Chemical Control

Emerald Ash Borer: Research and Technology Development Meeting

From: V. Mastro and R. Reardon (compilers), Emerald Ash Borer Research and Technology Development Meeting, Romulus, Michigan, Oct 5-6, 2004. USDA Forest Service publication FHTET-2004-15.

Evaluation of Various Insecticides Applied to the Bark to Control Emerald Ash Borer

Robert A. Haack and Toby R. Petrice, USDA Forest Service, North Central Research Station, 1407 S. Harrison Road, East Lansing, MI 48823

The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Buprestidae), a native of Asia, was first discovered in the United States and Canada in 2002. Within the area that is generally infested with EAB, homeowners and communities are typically either removing infested trees or treating them with various insecticides to protect them from further EAB attack. In addition, questions have arisen as to whether various insecticides will kill within-tree EAB life stages if applied to the bark surface soon before adult emergence is to begin. We report here the results of two studies that tested one systemic insecticide and four topically applied insecticides.

In a 2003-2004 study, we tested the product D-20 by Perma Guard (Albuquerque, New Mexico), which is composed of diatomaceous earth and natural pyrethrins (0.2 percent a.i.). In this study, we moved 40 uninfested green ash trees, 4-5 m tall, to an area that was heavily infested with EAB near Ann Arbor, Michgan. The trees were moved on 26 June, transplanted on 26-27 June, and treated on 27 June 2003. EAB adults were able to freely infest all trees. There were five treatments using eight trees per treatment: untreated control trees, one application of D-20, two applications of D-20, three applications of D-20, and trees treated with two applications of imidacloprid (Imicide by Mauget). We used a backpack sprayer to apply D-20 to both the foliage and trunk. D-20 was applied on 27 June, 14 July, and 30 July. D-20 was mixed with water at a rate of 1 tablespoon per gallon, which was recommended by the owner of Perma Guard, Mr. Wallace Tharp. The first set of Mauget capsules were applied on 27 June, but because uptake was poor on a few trees, we treated all eight trees again on 14 July. In fall 2003, we felled and debarked half the trees. EAB had completely colonized the trunk of all control trees as well as all trees that had been treated with D-20. We found no live EAB larvae on any of the Imicide-treated trees, and except for a few EAB galleries that had terminated early, there was no other evidence of EAB attack. In the spring of 2004, all of the remaining Imicidetreated trees leafed out, but none of the control or D-20-treated trees produced any foliage. This study showed that D-20 did not protect the trunks of trees from EAB infestation, but a double dose of Imicide was highly effective.

In a 2004 study, we sprayed EAB-infested ash logs with one of three products: Astro (permethrin, a pyrethroid by FMC,) Onyx (bifenthrin, a pyrethroid by FMC), and Merit (imidacloprid, by Bayer). One set of logs was treated twice with Merit. We sprayed the outer bark of all logs in mid-May or early June, and later placed the logs in rearing cages. Early estimates of EAB mortality range from 66 percent to 94 percent control. This study indicates that EAB life stages can be killed when the bark surface is treated with various insecticides.

Emerald Ash Borer Infestation of Ash Stumps

Robert A. Haack and Toby R. Petrice, USDA Forest Service, North Central Research Station, 1407 S. Harrison Road, East Lansing, MI 48823

The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Buprestidae), was first found in North America in 2002. Eradication efforts are currently underway for this insect in both Canada and the United States. As part of the eradication program, thousands of ash trees are cut and chipped. Ash trees are known to produce stump sprouts, and therefore, herbicides are often applied to the cut surface of the stump to inhibit sprouting. In 2004, we initiated three studies in southern Michigan to evaluate the degree of stump sprouting and subsequent EAB infestation in relation to 1) time of felling, 2) stump height, 3) tree species, and 4) application of herbicide (Garlon).

In the first study, we cut green ash trees at three Michigan sites during April, June, and September 2004. The trees were cut at three different heights (0-5 cm, 10-15 cm, 20-25 cm) during each felling period. We cut 9-11 trees per stump height class and cut date. EAB adults were free to lay eggs on the stumps of trees cut in April and June. However, for the trees cut in September, we had screened the lower trunk of each tree throughout the summer months of 2004 to protect them against EAB colonization. In late summer 2005, we will record the degree of sprouting on all stumps and inspect them for EAB exit holes. We will also debark half the stumps and inspect them for EAB larvae. In 2006, we will determine EAB adult emergence from the remaining stumps.

