Biology
- There are over 2,000 varieties of wasps, all of them beneficial in some way or another. Some are pollinators while some are predators of other nuisance insects such as caterpillars and aphids.
- Size: These insects are medium sized (10mm-25mm) and are readily distinguished by the bands of black and yellow or white on their abdomens. Yellowjackets, one of the more aggressive species, have a habit of scavenging in city garbage cans. They were introduced in the U.S. about 45 years ago.
- Stinging: Only the females possess stingers. As with honeybees and hive bees, both the queen and female workers develop from fertilized eggs laid by the queen. Males develop from unfertilized eggs laid either by the queen or by the workers.
- The Nest: Yellowjackets, hornets and wasps build colonies made of plant materials that are glued together and are formed in hollow stumps and logs, under eaves or steps and in stone piles.
- In early spring, the hibernating queen emerges from cracks in tree bark to look for a nesting site. Once found, she builds the first few paper brood cells and lays a single egg in each one. These workers will emerge and take over the queen's construction duties. In late fall, the colony will reach its maximum size, from 1,000 to 30,000 individuals. As the weather grows cooler in autumn, the queen will abandon the nest to look for a hibernation site. All the workers eventually die. The old nests are not used the next year.
- Vibration is the stimulus that renders them the most aggressive.
How to Control
- Only ever approach a colony at dusk on a cool evening. Wasps are less active in cooler temperatures. Always wear protective clothing (ideally a beekeeper's outfit).
- Stings can be soothed with ice and a bicarbonate-of-soda paste.
- If the nest is in a location that does not present a health hazard, it is best to leave it until November-December when it is sure that it is abandoned and thus safe to remove.
- Locate the opening of the nest (usually at the bottom). Direct a thin stream of at least 0.5% propoxur into the opening. One application should usually suffice, but if wasps are still seen entering or exiting the nest a few days later, repeat the procedure.
- This method requires a minimum of two people: Get a large bucket of water (room enough for the entire nest) with a lid. Add some cooking oil to ensure that the wasps will drown. Holding the bucket directly underneath the nest, cut the stem, allowing the nest to fall in the water. Without hesitation, slam the lid down and seal it. Only take the cover off when the wasps are surely drowned. Bury the waterlogged nest.
- Trap: Mix together one small tin of tuna, 16g of chlorine powder, 8g of vegetable oil. Add a bit of grenadine syrup (it has been found to be one of the best attractants). Place in an area where wasps are seen. Keep out of reach of both children and pets. Adult wasps will take portions back to the nest, thus killing all the inhabitants. This trap is useful if the location of the nest is not known. Traps should be placed 3-8 feet above ground.
- To make an area less attractive to yellowjackets: Do not litter, cover garbage cans with lids (swinging lid is one of the best kinds), empty trash cans more frequently, caulk small cracks and holes in external walls, screen larger entrances such as vents, and eliminate puddle water.
- To control ground wasps, press a small cone made out of window screening over the hole. At the same time, place a shoebox over the cone. The workers will exit the nest, enter the trap and be unable either to leave the box or to re-enter the cone. The colony will die in a week or two. Stuff rags and dirt around the base of the trap to prevent escapees.
- If the nest is in the soil, place diatomaceous earth in the entrance holes.
- For professional help with removing wasp or bees nests, or for a consultation, contact Eco Bug Doctor 514-422-8457.
- For more tips go to Horticulture/Insects