Pests, Disease & IPM

Definitions for the pests, diseases, and pest-management terms most often seen on labels and in grower guides. Each entry explains what the organism or condition is and how it affects plants, not how or when to treat it.

aphid

A small, soft-bodied insect that feeds on plant sap using piercing mouthparts, often clustering densely on new growth and the undersides of leaves. Aphids reproduce very quickly, with populations able to multiply many times over within a short period under favorable conditions.

banker plant system

A method of sustaining a population of beneficial insects by growing a separate, non-crop plant that hosts a harmless prey species for them to feed on. This gives the beneficial insects a continuous food source and breeding ground independent of whether the actual pest is currently present on the crop.

beneficial insects

Insects that help a crop rather than damage it, either by preying on pest species, parasitizing them, or pollinating flowers. In pest management they are often introduced deliberately to establish a population that keeps pest numbers down without chemical intervention.

biological control

Using living organisms — predators, parasitoids, or pathogens — to reduce a pest population, rather than a chemical treatment. It relies on a natural enemy already present or introduced into the growing area, and its effect builds over time as the beneficial population establishes rather than acting immediately.

broad mite

A microscopic mite too small to see without magnification, which feeds on young leaves and buds, injecting saliva that distorts new growth. Damage often looks like a nutrient deficiency or hormonal stress at first, since curled, hardened new leaves resemble other unrelated growth problems.

bud rot / botrytis

A fungal infection that develops inside dense flower or fruit clusters, such as grape bunches or berry trusses, where moisture becomes trapped and airflow is poor. Because the rot starts inside the cluster, it is often invisible from the outside until the tissue has already turned brown and mushy internally.

caterpillar / budworm

The larval stage of moths or butterflies, which chews through leaves, stems, or developing buds and flowers depending on the species. Budworms specifically target flower and fruit structures, boring into them rather than feeding externally, which makes their damage harder to spot early.

damping off

A fungal or water-mold disease that attacks seedlings at or just below the soil line, causing the stem to weaken, thin, and collapse, killing the seedling within days. It thrives in cool, overly wet, poorly ventilated conditions common in seed-starting trays.

dieback

The progressive death of shoots, branches, or roots starting from the tip and moving inward toward the main stem or trunk. It can result from disease, environmental stress, or physical damage, and the pattern of which parts die first often helps identify the underlying cause.

fungicide

A substance that kills fungi or inhibits their growth, targeting the organisms responsible for diseases such as powdery mildew, botrytis, or root rot. Different fungicides work through different mechanisms — some disrupt fungal cell membranes, others interfere with fungal respiration or reproduction — which is why product types vary in which diseases they affect.

fungus gnat

A small dark fly whose larvae live in moist growing medium and feed primarily on fungi and decaying organic matter, though they can also damage fine root hairs when present in large numbers. Adult gnats are most visible flying near the soil surface, and their presence usually signals a medium that stays wet longer than it should.

Integrated Pest Management (IPM)

An approach to pest control that combines multiple tactics — monitoring, biological control, cultural practices, and chemical control when needed — rather than relying on one method alone. Decisions are based on regularly checking plants for pest presence, so action is taken only when a problem is actually identified. See plant protection.

lacewing

An insect whose larvae are aggressive predators of soft-bodied pests such as aphids, feeding on many prey items during their larval stage before maturing into the winged adult, which mainly feeds on nectar and pollen. Lacewing larvae are released or attracted to a growing area specifically for their predatory stage.

ladybug (ladybird beetle)

A small round beetle whose larvae and adults both prey on aphids and other small soft-bodied insects. A single ladybug can consume large numbers of aphids over its lifetime, making it one of the most commonly released beneficial insects for aphid control.

leaf miner

The larva of certain flies, moths, or beetles that lives and feeds inside the leaf tissue itself, tunneling between the upper and lower leaf surfaces. This creates a visible winding trail or blotch on the leaf, distinct from surface-feeding damage since the insect never leaves the leaf's interior during this stage.

mottling

An irregular pattern of light and dark green or yellow patches on a leaf, often an early sign of viral infection though it can also result from nutrient imbalance or genetic variegation in some plants. The uneven color distribution is what distinguishes it from a uniform yellowing across the whole leaf.

