental Entomology. 21: 1308- 1318.
Brown, R. C. and R. A. Sheals. 1944. The present outlook on the gypsy moth problem. Journal of Forestry. 42: 393-407.
Burgess, A. F. 1930. Improvements in spraying equipment. Journal of Economic Entomology. 23: 132-136.
Campbell, R. W., M. G. Miller, E. J. Duda, C. E. Biazak, & R. J. Sloan. 1976. Man's activities and subsequent gypsy moth egg-mass density along the forest edge. Environmental Entomology. 5: 273-276.
Campbell, R. W. and R. J. Sloan. 1978a. Numerical bimodality among North American gypsy moth populations. Environmental Entomology. 7: 641-646.
1978b. Natural maintenance and decline of gypsy moth populations. Environmental Entomology. 7: 389-395.
Carroll, B. S. and F. W. Ravlin, eds. 1991. The gypsy moth in Virginia. Virginia Cooperative Extension Service Publication # 444-030.
Carroll, B. S., E. A. Roberts, and J. L. Knighten. 1994. Slow the spread gypsy moth management pilot project, male moth survey manual. Department of Entomology, VA Tech.
Carter, J. L. 1992. Egg mass sampling plans for gypsy moth management programs. M.S. Thesis, Virginia Polytechnic Institute and State University, Blacksburg, VA
Carter, J. L., F. W. Ravlin, and S. J. Fleischer. 1994. Sequential egg mass sampling plans for gypsy moth (Lepidoptera: Lymantriidae) management in urban and suburban habitats. Journal of Economic Entomology: 84: 999-1003.
Carter, M. C. 1991. Quantification and use of pheromone-baited milk-carton traps to monitor gypsy moth populations. Ph.D. Dissertation, Virginia Polytechnic Institute and State University, Blacksburg, VA.
Elkinton, J. S. 1987. Changes in efficiency of the pheromone-baited milk-carton trap as it fills with male gypsy moths (Lepidoptera: Lymantriidae). Journal of Economic Entomology. Vol. 80: 754-757.
Etter, D. O., Jr. 1979. Thresholds-appendix K. Comprehensive gypsy moth pest management system. National Gypsy Moth Management Board No. WIS-704-15-30. Madison, Wl.
Fleischer, S. J., F. W. Ravlin, and R. C. Reardon. 1991. Implementation of sequential sampling plans for gypsy moth (Lepidoptera: Lymantriidae3egg masses in eastern hardwood forests. Journal of Economic Entomology. Vol. 84: 1100-1107.
Fleischer, S. J., E. A. Roberts, J. Young, P. Mahoney, F. W. Ravlin, and R. Reardon. 1992a. Development of geographic information system technology for gypsy moth management within a county: an overview. USDA Forest Service Appalachian Integrated Pest Management paper # NA-TP-01-93 24 pp.
Fleischer, S. J., J. L. Carter, R. Reardon, and F. W. Ravlin. 1992b. Sequential sampling plans for estimating gypsy moth egg mass density. USDA Forest Service AIPM technology transfer Publ. # NA-TP-07-92
Gansner, D. A. and O. W. Herrick. 1982. Predicting the rate of change in timber value for forest stands infested with gypsy moth. USDA Forest Service research paper N E-311. 3 pp .
Gansner, D. A., O. W. Herrick, P. S. DeBald, and J. A. Cota. 1983. New turf for gypsy moth; there's more at risk downrange. USDA Forest Service research paper NE-519. 4 pp.
Gansner, D. A., D. A. Drake, S. L. Arner, R. R. Hershey, & S. L. King. 1993. USDA Forest Service research paper NE-354 4 pp.
Gansner, D. A., S. L. Arner, R. H. Widmann, and C. L. Alerich. 1993. Field Note-- After two decades of gypsy moth--are there any oaks left? Northern Journal of Applied Forestry. 10(4): 184-187
Gottschalk, K. W. 1992. Is silviculture the answer to northeastern forest insect and disease problems? Proceedings: North American Forest Insect Work Conference, Denver, CO.
Harris, R. W. 1992. Arboculture: Integrated management of landscape trees, shrubs, and vines. 2nd ed. Prentice Hall, Englewood Cliffs, NJ.
Johnson, W. T. and H. H. Lyon. 1988. Insects that feed on trees and shrubs. 2nd ed. Comstock Publishing Co., Ithace, NY.
Kirkland, A. H. 1905. The gypsy moth and brown-tail moths. Bull. 1. Wright and Potter Printing Co., Boston, MA.
Kolodny-Hirsch, D. M. 1986. Evaluation of methods for sampling gypsy moth (Lepidoptera: Lymantriidae) egg mass populations and development of sequential sampling plans. Environmental Entomology. Vol. 15: 122-127.
Leonard, D. E. 1981. Bioecology of the gypsy moth. In C. C. Doane and M. L. McManus Eds. The Gypsy Moth: research towards integrated pest management. USDA Forest Service Technical Bulletin #1584.
Lechowicz, M. J. and Y. Mauffette. 1986. Host preferences of the gypsy moth in eastern North America versus European forests. Revue d'Entomologie du Quebec.
Liebhold, A., D. Twardus, and J. Buonaccorsi. 1991. Evaluation of the timed-walk method of estimating gypsy moth (Lepidoptera: Lymantriidae) egg mass densities. Journal of Economic Entomology. Vol. 84: 1774-1781.
Mason, G. N. 1987. Rating stand susceptibility to gypsy moth defoliation. In Proceedings, Coping with the gypsy moth in the new frontier. West Virginia Books, Morgantown, WV.
McManus, M. L. and T. Mclntyre. 1981. Introduction, In C. C. Doane and M. L. McManus (eds.), The gypsy moth: research toward integrated pest management. USDA Forest Service Tech. Bull. #1584.
Montgomery, M. E. 1992. Why are gypsy moth numerical dynamics so irregular in North America? Proceedings: North American Forest Insect Work Conference, Denver, CO.
Ravlin, F. W., R. G. Bellinger, and E. A. Roberts. 1987. Gypsy moth management programs in the United States: status, evaluation, and recommendations. Bulletin of the Entomological Society of America. 33: 90-98.
Roberts, E. A., F. W. Ravlin, and S. J. Fleischer. 1993. Spatial representation for integrated pest management programs. American Entomologist. 39: 92-107.
Thorpe, K. W. and R. L. Ridgeway. 1992. Gypsy moth (Lepidoptera: Lymantriidae) egg mass distributions and smapling in a residential setting. Environmental Entomology. 21: 722-730.
Wald, A. 1947. Sequential analysis. Wiley, New York, NY.
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