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.
Print out these five standby remedies for yard and garden, including a natural fungicide for mildew and black spot: Simple Soap Solution. Pests affected: aphids, spider mites, and whiteflies. 2 Tbs. soap flakes. 2 litre warm water. Dissolve soap flakes in water and apply directly to infested areas every 5-7 days.