Protecting onion harvest with biological crop protection

An estimated 93,226,400 tonnes of onions are produced per year around the world, making onions the second most consumed vegetable globally after potatoes. Protecting onion harvests thus has a large impact on global food security. Recent trial results show that Koppert’s products Trianum and Capirel are key biological control agents against bean seed fly and onion fly that can contribute towards a successful IPM strategy for onions.

High efficacy in onion fly and bean seed fly control with Capirel 

Capirel, containing the beneficial nematode Steinernema feltiae, shows highly effective control of onion fly and bean seed fly. Onion fly and bean seed fly can attack young plants early in the growth cycle. Bean seed fly attacks right after sowing, where onion fly attacks young plants later in the season. By controlling the larvae with Capirel at this stage, the desired plant population can be maintained, and losses reduced. Pests, diseases, abiotic stresses, and other factors can compromise productivity, so effective protection helps keep actual yield as close to the potential yield as possible.

Capirel has a unique, soluble formulation with a long shelf life and the nematodes are cold tolerant, meaning they can be applied both early in the season and towards the end of the season when temperatures drop. A large advantage is that they can be used from as low as 5°C.

These beneficial nematodes can actively hunt and search for their prey from application. Millions of EPNs (entomopathogenic nematodes) are applied per hectare, and one nematode is usually enough to kill the pest once it penetrates. The nematodes then release pathogenic bacteria they carry with them. These actions kill and liquify the insect from the inside. The nematodes feed on the digested tissues of the dead insect and reproduce in large numbers. The pest insect stops feeding soon after being infested and dies within a few days. Trial results showed an 80% efficacy against onion fly and an effective decrease from seven plants per plot to an average of three plants per plot damaged due to onion fly.

12% decrease in damaged bulbs

Teaming up with Capirel to protect onion harvests, Trianum, with the active ingredient Trichoderma harzianum T-22, colonizes the root system of the plant and thus protects onions against soil pathogens. Available in two formulations: Trianum-P, wettable granules that can be mixed with water, and Trianum-G, granules that can be mixed with substrate or fertiliser and can be applied using standard machinery, which is particularly important for the use of Trianum onions. It is easy to apply with regular irrigation and it is highly unlikely that pathogens can develop resistance against it. While strengthening the plant and promoting growth, it also offers growers savings in terms of the use of soil fungicides.

Recent trials showed an increase in bulb weight of 54.17% on average and a 12% decrease in damage on bulbs at harvest. Damage occurs due to soil-borne diseases, specifically Fusarium, affecting onion bulbs. This implies that if the bulb is already damaged by the pathogen at the time of harvest, it is likely not fit for commercial sale. Even if the symptoms are minor, the storage life of the bulb will be compromised. Therefore, minimizing symptoms leads to higher commercial yield and fewer symptomatic bulbs mean better quality and longevity in storage. Trials also showed an increase of onion plants/ m² after 45 days from 84,1 grower standard to 86,8 and a decrease in plant losses from grower standard 5,63% to only 2,46%. By implication, the use of Trianum is promoting better root system health and nutrient uptake, resulting in more plants being retained per square meter.