Small Flies Are Big Pests

By: Stephen A. Kells

How to troubleshoot small fly infestations

As a pest management professional (PMP), how many times have you heard an irate customer say such finalities as“Sorry, but we are canceling because the company we use to manage our small flies can also manage the other pests under one contract — for cheaper.”

Recycling bins are a particular hot spot for breeding small flies.

This is a case of a company gaining business (at your loss) by marketing themselves as technically superior and gaining the all-important “foot in the door.” Essentially, it is providing a specific service that the customer perceives is not available from you, the current service provider.

Regardless of how much heartburn you have incurred over this group of pests, small flies are and will continue to be a challenge in a number of accounts. What follow are some methods to quickly troubleshoot fly problems during emergencies by understanding fly biology and a few key strategies. More importantly, there are indeed ways you can prevent emergencies in the first place.

Remember the 80:20 rule — 80 percent of the problem stems from the immature stages.

FOOD SOURCES

All structural infesting flies require a food source for the larvae to start the infestation. If there are small flies present, there is a source of food, or odors indicating sites to breed, lay eggs and produce more flies.

The food that flies most often seek is decaying organic matter — usually a food source that was left out too long and has started to rot. Common sources include:

• Fruit associated with a bar environment (limes, lemons, cherries, etc.) that fell under the counter and was not cleaned up;
• Produce placed on the counter and left for more than 24 hours;
• Salad bars not properly changed with fresh produce;
• Bread, meat, vegetables or other foods that were knocked off the prep counter and fall unnoticed into a hard-to-reach area;
• Improperly maintained mops (not properly rinsed and hung to dry);
• Food accumulated in anti-fatigue mats used in areas where people stand for extended periods; and
• Food accumulation inside drains.

Tougher examples include:

• Processing chemicals (glycine, glycerol) permitted to stagnate and grow fungal or bacterial blooms;
• Sewage, manure or food permitted to accumulate or leak in non-accessible areas, such as in walls, under and behind tiles, under concrete slabs or in elevator pits; and
• Landscaping with excess moisture (indoor and outdoor).

THE 80:20 RULE

The next important point to fly biology is the 80:20 rule. Controlling just the adult flies (spraying or fogging) means you are addressing just 20 percent of the problem. The remaining 80 percent of immatures will be left behind to produce more adult flies within 24 hours. True control must include source reduction.

How to troubleshoot small fly infestations

The “small fly” category actually encompasses several types, including drosophilid fruit flies, moth (drain) flies, minute dung flies, phorid flies and fungus gnat. Properly identifying the species will help lead you to the proper breeding sources. For example, moth flies tend to prefer the buffets they encounter in poorly maintained drains; fruit flies are usually more fond of decaying food left out in the open.

The concept of post-application inspections (“diagnostic fogging,” if you will) is long overdue as a part of regular service. When a pest control product is applied, there should be scheduled inspections after the application to spot if and where the insects died. Besides removing the “cloud” of flies, the inspection produces valuable information that will get you closer to the source of infestation. Inspections should include areas such as the floor, counters, windowsills, false ceilings and insect light traps.

PREVENTING INFESTATION

The key to preventing small flies is to start the program as early as possible and make sure the program is active over the entire season. There are a number of suppliers that provide a variety of fly traps, monitoring devices and products to clean up decaying organic matter, including drain cleaning and bioremediation products. Some suppliers will also help with more specific training, and provide information that will help you set up fly control as a contract service.

My Top 5 list for an effective preventative small fly control program is as follows:

1. Set up a proper contact with expectations of the customer and the technician.

2. Set up a proper pricing schedule, factoring in a realistic amount of time for proper inspection.

3. Get technician and management buy-in into the program. You have to build confidence that the program will work to prevent technicians from resorting to old ways. Remember, a prevention program controls flies gradually over the entire season, and once employed it is effective.

4. Properly equip your technicians. Besides the one-gallon sprayer and a fist full of sticky traps, give them magnifying glasses, spatulas and similar inspection tools, squeegees and wet/dry vacuums. Equipping the tech also means with knowledge.

5. Anticipate the season. One fly in April or May can result in 5,000 flies in July. Do not leave control procedures until July. Start at the beginning of the season, but make sure all programs are working at least two to three weeks before fly problems are typically encountered.

Kells is a board-certified entomologist and an assistant entomology professor at the University of Minnesota in St. Paul. Contact him at pccontributor@questex.com.

In this tile grout, fly larvae are thriving. Note the size of the larvae in relation to the tip of the knife blade in the lower left-hand