Pole Bean

A coppery, black-spotted beetle that looks like an oversized ladybug and is in fact a member of the same family - but this one eats plants. The spiny yellow larvae do most of the damage, feeding on the undersides of bean-family leaves and skeletonizing them into lace, which cuts the photosynthesis that fills the pods. Both adults and larvae feed, and over a long season the generations stack up.

Watch for: Fuzzy spiny yellow larvae and neat clusters of yellow eggs on the leaf undersides, lacy skeletonized leaves with only the veins left, and coppery black-spotted adults on the foliage. The larvae are usually well established underneath before the adults become obvious, so turn the leaves over.

Prevent: Float row cover over young plants, scout leaf undersides weekly from midsummer and crush the egg clusters before they hatch, grow early varieties that finish before peak beetle season where you can, clean up bean-family debris in fall, and rotate the bean bed.

Treat: Hand-crush eggs and larvae on the leaf undersides - done every day or two while the pods are filling, this alone controls a home planting. Insecticidal soap or neem knocks back a heavy larval outbreak, and the parasitic wasp Pediobius is available for large plantings. Do not spray anything onto open flowers.

The extended pole-bean season gives this pest more time to build up - stay ahead of it with weekly scouting of the leaf undersides.

Aphids are small soft-bodied sap-suckers - green, black, gray, pink, or waxy white, and mostly wingless - that gather in dense colonies on the tenderest new growth: shoot tips, buds, and the undersides of young leaves. They breed extremely fast in mild weather, so a few can become hundreds inside a week. Their feeding curls and distorts soft growth, and the sticky honeydew they excrete coats everything below and turns black with sooty mold. Ants often farm and defend the colonies for that honeydew. A few aphids are normal on almost any plant and a healthy plant shrugs them off; only dense, persistent colonies do real damage, and some aphids also spread plant viruses as they feed.

Watch for: Dense clusters of tiny insects packed onto shoot tips, flower buds, and the undersides of young leaves. Curled, cupped, or distorted new growth that never opens properly. A sticky shine on the leaves - and on whatever sits under the plant - that later goes black with sooty mold. Tiny white cast skins left behind where a colony has been feeding. Ants running steadily up and down the stems, which is often the first thing you notice. Mottled, streaked, or misshapen leaves that do not grow out can mean a virus the aphids brought with them rather than the feeding itself.

Prevent: Go easy on nitrogen: the soft, lush growth that heavy feeding produces is exactly what aphids breed on. Check new growth once a week through spring and early summer so you catch colonies while they are still small, and rub the first few out with your fingers. Leave flowering plants nearby and skip broad-spectrum sprays - ladybugs, lacewings, hoverflies, and parasitic wasps do most of this work for free, and they only stay if there is something for them to eat. Keep ants off the plant where you can, since they protect aphids from those predators. Water steadily so plants are not stressed, and check any new plant over before you bring it home or move it indoors, since aphids usually arrive on something else.

Treat: Knock the colonies off with a hard jet of water and repeat every few days - on most plants that alone ends it. Pinch out or prune off the worst-infested tips rather than treating the whole plant. If colonies keep rebuilding, spray insecticidal soap or horticultural oil directly onto the insects, covering leaf undersides, and repeat weekly until they are gone; treat early or late in the day, and never spray a wilted or heat-stressed plant. Avoid broad-spectrum insecticides - they kill the ladybugs, lacewings, and parasitic wasps that were about to solve the problem for you, and aphid numbers usually come back worse afterward. Anything you spray must be labeled for the plant you are treating; follow that label and observe its pre-harvest interval. On anything you eat, wash leaves, heads, and buds well before use, since aphids hide down in crowns, folds, and tight growth.

The main concern is the viruses aphids carry into the crop rather than the feeding, which is usually minor on vigorous vines.

Japanese beetles are metallic green-and-copper beetles about half an inch long that emerge in early summer and feed for six to eight weeks. They feed in aggregating masses - one beetle's feeding releases a scent that draws in more - so a plant goes from untouched to covered in a couple of days. They chew the soft tissue between the leaf veins and leave the veins standing, so the leaf ends up as a brown lace skeleton, and they shred open flowers and sometimes ripening fruit as well. They work the sunniest upper parts of a plant on warm afternoons. The white C-shaped grubs spend the rest of the year in turf and pasture soil eating grass roots, and the adults then fly in from wherever they hatched, which can be some distance away.

Watch for: Clusters of shiny metallic beetles massed together on the upper, sunniest foliage and down inside open blooms, heaviest on warm sunny afternoons from around late June. Leaves reduced to lace, with the veins left intact and the tissue between them gone - unmistakable, and quite different from the ragged chewing of a caterpillar. Ragged, chewed petals and blooms that never open properly. Beetles that let go and drop straight to the ground when you disturb the plant. Feeding damage on ripening fruit, on the plants they also take fruit from. Whole branches going brown and lacy at the top of a plant while the shaded lower growth stays untouched.

Prevent: Hand-picking is genuinely the main defense in a home garden. Go out in the cool of the morning while the beetles are sluggish, hold a tub of soapy water underneath, and knock them in - they drop when disturbed, so most fall straight into it. Do it daily through the flight: because the beetles call each other in, taking them off early stops a plant becoming a beacon. Do not put pheromone or lure traps anywhere near the garden - they demonstrably pull in far more beetles than they catch. And do not count on lawn grub control: milky spore has performed poorly and inconsistently in field trials across most of the US, and treating your own turf does not reduce the adults feeding on your plants, because they fly in from surrounding properties. Where it is practical, row cover or netting through the peak flight excludes them outright. Otherwise riding out the six-to-eight-week wave is a legitimate strategy, since most established plants absorb the damage.

