Alfalfa weevil

The genus Hypera, commonly known as alfalfa weevils, belongs to the order Coleoptera and the family Curculionidae. These insects are recognized as major pests globally, causing significant economic damage to alfalfa, clover, and other leguminous forage crops.

Alfalfa is the primary host for these weevils. Both adult beetles and larvae cause direct damage to the crop. The larvae are particularly destructive as they feed on the terminal growth, leaf buds, and then move to open foliage, leading to severe yield losses in the first and second cuttings.

The life cycle of Hypera typically involves a single generation per year in temperate climates. Adults undergo diapause during the summer and winter, emerging in early spring to feed and lay eggs. Eggs are laid in clusters within the stems of host plants, which protects them from environmental stressors and some contact insecticides.

Damage symptoms begin with small pinholes in the leaves caused by adult feeding, followed by skeletonization and shredding of the leaves by the larvae. In severe infestations, an entire field may appear grayish-brown as if scorched by frost, which drastically reduces both the biomass quantity and the crude protein content of the forage.

Integrated Pest Management (IPM) is the most effective approach to control this pest. Key strategies include early harvesting to remove larvae before they reach the final instar, promoting natural biological control agents like parasitic wasps, and applying insecticides only when economic thresholds are exceeded.

• Monitor fields weekly during early spring.
• Check terminal growth for signs of larvae.
• Use economic threshold guidelines for spraying.