Suited to all drilling dates but mainly start at mid/late August Target: Adults and larvae There is some evidence to suggest increasing seed rates can dilute flea beetle activity, but trials have shown mixed results, Dr White said.
“The reductions weren’t huge, but this has potential in poor establishment, so when it’s dry.”
However, recent trials data shows that crops drilled at a high seed rate tend to have lower levels of larvae.
Conversely, it’s possible plants sown at a low seed rate will be able to tolerate flea beetle attack because they will be larger, Dr White said.
One of the farms ADAS is working with on the study drilled at a very low seed rate aiming for 15 plants/sq.m, and although larvae numbers were 40-50 per plant, the crop still yielded four to five tonnes per hectare, Dr White added.
“We think these plants were just well able to tolerate damage.”
Suited to drilling in early to mid/late August Target: Larvae Dr White said: “We know grazing or topping reduces larval load, but it is risky.
We have done lots of trials and the majority leads to yield penalty.”
However, some farmers are seeing successes and persevering with the approach, he added.
“Timing is critical.
Do it in November, December at the latest.
Crop condition is important – forward crops have a high larval load and are best suited.
Defoliation doesn’t need to be very severe, you just need to take the leaves off and go no further.
Pay attention to other pests.
“Pigeon damage might be worse, pollen beetle might be worse because flowering is likely to be delayed and poor spring weather will hinder recovery.”