There are different baits for large and small roaches because different roach species have different food preferences.
Large and small roaches have different food preferences. Each roach bait is specially formulated to be attractive to specific roach species. Since roaches usually have several food sources, a bait has to be very attractive so that roaches will eat or come in contact with it for the bait to be effective.
The Difference Between Small & Large Roaches:
There are typically two different sizes of roaches you’re likely to encounter in your home - large roaches and small roaches. Large roaches measure over one inch in length. Both American and Oriental cockroaches are considered large roaches. Small roaches, on the other hand, are smaller than 1/2 of an inch. Both German and Brown Banded cockroaches are categorizes as "small roaches."
Spotting small roaches in your home likely indicates an infestation. Be sure to use Combat baits and gels to eliminate a cockroach infestation.