necrosis

The death of plant cells or tissue, appearing as brown, black, or dry patches on leaves, stems, or roots. It is a symptom rather than a specific disease, and can result from infection, chemical injury, nutrient imbalance, or physical damage to the affected area.

neem oil

An oil extracted from the seeds of the neem tree, containing azadirachtin and other compounds that disrupt insect feeding, growth, and reproduction. It affects a broad range of soft-bodied pests and has some activity against certain fungal pathogens as well, which is why it appears in both insect and disease contexts.

parasitoid wasp

A small wasp that lays its eggs inside or on a host insect, usually a pest species; the wasp larvae then develop by consuming the host, eventually killing it. Different parasitoid species target different host insects, so the wasp used depends on which pest is present.

powdery mildew

A fungal disease that appears as a white to gray powdery coating on leaf surfaces, stems, and sometimes flowers. Unlike many fungi, it can develop even in relatively dry conditions as long as humidity is high, and it spreads through airborne spores that land and germinate on new leaf surfaces.

predatory mite

A mite species that feeds on other mites and small insects rather than plant tissue. Used as a biological control agent against pest mites, it is released onto plants where it hunts prey directly and reproduces as long as a food source remains available.

pyrethrin

A group of natural insecticidal compounds extracted from chrysanthemum flowers, which act on the nervous system of insects on contact. Pyrethrins break down quickly when exposed to light and air, which is a key difference from the longer-lasting synthetic compounds — pyrethroids — modeled after them.

root rot (Pythium)

A disease caused by water-mold pathogens, most commonly Pythium, that attacks roots in overly wet or poorly oxygenated growing media, turning them brown, soft, and slimy instead of firm and white. Above-ground symptoms — wilting despite adequate water — often appear only after significant root damage has already occurred.

russet mite

A microscopic, cone-shaped mite that feeds on plant surfaces, causing leaves and stems to develop a bronzed or rust-colored, slightly greasy appearance as cell layers are damaged. It spreads quickly because its small size lets it move on air currents and contaminated tools.

rust (plant disease)

A fungal disease named for the orange, yellow, or reddish-brown powdery pustules it produces, usually on the underside of leaves. These pustules release spores that spread the infection to other leaves and plants, and heavy infection can cause significant leaf yellowing and premature drop.

scorch

Browning and drying of leaf tissue, typically starting at the tips or edges, caused by conditions that damage cells faster than the plant can compensate — such as intense light, high salt concentration, or low humidity combined with heat. The dead tissue does not recover once it has browned.

Septoria leaf spot

A fungal disease that produces small, circular spots with dark borders and paler centers on leaves, typically starting on lower, older foliage before moving upward. As spots multiply and merge, affected leaves yellow and drop, gradually reducing the plant's leaf area.

spider mite

A tiny arachnid, not an insect, that feeds by piercing plant cells and extracting their contents, typically on the underside of leaves. Heavy infestations produce fine webbing across the plant and cause leaves to show a stippled, pale discoloration as cell damage accumulates.

spinosad

An insecticidal compound derived from a soil bacterium, which acts on the nervous system of insects that ingest or contact it, particularly caterpillars, thrips, and leaf miners. Because of its bacterial origin, it is classified differently from both synthetic chemical insecticides and plant-derived ones like pyrethrin.

thrips

Slender, fast-moving insects that scrape plant surfaces and feed on the released cell contents, leaving behind silvery or bleached streaks and small dark specks of excrement. They also feed inside flower buds, and several species are known to carry plant viruses between hosts as they move.

whitefly

A small, moth-like insect that feeds on plant sap from the underside of leaves and excretes a sugary residue called honeydew as a byproduct. This honeydew can support the growth of sooty mold on lower leaves, and disturbed plants often release a visible cloud of adults from the foliage.

wilt

A drooping, limp appearance in leaves and stems caused by insufficient water reaching plant tissue, whether from drought, root damage, or a vascular disease blocking water movement inside the plant. Distinguishing which cause is responsible requires checking soil moisture and root condition rather than the wilting appearance alone.