In such cases the weeps consist of small-diameter plastic, clay or metal pipes extending through the wall to a layer of porous backfill. Typically, weeps are arranged to direct water which may have entered an assembly from outside back to the outside.
A few of several safe household chemicals to use are vinegar, dishwashing soap and rubbing alcohol, according to an Oregon State University Extension Service publication called Using Home Remedies to Control Garden Pests, (EC 1586). The publication, complete with photos, is available free of charge online.
Uses for this natural garden pest control are unlimited. Because it has oil and dishwashing liquid in it, it sticks to plants as well as suffocating pests such as scale and mealy bug. It will kill ants, aphids, caterpillars, grubs, bugs and just about any little invader.