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homeowner formulations of imidacloprid, Trunk injections with imidaclo- which are limited by the label to one applica-prid products have provided varying degrees tion per year. Homeowners wishing to protect of EAB control in trials conducted at different trees larger than 15-inch DBH should con-sites in Ohio and Michigan. In an MSU study, ® sider having their trees professionally treated.larval density in trees treated with Imicide injections were reduced by 60 percent to 96 Treatment programs must comply with any percent, compared to untreated controls. There was no apparent relationship between maximum amount of insecticide that can be applied per acre during a given year. pressure. In another MSU trial, imidacloprid trunk injections made in late May were more Trunk-Injected Systemic Insecticides effective than those made in mid-July, and ® IMA-jet injections provided higher levels of In several inten- ® control than did Imicide, perhaps because sive studies conducted by MSU and OSU ® the IMA-jet label calls for a greater amount researchers, a single injection of emamectin of active ingredient to be applied on large benzoate in mid-May or early June pro- ® trees. In an OSU study in Toledo, IMA-jet vided excellent control of EAB for at least provided excellent control of EAB on 15- to two years, even under high pest pressure. 25-inch trees under high pest pressure when For example, in a highly-replicated study trees were injected annually. However, trees conducted on trees ranging in size from 5- EAB larvae damage that were injected every other year were not to 20-inch DBH at three sites in Michigan, the vascular system of consistently protected. untreated trees had an average of 68 to 132 the tree as they feed, 2 EAB larvae per m of bark surface, which which interferes with In a discouraging study conducted in Michi- represents high pest pressure. In contrast, movement of systemic gan, ash trees continued to decline from one insecticides in the trees treated with emamectin benzoate had, year to the next despite being injected in tree. 2 on average, only 0.2 larvae per m, a reduc- both years with either Bidrin (Inject-A-Cide tion of > 99 percent. When additional trees ® B) or imidacloprid. The imidacloprid treat- were felled and debarked two years after the ments consisted of two consecutive years of emamectin benzoate injection, there were ® Imicide (10% imidacloprid) applied using still virtually no larvae in the treated trees, ® Mauget micro-injection capsules, or an while adjacent, untreated trees at the same experimental 12% formulation of imidaclo- sites had hundreds of larvae. TM (5% imidacloprid) in the second year with In two OSU studies conducted in Toledo TM both applied using the Wedgle Direct- with street trees ranging in size from 15- TM Inject System. All three treatment regimes to 25-inch DBH, a single application of suppressed EAB infestation levels in both emamectin benzoate also provided excel- ® years, with Imicide generally providing lent control for two years. There was no sign best control under high pest pressure in of canopy decline in treated trees and very both small (six-inch DBH) and larger (16-inch few emergence holes, while the canopies of DBH) caliper trees. However, larval density adjacent, untreated trees exhibited severe increased in treated and untreated trees from decline and extremely high numbers of emer- one year to the next. Furthermore, canopy gence holes. dieback increased by at least 67 percent in all One study suggests that a single injection of treated trees (although this was substantially emamectin benzoate may even control EAB less than the amount of dieback observed for three years. Additional studies to further in untreated trees). Even consecutive years evaluate the long-term effectiveness of of these treatments only slowed ash decline emamectin benzoate are underway. To date, under severe pest pressure. In another MSU this is the only product that controls EAB for ® study, ACECAP trunk implants (active ingre- more than one year with a single application. dient is acephate) did not adequately protect In addition, in side-by-side comparisons with large trees (greater than 15-inch DBH) under other systemic products (neonicotinoids), high pest pressure. emamectin benzoate was more effective. 9 Herms, McCullough, Smitley, Sadof, Williamson, Nixon