In the second study, we focused on the degree of sprouting and subsequent EAB attack in relation to tree species. We felled three black ash, green ash, and white ash trees of similar size at one site during June 2004. The stump height for all trees was 20-25 cm. In 2005, we will record the degree of stump sprouting and EAB colonization.

In the third study, we will evaluate the effectiveness of Garlon 3A in inhibiting stump sprouting and the ability of EAB to colonize Garlon-treated stumps. In this study, we cut green ash trees at three sites during May and June 2004. The stumps were cut to a uniform height of 20-25 cm. Garlon was applied to the freshly cut surface of half the stumps. We will record the degree of stump sprouting and EAB colonization in 2005.

Evaluation of Trunk Injections for Control of Emerald Ash Borer

Deborah G. McCullough1, Therese M. Poland3, David L. Cappaert1, Phillip Lewis4, and John Molongowski4

Departments of 1Entomology and 2Forestry, Michigan State University, 243 Natural Science Building, East Lansing, MI 48824
3USDA Forest Service, North Central Research Station, 220 Nisbet Building, East Lansing, MI 48823
4USDA Animal and Plant Health Inspection Service, Otis Methods Laboratory, W. Truck Road, ANG Base, MA 02542

In 2003, we evaluated trunk injections of imidacloprid for control of emerald ash borer (Agrilus planipennis Fairmaire) (EAB). Results were variable and indicated that efficacy could be affected by injection timing and method and by tree size and vigor. In 2004, we continued studies to assess the optimal timing for imidacloprid trunk injections and the persistence and translocation of imidacloprid in ash trees.

One project involved a two-year evaluation of two popular trunk injection methods on street trees growing in two subdivisions in Ann Arbor. In May 2003, we randomly assigned 30 green ash trees at Site 1 (average of 42 cm dbh) to one of five treatments: untreated Control, Imicide (10 percent, 3 ml Mauget capsules, 1 capsule per inch dbh/2), Pointer (12 percent in 2003, 5 percent in 2004, wedgle, 1 ml per 10.2 cm basal circum), an early Bidrin treatment or a late Bidrin treatment (12 percent, 2 ml Mauget capsules, 1 capsule per inch dbh/2). Imidacloprid (Imicide or Pointer) was injected on 21 May 2003. Bidrin was injected on either 2 June or 14 July in 2003. Trees were injected with imidacloprid (Imicide or Pointer) again on 19 May 2004 or with Bidrin on 15 June 2004. At Site 2, we injected and monitored 18 green ash (16 cm dbh) and 18 white ash (13 cm dbh) trees. These trees were randomly assigned to treatments in May 2003 and were injected with either Imicide or Pointer on 21 May 2003 and on 19 May 2004.

Canopy condition of each tree was estimated periodically in 2003 and 2004. The number of exit holes per m2 was determined in September 2004 on five sections (each 3800 cm2) of each tree to estimate the density of EAB adults emerging in 2004. Density of larval EAB was quantified in three to four bark windows (each approximately 300 cm2) excavated on each tree.

At Site 1, canopy dieback on untreated Control trees jumped from an average of roughly 20 percent in June 2003 to an average of 50 percent in September 2004. Pre-treatment canopy dieback on all injected trees ranged from 15-19 percent in June 2003 and dieback remained low, averaging 25 to 30 percent in September 2004. On average, about 10 EAB adults per m2 emerged from Control trees in 2004, but an average of 80 larvae per m2 were feeding in those trees in September. Significantly more EAB adults emerged from untreated Control trees in 2004 than from any of the injected trees. Larval density on all injected trees was 82-96 percent lower than on the Control trees.

At Site 2, canopy dieback progressed from roughly 10 percent in June 2003 to over 60 percent in September 2004 on the green ash Control trees. On the white ash Control trees, average dieback remained below 10 percent in 2004. On the green ash Control trees, an average of roughly 35 adult beetles emerged in 2004, while larval density averaged 80 per m2. Green ash trees injected with either Imicide or Pointer had significantly lower adult emergence than Control trees. Larval density on green ash trees was roughly 89 percent lower in Imicide trees and 45 percent lower in Pointer trees than in the Control trees (with various applications—all treatments differed significantly from each other). On the white ash trees, density of emerged adults and larvae was consistently low.

