Cylindra Beets

A virus spread by the beet leafhopper (*Circulifer tenellus*), mainly a problem in the western US — California, Arizona, Colorado, Idaho, New Mexico, Utah, and Washington. It has a broad host range, infecting beets, tomatoes, peppers, beans, and cucurbits. Infected plants develop curled, thickened leaves with purple-tinged veins on the undersides, stunted growth, and fruit that ripens prematurely. The leafhopper transmits the virus while migrating: it lands and briefly probes plants, and a single feeding of just a few seconds is enough to infect.

Triggers: Driven by leafhopper migration, not weather directly. The bugs overwinter in foothill weeds and head for gardens in late spring once the wild vegetation dries up. Hot, dry years push more of them into populated areas. Symptoms show up 7-14 days after a single leafhopper visit — and a single bite is all it takes.

Risk fades when: Migration peaks in late spring; once the main wave passes, transmission risk drops sharply. The virus doesn't hide in soil or plant debris between seasons, so risk resets each year.

A soil-borne fungus (*Sclerotium rolfsii*) that attacks plant stems right at the soil line during hot weather. It hits over 500 different plant species. Two telltale signs to look for: white fan-shaped fungal growth on the lower stem, mulch, and soil surface, and tan-brown spherical sclerotia (they look like mustard seeds) on infected tissue. Most active during sustained heat with humid conditions.

Triggers: Optimal at 86°F (30°C) soil and air temperature with humid conditions. Inactive below 70°F. Most damaging during sustained mid- to late-summer heat waves. It extends further north in warmer-than-normal seasons.

Risk fades when: Sustained cooler weather — highs below 80°F and overnight lows below 70°F for 5+ days — reduces fungal activity. The sclerotia (resting bodies) persist in soil for years, so resolution is seasonal, not curative.

A seedling killer caused by several different fungi working together. It hits vegetables, flowers, herbs, microgreens, and cover-crop seedlings the same way — seeds rot before they emerge, or young seedlings collapse right at the soil line. Wet seed-starting mix and poor airflow in seedling trays are the classic conditions.

Triggers: Wet soil or starting mix, poor drainage, seedlings packed too tightly, contaminated trays or media, and stagnant air all favor damping-off.

Risk fades when: Drying the soil surface and improving airflow slows new spread. Collapsed seedlings don't recover, but the rest of the tray can be saved.

The Delia root-maggot complex includes the cabbage maggot (D. radicum) on brassicas and root crops, the seedcorn maggot (D. platura) on bean/pea/corn seedlings, and several other species. Larvae tunnel into roots, basal stems, and seeds, killing seedlings outright or creating tunnels that ruin root crops for market. A 2021 Oregon industry survey found 100% of root crop growers reported cabbage maggot damage; 44% with 10-25% yield loss.

Triggers: Overwinter as pupae in soil/crop residue. Adults emerge early spring (300-600 GDD base 40°F after Jan 1 in PNW). Cool moist soils favor egg survival; soil >95°F in top 2-3 inches kills eggs. Multiple generations per year. Seedcorn maggot attracted to decaying organic matter — high risk after fresh-incorporated cover crop.

Risk fades when: Cool, wet weather favors root maggots and damage is worst in early spring, dropping to its lowest in midsummer when soil temperatures above about 95 F kill the eggs; a late-summer flight can still injure fall root crops, so risk returns as weather cools (UMaine Extension, Wisconsin Hort, UNH Extension).

Aphids are soft-bodied sap-sucking insects that cluster on tender new growth. Most established plants tolerate moderate populations and will outgrow damage on their own, but aphids are the most important plant virus vectors in the garden, transmitting more than 100 plant viruses including potato leafroll, cucumber mosaic, and turnip mosaic. Honeydew excreted while feeding supports sooty mold growth and attracts ants that protect aphids from natural enemies.

Triggers: Optimal development at ~75°F (green peach aphid) per UC IPM Floriculture; melon aphid develops fastest above 75°F. Many species heat-intolerant above 90°F and crash in mid-summer. Soft new growth and over-fertilization with high N favor population buildup. Females give live birth parthenogenetically most of growing season — one generation in ~1 week under optimal conditions.

Risk fades when: Per UC IPM and Clemson HGIC, populations crash in mid-summer heat (>90°F) for many species, return in cooler conditions

Root crops are biennials that flower in their second year after winter cold. When spring-sown plants experience cold exposure (below 50°F for 1-4 weeks) during their juvenile stage, then warm days arrive, they may interpret the cold as 'winter complete' and flower in their first season instead of bulking up roots. Beets, chard, spinach, lettuce, radishes, and turnips have short vernalization requirements (1-4 weeks) — direct-seeded crops are most at risk. Carrots, parsnips, storage onions, and fall-set shallots need much longer vernalization periods, so they bolt less from spring cold. Once the plant commits to flowering, root development slows or stops.

