Related Topic: Honey Bee Parasites, Pests and Predators - New slide set, viewable on Web

Currently, Apistan is the only legal chemical registered for the control of varroa mites in the United States. The active ingredient, fluvalinate, is a contact pesticide; the mites must come in contact with the strips in order for the material to be effective. For this reason, the strips are hung vertically inside the brood nest. Zoecon has recently revised their Apistan label. Current label recommendations require that all honey supers be removed before treatment but can be replaced immediately after the strips are removed (if treating in spring or during the summer dearth). Any honey left in the hive during treatment must be used as bee food or destroyed. Strips must be left on colonies for a minimum of 42 days and a maximum of 56 days. The number of strips placed in a colony is now dependent on the number of frames of bees in each colony. Use one strip per five frames of bees or fractions thereof. They should be evenly distributed throughout the brood nest.

TO USE OR NOT TO USE, USED APISTAN STRIPS
Today's pesticides are designed to act swiftly and be highly lethal. In order to make it onto today's market, new pesticides must kill 99% or better of a target population and must do it in a matter of days if not hours (depending on whether it is a contact pesticide or one that needs to be ingested). The reason for this can be summed up in one word - resistance!

Arthropod (insects, mites, ticks etc.) pests are extremely efficient at making chemical pesticides useless. They do this by developing resistance to the chemicals. No pesticide ever developed has been effective in killing 100% of a target population. While most of the pest population is susceptible and can be eliminated by the chemical pesticide, some small proportion is always resistant and able to survive. Over time and after many treatments, the susceptible portion of the population is eliminated. Only the resistant portion survives and is able to reproduce (producing resistant offspring). Eventually, the number of resistant insects or mites reaches a level where it again causes damage (economic injury level) and the chemical becomes useless. Because of their rapid rate of reproduction and simple genetic make-up, mites are particularly good at changing or adapting to survive in the presence of chemicals that are meant to kill them. By designing pesticides that kill the greatest number of pests in a short time, fewer will be able to reproduce and it will take longer for the population to develop resistance. The development of resistance can be slowed further by alternating different pesticides. This "throws off" the pest's ability to change or adapt to a single pesticide.

Full strength Apistan strips are designed to kill nearly every varroa mite in a susceptible population (newly exposed to fluvalinate). Because the mites in brood cells are protected from this contact pesticide, the material must be kept in colonies for a minimum of two brood cycles (42 days). However, as soon as Apistan strips are exposed to the air, the active ingredient, fluvalinate, begins to break down. Used strips and strips left in colonies over a long period of time will eventually deliver an ineffective dose of pesticide; they do not deliver the same chemical "punch" as new strips. The mite population is knocked down but not out. Many mites are killed but undoubtedly a higher number will survive and reproduce. The population will quickly build up to a damaging level and the chemical will become useless. What's more, we have no alternative materials currently registered for varroa mite control. We can not slow resistance by alternating chemicals.

When we use pesticides in doses or formulations not labeled for varroa or tracheal mite control we can kill mites, (if the mite population is high, thousands might be killed) but what proportion are we killing? Are we administering an effective dose? Treated colonies may survive a year or two speeding up resistance? What risks are associated with untested material killing bees or accumulating in honey, wax or wood over time? Is it a risk worth taking?

Related Topic: Honey Bee Parasites, Pests and Predators - New slide set, viewable on Web