Additional trunk injection studies were initiated in 2004 at two different sites in Ann Arbor to evaluate relative levels of imidacloprid residues in xylem sap, foliage and phloem (using ELISA) over the growing season. Trees were injected with imidacloprid via Arborjet micro-infusion, Arborjet micro-injection, or Mauget capsules. Rates of imidacloprid included 0.15 g AI per injection port (Imicide), 0.20 g AI per injection port (Arborjet – small trees), or 0.4g AI per injection port (Arborjet – large trees). Number of injection ports per tree was equal to dbh divided by 2. Half of the trees were injected on 21 May 2004; the other trees were injected on 19 July 2004. Preliminary samples from trees injected in May suggest that imidacloprid residues in the Imicide trees peaked about 4 weeks after injection at roughly 45-50 ppb. Residues in trees injected with either Arborjet device peaked about two weeks after injection at over 300 ppb. Results from six-day bioassays conducted with adult EAB indicated that beetle mortality was related to imidacloprid residues. Imidacloprid residue in xylem sap decreased in all trees during the summer, a pattern consistent with 2003 results. Processing of tissue samples for residue analysis and larval density sampling is continuing.

Imidacloprid Residue Levels from Soil-injected Street Trees

Phillip A. Lewis, USDA-APHIS-PPQ, Pest Survey, Detection and Exclusion Laboratory, Bldg 1398, W. Truck Rd., Otis ANGB, MA 02542

Soil injection of Merit products (imidacloprid) is a common technique used by the asian longhorn beetle eradication program to treat at-risk trees that are in proximity to areas where trees have been removed due to beetle infestation. Similar applications may be used to protect trees and control populations of the emerald ash borer (EAB). An earlier presentation by Deb McCullough demonstrated that greater than 80 percent adult EAB mortality was seen for trees averaging 100 ppb imidacloprid residue in xylem sap.

Street trees in Chicago were injected in a circular pattern at the maximum labeled rate at three times, pre-leaf drop (October), post-leaf drop (December), and spring (April / May). For analysis, maple and ash trees were grouped by diameter at breast height (dbh). Small trees averaged 8” and medium sized trees averaged 12”. Xylem sap from treated trees was collected in May, July and September of 2004. One group of trees was treated once; a second group of trees was treated twice over a two year period. Imidacloprid residue was assessed using an ELISA assay from a commercially available kit (Envirologix).

Results demonstrated that residue levels in both ash and maple generally increased between the sampling periods in May and July. For trees treated only once, the two fall treatments were generally not as effective as the spring treatment for new treatment areas; small trees of both species had significantly more residue in spring than in pre-leaf drop treatments, while residue in medium sized trees did not differ between treatments. Trees treated over two consecutive years had similar residue levels between all treatments, and were higher than those trees that were treated only one time.

2004 Update on Studies of Botanigard® for Control of Emerald Ash Borer Adults and Larvae

Houping Liu1, Leah S Bauer1, 2, and Deborah L. Miller2

1 Department of Entomology, Michigan State University, 243 Natural Science Building, East Lansing, MI 48824
2 USDA Forest Service, North Central Research Station, 1407 S. Harrison Rd., East Lansing, MI 48823

The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), native to northeastern Asia, was identified as the cause of ash (Fraxinus spp.) mortality in southeastern Michigan and southern Ontario in 2002. Subsequent infestations were found in Ohio, Indiana, Maryland, and Virginia due to transport of infested nursery stock, firewood, timber, and natural spread. Programs designed by regulatory agencies to eradicate localized infestations of EAB involve detection and removal of infested ash trees (Fraxinus spp.) and creation of an ash-free zone around each epicenter to prevent EAB spread. Conventional insecticides are being tested to aid in the eradication effort and to protect landscape ash trees; however, methods are also needed to manage EAB in more environmentally sensitive areas such as forests and riparian areas. To this end, we are studying the efficacy of BotaniGard®, a biopesticide formulated with the insect-pathogenic fungus Beauveria bassiana var. GHA.

