Red-Stem Malabar Spinach

Microscopic soil-dwelling roundworms that burrow into plant roots and cause swollen knots (galls). Above ground, the plant looks stunted, yellowed, and wilted even with plenty of water. They attack over 2,000 plant species, so almost nothing is safe. They're most active in warm soil (70-85°F) and do more damage in sandy soils, where they move easily. Once a bed has them, populations stick around for years.

Triggers: Soil temperatures of 70-85°F are ideal for them; below 60°F they go dormant. Sandy soils make it easy for them to move and reproduce, while heavy clay slows them down considerably. In warm soil, a full generation completes in about 27 days.

Risk fades when: Activity drops sharply once soil cools below 60°F. Damage stops accumulating for the season, but the population stays in the soil and returns when warmth does.

A foliar disease that produces small, irregular tan to brown spots peppered with tiny dark fruiting bodies, usually starting on the older outer leaves. Heavy spotting reduces quality and can cause leaves to yellow and die. It spreads in wet weather and from infected seed or debris.

Triggers: Wet foliage and splashing water spread the spores. Favored by extended leaf wetness; spots carry tiny dark fruiting bodies visible up close.

Risk fades when: Dry foliage stops new spread. Three dry days exits the active window; existing spots remain.

Slugs and snails are nocturnal mollusks that chew irregular holes in leaves and clip off succulent seedlings. They leave characteristic silvery slime trails. Hermaphroditic and prolific, brown garden snails lay around 80 eggs per month for up to six clutches per year.

Triggers: Active at night and early morning in damp conditions. Coastal CA and southeast — active year-round. Spring rains and dense ground cover (mulch, debris, weeds) create harborage.

Risk fades when: Hot, dry summer weather drives slugs and snails into inactivity, so risk drops sharply once conditions turn warm and dry; populations are highest in cool, wet spring and fall, and in mild-winter coastal regions they can stay active year-round (UMN Extension, Penn State, UC IPM).

Thrips are tiny (1/16 inch) slender insects with fringed wings that puncture and rasp leaf surfaces, leaving silver stippling with black frass dots. The biggest concern is virus vectoring: western flower thrips is the principal vector of tomato spotted wilt virus (TSWV) and impatiens necrotic spot virus (INSV), which affect more than 600 plant species. Greenhouse and high tunnel infestations can be devastating.

Triggers: Hot dry weather; greenhouse/high tunnel environments. Female lays eggs inside leaf tissue. 2 larval stages feed; 2 non-feeding pupal stages in soil/litter. Lifecycle 10-21 days. Many overlapping generations. Bridge crops (spring wheat, peach, strawberry per NC State) build populations before vegetable hosts available.

Risk fades when: Infestations are worst in hot, dry weather; cool conditions slow development and heavy rain or overhead irrigation knocks populations down sharply, so risk fades as the weather turns cool and wet and rebuilds the following spring (UK Entomology, Cornell IPM).

Tiny sap-sucking insects that erupt off the leaf in a white cloud when you brush the plant. Despite the name they are not flies at all - they are Hemiptera, relatives of aphids, scales and mealybugs, and the name comes from the mealy white wax coating the adult's wings and body. They pierce the phloem and drain sap, so heavy populations yellow the leaves, dry them, and drop them. The bigger nuisance is honeydew: a sticky sugary excretion that coats the foliage, grows black sooty mold, and draws ants, which then chase off the natural enemies that would otherwise keep whitefly in check. UC IPM notes outbreaks often begin exactly that way - when biological control gets disrupted - and that once populations are high the pest is genuinely hard to manage. Bemisia nymphs go further, causing distortion, discoloration, and the leaf silvering that gives silverleaf whitefly its name. Both species vector plant viruses. Indoors and under cover they are far worse than in the open garden, because it never gets cold enough to knock them back and their generation time collapses to about 18 days at 80-90°F. The single highest-value habit is inspecting every new plant, undersides included, before it enters the greenhouse or the garden.

Triggers: UC IPM: whiteflies become abundant in vegetable and ornamental plantings especially during warm weather, and outbreaks often occur when natural biological control is disrupted. Greenhouse whitefly develops egg to adult in as little as 18 days, with fastest development between 80 and 90°F, so populations compound quickly under cover or on overwintered indoor plants. They favor succulent, actively growing tissue. Host range is broad - UC IPM lists alfalfa, beans, cucumbers, eggplants, grapes, lettuce, melons, peas, peppers, potatoes, strawberries, tomatoes and many ornamentals. Ants tending the honeydew interfere with the natural enemies that would otherwise suppress them.

