Research has been under way during 2021 to understand false blossom and its spread, considering both the disease itself and the vector. The Wisconsin Cranberry Board has funded research into the distribution and diversity of leafhopper populations across Wisconsin, and the distribution of cranberry false blossom in Wisconsin cranberry marshes.

Leafhoppers

Leafhoppers were swept at <10 Wood County and Jackson County marshes, both in the nymph stage and the adult stage. Populations declined in mid-July, and numbers in early August were quite small.  No significant feeding damage was observed at the sites sampled.

Cranberry False Blossom

Cranberry plants (the whole plant, root-to-shoot) with false blossom symptoms were sampled during the periods of early bloom, late bloom, and early fruit set. Additional samples will be collected during late fruit set, harvest, and post-harvest. In 2022, sites where leafhoppers were observed will have follow-up samples collected.

In these plants, DNA of false blossom is being amplified and compared across flowers, uprights, leaves, runners, roots, and last year’s fruits. We are currently using an extensive nested PCR assay to confirm the identity of the pathogen but hope to use other molecular tests to speed up this process. Our next line of inquiry will focus on whether false blossom can be detected in asymptomatic plants near symptomatic plants.

Symptomatic, infected plants showing abnormal floral structure with deep pink petals, erect pedicels, and the retention of pistils in last season’s infected fruits.

Leaf Spot Diseases

Leaf spot diseases are common in Wisconsin marshes but typically do not result in significant yield losses. 2021 is seeing more reports of leaf spots, and some reasons might be dense vine growth, excessive moisture, lack of fungicides, or secondary fungi—but no answer is certain currently. Common leaf spot diseases growers may encounter include Protoventuria leaf spot, Cladosporium leaf spot, and Red leaf spot—these diseases can co-occur, and all flourish in similar environmental conditions. To address leaf spot diseases, manage moisture and fertility levels to promote a less dense canopy.

This article was posted in Cranberry and tagged Allison Jonjak, Casey Trickle, Cranberries, cranberry, cranberry false blossom, disease, Emma Nelson, leaf spot, Leslie Holland.