In 2002-2003, we began studying the natural enemy complex of EAB in Michigan. We found insect-pathogenic fungi were the most prevalent natural enemy of immature EAB (approximately 2 percent). Thus, we began laboratory and greenhouse studies of BotaniGard®, a registered biopesticide for control of insect pests of forests, shade trees, and agriculture. To summarize, we found both BotaniGard ES (petroleum based) and BotaniGard O (vegetableoil based) were highly virulent against EAB in standardized laboratory studies. Subsequent studies of caged EAB-infested trees in the field demonstrated >80 percent adult mortality due to B. bassiana infection when BotaniGard® was applied before EAB emergence (pre-emergent trunk sprays). The application of BotaniGard® to EAB-infested tree trunks in the fall resulted in 10-20 percent larval mortality due to B. bassiana infection.

This spring, we initiated two field trials of BotaniGard® in Ann Arbor, Michigan:

1. In a 20-year-old ash plantation, a commercial applicator sprayed 73 ash trees with BotaniGard ES at the rate of 6 qts/100 gallons of water every two weeks from June 23 to August 3, 2004. Prior to application, levels of EAB infestation were ranked as low, moderate, or high for each tree. To achieve good coverage on these relatively large trees (approximately 20 feet tall), two to three gallons of BotaniGard® suspension was needed to spray the crown and trunk of each tree to drip point. The trees are being felled and dissected to evaluate the efficacy of this treatment.

2. In a separate study, uninfested ash trees, transplanted from a nursery apparently outside the infestation during the previous summer, were sprayed with BotaniGard ES using a CO2 backpack sprayer every two weeks from June 25 to August 5, 2004. The canopies of these trees were small, and 600-ml of BotaniGard® suspension was sprayed to drip point on leaves, branches, and trunk of each tree at the rate of 6 qts/100 gallons of water. A gallon of fungal suspension can treat as many as six trees of this size. We evaluated the persistence of B. bassiana spores on ash foliage in full sun by exposing EAB adults for 72 hours to ash leaves harvested 0, 4, 7, and 11 days after BotaniGard application. After 7 days, EAB mortality due to B. bassiana infection was 100, 96, 88, and 78 percent, respectively. This is good persistence for a biopesticide, and the addition of UV protectants to the BotaniGard® tank mix may improve these results. The ash trees are being felled and dissected to evaluate efficacy of BotaniGard® in reducing EAB infestation.

Systemic Trunk Injections of Imidacloprid and Azadirachtin: A Control Option for Emerald Ash Borer Larvae

Nicole G. McKenzie1, Blair V. Helson2, Gard W. Otis1, and Dean G. Thompson2

1Department of Environmental Biology, University of Guelph, Guelph, Ontario N1G 2W1 Canada
2Canadian Forest Service, Natural Resources Canada, 1219 Queen St. East, Sault Ste. Marie, Ontario P6A 2E5 Canada

The emerald ash borer (EAB), Agrilus planipennis, was discovered in Windsor, Ontario, in the summer of 2002. Since its detection, EAB has caused the death of more than 200,000 ash trees (Fraxinus spp.) in Essex County. In this study, small potted green ash trees (average dbh = 2.2cm, sd = 0.31) in Windsor were injected with either imidacloprid or azadirachtin to evaluate potential larval EAB control. Imidacloprid trunk injections provided complete control of EAB attack in trees treated with concentrations e•0.03g a.i./tree. Azadirachtin trunk injections provided control of adult emerging beetles at a concentration e•0.0075g a.i./tree, but did not control larval beetle or gallery development below the second instar stage. These indicate that both imidacloprid and azadirachtin have excellent potential for EAB larval control. These results are complemented by several additional trials involving injection of medium-sized ash trees with imidacloprid. Collectively, our results indicate that systemic trunk injections of imidacloprid have very high efficacy in controlling EAB infestations.

Using Tempo to Control Emerald Ash Borer: A Comparison of Trunk and Foliage Sprays

Deborah G. McCullough1,2, David L. Cappaert1, and Therese M. Poland3

Departments of 1Entomology and 2Forestry, Michigan State University, 243 Natural Science Building, East Lansing, MI 48824
3USDA Forest Service, North Central Research Station, 220 Nisbet Building, East Lansing, MI 48823

Insecticide sprays may provide arborists, landscapers, and regulatory officials with a useful option to control emerald ash borer (EAB) in some situations. In our 2003 studies, we found that two applications of Tempo (a pyrethroid insecticide) significantly reduced the density of EAB larvae relative to unsprayed trees. It was not clear, however, whether this control reflected mortality of adult EAB that fed on sprayed foliage or mortality of newly eclosed larvae chewing through the bark. In 2004, we set up a study to determine if EAB could be controlled by spraying only the foliage or only the trunk and large branches of trees. We also compared larval density between trees that received one spray with those that received two sprays.

