Empress of India Nasturtium Flowers

Corn earworm is the same species as tomato fruitworm and cotton bollworm — a polyphagous caterpillar that bores into ears of corn through fresh silks, into tomato and pepper fruit, into lettuce heads, and into bean and pea pods. In sweet corn, losses can reach 50%. The species migrates north annually from southern overwintering grounds; in much of the northern US, it does not survive the winter when temperatures drop below 30°F.

Triggers: Overwinters as pupa in top 2-4 inches of soil where winter temps permit. North of I-70 (Illinois IPM): does not reliably overwinter — populations arrive via migration mid-July through September. Females prefer fresh corn silks for egg-laying; older silks rejected.

Risk fades when: Wisconsin Hort, Illinois IPM

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.

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.

On Empress of India: Tender new growth attracts aphid colonies.

Prevention: Encourage beneficial insects and hose off colonies early.

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

Birds cause significant damage to ripening fruit (berries, grapes, figs, cherries), to newly-planted seeds, and to seedlings. Damage peaks during fruit ripening on berries and during seed-head ripening on sunflowers. Robins feed low on bushes; starlings feed in upper canopy; species and feeding patterns vary widely. Even partial damage opens entry points for diseases and insects.

Triggers: Damage seasonal — peak during fruit ripening (June-August in north). Dry years intensify damage as birds use fruit for water. Proximity to forest edges or harvested grain fields amplifies pressure.

Risk fades when: OSU EM 9286

Waterlogged soils can rot seeds, stems, or roots.

On Empress of India: Waterlogged soils can rot seeds, stems, or roots.

Prevention: Use well-drained soil and avoid overwatering.

A group of cool-weather water molds that attack many ornamentals, including snapdragons, sunflowers, and impatiens-type bedding plants. It shows as pale or yellow patches on the upper leaf surface with a downy gray-to-purple growth on the underside, and young plants can collapse. It needs cool temperatures, high humidity, and leaf wetness.

Triggers: Favored by cool temperatures (about 50-70°F), humidity of 90% or higher, and free moisture on the leaves. Distinct from powdery mildew, which prefers dry leaves.

Risk fades when: Warm, dry weather suppresses it. Three dry days with highs above 75°F exits the active window; infected leaves stay damaged.

Flopping happens when stem strength can't support the plant's mass — usually because the plant grew too fast, didn't get enough sun to build strong stems, or got too much nitrogen which pushes soft leafy growth at the expense of structural strength. Rain and wind compound the problem by weighing down soft tissue. Some plants are inherently floppy — peony, dahlia, delphinium, large mum, tall sunflower — and need staking from the start. Others normally hold themselves up but flop when grown in shade or overfed. Stake early (in spring before plants have grown into their support) rather than late (when stems are already bent and a stake just preserves the deformity). Pruning or pinching tall plants when young encourages branching and reduces flop risk.

Triggers: Per MSU Extension: full sun produces sturdy self-supporting plants; shade or over-fertilization produces soft top-heavy growth. Rain and wind accelerate flop. Plants with naturally heavy blooms (peony, dahlia, large lily, hollyhock) need staking from start.

Risk fades when: Stake early in spring before too much growth. Late staking just preserves the bend. Pinch tall plants when young to encourage branching. Reduce nitrogen feeding if plants are floppy and overgrown.

Fuzzy gray mold on flowers, fruit, and wounded tissue. It thrives in cool, humid, enclosed spaces — University of Minnesota notes this is unlikely to be a problem in open home gardens and rare even in field tomatoes. It's mostly a greenhouse and high-tunnel concern, included here because SoilStack supports those growing environments.

Triggers: Develops at 60-75°F with humidity above 80%. Infection requires 4-6 hours of standing water on the plant tissue. UMN's data shows it's unlikely in open home gardens.

Risk fades when: Temperatures above 82°F suppress growth and spore production. That's the published threshold.

Japanese beetle adults feed gregariously on the foliage and flowers of more than 300 host species, skeletonizing leaves by chewing tissue between the veins. Larvae (white C-shaped grubs) damage turf and root systems. Adults are active during the warmest part of sunny summer days, when populations can rapidly defoliate roses, grapes, and ornamentals. Do not use Japanese beetle traps near plants — the lures attract more beetles than they catch.

Triggers: One generation per year. Overwinters as larva in soil. Adults emerge late June-early July (peak July). Adults active during warmest part of sunny days. Females lay 40-60 eggs in turf 3 inches deep.

Risk fades when: Multiple sources confirm one generation, peak July

Nasturtium leaf spot — includes both a bacterial leaf spot caused by *Pseudomonas* spp. and a fungal Cercospora leaf spot. Both produce spotted leaves and can collapse plants during wet weather. The bacteria persist in soil debris and can infect through roots; both pathogens spread by splashing water.

Triggers: Splashing water, overhead irrigation, infected debris, contaminated tools, and infected planting locations all spread these pathogens. Roots can also become infected by Pseudomonas through wet soil contact.

Risk fades when: Splash-driven spread requires wet foliage. A dry period interrupts new infection pressure.