It sometimes seems like a healthy flower garden can turn into one wracked with insects and pestilence overnight. However, there are subtle signs gardeners must watch for that indicate early insect activity. Insect garden pests are much easier to control with organic or low-chemical methods when gardeners check the problem before it spreads throughout the landscape.

Sudden Seedling Death

It’s baffling to see a new batch of seedlings lying on their sides like a miniature forest visited by a team of nocturnal lumberjacks.

Cutworms hide under mulch during daylight hours, coming out at night to chew through young seedlings at the base. Protect new growth with a cardboard collar made from a toilet paper tube, or insert a thin wire beside each seedling to prevent the worm from curling around plant stems.

Deformed or Mottled Leaves

Gardeners who observe deformed leaves with mottling may think a fungicide is a possible solution, but if a virus like the tobacco mosaic virus is the culprit then no spray is effective. What gardeners may not know is that insect pests are responsible for spreading many plant viruses. Leafhoppers, whiteflies, aphids, and cucumber beetles spread viruses with their mouthparts when they pierce plant tissues. Prevent these pests from introducing viruses to the garden by using floating row covers or insect soap.

White Spots on Leaves

Whiteflies and spider mites are tiny garden pests that are easy to miss in the early stages of infestation. A single mite is about the size of the period at the end of this sentence, but gardeners can see them by examining foliage closely with a magnifying glass during drought or dusty conditions.

Rinse leaves frequently to discourage mites. Whiteflies are slightly larger than mites and are easy to see when leaves are disturbed, so don’t ignore these seemingly innocuous insects with powdery wings. Trap them with yellow sticky traps, or suck them off houseplants with a handheld vacuum.

Wilted Plants

Gardeners may mistake wilted plants for thirsty plants, when in fact wireworms may be at work. These 1 ½ inch long orange pests are most active in the spring and fall, but they are easy to trap and kill without chemicals. Simply bury chunks of raw potato, their favorite food, in affected areas. Remove and discard the potato chunks every two days until warm weather arrives and the pests leave.

Puckered or Distorted Leaves

Aphids are expert camouflage artists, their bright green bodies blending into the underside of leaves, but the damage they inflict on affected plants gives them away. If the puckered leaves don’t reveal their presence, the ants they partner with may alert the gardener to an aphid problem. Blast them away with a jet of water from the hose.

Leaking Tree Sap

Boring insect pests that affect trees in the garden are insidious, because sometimes the first sign the gardener notices is total defoliation of the tree, when it’s too late to treat the problem. Borers can girdle the trunk of young flowering trees, especially peaches and plums, causing death within one season.

Gardeners can prevent tree death from borers by looking closely at the base of the trunk for leaking sap, which indicates an entry hole for the larval stage of some beetles, wasps, moths, or flies. A small amount of sawdust at the base of the tree is also suspicious. Treat insect borers with pheromone traps, or insert a thin wire into the entry hole to impale the grub.