Why are cockroaches on the rise?

The general consensus throughout the country, German cockroaches are making a vigorous comeback. There are two significant factors driving this:

• In low-income housing, where pest management budgets are stretched thin, many resources have been redirected to manage bed bugs. Something had to give. Less attention is paid to controlling cockroaches. They were always there but were minimized with constant reoccurring service using gel and solid cockroach baits. Now, budget and labor restraints require less focus on cockroaches and more on bed bugs.
• We have a new generation of technicians who never had to dig deep and work hard to eliminate persistent and heavy cockroach populations. They placed a few dabs of bait and left. Now the pendulum has shifted back in favor of the cockroach. I’ve always said my money is on the roach. When low numbers of cockroaches appear, technicians don’t overextend themselves to wipe the pests out. Ninety-five percent of the work to eliminate cockroaches is to eliminate the last 5 percent of the population. With the discovery of cockroach bait aversion, you can eventually select for cockroaches that survive.

What to do about it

1. Use sticky trap monitors on all accounts, and take early action when any cockroaches appear.
2. Try different gel baits to see whether bait acceptance is present.
3. In some situations, using dust in
   hard-to-reach voids is needed along
   with cockroach baits. You might need to drill to reach wall voids where the cockroaches are harboring.
4. Ask for help as soon as you see you’re not gaining ground. With a short life cycle and a high reproductive rate, numbers rebound within a month.

Do the math

If you start with 1,000 cockroaches (500 nymphs, 250 adult females and 250 adult males) and kill 90 percent of those present, you end up with 100 cockroaches. If the ratio stays the same, you have 25 adult females. At 40 offspring per egg capsule, you end up with 1,000 new cockroaches plus 100 original ones. You have 10 percent more cockroaches than you started with, assuming no new cockroaches are brought into the account. You must achieve 98 percent kill or better on each visit to win the battle. Even with the so-called ease of baits, it takes time and hard work.

As with any control program, if you ease up, the pest rebounds. This is true for cockroaches, ants, flies, mice, rats and whatever other pest can breed indoors. pmp

You can reach Frishman, an industry consultant since 1967 and president of AMF Pest Management Services, at mypmp@northcoastmedia.net.