Several marshes scouted Tuesday May 18, 2021 revealed the presence of small leafhopper nymphs that are strongly suspected to be blunt nosed leafhoppers (BNLH). As a reminder, it is strongly recommended to monitor for BNLH by sweeping beds from mid-May to mid-June. Tentative thresholds from Cesar Rodriguez-Saona at Rutgers University suggest: 20 BNLH nymphs per sweep set in young beds, new varieties, and/or beds with false blossom disease incidence or 40 BNLH nymphs per sweep set in older beds, older varieties, and beds with no incidence of false blossom.
In 2020, we experienced severe feeding damage at a few marshes and extensive feeding by 100 to 200 leafhoppers (not just BNLH) can significantly drain the water and sugar from vines, leading to feeding damage (University of Maine). If you have a history of leafhopper feeding damage, the threshold would likely need to be lowered this year to about 20-30 leafhoppers per sweep set.
If you reach any of these thresholds prebloom, several insecticides provide good control against BNLH nymphs and these include the broad spectrum organophosphates (e.g., Lorsban, Orthene, Imidan, Diazinon), carbamates (e.g., Sevin), or pyrethroids (e.g., Danitol, though Danitol is not allowed this year by some handlers). Neonicotinoids are also efficacious against leafhopper nymphs but are not recommended prebloom as the active ingredients can be found in flowers and affect pollinators. For organic growers, while we did not assess organically-approved insecticides against leafhoppers yet, Pyganic is likely to be the most efficacious pre-bloom.
If you find high numbers of BNLH adults postbloom (>40 per sweep set), you may consider a postbloom application after mid-July with either an organophosphate (see above) or a neonicotinoid (Actara or Venom), depending on the timing and PHIs. Pyganic will likely remain your best option for organic production.
Happy growing season!This article was posted in Cranberry, Insects and tagged Christelle Guédot, Cranberries, cranberry, Leafhoppers.