The defoliating Duponchelia caterpillar can be a real pest. A half-devoured crop leads to irrevocable economic losses. Luckily, the caterpillars can be effectively controlled using Delfin. Last year, the first experiences with this new insecticide were gained. Biobest advisor Stefan Bohté explains to growers the correct use of the bacterial preparation.
Delfin works just like other Bt agents. The preparation is sprayed on the leaves. The caterpillars eat the spores and crystals formed by Bt and these are then transformed into toxins in the caterpillars' digestive tracts. These toxins are lethal. However, Stefan notes, Duponchelia are not only present on the leaves but are also seen lower down on the plants.
“When treating the plant, it is important to cover the entire plant. So, spray all the way down to the root collar. In other words, the more of the crop you cover, the more effective you'll be against the caterpillar.” Stefan recommends making the whole plant wet. To do this, use 1500 litres of Delfin solution per ha, where the solution contains 50 grams of insecticide per 100 litres of water. Read the label for details. “If the plant is sprayed down to the root collar, we see that the Duponchelia population is considerably reduced with 3 treatments.”
“After the withdrawal of many chemical products, Delfin provides a reliable alternative. That is certainly the case in combination with other Bt preparations.” Bt stands for Bacillus thuringiensis, the oldest and most well-known biological crop protection product. Delfin contains the Btk variant, or Bacillus thuringiensis subspecies kurstaki. This product is a good supplement to the Biobest product range, which already includes a Bta product containing the subspecies aizawai. Each subspecies has a different effect on caterpillars, so the products are complementary. Stefan: “To maintain the effectiveness of Bta and Btk in the future, it is best to alternate between the two products.”