Crimson Clover

An establishment-stage problem in cold wet soil - sowing into a warm, moist, well-drained bed at the right time avoids it.

Seedlings that fail to emerge or collapse at the soil line soon after germinating, and thin, patchy establishment in cold wet conditions.

None for affected seedlings; reduce watering, improve drainage and airflow, and resow more thinly if needed.

Sow into warm-enough, well-drained, moist (not soggy) soil with good seed-to-soil contact, and don't sow too deep or too early into cold ground.

A seedling rot that collapses young desert marigold seedlings sown too thickly or kept too wet in cool conditions - a minor issue easily avoided by lean, well-drained sowing and careful watering.

A minor pest of clover stands; because crimson clover is a short-lived cover terminated at bloom, curculio seldom causes real harm.

Crescent-shaped notches chewed along leaf edges by adults, and weakened, poorly nodulated plants from larval root feeding.

Rarely warranted in a cover crop - rotation and timely termination are enough; the stand is turned in before damage matters.

Rotate clover plantings, maintain vigorous stands, and terminate on schedule so pests don't build up; healthy fall covers usually outpace the damage.

A small weevil whose larvae feed on clover roots and nitrogen nodules and whose adults notch the leaf margins, occasionally weakening stands, though rarely a serious problem in a fall-terminated cover crop.

Seldom a real problem, since crimson clover attracts abundant aphid predators - it's more often part of the pest solution than a victim.

Colonies of large pale-green aphids packed onto shoot tips, tendrils, and flower stalks, thickest on the softest new growth. Aphids dropping off the plant the moment you brush against it - a habit fairly specific to this species. Sticky honeydew on the foliage below, ants running the stems, and white cast skins where a colony has been. Yellowing, stunting, downward-rolled leaves, or a mottled stand that does not grow away, which points to a virus the aphids brought rather than the feeding itself.

On a cover crop, usually nothing at all - the predators arrive and the stand outgrows it. Knock heavy colonies off with a jet of water, or pinch out and remove the worst-infested tips. Insecticidal soap sprayed directly onto the insects works if a stand is genuinely being checked, but it also hits the beneficials, so keep it to spot treatment. Never spray a stand you intend to pick shoots or flowers from without checking the product label for that use and its pre-harvest interval.

Encourage the beneficial insects that legume flowers already draw, and skip broad-spectrum sprays that remove them. Do not over-feed nitrogen, since soft lush growth is what the colonies build on - and a legume should not be getting nitrogen anyway. Check the growing tips weekly through spring, and rub out the first colonies by hand while they are small. Where virus has been a recurring problem in a legume rotation, avoid planting a new stand immediately downwind of an old one, since that is how the winged aphids move.

The pea aphid is a large, long-legged, pale-green aphid that specializes on legumes - peas, vetch, clover, alfalfa, lentil, faba bean - and colonizes the growing tips, tendrils, flower stalks, and developing pods. It builds fastest in the mild weather of spring, when a handful of overwintered females can become a coating within two weeks, and it drops off the plant readily when disturbed. On a vigorous cover-crop stand the feeding itself is usually cosmetic and is held in check by the ladybugs, lacewings, hoverflies, and parasitic wasps that legume flowers attract. What matters more is that it transmits viruses between legumes, including pea enation mosaic and bean leafroll, which stunt and yellow a stand out of all proportion to the number of insects present.