Integrated Pest Management Program Department of Plant Science and Landscape Architecture UConn Extension
Small Fruit and Grape Update: July 29, 2016
Written by Mary Concklin, Visiting Associate Extension Educator – Fruit Production & IPM
Impacts of Heat: The heat this summer has impacted fruit and the plants. These blueberry leaves with the red center were interesting because of the pattern which did not fit a biotic disorder or nutritional problem. When the leaf was moved in the picture to the right it became apparent the upper leaf was protecting part of the lower leaf and that this disorder was related to the environment. Several diagnosticians in the country weighed in and said it was related to extreme heat and they had seen this same pattern in azaleas and rhododendrons.
Blueberry Mosaic virus is not very common but I have seen it at 2 blueberry farms in CT this summer. It does not always impact the entire bush, and in these cases it is only apparent on a few canes in the bushes. It will have a negative impact on the fruit quality and yield as well as reducing vegetative growth. It can spread in the field but the vector is not known, or why symptoms appear one year but not the next. If you find this in a young planting, rogue out the plants and be sure to replace with virus free plants. For older plants, you could leave them the plants and continue to harvest the fruit until the plants decline past the point where it is not worthwhile.
Grape Phylloxera is a very destructive insect pest of grapes because it impacts the foliage as well as the roots. Once it is in the vineyard it is difficult to completely eradicate. Foliar symptoms are evident from the overwintering generation feeding in late spring and in July from second generation. Multiple generations occur per season. Overwintering occurs as eggs on the vine. In the fall, some of the nymphs move to the soil and hibernate on the root system. In the spring those nymphs feed on the root system, reproduce and the next generation continues to feed. Foliar feeding injury can cause early defoliation, and negative impacts on fruit quality. Root feeding is the most destructive because it can cause the plants to be stunted.
Management: Varieties vary to susceptibility to the Grape Phylloxera with American varieties tend to be resistant. Plant resistant rootstocks.
Scout the vineyard now and if you find foliar symptoms, particularly heavy infestations, make a note of the variety and extent of damage. In 2017, record the date of the beginning of leaf expansion – this is the biofix. Crawlers are expected at 554-800 DD, base 430F, from the biofix. Apply an insecticide when they are seen which is usually immediately after bloom, then follow this with a second application 10 days later. Movento is highly effective, followed by Admire Pro, Assail, Danitol, Des-X, Pasada, Platinum and Volium Flexi. There are no effective organic materials although multiple applications of Surround (kaolin clay) may cause some suppression. Summer and fall applications have not been shown to be effective.
Rust on Brambles: Late Leaf rust is a fungal disease that impacts fall raspberry varieties, is not systemic and can be easily managed by (1) maintaining an open planting for optimal air circulation, and (2) apply fungicides, rotating between – Cabrio (FRAC 11), Pristine (FRAC 7,11) and Rally (FRAC 3). (Picture of rust on berries from Cornell University).
Orange Rust is SYSTEMIC fungal disease that infects blackberries and black raspberries, but not red raspberry. Once it is in the plant it will always be there. Rogue out any plants that show symptoms of Orange rust. Remove any wild blackberries and black raspberries – they will harbor the fungus. Maintain an open planting for optimal air circulation. There are no fungicides that are considered effective against this disease.
Gypsy Moth on Blueberries This is a Gypsy moth pupa found on a blueberry bush with the curled and narly looking leaves. Because it was so dry the Gypsy moths did not die off from the fungal disease this summer – bummer. Be prepared for next year’s expected high population.
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