We selected 40 green ash street trees in Ann Arbor and randomly assigned them to one of five treatments: 1) Control (no spray), 2) Foliage-only spray (twice), 3) Trunk-only spray (twice), 4) Trunk &: Foliage spray (twice), 5) Trunk &: Foliage spray (once). A private contractor applied Tempo SC Ultra (160 ml per 378 l) on 10 June and again on 2 July for trees that were sprayed twice. During sprays, the trunk and large branches of Foliage-only trees (Treatment 2) were wrapped with plastic wrap and the ends sealed with clay to ensure that the spray did not contact the bark. On average, Trunk only trees (Treatment 3) received 1.1 gal of spray compared with 4.3 gal of spray applied to Foliage only trees and 5.3 gal applied to Trunk &: Foliage trees. Similarly-aged adult EAB were caged with bark or with a leaf from each treated tree on July 7 (27 days post-spray) for five days. Mortality of beetles in the bioassay was recorded daily. In September, bark was removed from three to four windows (ca 400 cm2) on the trunk and three to four windows in the canopy to estimate larval density.

Bioassay results showed that Tempo remained toxic to EAB adults for at least 27-30 days post-spray. More than 80 percent of beetles had died by Day 3 of the bioassay when they were caged with either bark or foliage that had been sprayed. During the same period, average mortality of beetles caged with unsprayed trees, unsprayed bark or unsprayed foliage was less than 20 percent.

Density of young EAB larvae (L1 to L3) feeding on tree trunks was reduced by 88 percent compared with Control trees when only the foliage or the trunk and foliage had been sprayed, and by 40 percent when the only the trunk had been sprayed. Density of young larvae feeding in the canopy was reduced by 66 percent to 90 percent when only the foliage or both trunk and foliage were sprayed, but only by 14 percent when only the trunk was sprayed. Efficacy did not significantly differ between trees that were sprayed only in June and those sprayed in June and July.

We also noted that some of the late instar larvae (L4) feeding on trees in September were actually two-year-old larvae—i.e., they began feeding in 2003, overwintered as immature larvae, and were still feeding in 2004. These larvae could be distinguished from the current-year L4 larvae by the dark, discolored appearance of the oldest part of the gallery and the presence of wood and callus tissue formed by the tree over the early part of the gallery. Obviously, cover sprays will have no effect on larvae that are already feeding below the bark when sprays are applied. Preliminary data indicated that roughly 60-70 percent of L4 larvae on unsprayed trees were two-year-old larvae while at least 90 percent of the L4s on twice-sprayed trees were two-year-old larvae. Additional sampling is planned to refine estimates of the density of one-year and two-year L4 larvae.

Distribution and Metabolism of 14C Imidacloprid in Fraxinus spp. and Effects of Imidacloprid on Adults of the Emerald Ash Borer

Bert M. Cregg1, David Mota-Sanchez2, Deborah G. McCullough3, Therese Poland4, and Robert Hollingworth2

1Department of Horticulture and Department of Forestry, Michigan State University 214 Plant and Soil Science Building, East Lansing, MI 48824
2Department of Entomology, Michigan State University 106 Center for Integrated Plant Systems, East Lansing, MI 48824
3Department of Forestry and Department of Entomology, Michigan State University, 243 Natural Science Building, East Lansing, MI 48824
4USDA Forest Service, North Central Research Station, 1407 S. Harrison Rd., Rm. 220, East Lansing, MI 48823

Trunk or soil injection of systemic insecticides is often a preferred method for controlling insect pests in landscapes because it minimizes potential spray drift, applicator exposure and impacts on non-target organisms. Recent field trials and anecdotal evidence indicate that imidacloprid, applied as either a soil drench or trunk injection, can significantly reduce emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), populations in ash trees and canopy dieback associated with EAB. The persistence and translocation of imidacloprid in ash trees, however, is not well understood. In this study we used radiolabeled 14C imidacloprid to assess the distribution, persistence, and movement of imidacloprid in green ash and white ash trees following trunk injection. We also determined EAB mortality and LD50 in bioassays of adult beetles fed leaves from trunk-injected trees and the LD50 of adults of EAB treated in topical bioassays.