Treat: Persistent morning hand-picking into soapy water is the most effective home control there is, and on a vigorous established plant the damage is usually cosmetic and needs nothing else. Neem deters feeding rather than killing, and has to be reapplied. For heavy pressure, spinosad or a targeted insecticide labeled for the plant will work - but time any spray away from bloom and apply it at dusk to protect bees, and observe the pre-harvest interval on anything you eat. On flowering plants, some gardeners simply shear the blooms off for a couple of weeks and let the plant rebloom once the wave has passed, which removes the lure as well as the damage. Young plants and young trees are the ones worth defending: a mature tree or an established vine tolerates several weeks of leaf loss without lasting harm.

A shared generalist pest across the legume group; worst during the few weeks of peak flight. Row cover is not practical on tall vines, so hand-picking is the mainstay.

Spider mites are not insects but tiny sap-feeding arachnids, smaller than a grain of salt, and you almost always notice the damage before you notice them. They live on the undersides of leaves and drain the cells one at a time, which is why the leaf goes finely stippled with pale dots before it bronzes and dries. They breed explosively in hot, dry, dusty, still air - a generation can pass in a week at high temperature - so a barely visible population becomes a webbed, bronzed plant within a fortnight. Drought-stressed plants and plants wintered indoors in dry heated air are the classic hosts. Broad-spectrum insecticides make matters worse rather than better, because they kill the predatory mites and lady beetles that normally hold mites in check.

Watch for: Fine pale stippling or speckling across the upper leaf surface, as though the color had been sandblasted out of it, and later a dull bronze or rusty cast over the whole leaf. Delicate webbing across leaf joints, shoot tips, and undersides - that comes with a heavy infestation and means you caught it late. Leaves that dry, curl, and drop early while the plant looks thirsty no matter how much you water it. Hold a leaf over a sheet of white paper and tap it: the specks that fall and then start walking are mites. With a hand lens, look on the undersides for the mites themselves, pale or reddish, and their round translucent eggs. Damage that shows up first on the hottest, dustiest, most sheltered side of a plant, or on a pot sitting near a radiator indoors.

Prevent: Do not let plants get drought-stressed - that is the single strongest trigger, and a plant watered steadily through heat is far less likely to have a mite problem at all. Hose the foliage down, undersides included, during hot dry spells: it knocks mites off, washes away the dust they thrive in, and raises the humidity around the plant for a while. Indoors and under cover, keep the air from going hot, dry, and stagnant, wipe or rinse the leaves occasionally, and keep pots away from radiators and heating vents. Inspect any plant carefully before you bring it indoors for winter or set it among others, since mites almost always arrive on something else. Avoid broad-spectrum insecticides: they wipe out the predatory mites, lacewings, and lady beetles that do most of this work for you, and reliably leave you with a worse outbreak than you started with.

Treat: Start with water. A strong jet aimed at the leaf undersides, repeated every few days for a couple of weeks, knocks populations down and breaks the cycle - on many plants that alone ends it. On anything that regrows quickly, shearing back badly infested growth resets the plant to clean foliage. If it keeps building, spray insecticidal soap or horticultural oil directly onto the undersides where the mites actually live, and repeat every five to seven days for three rounds: contact sprays do not kill the eggs, so a single application always fails. Anything you spray must be labeled for the plant you are treating - follow the label and observe its pre-harvest interval on anything you eat. Predatory mites are an effective release in a greenhouse or on an indoor plant. Above all, correct the heat, dust, and drought stress that caused it, or the mites simply come back.

A hot-dry-season pest that the long pole-bean season is especially exposed to, and the dense canopy is a favorite haunt. Steady watering is the best prevention; observe the pre-harvest interval on anything you spray on a crop you are picking.

A seed- and splash-borne fungus (Colletotrichum lindemuthianum) causing dark, sunken lesions on pods, stems, and leaf veins - and because it is seed-borne, it carries straight into next year's crop through saved seed, making it especially serious for dry-bean growers.

Watch for: Sunken, dark-bordered spots on pods (pink ooze in humidity), reddish-brown streaks on stems and leaf veins, seed with dark blotches.

Prevent: Start with clean, disease-free seed; never save seed from infected plants; never work wet plants; rotate 2-3 years; clear debris.

Treat: Remove and destroy infected plants; copper can protect healthy foliage in a wet season. Don't save seed from infected plants.

Shared host-specific slug across the Phaseolus bean files - clean seed is the key defense.

A fungal disease (Uromyces) of bean-family plants, producing raised rusty orange-brown pustules on the leaves and sometimes the stems, mostly on the undersides and ringed with yellow. Heavy infection browns and drops the foliage, and losing leaf area during pod fill directly shrinks the crop. It is worst in warm, humid weather and wherever the leaves stay wet.

Watch for: Small raised rusty-orange pustules ringed with yellow, mostly on the leaf undersides and usually starting low in the plant where humidity is highest, followed by yellowing, browning and early leaf drop once it takes hold.

Prevent: Grow resistant or tolerant varieties where they are offered, space and train for airflow, water at the base so the leaves stay dry, and rotate beans on a two to three year cycle. Remove crop debris after harvest rather than leaving it to carry the fungus over.

Treat: Strip the worst-affected leaves early, starting with the lower ones. Sulfur slows the spread in a wet season; copper is not effective against rust. A late infection often still allows a full harvest, and fungicides are rarely needed in a home garden.

Pole beans' dense canopy holds humidity, so rust starts deep in the vine where you cannot see it. Vertical training and watering at the base are the best defense.