Sunflower

Rodents raid at both ends of the season - sprouting seed in spring and ripe seed in fall - so protect the crop at planting and again at maturity. Cutting the heads and drying them somewhere rodent-safe is the surest way to save the seed.

Chewed husks, shells or hulls scattered under the plant, fruit and nuts vanishing as they ripen, and gnawed or half-eaten windfalls. On new plantings: freshly dug holes and scattered soil, bulbs missing or gnawed, dug-up seed rows, vole runways under the mulch, and gaps in spring where you know you planted.

There is no rescue for what has already been eaten, so this is a prevention problem. Re-cover disturbed plantings with mesh promptly, replant losses inside cages, and trap or exclude persistent diggers where that is legal locally. On a large tree, accept that you will share the crop and concentrate on gathering promptly.

For a crop on the plant, timely and frequent harvest is the real defense - gather daily through the ripening window rather than leaving anything to hang, and pick slightly early to finish indoors where the crop allows it. Net or bag what you can reach. For bulbs and sown seed, lay wire mesh or hardware cloth over the planting, plant deeper, use buried wire baskets, and clear away the papery tunics and debris that advertise a fresh planting. Trunk baffles slow climbers on isolated trees, clearing jumping routes from nearby trees and roofs helps, and removing brush cover reduces the rodents sheltering nearby.

Squirrels, chipmunks, voles and mice are the wildlife that competes with you most directly for a crop. They take ripening nuts, seed and fruit off the plant, usually before you judge it ready, and cache what they do not eat. They also dig up freshly planted bulbs and sown seed, and voles tunnel in to gnaw bulbs and roots underground through winter. They climb anything, they know exactly when a crop is ripe, and a determined pair can clear a small tree or a new planting in a few days.

Most damaging to young seedlings in cool, wet springs; established plants that escape early infection usually grow through it.

Stunted, pale, thickened seedlings, yellow blotches on upper leaf surfaces with white fuzzy growth beneath, and sometimes downward-cupped leaves.

No cure for infected plants - remove and destroy them; the pathogen persists in soil, so rotation and resistant seed are the defense.

Plant resistant varieties and clean seed, ensure good drainage, avoid overwatering young plants, and rotate away from sunflowers.

A soil- and seed-borne water mold (Plasmopara halstedii) that stunts and yellows seedlings and young plants, with white downy growth on leaf undersides in cool, wet conditions.

Mostly a threat to seedlings and young plants; a full-grown sunflower shrugs off the leaf damage.

Chewed and skeletonized leaves, and small cream-and-brown striped beetles (or humpbacked greenish larvae) feeding on the foliage.

Hand-pick beetles and larvae; spot-treat heavy infestations on young plants with spinosad or neem if defoliation is severe.

Rotate plantings, clean up debris, and encourage natural enemies; vigorous established plants outgrow light feeding.

A striped beetle (and its larvae) that chews sunflower foliage, defoliating young plants when numerous, though established plants usually tolerate the damage.

Usually cosmetic on a healthy plant, but heavy rust late in the season can shrink seed heads.

Small rusty-orange to reddish-brown raised pustules scattered on the leaves (mostly undersides), which rub off as powder; heavy infection yellows and kills leaves.

Remove badly affected lower leaves; fungicides are rarely needed in home gardens on plants maturing before rust peaks.

Grow resistant varieties, space for airflow, avoid overhead watering, rotate, and remove crop debris where spores overwinter.

A fungal disease (Puccinia helianthi) producing cinnamon-brown pustules on leaves that reduce photosynthesis and vigor in warm, humid weather.

Sunflower is fairly tolerant and often still produces despite infection, but badly affected plants stunt and wilt in summer heat, and the wilting leaves are mottled yellow and green between the veins.

One branch, one limb or one side of a plant wilting, yellowing and browning in summer while the rest carries on normally - the lopsided pattern is the tell - and leaves that wilt and then hang on rather than dropping cleanly. Cut into affected wood and look for olive-green, grey or brown streaking along the grain; in a cut vegetable stem it shows as a ring of discolored dots. On vegetables, lower leaves yellow in a wedge from the margin inward, and the plant wilts at midday but recovers overnight in the early stages.

There is no cure and nothing to spray. On a tree or shrub the aim is to keep it alive long enough to compartmentalize the fungus, which many plants manage for years: prune out dead and wilting branches well below the discolored wood, sanitize the pruners between cuts, water deeply through dry spells, mulch, and feed lightly rather than pushing it with a heavy feed. On vegetables, pull and bin affected plants rather than composting them, and move that crop to clean ground or to containers of fresh mix. Do not replant the same species where one has died.

There is no way to sterilize garden soil of it, so prevention is plant choice and plant vigor. Do not replant a susceptible species where one has already died of it. Grasses, conifers, ginkgo, hawthorn, hornbeam, honeylocust, oak and beech do not get it, and many vegetable varieties carry bred-in resistance - the V in a VFN code on the seed packet. Rotate susceptible vegetables on a long cycle and keep them off ground where the disease has shown. Buy clean stock, avoid wounding roots with spades and machinery, and keep woody plants steadily watered, mulched and only lightly fed, because a vigorous plant walls the fungus off far better than a stressed one.

A soil fungus (Verticillium dahliae and relatives) that enters through the roots and grows upward inside the water-conducting tissue, plugging it from within. The plant is not being eaten or rotted, it is being cut off from its own water supply, which is why the signature symptom is one branch or one side wilting and browning while the rest looks perfectly healthy. Cut into affected wood or stem and the tissue is streaked olive-green, grey or brown. The host range is enormous - maples, redbud, olive, tomato, potato, pepper, eggplant, strawberry and many more - and the fungus survives in soil for years as tough resting structures, so infected ground stays infected. Grasses and conifers do not get it.