Tortricidae

The key biological characteristic of this group is the behavior of their larvae, known as caterpillars. They possess an instinctive drive to roll leaves into tubes or packets, securing them with silk webbing. This structure provides the caterpillar with a protected shelter against adverse weather and natural predators.

The life cycle of most species includes the stages of egg, larva (caterpillar), pupa, and adult (moth). Depending on the climate, leafrollers can complete one to several generations per growing season, which significantly complicates management efforts.

Taxonomically, leafrollers belong to the order Lepidoptera. In agriculture, they are categorized by their feeding preferences: fruit, berry, ornamental, or polyphagous species capable of damaging a wide range of woody plants and shrubs.

Most species overwinter as larvae inside dense cocoons or as eggs laid on branches. In spring, as sap flow begins, the larvae become active and start feeding on developing buds and young leaves.

Leafrollers are polyphagous pests that attack nearly all fruit crops: apples, pears, plums, cherries, and vineyards. Certain species cause critical damage to berry crops, including currants, raspberries, and strawberries.

Damage begins with the destruction of buds, which fail to open, leading to significant potential yield loss. Later, caterpillars move to young leaves, skeletonizing them or consuming the entire leaf blade.

A particular danger involves damage to reproductive organs: buds, flowers, and fruitlets. Damaged flowers shed, and fruitlets stop developing and often drop prematurely, reducing both the quality and quantity of the harvest.

Fruits damaged by older caterpillars develop deep grooves, wormholes, and surface ulcers. Such damage makes the produce unsuitable for storage and facilitates the development of fungal diseases, such as fruit rot.

Mass outbreaks of leafrollers lead to significant stress on trees, reduced winter hardiness, and interference with flower bud formation for the following season, which can lead to biennial bearing patterns.

Leafroller activity begins in early spring, when mean daily temperatures reach +10...+12°C. During this period, overwintering larvae emerge from their shelters to feed intensively on buds.

The flight of first-generation moths typically coincides with the budding and flowering stages of fruit crops. This is the period when females actively lay eggs on the upper or lower leaf surfaces or on tree bark.

During the summer months (June–July), the damage caused by subsequent generations of caterpillars peaks. Depending on the species, larval development can continue until early autumn, requiring multiple protection stages.

Under favorable weather conditions (moderately warm and humid), leafroller reproduction rates increase sharply. Hot and dry summers may slightly delay the development of some species but do not eliminate the problem.

By the end of the season (September–October), the last generation of caterpillars searches for overwintering sites, such as bark crevices, fallen leaves, dry weed stems, or soil, where they pupate or enter diapause until the following spring.

The primary sign of infestation is the presence of rolled, silk-bound leaves shaped like cigars or envelopes. If such a leaf is unrolled, a caterpillar is always found inside, which will begin to squirm when disturbed.

• Damaged buds that appear withered and fail to open in spring.
• Silk webbing on shoots, between leaves, and near fruit stems.
• Eaten leaf edges or large holes within leaf blades.
• Shedding of fruitlets and presence of shallow surface scarring on young fruit.
• Drying of flower clusters encased in silk webbing that remain hanging on branches.

A leafroller control strategy must be integrated, involving cultural, biological, and chemical methods. It is crucial to time applications according to the pest's phenological development.

Cultural practices include regular cleaning of tree trunks to remove loose bark where larvae overwinter, as well as raking and destroying fallen leaves. Pruning affected branches with caterpillar nests is an essential preventive step.

Pheromone traps are effective for monitoring populations, allowing growers to identify the start of moth flight and precisely time insecticide applications when young larvae are emerging.

Biological control involves using products based on Bacillus thuringiensis, which are effective against young larvae. Encouraging natural enemies in the garden, such as Trichogramma wasps that parasitize eggs, is also highly recommended.

Chemical treatments should be applied only when economic thresholds are exceeded. Use systemic or contact-stomach insecticides from groups such as pyrethroids, neonicotinoids, or insect growth regulators, strictly following intervals to prevent resistance development.