Sunflower

Birds find ripening fruit and seed before you do. Robins, waxwings, starlings, catbirds, jays, sparrows, finches, blackbirds, and doves all work a garden, and the pressure arrives in a narrow window - the last days before harvest, when sugar rises, color changes, and the crop softens or the grain hardens. A flock can strip a small planting in a day or two, and birds that only peck rather than take whole fruit still leave wounds that rot or draw wasps. Squirrels, chipmunks, and other wildlife usually turn up on the same crop at the same time. This is competition rather than disease: the birds are not harming the plant, and a big tree or a heavy-cropping bush often has enough for everyone - but on a small planting it can be the difference between a harvest and none.

Watch for: Fruit disappearing from the outermost, most exposed parts of the plant first, and from the top of a tree where you cannot reach anyway. Single neat pecks and gouges in ripening fruit, with several fruits sampled rather than one eaten through - the classic sign that it was birds rather than an animal. Heads of grain or seed going visibly lighter and emptier as they ripen, with hulls and chaff scattered underneath. Freshly sown seed vanishing off the surface of a bed before it germinates. Bird traffic in and out of the plant picking up as the crop colors, and birds waiting on nearby wires and branches. Wasps arriving at the pecked and split fruit shortly afterward.

Prevent: Net, and net early. Bird netting draped over a frame or hoops so it stands off the fruit, with the edges closed at ground level, is the only thing that reliably works at harvest scale - and it has to go on before the crop starts to color, because once birds have found the food they are far harder to displace. Keep fruit trees small enough that netting them is actually feasible; that decision gets made years earlier, at planting. Bags of mesh, organza, or paper slipped over individual heads, clusters, or prize fruit protect a small crop without netting the whole plant. Then shorten the exposure: pick promptly and completely rather than leaving ripe fruit hanging as a lure, clear split and dropped fruit that draws birds and wasps alike, and where a crop can finish off the plant, harvest a little early and ripen or dry it under cover. Rake in or cover broadcast seed so it is not lying in plain view.

Treat: There is no treatment once a crop is being taken - only protection and timing, so the answer is to get netting on and to pick what is ready. Reflective tape, flash ribbon, spinners, and decoy predators do work, but only for a few days at a time: birds habituate fast, so move and rotate them and never rely on them as the main defense for a crop you care about. Cut and gather grain or seed heads a little early, at firm dough, and finish drying them under cover instead of leaving them standing for the flocks. Plant a little extra, or a decoy crop the birds prefer, and accept sharing anything that crops heavily. On a wild or foraged patch, fruit going to birds and small mammals is the point of the plant rather than a problem to solve.

Sunflowers are a wildlife magnet by design. If you want the seeds yourself, tie cheesecloth, fine mesh, or paper bags over the heads as the seeds plump, or cut and dry the heads indoors once the backs start to brown. If you love birds, leave the heads standing as a natural feeder.

A moth whose larvae are the main seed pest of sunflowers: they web and tunnel through the flower head, feeding on developing seeds and opening the head to rot.

Watch for: Silk webbing across the face of the flower head, frass (sawdust-like droppings) among the seeds, and hollowed or tunneled developing seeds.

Prevent: Plant early to bloom before peak moth flight, encourage natural predators and parasitic wasps, and check heads as they flower.

Treat: Bt (Bacillus thuringiensis) or spinosad applied to the flower head as it opens catches young larvae before they bore in; remove and destroy badly infested heads.

The most damaging pest if you're growing sunflowers for seed - timing the bloom to dodge the moth flight is the best home defense.

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.

Watch for: 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.

Prevent: 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.

Treat: 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.

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.

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.

Watch for: 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.

Prevent: 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.

Treat: 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.

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.

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

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

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

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

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

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

Watch for: 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.

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

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

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

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.

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

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

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

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

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.

Watch for: 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.

Prevent: 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.

Treat: 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.

Sunflowers draw a lot of beneficial insects, so aphid outbreaks are usually kept in check naturally; heavy honeydew is the main nuisance.