The specific objectives of the study were to:

  1. Determine the translocation and persistence of 14C imidacloprid over time in trunk-in-jected white and green ash trees,
  2. Determine the effects of water availability on imidacloprid translocation and distribution,
  3. Determine the mortality and knockdown of EAB adults fed leaves from injected trees,
    1. Determine the LD50 of adults of EAB, and
    2. Identify the major the metabolites of imidacloprid in ash trees.

On June 14, 2004 we injected twenty container-grown green ash (Fraxinus pennsylvanica) trees (7.6 cm dbh) and twenty white ash (F. americana) trees (10.1 cm dbh) with 6 ml of imidacloprid (10 percent a.i.). The trunks of the trees were injected at 15 cm above ground level via two injection ports on opposite sides of the tree. Each tree received 25 mCi of 14Cimidicloprid in a ratio of 1:2400 (labeled:non-labeled imidacloprid). After injection, half of the trees were kept well watered (3.8 cm irrigation week-1) and half were subjected to water stress (1 cm irrigation week-1). Imposition of water stress was verified with periodic measurements of soil water content and leaf gas exchange. We collected leaf, twig, trunk, and root samples 0, 2, 7, 21, 60,105, and 150 days after treatments (DAT). After 105 DAT five trees from each species were covered with netting to collect litterfall samples. All samples were brought to the lab, oven dried, ground, weighed, and oxidized in biological tissue oxidizer. The resultant 14CO2 was trapped in scintillation cocktail and radioactivity was determined by scintillation counting.

A subsample of fresh leaves was collected 21 and 45 DAT for bioassays on adult EAB. Single leaves were put in a vial with distilled water placed in a cup. Four beetles (10 days old) were introduced in the cups. The beetles were kept at 28°C, 50 percent relative humidity, photoperiod of 16:8 (L:D) while inside the cups. Mortality and “knockdown” were assessed at 24, 48 and 72 hours. Beetles that were unable to stand on their legs and walk a distance equal to their own body length were counted as knocked down.

For topical bioassays, technical grade insecticide was diluted with acetone. Five doses that resulted in more than 0 percent and less than 100 percent mortality based on preliminary assays were used. Four beetles (about 10 days old) were treated with 1 ml of solution on the ventral area of the abdomen with a 50 ml microsyringe connected to a microapplicator. The control beetles were treated with 1 ml of acetone only. Three to five replications per concentration were performed. After treatment, beetles were placed in cups and fed ash leaves and kept at 28°C, 50 percent relative humidity, photoperiod of 16:8 (L:D). Mortality and knockdown were assessed at 24, 48, and 72 hours after treatment.

Radioactivity in leaves increased steadily from 2 DAT to DAT 60. Through 21 DAT radioactivity in twigs and roots was not significantly different from zero. Radioactivity in leaves collected after leaf-fall was as high or higher than samples collected at 60 DAT, indicating little re-translocation of imidacloprid or imidacloprid metabolites from leaves before leaf-fall. Specific activity (cpm g-1) was somewhat lower in white ash than green ash, reflecting a dilution in the larger trees. Initial results did not indicate a significant effect of water stress on 14C imidacloprid movement. We are continuing processing and analysis of later sample dates and trunk tissues.

In the bioassays, a high percentage of knockdown in EAB adults was observed 24 hours after treatment (40 percent at 20 days and 36 percent at 45 days). Beetle mortality was less than knockdown (11 percent at 20 days and 17 percent at 45 days). However, three days after exposing the adults to the foliage, the mortality increased. Translocation of labeled and unlabeled imidacloprid was effective to control adults of EAB. The percent of knock down plus dead beetles was 71 percent at 20 days after treatment and 77 percent at 45 days after treatment.

Other sublethal effects, including reduced feeding, and slowed movement were also observed. These effects may severely affect the fitness of surviving beetles. The LD50 for the adults of EAB was 7.1 ng/beetle, which confirms that EAB is very susceptible to imidacloprid in comparison to other insect species.

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