Carrot psyllid

Systematic position. The carrot psyllid (Trioza nigricornus) belongs to the order Hemiptera and the family Triozidae. It is a small jumping plant louse that is recognized as a significant pest in vegetable production, particularly affecting plants in the Apiaceae family.

Host plants. The primary host is the common carrot (Daucus carota). However, the pest also infests other Umbelliferae crops, including celery, parsley, parsnips, and dill. Wild species of the Apiaceae family serve as secondary reservoirs for the population during the growing season.

Biology and life cycle. This species overwinters as adults on coniferous trees, such as spruce and pine. In early spring, when temperatures rise, the adults migrate to vegetable fields. The insects undergo several generations per year, with the lifecycle involving egg-laying on the leaves followed by nymphal development on the underside of foliage.

Damage symptoms and economic impact. Both adults and nymphs feed on plant sap. Their feeding induces a toxic reaction in the plant, causing the leaves to curl, thicken, and develop a characteristic reddish or yellow discoloration (often called "carrot yellows" or "curly leaf"). Heavily infested plants show stunted growth, and the quality and yield of the roots are severely compromised.

Control measures. Management of Trioza nigricornus requires a combination of strategies:

• Avoid planting carrots near coniferous windbreaks or forests.
• Use row covers or netting to physically prevent psyllids from reaching the seedlings.
• Implement proper crop rotation to break the pest's reproductive cycle.
• Apply systemic insecticides during periods of peak adult migration if infestation levels are high.
• Practice rigorous weed control, specifically targeting wild Apiaceae plants that host the pest.