Although mealworms have their beneficial uses, they can become real pests if they proliferate. No one wants to find them in the pantry, but fail to seal your grain containers and you may get an unpleasant surprise. They also plague poultry enclosures such as chicken coops since they are strongly attracted to the chicken feed. Fortunately, it is not difficult to learn how to kill mealworms if you have the necessary items on hand.
Clean kitchen thoroughly. Throw out all old or infested food. Check corners and areas under appliances to make sure no scraps of food remain.
Double check to make sure the insecticide you are using is labelled "safe for kitchen use." Spray the infected area thoroughly according to directions on the bottle. Follow the safety instructions on the bottle.
Monitor the area to ensure the mealworms have been eradicated. Since mealworms reproduce with eggs, it is possible that you could kill all the living mealworms and still get a reinfestation when the eggs hatch. Repeat as necessary until there are no more mealworms.
Store all grain products in sealed containers to prevent new infestations.
Use garden insecticide labeled for perimeter treatment to kill mealworms outside. Spray grass, siding, shrubbery and porches thoroughly. Check periodically for reinfestation, and repeat as necessary. You can also place a blacklight electrocuting unit in areas where the mealworms congregate. Operate the unit as per directions on its packaging. Follow all safety warnings listed there, and make sure to locate it at least 20 feet from the house or any other buildings on your property.