Practical experience of weed seed control with hot steam in horticulture

Since the middle of the last century, the effectiveness of humid heat to fight weeds, in particular their seeds, has been researched thoroughly. Within just 5 minutes all seeds can be rendered ungerminable as long as hot steam of 95°C is used steadily.

In practice today there is a trend of shorter treatments with hot steam in particular when fighting weed seeds on open fields. In particular in France, the Netherlands and in Denmark big areas of beet cultures are superficially sterilized to up to 5-10 cm depth using steaming automats. Special hoods with a total area of up to 20 square meters are moved step by step after just 5 minutes of steam injection.

The goal of using short steaming periods however is not the total abolition of resistant pathogens. Here longer steaming times and larger steaming depths are necessary. Instead the focus is the killing of weed seeds on the surface in order to give beet cultures a headstart so they can prevail against other growing weeds.

The results show success. Despite short steaming periods, hot steam can sufficiently harm seeds sufficiently to avoid the penetration of weeds.

This steaming method for superficial seed control is further propagated in Germany as well. This development can be traced back to the lack of available alternatives. In earlier times chemical means were used which are meanwhile prohibited or considered risky.

Furthermore the present discussion about the spread of ragwort and similar plant types drives the promotion of steaming. The market demands even more weed=free products, but due to the market price situation there is no alternative for automatic harvest methods. Hence, beets need to be free of weeds when harvesting.

Steaming as ecological method for seed control gains importance nationally as well as internationally.

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