How to Kill Bumble Bees If They Become a Pest
As stated in the Bumble Bee web page, these flying, stinging insects are usually considered beneficial and should be left alone. In most cases, their benefits far out weigh dangers they may present. This article addresses problems where the bees have become a pest, usually due to the location of their nests
Chemical and non-chemical controls should both be considered. Non-chemical control mainly consists of prevention methods. Pesticide free control of bumble bees is discussed on the bumble bee information page.
When the location of a bumble bee nest dictates elimination for safety’s sake, certain products, techniques and timing are essential. Using the wrong pest control products or using any control products during the peak of bee activity usually results in failure to control the pests and (very often) being stung by angry bees.
First, there is timing to consider.
Stinging insects such as bees, wasps, hornets or yellowjackets tend to be very active in daylight hours and rest (in their nests) after sundown. If you treat an active nest in daylight hours there are two possible bad results: you are at much greater risk of being stung and will not kill as many bees with initial application. Once you have located the nest, make note or mark the area so that you can find the nesting area at dusk or in the darker hours.
During daylight hours, bees are busy foraging for all of the colony’s needs. Treating the nest during these hours will kill a few bees. Workers returning to the nest are exposed to the treatment but the treatment will not be as fast or as effective. Early evening treatment will catch the majority of the workers in the nest, trapped and unable to escape safely.
Nests located beneath loose objects (mulch, grass clippings) or covered by over-grown grass and weeds are treated differently than those that lie simply beneath a brick, stone or other similar object.
If a bumble bee nest is located in an over-grown area, do not use lawn mowers or other motorized grass and weed trimmer before bumble bee nest has been neutralized!
The sound of such machinery will stir up and agitate the colony into attack mode.
First eliminate the nest, then finish your landscaping chores. There are two basic methods for treating bumble bee nests. Read this entire section before deciding on methods and products needed. Most people will need only one type of bee control; others may have such a severe problem that a combination of these two methods might be needed.
Treating nests in covered or over-grown areas is best done by first broadcasting an insecticide over the area. This is especially important when the entrance hole is not visible due to loose materials. (If entrance hole is visible, skip down to Treating Bumble Bee Nests Beneath Rocks, Decking, Tarps)
The area should be fairly well drenched both on and around the suspected entrance to the nest. Products containing Cypermethrin work well for this job. Cypermethrin is available in both liquid and wettable powder concentrates. Either formulation can be used; Demon EC, Cynoff EC are professional liquid concentrates and
Demon WP, Cynoff WP are professional wettable powder concentrates.
Once you have sprayed the area (or areas), make note of bumble bee population over the next 10 to 14 days. A repeat application might be necessary. If you think that you are dealing with multiple nests, pushing an insecticide dust into the entrance holes might also be necessary. This is especially important during the time of year when there could be many bee grubs or larvae that will soon be hatching out, producing even more worker bees. Dusting bee colonies is discussed in the section where elimination of underground bee nests is explained.
Besides bumble bees, any of these products can be used for general purpose pest control in and around the home. Liquid concentrates are more cost effective for this particular job. If you are positive that you are dealing with only one nest, a 4 ounce bottle of Cypermethrin concentrate may be all that you will need, especially if you have no other pest control needs.
Pump type sprayers can be used for this type of pest control job but most people feel safer using a hose end sprayer. A hose end sprayer will give you the ability to treat the targeted area from a better distance and will also provide a more thorough soaking of the nest area. When using a hose end sprayer, liquid concentrate insecticides work better than wettable powder concentrates.
The type and amount of loose materials covering the entrance to the nest will dictate the amount of spray needed. If cover is heavy, more than one application is often called for. There are three different sizes of liquid concentrate Cypermethrin: 4 ounce, 16 ounce, 32 ounce. If you do not intend on doing your own general household pest control, you will usually not need the larger containers. Only when there is a great deal of landscape area to deal with will you need larger volumes of liquid insecticides. In this case, Demon Max (Demon EC) is your best bet. For smaller jobs, buy one or two 4 ounce bottles of Cypermethrin.
Keep pets and children off of any treated area until area has been allowed to thoroughly dry. Once dry, the area will be safe for re-entry – unless bumble bees are still noted flying in the area. Bumble bees do not always die as quickly as we would like; they are tough and stubborn.
When the entrance to bumble bee nest is easy to locate and is not covered with tall grass or mulch, the best control method is dusting. A professional grade insecticide dust is formulated with tiny particles that will float through targeted area, almost floating like smoke. When properly applied into the nest entrance hole with a good hand bellows duster, the dust will travel deep into the nest.
There are two different dusts that will work: Drione Dust and Delta Dust. The advantage of Drione Dust is that it has a very fast knock-down or kill of targeted pests. Delta Dust has the advantage of being water-proof, an asset that is very attractive when treating soil that might contain any type of moisture. Delta Dust is the most popular of the two insecticides. Pest control technicians who have more products at their disposal have reported great results when combing the two dusts for a single application. This combination gives them a quick knock-down of existing bees and fewer call-backs when young bees can emerge.
Apply your insecticide dust with a hand bellows duster. There are two good hand bellows dusters to choose from: 360 DustWand and Crusader Duster. Either of these dusters will due a good job. The advantage of the Dust Wand is that the extensions provide a longer reach.
When applying pesticide dusts into cracks, crevices or entry points, proper filling of the dusting device is of utmost importance. When a hand bellows duster is completely filled to its capacity or when dust is packed down inside the duster, dust does not come out in proper form. Never over fill a hand bellows type insecticide duster. Fill duster 1/2 to 2/3 from top. After replacing the fill opening, gently shake the duster just prior to application. The small area inside the duster (created by NOT over-filling the duster) creates a space that is sorely needed. When the duster is shaken, a small “cloud” of insecticide dust is formed in the empty space.
By gently shaking a properly filled duster, the dust particles will exit the duster nozzle in a thin, smoke-like cloud as the hand bellows duster is squeezed. This thin cloud of duster will travel further through the targeted area (in this case, an underground bumble bee nest), reaching far more adults, eggs and larvae. The next effect of proper application is over-all coverage.
If large amounts of Delta Dust or Drione Dust are merely “dumped” into the nest entrance, the majority of the dust will merely pile up in one place. Properly applied dust will “float” through the chambers and most of the particles will tend to stick to top, bottom and sides of the tunnel as well as the nest itself.
Treatment of a bumble bee nest involves coating the nest entrance, nest, eggs, grubs and adults. For most nests, you will need to apply two applications: partially fill your duster, shake thoroughly, empty contents into nest; repeat. This double application will assure better control over all stages of the bee and will contaminate the nest and void, which will kill bees returning to the nest area.
As mentioned previously, the best time to kill bumble bees is when they are at rest or as they sleep. Avoid treatment during daylight hours; treat the bumble bee nest at dusk or when it is dark enough for the bees to cease their activity but just light enough for you to see what you are doing.
You can (using a flashlight) kill bees at night but there are a couple of possible hazards that you might run into: stumbling over unseen objects and actually attracting angry bees. The first possible hazard listed is mainly common sense. If you trip and fall over any unseen object in the area, you not only risk possible harm from the fall but also risk waking up the resting bees. Using a flashlight to navigate to the sight or while treating the nest can be a problem.
If the bees are disturbed and exist the nest, they could very well be attracted to light emitted from your flashlight. (If light is needed, try setting your flashlight in one area before you approach the nest from another area.)