Susan O’Connell, Fertile Crescent Farm Hardwick, Vermont

Using Systemic Insecticides Wisely

One of the commonly-used systemic insecticides used by cut flower growers is Acephate (Orthene). It has been a reliable systemic insecticide that works well on sucking insects and some for chewing insects such as Japanese beetle adults. Acephate has some impact on mite populations but is the not the preferred material for mite control. Though Acephate is still very effective it is older chemistry, in the group organophosphates, that is available to cut flower growers. Growers should not become reliant on just one class of chemicals or resistance can develop.

In the last 10 years a newer class of chemistry was introduced called the chloronicotinyl, also referred to as neonicotinoids. The first introduced to the cut flower industry was imidacloprid (Marathon) distributed by Olympic Chemical Company. Imidacloprid takes out the really tough sucking insects like melon aphid and green peach aphid very effectively. Imidacloprid will rapidly reduce a population of harlequin bugs, four-lined plant bugs, tarnished plant bugs and whiteflies. In 1999 we conducted trials for controlling potato leafhopper on dahlias and it provided outstanding season-long control. This has been available for foliar sprays, which give you about 2 –3 weeks of control. Applied as a soil drench and absorbed by the root system it provides 8 –12 weeks of control.

In the fall of 2003, Syngenta Crop Protection introduced thiamethoxam (Flagship) to the market place. This is also a systemic insecticide in the class chloronicotinyl. Like imidacloprid, this systemic can be applied as foliar spray or a drench.

Another systemic chloronicotinyl that is owned by Nippon Company but distributed through Cleary Chemical Company is Tri-Star. Under the Tri-Star label pretty similar insects  are controlled as listed on the Marathon and Flagship labels. The big difference is that Tri-Star is labeled for foliar application only. Tri-Star has translaminar properties, which means that it penetrates leaf tissue and forms a reservoir of active ingredient within the leaf tissue. It should provide control for 2–3 weeks.

Chemicals such as Acephate (Orthene) and other organophosphates, kill insects by inhibiting the enzyme cholinesterase. This prevents the termination of nerve impulse transmission. Insects that ingest or contact the chemical get hyperactive, and run out their metabolic energy and die. Like a human on an extreme caffeine lift.

Chloronicotinyl insecticides by acting on the central nervous system. They cause irreversible blockage of the postsynaptic nicotinergic acetylcholine receptors. Nerve transmission is blocked causing uncontrolled firing of the nerves. This results in rapid pulses from the influx of sodium, leading to hyperexcitation, convulsions, paralysis and death.

Why do you need to know this? Good question. It has to do with understanding resistance management. You want to use insecticides from one class of chemistry, and then rotate to another class of chemistry. For example if you are using Orthene you can switch to one of the chloronicotinyls. It is very important not to rotate from one chloronicotinyl to the next as this will increase the selection pressure on the target pest population and can lead to insect resistance.
Keep in mind that none of the chloronicotinyl insecticides give any level of control of either mites or caterpillars. We have several non-systemic miticides that work well on mites such as Akari, Floramite, and Avid. An effective non-systemic to control caterpillars is Bacillus thuringiensis (Bt) or Conserve.

May only good bugs enter your cut flower garden. In case the bad one shows up, though, be prepared and make sure to rotate your products used for control.