Apple Blossom Weevil

The apple blossom weevil, Anthonomus pomorum, is a flower-bud-feeding weevil primarily associated with apple trees. Adults emerge from overwintering sites in early spring, feed briefly on expanding buds, and lay eggs inside individual flower buds. Infested buds often turn brown, fail to open, and remain attached as characteristic “capped” blossoms, reducing fruit set when populations are high.

Anthonomus pomorum, commonly called the apple blossom weevil, is a univoltine weevil in the family Curculionidae. Apple is its principal documented host. Adults overwinter in sheltered sites near orchards, become active during mild spring weather, and feed on expanding apple buds before females insert eggs into developing flower buds.

The larva remains concealed within the bud and consumes floral tissues. The most recognizable result is a brown, unopened “capped” blossom. This pest is well documented in Europe and other apple-growing regions, but it is not generally treated as a widespread established pest of U.S. orchards in standard federal pest resources. Suspect finds in the United States should be confirmed locally, especially where an exotic-pest concern or unusual damage pattern is possible.

• Individual apple flower buds turn brown, dry out, and fail to open.
• Dead buds remain attached and are often covered by a characteristic dried, papery petal cap.
• Opening the bud may reveal a cream-colored legless larva, feeding damage, frass, or a developing pupa.
• Adults make small feeding punctures in swelling buds and may cause minor shot-like injuries on young foliage.
• Fruit set is reduced where a substantial proportion of flower buds are infested; scattered capped blossoms may have little practical effect on a heavily flowering tree.

Damage can resemble frost injury, poor pollination, blossom blight, or other causes of flower abortion. Confirmation requires examining representative buds and, ideally, obtaining an expert identification of the insect.

Damage is caused by adult and larval feeding, with the larval stage protected inside the apple flower bud. Adults usually move into trees from nearby overwintering shelters such as leaf litter, loose bark, hedgerows, woodland margins, orchard borders, or neglected apple plantings. Cold, prolonged spring weather can extend the period during which suitable flower buds are available and may increase the proportion of buds attacked.

Movement is mainly local, although adults can disperse between neighboring trees and orchards. Infested nursery stock, cut branches, or transported plant material may provide a pathway for movement where regulations apply.

There is normally one generation per year. Adults leave overwintering sites in late winter or spring when temperatures become favorable and feed on swelling apple buds. After a maturation-feeding period, females lay eggs singly inside flower buds, commonly around the tight-cluster to pink-bud stages.

Eggs hatch within the bud. The larva feeds on the reproductive tissues and inner flower parts, then pupates in the damaged bud. New adults emerge around late spring or early summer, feed briefly on leaves, and then enter a period of sheltering and overwintering until the following spring. Timing varies with latitude, cultivar development, exposure, and spring temperatures.

Begin with confirmation and monitoring rather than treating solely from the presence of a few dead blossoms. On small trees, hand removal of capped buds and repeated branch tapping during early spring can reduce local populations. If monitoring shows economically important pressure before bloom, consult the current apple pest-management recommendations from the relevant state extension service and confirm that any proposed treatment is appropriate for the crop, timing, pollinator risk, and site.

After larvae are inside unopened buds, contact treatments are less reliable because the insect is protected within plant tissue. Avoid broad-spectrum applications during bloom whenever possible, and protect bees and other pollinators by following all label restrictions and orchard IPM guidance.

• Hand-pick and destroy confirmed capped blossoms on young or small apple trees.
• Shake branches over a white sheet or tray during cool spring mornings and remove collected adults.
• Improve orchard-edge inspection and sanitation by removing abandoned prunings and fallen debris that may provide shelter, without stripping soil of beneficial habitat indiscriminately.
• Encourage birds, predatory insects, and naturally occurring parasitoids by minimizing unnecessary broad-spectrum insecticide use and maintaining diverse, flowering non-crop habitat away from spray-sensitive bloom.
• Use resistant or less-susceptible apple cultivars only where local trial information supports the choice; susceptibility can vary among apple genotypes and flowering phenology.

Biological control may contribute to natural suppression, but commercially available biological products or release programs specifically targeting A. pomorum are not uniformly available to U.S. home gardeners. Do not assume that a general-purpose beneficial insect release will control this pest.

• Inspect apple trees weekly from bud swell through bloom, concentrating on the tight-cluster and pink-bud stages.
• Use a white sheet or tray beneath branches and gently shake or tap limbs on cool mornings to detect dislodged adult weevils before egg laying.
• Pay particular attention to trees near woodland edges, hedges, neglected apple trees, or protected groundcover.
• Maintain a well-pruned canopy that improves inspection and makes monitoring more effective; avoid unnecessary removal of flowering wood.
• Remove and discard confirmed capped buds from small backyard trees when practical, before adult emergence.
• Keep records of the date of first adult activity, bud stage, number of weevils found, and the percentage of damaged buds.
• Do not move suspect insects or infested plant material across state or national borders without checking current plant-health requirements.

• The dried petal cap over an unopened brown bud is the classic field clue and reflects larval development inside the flower.
• Apple blossom weevil is associated primarily with apple, while pear and some other pome fruits have been reported as occasional or less important hosts in certain regions; host records should not be generalized without confirmation.
• Damage is often more conspicuous after a cool spring because apple bud development is prolonged and remains suitable for egg laying.
• On trees with excessive bloom, limited weevil injury can act like natural thinning, but heavy injury can reduce the crop below an acceptable level.
• Adult abundance and damage often vary substantially among apple cultivars, tree phenology, orchard edges, and local overwintering habitat.