I have sweat bees that hang around the pool and sting whoever is swimming. They also sting when I am mowing the yard because I am sweating. What can I do to get rid of them in my area?
Sweat bees will become very active in late spring and as summer sets in and people start to sweat, their presence will become more pronounced as they conflict with humans in the vicinity where they're nesting. Sweat bees are mostly ground nesting meaning they commonly nest in soil. They'll also nest in trees, just under the bark or in old abandoned holes left by other insects, so any stumps or wood piles are prime locations for sweat bee nests. We have several hundred species of sweat bees here in the United States and they have a wide range of looks and sizes. But the one thing they all have in common is that controlling them at their nest site can really help eliminate direct conflict and getting stung. Since they like to nest close to water and in a protected area, it's quite common to find them around the pool and in the yard.
To see if you have nests in your yard, do a good inspection of the turf looking for any flying insects coming and going that are using a sort of "path". Sweat bees can be solitary meaning only one will occupy a single nest. But some species will have multiple members in the colony. In these larger nests you'll stand a greater chance of seeing them active. Solitary nests can be tough to locate but in most cases where there is a single nesting sweat bee there will be multiple nests all independent of one another. In fact, it's not uncommon to have hundreds and even thousands nesting in the yard if left untreated for just a few years. Since sweat bees will tend to migrate back to where they were born, a single nest will rapidly become many in very little time. If you have a lot of them flying around you in the yard or by the pool, chances are high you have a lot of nests somewhere on the property adjacent to all the activity.
Two other things worth noting; lawns which are watered or otherwise moist will tend to attract sweat bees as will turf where the grass is recycled and not removed. In other words, if you don't bag your grass clippings you are only inviting more bees. The point is both decreasing the amount of water being used in the yard along with removing grass clippings will help cut back on their propensity to nest on your property.
If you're seeing some activity in the turf or have the kind of experience you mention at the pool, a good way to start a sweat bee treatment program is to apply some CYFLUTHRIN GRANULES in the yard followed by a liquid treatment with the CYONARA RTS. The granules are slow release and will take 2-4 weeks to penetrate down where the nest eggs are lying. Once it gets there and the eggs start to hatch (which will happen in mid to late summer), the active ingredient will kill off the larvae. But since it can take 3-6 days for the adult bees to be affected by the granules (if even at all), we recommend spraying the Cyonara over the top of the granules. This will provide much faster control of any current live activity. In most cases you'll kill 80-90% of the live ones right away with the Cyonara and over the next few weeks, the granules will kick in killing off the young larvae down in the soil.
Lastly, followup treatments should be made every month with the granules to insure you have plenty of active in the soil throughout the summer months. This way eggs that are hatching down deep will be killed and in the end, the cycle will be broken. Just remember the third stage of this bee, the pupae, will be hatching all summer and as they do, you should expect to see a resurgence of adults every week as these pupae will be released as adults. Nothing can kill this stage so the only way to reduce these numbers is to liquid spray with the Cyonara as needed till they're depleted. This can be as frequently as once a week for awhile in extreme cases. Most cases you'll find 1-2 treatments per month to be plenty but if you had this problem for a few years, chances are they will be resilient so make sure you stay the course if you wish to knock them out once and for all.
Here are direct links to the products and information mentioned above:
Cyfluthrin Granules: http://www.bugspray.com/catalog/products/page1271.html
Cyonara RTS: http://www.bugspray.com/item/cyonara_rts.html