The speed with which insecticides are taken up is vital to tree recovery and health
For preventive maintenance, most arborists are not concerned with how quickly chemicals move through a tree’s vascular system. However, when you need control right away, you don’t want to wait six months for uptake.
“Neonicotinoids [insecticides such as dinotefuran and imidacloprid] are systemic and are taken up in the xylem of the tree following a soil application,” said Dr. Joe Chamberlin, field market development manager, southeast, for Valent Professional Products. “However, the varying chemical structure of those compounds can significantly affect the rate at which they are taken up into the tree and, therefore, the results you will see on the control of the pests.”
Chamberlin explained that two key factors influence a systemic insecticide’s uptake rate: its solubility in water and how tightly it binds to organic matter in the soil and inside the tree.
Water solubility differs greatly among neonicotinoids. For example, Chamberlin said dinotefuran is 80 times more water soluble than imidacloprid — meaning that more dinotefuran can dissolve in each water droplet that is taken up into the tree.
Additionally, how tightly the insecticide binds to organic matter in soil and inside the tree is also important to uptake. Some compounds like pyrethroids are tightly bound to soil and, therefore, do not provide systemic insect control. Neonicotinoids vary in their tendency to bind to organic matter, with dinotefuran being much less tightly bound than imidacloprid, and therefore more easily absorbed by roots and more quickly transported in the xylem.
Chamberlin said both factors contribute to how an arborist may approach selecting a soil-applied systemic insecticide, especially in more severe situations.
“When you have time on your side, slower-acting products like imidacloprid are fine,” said Chamberlin. “But when you have a 911 emergency — a crisis situation — speed of uptake becomes very important.”
The uptake and movement of systemic insecticides is driven in great part by transpiration. According to Chamberlin, a tree may be in varying states of distress, which can affect transpiration by the plant. For example, a tree may be partially defoliated from pest damage, suffering from drought stress, or growing in shade. These situations can decrease the rate of transpiration, in turn affecting how quickly a tree is physically capable of absorbing the insecticide into roots and transporting it in its xylem. In these cases, the amount of product absorbed by roots and the speed of xylem transport become critical factors in product selection.
“Under any situation, it is obviously desirable for the tree to absorb as much active ingredient as possible from the soil,” said Chamberlin. “However, when a tree or shrub is experiencing conditions where it is in decline and absorption of water from the soil is lessened, it is critical you get as much product dissolved into that water as possible. That’s when a highly systemic, quick-uptake product like dinotefuran can really make a difference.”
Chamberlin said that doesn’t mean that dinotefuran (the active ingredient in Valent Professional Products’ Safari® Insecticide) shouldn’t be used preventively, but is extremely effective as part of an integrated approach to treatment and restoration of the tree.
“Safari is excellent at quickly bringing tree pests under control,” said Chamberlin. “Then other neonicotinoids can be incorporated into an IPM program once the tree has regained its health and is capable of handling slower-uptake compounds.”
Speed of Safari at work
Safari is currently being used in the tree care industry to control hemlock woolly adelgid, emerald ash borer, ficus whitefly and several species of soft and armored scale.
An untreated hemlock tree suffering from Hemlock Woolly Adelgid. Very little new growth is present.
“We began using dinotefuran to control hemlock woolly adelgid on a trial basis in 2007,” said Will Blozan, president of North Carolina-based Appalachian Arborists, Inc. “When we checked the trees last spring [in 2008], we were blown away by the results.”
According to Blozan, who has been battling this pest for 7 years, 2007 was extremely dry for his region, and the drought-like conditions continued into 2008. Hemlock trees treated with imidacloprid were not showing any improvement, but the trees treated with dinotefuran were showing a tremendous amount of recovery. Blozan attributes this to the high solubility of dinotefuran.
“Safari seems to work even under drought conditions,” said Blozan. “It seems to buy the trees a year to a year-and-a-half of recovery time.”
According to Blozan, trees that were beyond hope with imidacloprid are now being treated with dinotefuran. Once they recover enough vigor, imidacloprid can be incorporated back into the pest management program, but many trees would not recover their vigor without dinotefuran.
Armored scale is another pest group that has traditionally been difficult to control with systemic insecticides, which is believed due to the fact that armored scale feeds outside the vascular system. Therefore, systemic insecticides must be able to move out of the xylem to plant tissues where armored scale feeds.
“Dinotefuran has been very effective as a soil treatment in controlling armored scale, whereas other soil-applied neonicotinoids have not,” said Dr. Dan Herms, professor of entomology at Ohio State University and entomologist with the Ohio Agricultural Research and Development Center. “This is just a hypothesis, but we attribute it to the much higher solubility of dinotefuran.”
A hemlock tree treated with dinotefuran shows abundant new growth two years after treatment.
Photos by Joe Chamberlin
In addition, dinotefuran has systemic activity against emerald ash borer, hemlock woolly adelgid, ficus whitefly and scale when applied as a concentrated spray to the lower trunk. Following a trunk spray, dinotefuran is absorbed through the bark into the xylem and then transported to where pests feed. Trunk sprays can be done using a pump sprayer, aiding in overall ease of application. The method is also of use in cases where a soil application is not possible, but a systemic treatment is still desired. Based on university data, efficacious concentration of Safari are present in ash foliage within 3 weeks after a soil application or trunk spray. Safari was recently registered for control of emerald ash borer when applied as a soil application or trunk spray.
Dinotefuran is also highly flexible in that it can be applied as a foliar spray, soil drench, soil injection, bark spray or soil broadcast. The optimal timing of application is pest specific, but, in general, it should be applied when the tree is actively absorbing water and when the pests are waking up and beginning to reproduce (spring or early summer, or year-round in warmer climates).
Chamberlin believes the overall effectiveness and flexibility of dinotefuran help it fit well into a variety of treatment programs, especially when speed is of the essence. He said he often hears “Saved by Safari” stories from arborists impressed with the quick activity of the product.
“Regardless of the pest, there are times when it is really important to rapidly bring a pest outbreak under control,” said Chamberlin. “Safari controls pests quickly and effectively, and gets the tree back on the path to recovery.”
Dinotefuran is currently registered on the following pests:
Armored and soft scale
Emerald ash borer
Hemlock woolly adelgid
Japanese beetle (adults)
For more information, visit the Valent web site.