Southern Pea

The cowpea aphid is a shiny black species that builds fast on flower stalks and pods. Watch through bloom, mainly for the viruses it can spread - the feeding itself is usually cosmetic on vigorous plants.

Dense clusters of tiny insects packed onto shoot tips, flower buds, and the undersides of young leaves. Curled, cupped, or distorted new growth that never opens properly. A sticky shine on the leaves - and on whatever sits under the plant - that later goes black with sooty mold. Tiny white cast skins left behind where a colony has been feeding. Ants running steadily up and down the stems, which is often the first thing you notice. Mottled, streaked, or misshapen leaves that do not grow out can mean a virus the aphids brought with them rather than the feeding itself.

Knock the colonies off with a hard jet of water and repeat every few days - on most plants that alone ends it. Pinch out or prune off the worst-infested tips rather than treating the whole plant. If colonies keep rebuilding, spray insecticidal soap or horticultural oil directly onto the insects, covering leaf undersides, and repeat weekly until they are gone; treat early or late in the day, and never spray a wilted or heat-stressed plant. Avoid broad-spectrum insecticides - they kill the ladybugs, lacewings, and parasitic wasps that were about to solve the problem for you, and aphid numbers usually come back worse afterward. Anything you spray must be labeled for the plant you are treating; follow that label and observe its pre-harvest interval. On anything you eat, wash leaves, heads, and buds well before use, since aphids hide down in crowns, folds, and tight growth.

Go easy on nitrogen: the soft, lush growth that heavy feeding produces is exactly what aphids breed on. Check new growth once a week through spring and early summer so you catch colonies while they are still small, and rub the first few out with your fingers. Leave flowering plants nearby and skip broad-spectrum sprays - ladybugs, lacewings, hoverflies, and parasitic wasps do most of this work for free, and they only stay if there is something for them to eat. Keep ants off the plant where you can, since they protect aphids from those predators. Water steadily so plants are not stressed, and check any new plant over before you bring it home or move it indoors, since aphids usually arrive on something else.

Aphids are small soft-bodied sap-suckers - green, black, gray, pink, or waxy white, and mostly wingless - that gather in dense colonies on the tenderest new growth: shoot tips, buds, and the undersides of young leaves. They breed extremely fast in mild weather, so a few can become hundreds inside a week. Their feeding curls and distorts soft growth, and the sticky honeydew they excrete coats everything below and turns black with sooty mold. Ants often farm and defend the colonies for that honeydew. A few aphids are normal on almost any plant and a healthy plant shrugs them off; only dense, persistent colonies do real damage, and some aphids also spread plant viruses as they feed.

Resistant varieties are the practical defense where wilt has appeared.

Wilting, yellowing, and browning of plants (often in patches), stunting, and death, worse where flax has grown before ('flax sick' ground).

No cure for infected plants - remove them, and rotate away from flax for several years; resistant varieties and rotation are the real controls.

Grow resistant varieties; rotate away from okra (and related mallows) for several years; ensure good drainage; control root-knot nematodes, which open the door to wilt.

A soil-borne fungus (Fusarium oxysporum f. lini) that infects flax roots and clogs the water-conducting tissue, causing wilting, yellowing, stunting, and death, and persisting in the soil for years - the classic 'flax sick' soil problem.

Cowpeas are both a host and, in resistant varieties, a tool for managing nematodes - variety choice is everything in sandy soil. California Blackeye and Mississippi Silver are among the resistant ones.

Stunted, yellowing, unthrifty plants that wilt in the heat even though the soil is moist, and poor yields for no obvious reason. Confirm by digging: beady swellings strung along the roots and side rootlets, and root crops that are forked, branched, cracked or knotted rather than clean.

There is no in-season cure. Pull and destroy affected plants rather than composting them, and bring that ground back over several seasons with rotation, resistant varieties and marigold cover crops. Where a crop can be grown in a container of fresh mix, that sidesteps the problem entirely.

Rotate to non-hosts, and grow resistant varieties where they exist for your crop. A French marigold cover crop grown thickly the season before and turned in genuinely lowers populations. Build organic matter and mulch heavily, which feeds the soil life that suppresses them. Plant only clean stock, never move soil from an infested bed around the garden, and solarize badly infested ground through the hottest part of summer.

Microscopic soil roundworms (Meloidogyne species) that invade roots and force them to swell into beady galls. A galled root cannot take up water and nutrients properly, so the plant stunts, yellows, wilts in heat despite watering, and yields poorly, and root and tuber crops come up forked, knobbly, hairy or cracked instead of clean. They are worst in warm, sandy soils and build up steadily wherever a susceptible crop is grown in the same ground year after year. The wounds they leave also open the way for fusarium wilt and rots.

A generalist hot-climate soil disease shared with many vegetables; the tan sclerotia at the stem base are the giveaway.

Sudden wilting of individual plants, white fungal fans on the lower stem and surrounding soil, and tiny round tan-to-brown sclerotia at the base in hot, humid weather.

Remove and destroy affected plants along with the surrounding soil crust; the sclerotia persist, so rotation and sanitation are the long game.

Rotate with non-host crops (grasses/corn), improve drainage, bury or remove old debris, avoid deep mulch against stems, and don't overcrowd.

A hot-weather soil fungus (Sclerotium rolfsii) that attacks the stem at the soil line, collapsing plants; recognizable by white fan-like fungal growth and tan mustard-seed-sized sclerotia at the base.