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Virginia Pierce’s Disease Management Update

Since the past winter was more or less steady and mild, in terms of temperature fluctuations, there are less likely that many of us saw the minimum temperature at 15F or lower. For example, at Winchester, we saw 14.5F on the 21st of February, and that’s it for this winter. The risk of Pierce’s disease will increase with a warmer winter. I.e., less than three nights with a minimum temperature of 15F or lower will decrease the risk of Pierce’s disease.

Thus, especially people in the south and eastern part of the state may need to prepare for the management of sharpshooter leafhoppers, which are the vectors of Pierce’s disease. Some growers in the eastern VA use insecticides for sharpshooter leafhoppers from May to June, so, I thought it is probably a good idea to sent out a reminder.

Entomology is not my area of expertise, thus, I will copy the information from our Pest Management Guide, page 8.

In some vineyards in the eastern part of the state, sharpshooter leafhoppers, the vectors of Pierce’s disease are of concern. While research is needed on the vector relationships and timing in Virginia, the neonicotinoids Admire Pro (1.0 fl oz). Assail 70WSP (1.1-2.3 oz/A), Assail 30SG (2.5-5.3 oz/A), Belay Insecticide (4.0-6.0 fl oz), Scorpion 35SL (2.0-5.0 fl oz), Venom 70SG (1.0-3.0 oz/A), and Venom 20SG (0.44-0.66 lb/A) are registered for control of sharpshooters. Use the higher rates for higher pressure. In addition, Scorpion and Venom are registered for soil application (9.0-10.5 fl oz; 5.0-6.0 oz/A respectively), as is Admire Pro (7.0-14.0 fl oz/A). Soil applications should be applied between bud-break and pea-berry stage and should be considered when there are three or fewer nights below 15˚F during the preceding winter. The neonicotinoids share a common mode of action; avoid overuse to avoid resistance.

Besides neonicotinoids, the following pyrethroids are registered for sharpshooter control: Esteem (5 oz/A), Danitol 2.4EC (10.67-21.33 fl oz/A), Brigade 2EC (6.4 fl oz/A), and Baythroid 2EC (1.6-3.2 fl oz/A). Danitol is limited to two applications, Baythoid to four applications, and Brigade to two applications at the low rate, one at the high. In blocks where Spotted-wing drosophila will need to be controlled, early use of pyrethroids will decrease the number of applications available in late season.

Consult http://www.virginiafruit.ento.vt.edu/PDsharpshooters.html for updated information.  — Mizuho Nita, Virginia Tech Grape Pathologist

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