Polydrusus dohrni

Polydrusus dohrni is a species of broad-nosed weevil belonging to the Curculionidae family within the order Coleoptera. As a phytophagous insect, this beetle is recognized for its ability to cause significant defoliation in various deciduous plants, making it a subject of concern for orchardists and nursery managers during the spring season.

The host range of this pest is diverse, primarily focusing on fruit-bearing trees such as apple, pear, cherry, and plum. Additionally, it frequently inhabits and damages native deciduous trees like oak and hazel. Its proximity to orchards allows for easy migration and rapid infestation, particularly in young plantations where the foliage is tender and vulnerable.

The life cycle of this weevil is primarily soil-based during its larval stages. Larvae overwinter underground, feeding on the fine root systems of herbaceous plants and trees. Upon the arrival of warmer spring temperatures, the larvae pupate in the soil. Adults emerge between late spring and early summer, immediately beginning to feed on the foliage to gain energy for reproduction.

The primary damage caused by Polydrusus dohrni is the distinctive feeding pattern on leaves. Adult weevils chew semi-circular notches along the margins of leaves. In cases of high population density, this feeding can lead to severe loss of leaf area, impairing the photosynthetic efficiency of the tree, which subsequently stunts growth and reduces overall plant vigor.

Control measures must be timed carefully to coincide with the adult emergence phase. Integrated Pest Management (IPM) strategies are highly recommended, including mechanical shaking of branches to remove beetles during the morning, and the application of selective insecticides when the threshold of damage is exceeded. Soil management and the removal of host weeds near tree rows also play a vital role in population suppression.

• Monitor leaf edges for characteristic notch damage.
• Utilize sticky traps or branch shaking for manual collection.
• Apply contact insecticides during the peak of adult activity.
• Maintain orchard hygiene to reduce overwintering sites.