Bean fly on the rise, effective remedies gone

The bean fly is quite active on the Dutch onion fields this spring. Several growers and advisors are sounding the alarm about the increase in damage, especially in the north of the country. There is also a discussion among growers and crop advisors about the effect of primed seed versus unprimed seed under the challenging circumstances this season.

The bean fly is rearing its head again this season. "The bean fly has also visited us in large numbers this year! Fortunately, growing weather, stage two pipe is coming", says Peter Holster from Marknesse (Flevoland). Jesse Torringa Commercial promoter van De Groot en Slot confirms. "The pressure on the bean fly has increased rapidly in recent times. We have several plots in the north where many bean flies are caught. Unfortunately, the first plots with enormous damage are also known."

The larvae of the bean fly eat the growing points of the seedlings, causing the onions to disappear. Arjen Jacobs from Wezup (Drenthe) reports that he also suffers from bean fly in his red onions. "What could you do about it?", he wonders. Reinder Hogenhout from Kimswerd (Friesland) points to possible control with agents such as Capirel or Nemasys, but according to Peter Holster this does not offer sufficient protection: "There is actually no agent to really control this properly. Previously there was an insecticide coating for the seed, which is now a great loss for the growers."

This is confirmed by Hubert Linders from Nederweert (Limburg): "I think the seed used to be disinfected with Fipronil, but that was banned after the egg crisis." Jan Berend Biesheuvel from Zeewolde (Flevoland) also emphasises the importance of the old seed coating: "That seed coating is a huge loss. All other options do not work well enough, or are applied too late and under the wrong conditions. And often with more active substance."

Primed or unprimed: effect on turnout
Another theme that is alive among onion growers in the crop tour is the differences in emergence between primed and non-primed seed. Opinions differ on this.

Xam Hage, student of Aeres Hogeschool Dronten, shares his experience at his home farm in Steenbergen (North Brabant): "We have 1 plot of shallots and 1 plot of seed onions unprimed, and the rest are all primed. I find that everything that is unprimed comes up very irregularly. Some are almost past the clump stage while their neighbour still has to come up, very annoying with regard to weed control."

Wilbert Lindhout Commercial promoter van De Groot en Slot agrees: "I see that more often, yes. Primed is definitely a (big) advantage this year with big differences compared to non-primed on most plots. Primed is especially nice if you can still take advantage of the available moisture."

However, there is not one truth, as is evident from the reactions of other growers. Klaas Jan Boer from Kortgene (Zeeland) says: "I have primed and unprimed on the same plot. I really see no difference. And on both plots they have been dry and are still coming afterwards. I cannot say that the primed have a better emergence."

David de Wit from Lepelstraat (North Brabant) notices the exact opposite: "With us, it's exactly the opposite. It's more even without priming. I suspect that lying half-dry for five days with priming makes a bigger difference than without priming."

Xam Hage agrees: "Yes, that is correct. Primed seed that is dry does not work very well." Wilbert Lindhout clarifies this further: "If primed seed has just had a little moisture and it is just getting started and then falls dry, it dries under the plant. This is also usually because it has no connection with the substrate. This can happen just as well with normal seed, but with primed the chance is greater because it starts growing earlier."

Winter onions at Xam

Onions by David de Wit

Difference in left unprimed and right primed

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