Risk fades when: UC IPM: abundant especially during warm weather. Development is fastest at 80-90°F, so protected culture and indoor overwintering sustain populations outside the normal outdoor season - which is exactly when houseplants and tender herbs brought inside get hit.

Leafminers are tiny fly larvae that feed between the upper and lower surfaces of leaves, creating winding pale tunnels or blotchy patches. They rarely kill plants but can ruin the marketability of leafy greens grown for foliage. Allium leafminer is an emerging pest in the eastern US (first detected in Pennsylvania in 2017) that damages onions, garlic, leeks, and chives.

Triggers: Liriomyza trifolii: 1 generation in ~1 month at typical greenhouse temps, 14 days at 95°F, 64 days at 59°F (UC IPM). Adults active mid-day. Allium leafminer emerges late March-early April, second flight September-October. Broad-spectrum insecticides trigger outbreaks by killing parasitoids.

Risk fades when: Parasitic wasps usually bring populations down as the season progresses unless broad-spectrum sprays disrupt them; damage peaks in warm spring and summer flushes and eases in cooler weather, so risk fades with natural-enemy buildup and falling temperatures (USU Extension, PNW Pest Handbook, UC IPM).

Some seeds are simply slow, and the commonest way to lose them is to assume they have failed. Parsley is the classic. UMN Extension gives the range plainly - germination takes two to five weeks depending on seed freshness - and adds the practical instruction that matters most: because germination is so slow, mark the row. Gardeners who do not, dig the bed over or resow on top of seed that was working perfectly well. UMN also notes that emerging parsley seedlings look almost grass-like, with two narrow seed leaves, which is how they end up weeded out by mistake. New Zealand spinach is slow for a different reason - a hard, spiky seed coat that water struggles to penetrate. USU Extension: it germinates slowly, soaking the seeds in water for 24 hours before planting hastens germination, and seeds take up to two or three weeks to emerge and do not emerge uniformly. That last clause is the one to remember. Uneven emergence is normal here, not a sign of bad seed. Two remedies cover both mechanisms: soak the seed before sowing, and never let the surface of the seedbed dry out, because a seed that has begun to imbibe water and then dries will die.

Triggers: UMN Extension (parsley): the rate of germination depends on seed freshness, ranging from two to five weeks; to speed the process, soak the seeds in warm water for up to 24 hours before planting; cover seeds with one-eighth inch of soil and keep them moist; since germination is so slow, it is a good idea to mark the rows; emerging seedlings appear almost grass-like, with two narrow seed leaves opposite each other. USU Extension (New Zealand spinach): germinates slowly, but soaking the seeds in water for 24 hours before planting hastens germination; seeds take up to two or three weeks to emerge and do not emerge uniformly; the soil should be kept moist until seedlings begin to emerge; sow only after the last frost date, since this is a warm-season crop. NOTE ON EVIDENCE: parsley and New Zealand spinach are covered directly by the extension sources above. Malabar spinach (Basella alba) and horehound (Marrubium vulgare) are included here because they share the same practical remedy - soak, sow into warm soil, keep the surface evenly moist, and wait - but no extension source specific to their germination was found. Malabar spinach in particular is a tropical vine that will sit dormant in cold soil regardless of seed treatment.

On Red Stem Malabar Spinach: Seeds and seedlings dislike cold soil and may sit for weeks.

Prevention: Wait for real warmth and soak seeds before sowing.

Risk fades when: The most important intervention happens before sowing: soak the seed in warm water for up to 24 hours, and discard the soak water rather than pouring it onto the bed. Then sow shallowly - about an eighth of an inch for parsley - and keep the surface constantly moist. A seed that takes up water and then dries out dies, so fluctuating surface moisture is the real killer, not slowness. Mark the row. Parsley germinates so slowly that gardeners routinely dig the bed over or sow something else on top before it appears, and the grass-like seedlings are easy to weed out by mistake. Do not resow, and do not conclude the seed was bad, until five weeks have passed. Expect uneven emergence: some seed will come up in a week and stragglers three weeks later. For warm-season species such as New Zealand and Malabar spinach, wait for genuinely warm soil - cold ground stalls them no matter how the seed was treated.