Lebanese wheat stem sawfly

The Lebanese wheat stem sawfly (Trachelus libanensis) is a significant pest of cereal crops, belonging to the order Hymenoptera and the family Cephidae. This insect is primarily known for causing structural damage to wheat and barley stems, leading to potential yield losses in agricultural regions where small grains are cultivated.

The primary host plants for this species include winter and spring wheat, barley, rye, and various wild grass species. The pest is particularly active during the heading and grain-filling stages of the crop, making it a critical threat during the period when the plant directs all energy toward grain development.

The biological cycle of this insect involves one generation per year. Larvae overwinter inside the stubble of cereal plants, near the base of the stem. During the spring, the larvae pupate, and the adults emerge around the time of crop flowering. The female uses an ovipositor to insert eggs into the stem tissue, where the larvae will later develop.

The damage caused by the Lebanese wheat stem sawfly is direct and mechanical. As the larva feeds inside the stem, it creates a tunnel, which interferes with the nutrient flow to the grain head. Key symptoms and consequences of infestation include:

• Premature ripening or whitening of the grain heads.
• Significant shriveling and reduction in grain weight.
• Stem lodging, which makes harvesting difficult and causes grain loss on the ground.
• Reduction in total harvest volume due to damaged and fallen stems.

Management and control rely heavily on cultural practices. Deep plowing of the soil after harvest is highly effective, as it buries the stubble and destroys the overwintering larvae. Implementing a balanced crop rotation system is also essential to break the pest's life cycle. If populations exceed economic thresholds, timely application of insecticides during the adult flight period can prevent further egg-laying.