Sweet Potato

A major cause of storage losses; careful handling, proper curing, and clean slips prevent most of it.

Firm, dark, sunken circular lesions on roots (especially after digging and in storage), and blackened stem bases with yellowing vines.

No cure - discard affected roots whole (don't store them, as it spreads in storage). Don't trim out the bad spots and eat the rest, and don't feed culls or peelings to livestock or poultry: a rotting root makes bitter toxins that spread past the visible lesion, and cooking does not make them safe. Start clean next season with certified slips and fresh ground.

Use clean certified slips, rotate 3-4 years away from sweet potato, handle roots gently at harvest to avoid wounds, cure properly, and sanitize storage areas and tools.

A fungal disease (Ceratocystis) causing sunken, dark, greenish-black circular spots on roots and dark cankers on stems, worsening in storage and making roots bitter and inedible.

Leaf damage is usually cosmetic, but the sweet potato flea beetle's larvae also scar the roots with narrow grooves, which downgrades the crop's appearance - a bigger deal for market growers than home cooks. The larvae cannot be reached by a foliar spray, so rotation and clean beds matter most.

Dozens of pinhead-sized round holes peppered across the leaves, thickest on the youngest, most tender growth. Tiny beetles that spring away as you brush the plants or lean in for a closer look - that jump is the identification. Seedlings that go lacy and stop growing, and transplants that sit and sulk instead of taking off. Damage heaviest in warm, dry weather and along the edge of a bed nearest weedy ground or last year's crop debris. On root crops, shallow narrow grooves or channels scarring the skin at harvest, from larvae feeding underground.

Row cover and healthy fast growth carry most crops through, and on an established plant the damage is usually cosmetic and needs nothing at all. Where a young planting is genuinely being stripped, kaolin clay coats the leaves and deters feeding, and spinosad will knock the beetles back. Spinosad is acutely toxic to bees while the spray is still wet - apply it at dusk when bees are not flying, never onto plants in flower, and follow the product label. Anything you spray must be labeled for the plant you are treating, and you must observe its pre-harvest interval on a crop you are picking. Yellow sticky traps are useful for telling you when the beetles have arrived. Where the damage falls on the part you eat, harvesting young often beats them outright; where you are growing for a root or a fruit, leaf damage can simply be tolerated. Larvae feeding underground cannot be reached by a foliar spray, so rotation and clean beds are what work against those.

Floating row cover or fine insect mesh, laid over the bed from the day of sowing or transplanting and sealed at the edges so nothing can walk in underneath, is the single best defense - and on the crops they favor it is close to essential. Leave it on until plants are large and growing strongly, or until flowering on anything that needs pollinating. Push growth: a well-watered, unchecked plant outgrows the damage, so the whole game is getting seedlings through their vulnerable weeks fast. Keep beds weed-free, since related weeds host the beetles alongside your crop, and clear crop debris at the end of the season where the adults overwinter. Rotate away from a bed that grew a related crop last year. Where you can, shift sowing dates - cooler-season and fall plantings often miss the peak of adult feeding entirely.

Flea beetles are tiny dark beetles - often shiny black or bronze, rarely more than a couple of millimeters long - with enlarged back legs that let them spring away like fleas the moment you lean in. The adults chew countless small round pits and shot-holes through leaves, giving the foliage a peppered, buckshot-riddled look. They overwinter as adults in leaf litter, hedgerows, and crop debris, emerge hungry in spring, and are worst in warm dry spells. The damage is mostly a seedling and transplant problem: a small plant with a few leaves can be checked, stunted, or killed outright, while the same plant shrugs them off once it is large and growing strongly. Different species specialize on different plant families, so the beetles hammering your brassicas are not the ones on your nightshades. Some species also have larvae that feed on roots and tubers underground.

Damage is cosmetic tunneling that opens roots to rot; new gardens broken from lawn are the classic trouble spot.

Thin, clean holes and shallow tunnels in roots at harvest, and stiff orange-brown 'worms' in the soil - worst in beds recently converted from lawn or sod.

No rescue for holed tubers - trim and eat them soon (they don't store); trap with buried potato or carrot pieces before planting to gauge and reduce numbers.

Avoid planting potatoes into ground that was grass/sod the year before; rotate; cultivate the soil to expose larvae to birds; bait with buried potato chunks and remove them with their feeders.

The tough, wiry, orange-brown larvae of click beetles, which live in soil for years and bore narrow holes and tunnels through storage roots.

Sweet potato greens are genuinely palatable to deer and rabbits, so in deer country the foliage needs protecting even though the crop is underground. Vines usually regrow if the roots are undisturbed, but heavy repeated browsing cuts the harvest.

Growth cleanly missing overnight, with the plant browsed back to a level line about as high as a deer can comfortably reach. Ragged, torn stem ends rather than the clean angled cut a rabbit leaves - the single most reliable identifier. Buds and flowers gone while the foliage below is untouched, since deer often take the best part first. Hoof prints and droppings in soft ground near the damage. Repeat visits, with fresh damage each morning once a planting has been found. On young trees, shredded and stripped bark and broken low branches in autumn - that is antler rubbing rather than feeding.

There is no chemical fix, only exclusion and recovery. Get physical protection up immediately after the first damage, because deer return to a known meal, and reinforce or rotate whatever you were relying on before. Most plants regrow from browsing if the crown and roots are intact - feed and water a grazed plant and protect the regrowth while it comes back. What does not recover in the same season is anything whose buds or flowers have been taken, and a young tree whose bark has been rubbed right around the trunk is usually lost. Where deer pressure is genuinely heavy, the honest answer is to fence properly or to grow the plants deer leave alone, rather than to keep replacing losses.

Fencing is the only thing that reliably works. Eight feet is the standard for excluding deer, or two parallel four-foot fences a few feet apart, which they will not jump because they cannot judge the landing. Short of that, cage individual plants: a sturdy wire cage or trunk guard around every young tree, left on until the trunk is thick and the canopy is above browse height, prevents both browsing and antler rubbing and is the single highest-value thing you can do for a young tree. Repellent sprays do help at moderate pressure, but they wash off and deer habituate, so reapply after rain and rotate between different types through the season. Motion-activated sprinklers, scent deterrents, and noise devices work for a while and then stop. Siting matters too: plants close to the house, in daily traffic, and screened behind other planting get browsed less than the same plant out at the boundary.

Deer are the largest garden problem across much of the country, and where pressure is high they set the limit on what you can grow at all. They browse at night and around dawn and dusk, taking tender shoots, leaves, buds, flowers, and fruit within about five feet of the ground, and they come back night after night to anything they have found and liked. Because they have no upper incisors they tear rather than cut, leaving ragged stem ends - that is how you tell deer damage from a rabbit's clean angled cut. In fall, bucks rub their antlers on young trunks and can strip the bark right around a stem, which kills a young tree outright. Palatability varies enormously between plants and between seasons: a herd short of food in late winter eats things it ignores in June, and no plant is truly deer-proof.

Clean, certified slips are the front-line defense, since the fungus rides in on infected planting stock.

Lower leaves yellowing and wilting, stunting, and brown-streaked, rotted stem bases; whole plants may collapse in heat.

No cure once infected - remove and destroy affected plants and rotate the bed.

Grow resistant varieties (many sweet potatoes list fusarium resistance), plant clean slips, rotate away from sweet potato, and ensure good drainage.

Soil-borne fungus that plugs the plant's water vessels, causing yellowing, wilting, and stem rot, often persisting for years in soil; spread on infected slips.