Two old-fashioned, but still very effective, weapons for
combating rose pests are companion plantings (Lavender, Catmint, Clematis) and nontoxic sprays (dormant oil).
Most insects despise the scent of members of the onion
family, and of some other pungent herbs .
Successfully head off trouble by scatter garlic, chives,
oregano, and tansy plants throughout the garden.
Marigolds (the Tagetes minuta or Calendula officinalis
species) can provide attractive borders while keeping the destructive nematode (a microscopic rootattacking worm) at bay.
Tomatoes, petunias, lavender, and chrysanthemums can also
serve as effective pest repellents in the rose garden.
You can concoct a homegrown insect discourager by mixing
ground onions, garlic, and hot peppers—in just about any proportion you have on hand—in a gallon of water. Let the smelly solution steep overnight, strain the liquid, and spray the brew over your rosebushes.
Forceful streams of just plain water will help to break up
invasions of spider mites.
For serious insect infestations, however, you may need to apply a product whose sole active ingredient is natural pyrethrum (an insecticide made from the dried flowers of Chrysanthemum cinerariaefolium).
Sink banana peels in the rose bed, they'll love the potassium!