Sep. 28, 2016
Biobest’s combination strategy has been developed, comprehensively tested and adopted in the UK. Biobest UK has a wealth of experience using these two complementary parasitic wasps, Dacnusa sibirica and Diglyphus isaea. With the introduction of D. sibirica early season and D. isaea later on, the biological traits of both wasps are exploited.
Dacnusa - a fast prey seeker...
Leon van Klink, a grower of snack tomato Babeno and manager of Vitensa, testifies; “Our strategy is to scout the crops to spot early symptoms of leafminer. We check the sticky traps and inspect the crop leaves for signs of dots, or the start of tunnels, to determine the start date for Dacnusa introductions.”
Yann Jacques, Biobest’s Product Manager for Macrobials, explains; “Ideal to introduce in the early season, Dacnusa parasitises at low temperatures and is highly effective at seeking out prey. When pest pressure is low, Dacnusa actively search for larvae in the tunnels mined through the leaves. Being an endoparasite, it deposits its eggs inside the body of the larvae. An added advantage is that it only seeks out healthy larvae − not the parasitized ones. To help spot the first leafminer adults − to determine the start date of introductions − we recommend using Bug-Scan sticky traps.”
Diglyphus finishes the job
“While not as skilled at seeking out prey, Diglyphus works best at greater leafminer tunnel densities,” says Leon van Klink. “After introducing Dacnusa, we monitor weekly and collected pupae to check the percentage parasitism. When the leafminer pressure is seen to be going up, we introduce both Diglyphus and Dacnusa. Later on we just use Diglyphus.”
Yann Jacques says: “After a few introductions of Dacnusa, it is indeed Diglyphus’ turn. Diglyphus should only be introduced at a certain threshold – the timing is best discussed with a Biobest advisor. Complementing Dacnusa perfectly, Diglyphus is capable of building up a population very fast controlling the remaining leafminers. When Diglyphus females encounter leafminer larvae, they paralyse their prey and lay eggs next to them – they are ectoparasites.”
Leon advises: “It is important not to remove the infected leaves so the Diglyphus can complete its lifecycle and is ready for the next generation.”
Leon van Klink was delighted with the results achieved last year: “The strategy has worked really well this year,” he says. “At the start of the season we saw significant leafminer pressure and were therefore apprehensive. However, we observed almost 100% parasitism with the Dacnusa followed by complete control with the Diglyphus. We didn’t need any chemical treatments, the biological products were sufficient on their own.”
At the first sign of the pest it is best to start weekly Dacnusa-System introductions at 0.25-0.5 adults m2/week. The Dacnusa-System is supplied as 250 adults in a 250ml tube.
Once the threshold has been reached, start Diglyphus-System introductions at 0.5-1 /m2/week. It is necessary to monitor pest population levels carefully. The Diglyphus-System is also supplied as 250 adults in a 250ml tube.