Triggers: Per MSU Extension: beets, chard, spinach, radishes, turnips have 1-4 week vernalization requirements — direct-seeded plantings most at risk in cold springs. Carrots, parsnips, storage onions need 8-12 weeks vernalization, so rarely bolt from spring cold. Plants must have reached juvenile size threshold to be vernalization-susceptible.

Risk fades when: Once bolted, root development stops. Harvest whatever's usable. Fall sowings rarely bolt because plants don't reach vernalization-susceptible size before harvest.

*Cercospora beticola* causes circular gray-tan spots ringed with dark purple-brown margins on the leaves. It primarily affects beets and Swiss chard, with documented cross-infection to Malabar spinach (*Basella alba*) and New Zealand spinach (*Tetragonia tetragonoides*) — even though those are different botanical families, peer-reviewed cross-inoculation studies confirmed the same pathogen. Favored by warm, humid conditions with leaf wetness.

Triggers: High humidity, extended leaf wetness, rain or splash, and infected debris or seed all favor infection and spore production.

On Cylindra: Humid weather can trigger Cercospora on older leaves.

Prevention: Water at soil level and rotate crops.

Risk fades when: Dry leaves reduce both new infections and the spore production that fuels spread.

Flea beetles are small (1/16-inch) shiny beetles that jump like fleas when disturbed. They chew small round 'shothole' or 'pinhole' damage in leaves and can destroy emerging cotyledons of broccoli or eggplant in 24 hours. Most species are host-family specific — crucifer flea beetle on brassicas, tuber flea beetle on potatoes, eggplant flea beetle on solanaceous crops.

Triggers: Overwinter as adults in leaf litter and field margins. Active at mid- to late-spring temperatures. Warm winter → higher next-spring populations (NC State). Hot dry conditions amplify damage on stressed seedlings.

Risk fades when: UMN: 1-2 generations in Minnesota, populations crash after mid-June

Forked roots happen when a taproot hits a physical obstruction — a stone, hard clod, buried debris, compacted subsoil — and splits into two or more roots going around it. Common in heavy clay or rocky soils, especially when the bed wasn't loosened to a full 12-inch depth before sowing. Other contributors: excessive nitrogen fertilization pushes hairy lateral roots, transplanting damages the taproot, crowded sowing forces neighboring roots to twist together, and root-knot nematodes mimic the symptom. Prevention is in bed prep — loosen soil to 12 inches, remove stones larger than 1/2 inch, avoid fresh manure or heavy nitrogen the season of planting. Direct-seed rather than transplant. Thin seedlings to proper spacing.

Triggers: Per UMN/UIllinois Extension: forking from physical obstructions in soil (stones, clods, debris), compacted subsoil, excessive nitrogen, or crowded plantings. Root-knot nematode infestation causes a similar symptom but with visible galls.

Risk fades when: Affected roots are still edible but cosmetic. For next planting: deep-loosen bed 12 inches, sieve out stones, work in compost (not fresh manure or high-N), direct-seed not transplant, thin to proper spacing.

Beet rows come up in clumps no matter how carefully you sow, and the reason is that a beet 'seed' is not a seed. It is a dried fruit - a seedball - containing two to five embryos fused together, so a single sown seed sends up a tight cluster of seedlings with intertwined roots. This is normal beet biology, not bad seed. Left alone, those seedlings strangle each other and you get a bed of leafy tops with small or misshapen roots beneath. SDSU Extension lists exactly that outcome: all tops with no roots or small roots is usually caused by planting too close or by not thinning, with excess nitrogen contributing. The thinning has a deadline. Do it once the seedlings have two sets of true leaves, before the roots tangle, and cut them off at soil level with scissors rather than pulling - pulling drags up the neighbours you meant to keep. Thin to 3 to 4 inches. The thinnings are the first harvest: roots and greens are both edible. A handful of monogerm table-beet cultivars exist and need no thinning, but most beets, and chard too, are multigerm.

Triggers: Beet seed is naturally multigerm: two or more flowers fuse into a cluster and produce a seedball, so when it germinates several seedlings emerge close together and often intertwined, requiring thinning (Nebraska Extension, R. Harveson). SDSU Extension: all tops with no roots, or small roots, is usually caused by planting too close or by not thinning; excessive nitrogen fertilization also contributes to top growth at the expense of root growth. Thin at the two-true-leaf stage before roots tangle, cutting at soil level rather than pulling. A few monogerm table-beet cultivars carry a single embryo and do not need thinning. Note that Swiss chard shares this multigerm seed structure, while turnip and radish seed is single-germ and this disorder does not apply to them.

On Cylindra: The seedball often contains multiple embryos and needs thinning after emergence.

Prevention: Thin promptly so roots do not crowd each other.

Risk fades when: Crowded roots do not recover once they have pressed against each other. Thin early: at two sets of true leaves, or when seedlings are about 3 inches tall, snip the surplus at soil level with scissors. Pulling them out dislodges the roots of the plants you are keeping. Eat the thinnings - both roots and tops. If a bed is already past that stage, harvest the crowded clumps young as baby beets and greens rather than waiting for roots that will not size up. Keep nitrogen moderate; a rich bed makes the all-tops problem worse.