Rana Sarfraz: Are Indian meal moths invading your home? Here’s what you can do
A friend of mine discovered that her bag of brown rice was suddenly full of bugs and it smelled awful in the pantry. I visited her home the next day and found out that her rice was infested with the Indian meal moth. It has become a serious pest of pantry items and stored products across Canada, including British Columbia.
We recently inspected several grocery stores throughout the Lower Mainland that sell bulk produce and found that over 75 percent of stores in the area were infested with Indian meal moth. This insect is difficult to get rid of in commercial storages and warehouses as it has become resistant to most of the insecticides that are commonly used for its control and can easily reach your home along with the infested produce.
The adult is a small moth, about 10 to 12 millimetres long with a wingspan of 16 to 20 millimetres. The tip half of the front wings is rusty brown or nearly bronze, while the base half is yellowish gray. This wing pattern distinguishes Indian meal moths from other household moths. Female moths lay 60 to 400 eggs in or near a suitable larval food source.
The larvae are usually cream colored, sometimes with yellowish green or pinkish shades, and have a dark brown head. They feed on nuts, herbs, coarsely ground grains, and other pantry items. Normally they stay associated with foods, but the full-grown larvae, about 13 millimetres long, may be seen as they wander in search of a place to pupate. The larval stage lasts for two to three weeks under optimum conditions. The larvae pupate in silken cocoons on the surface of the food materiel or nearby. Moths emerge in one to four weeks.
The larvae can seriously spoil food items and the adult moths can become annoying as they fly through the home. Here’s what you can do to avoid or get rid of these moths in your home:
• Prevention: Don’t buy bulk food from a store that is apparently infested with Indian meal moths. Food items should be stored in sealed, airtight glass or plastic containers. Paper, cardboard, or cloth containers will not prevent infestation. All dried items should be rotated, using the older materials before the recently purchased items, as severe infestations generally occur in foods that have been stored for long periods of time.
• The first stage of control is to identify all potential sources of infestation in a home. Go through items in the pantry, which may host Indian meal moths. They are commonly found in coarse cereal products such as oatmeal and breakfast cereals, nuts, herbs and spices, dried soups, and dried fruits and vegetables. Brown rice is the most favourite food for them. Examine all stored food items for signs of infestation—moths, larvae, shed larval skins, webbing, cocoons, or off-odours and colours.
• Infested materials should be discarded, promptly used up, or treated with heat or cold to kill insects present in the food. Cold treatment requires putting infested items in deep freeze for at least three to four days. Heat treatment involves oven heating at around 55°C to 60°C for 30 minutes (or as long as it takes to heat the food item all the way through). Do not attempt to heat treat finely ground foods such as flour due to the danger of fire.
• A thorough clean out of all food sources is critical to managing Indian meal moth. Wipe out the cupboards and storage areas and vacuum the cracks and crevices to remove food particles. Insects also can develop on spilled food and therefore thoroughness of the cleaning is important to eliminate food source for surviving insects.
• Nontoxic pheromone traps are available to attract and kill adult moths. Typically male moths are attracted by the female sex pheromone (the lure) and then get stuck against the sticky walls of the traps. However their ability to control Indian meal moth is doubtful because the traps only capture males (mated females are not captured, which will continue re-infestation).
• For current chemical control options, consult your local pest management representative. Do not apply insecticides in a manner that allows direct contact with food, food preparation surfaces, or food utensils.
Rana Sarfraz is an entomologist who is currently working at the University of British Columbia.