Golden-ringed dragonfly

Taxonomic classification: The Golden-ringed dragonfly (lat. Zoraena bilineata) belongs to the order Odonata, family Cordulegastridae. While recognized as a beneficial predator in natural ecosystems, in highly controlled agricultural environments or commercial greenhouses near water, it can sometimes interfere with optimal cultivation processes.

Susceptible crops and impact: The pest is primarily a concern for hydroponic greenhouse operations or crops grown in high-humidity zones. Damage is characterized by structural interference with plant root zones, which can act as a precursor for soil-borne pathogen outbreaks if the root health is already compromised.

Biology and life cycle: The life cycle is complex and largely aquatic. Females deposit eggs in damp substrates or water sediment. The nymphal stage is prolonged, lasting several years, during which they thrive as predatory invertebrates. Emergence to the adult stage occurs when environmental conditions are favorable, leading to the presence of highly mobile adult dragonflies.

Damage assessment: The primary issue is the physical disruption caused by nymphal activity in artificial growing media, such as rockwool or coco coir. Furthermore, high populations of adult dragonflies have been observed to disturb the behavioral patterns of essential pollinators like honeybees and bumblebees, leading to reduced fruit set in crops relying on cross-pollination.

Management and control: Maintaining high levels of biosecurity is key to preventing infestation. Agronomists recommend the following strategies:

• Screening greenhouse vents with fine-mesh netting to exclude adults.
• Implementing rigorous filtration for recirculating water systems.
• Monitoring substrate moisture to discourage egg-laying in pots.
• Applying preventive bio-fungicides to protect roots against secondary infections.