We would like to present some ideas for rose culture based on our understanding of the biology and ecology of roses. To biologically prevent and manage pests we start in the root zone.

Roses historically are forest plants and benefit from an association with endomycorrhizal fungi. They thrive in a soil that is dominated by a diversity of soil fungi (as opposed to soil bacteria). Woody mulch on the soil around the plant favors soil fungi over soil bacteria. Water washes through the mulch carrying humic materials into the soil, which helps feed the fungi. Avoid incorporating raw organic matter as it stimulates bacterial growth, which is not best for roses.

Healthy rose bushes resist pests and diseases and the planting bed makes a big difference. Prepare beds by double (or triple) digging and incorporate mature compost with a priority to increase organic matter in the second spade depth layer of soil. Inoculate the roots of new plants with endomycorrhizal fungi to get transplanted bushes off to a good start. Space plants to provide good air flow between plants, away from tree roots (or install a root barrier).

For established bushes mulch the inoculant vertically into the root zone. Use a spading fork to make small holes in the soil and drop a pinch of inoculant into each hole.

Foliar feed with “compost tea” at regular intervals through the growing season. This feeds both the leaves and the soil fungi. The tea runs off after colonizing the leaf surface with beneficial microbes that are antagonistic to plant diseases. Pests like aphids and whitefly are also decreased by compost tea sprays.

Habitat plants will draw beneficial insects to help control insect pests. Alyssum, clover, yarrow, creeping oregano and members of the carrot family (dill, fennel, coriander, bishop’s weed) can be grown near roses. These plants attract a wide range of parasitic wasps and flies that control aphid, worms, whitefly, leafhoppers and many other pests. Garlic, onions and chives are good companions repelling aphids. Gopher Stopper sour clover repels gophers and its flowers attract bees.

Honeydew seeking ants farm aphids, whitefly, mealybug, and lacebug (honeydew producing pests) just as we farm dairy cattle. They carry them on to plants, protect them from beneficial insects that try to eat them, and harvest honeydew from them. Honeydew is like candy to the ants, only more complete nutritionally. To control any of these pests (and often spidermites) you need to manage the ants by disrupting their nests and baiting the colony. We offer materials and suggestions for managing ants.

Lacewing and ladybugs are attracted to this honeydew. You can use our Insect Food to draw them to suppress pests on your roses. We offer this Insect Food product that can be mixed with water and sprayed to attract them before pests appear in the spring.

Enhance the habitat around your rose garden for birds, frogs and toads to feed on insect pests year round. These creatures appreciate ponds and fountains.

If rose slugs and rose worms, that escape the naturally occurring biological controls, require different biological treatments for worms (caterpillars) and wasps. Like cutworms in turf, leafroller and budworm caterpillars can be sprayed with Condor or Troy Bt., Bristly roseslugs and coiled roseslugs are primitive wasps called sawflies (not caterpillars) so they are not affected by Bt. A more effective treatment for these sawflies is spraying and drenching these wasp larvae with Steinernema carpocapse beneficial parasitic nematodes, the same ones that attack the larva of fleas in turf and soil.

When you follow these basic guidelines you can minimize or control the insect pests and diseases on roses and promote healthy plants. For more on particular pest control solutions, see the pest index on our website and call us.