As late summer arrives, Contra Costa County residents may notice more yellowjackets buzzing around yards, patios and outdoor meals — especially near sugary foods and drinks. The Contra Costa Mosquito and Vector Control District says there are four types of yellowjackets commonly found in the county, including two that build nests above ground and two that nest underground. The District provides treatment specifically for ground-nesting yellowjackets because they are more likely to come into contact with people.
Ground-nesting yellowjackets often make their homes in abandoned rodent burrows and other holes or cavities in the ground. Colonies can contain hundreds of yellowjackets. During late summer and early fall, yellowjackets are especially attracted to sugar sources such as fruit, candy, soft drinks and other sweet foods and beverages. Residents often discover underground nests accidentally while mowing lawns, gardening or doing yard work. If yellowjackets begin emerging from the ground, officials recommend immediately stopping work and moving away from the area. Yellowjackets can both bite and sting and may become aggressive when defending their nest.
Residents who suspect a nest can watch their yard from a safe distance during the morning or evening to see whether yellowjackets are repeatedly entering and leaving the same hole or area. If a ground nest is located on a Contra Costa County property, residents can request service from the Vector Control District. A technician will inspect the area and, if ground-nesting yellowjackets are confirmed, treat the nest with an insecticidal dust. The area should then remain dry and undisturbed for at least four days.
The District cautions residents against applying liquids or other substances to a suspected nest before requesting service because wet soil can interfere with the treatment. Yellowjacket traps can also help when used properly. During late summer and fall, the District recommends placing traps away from homes, walkways and areas where people gather. Sugar-based bait, such as fruit juice, sugar water or jam, can attract worker yellowjackets searching for food. Earlier in the year, the District recommends putting traps out around Valentine’s Day and removing them around Father’s Day to target emerging queens before they establish new colonies.
Contra Costa County residents do not pay an additional fee for the District’s residential yellowjacket service because it is funded through property taxes and benefit assessments.
Put out traps at Valentine’s Day & remove at Father’s Day?! …. around here they’re out more when it’s dry – like July – October