Author: Annie Klodd, Extension Educator - Fruit and Vegetable Production
Below are four of the fruit-related questions that I received this week from growers in Minnesota, with my responses. I hope that these are helpful to growers who are encountering similar issues. Please let me know if you like this format, as I am working out the best way to give weekly fruit updates throughout the growing season.
At this point, most grapevines in Minnesota are past bud break and are somewhere between 2-5 inch shoots. Buds that have not swollen at this point, or have swollen but look yellowed or brown, may be dead. Another possible but less likely scenario is that some buds may have been delayed due to environmental conditions and could put out secondary or tertiary buds later. The best way to tell is to cut into some of the buds and see if they are green on the inside. Green inside the buds indicates live tissue.
If a large percentage of the tested buds are dead, then it is time to consider the possibility that the above-ground part of the vines will not produce a crop this season. They are likely to still put up new suckers if the root system is healthy. However, if this problem has occurred multiple years in a row, evaluate the causes of the problem and then consider appropriate options to renovate the vineyard such as replacing vines, switching varieties, installing drainage tile, applying necessary soil amendments, or relocating the vineyard to a better site altogether.
Yes, I would still spray for fire blight this year, especially if you had it last year. While Minnesota has been below average precipitation for the last month, much of the state has still received rainfall events in the last week. More rain is expected this weekend for much of the state. If temperatures are warm, it just takes a few hours of wetness for fire blight to spread and infect plant tissue. It is slow, but active between 50-70 degrees F, and it spreads more rapidly between 70-85 degrees F. Read more about how fire blight spreads here.
Fire blight should be managed with appropriate fungicide applications at silver tip, bloom, and petal fall.
A list of resources on apple fruit thinning can be found here on University of Wisconsin-Madison Extension's fruit website. You may also download a free pdf of the Midwest Fruit Pest Management Guide to read about fruit thinning options.
We will be recording a podcast episode on apple crop thinning today, and will have that posted in the next few days, in time for growers to purchase products for thinning. Please keep an eye out for this.
This question on the sustainability of Indar stems from data showing that American brown rot is establishing resistance to Indar in Michigan and the Northwest, where it is relied upon heavily for control of brown rot in cherries. Read more here.
Cherry growers should incorporate other options, and employ good canopy management, to eliminate or minimize reliance on Indar. Synthetic options with excellent control of American brown rot include strobilurins like Flint Extra, and Merivon/Luna Sensation, which are premixes of SDHI plus strobilurin. These should be mixed with Captan to help decrease risk of resistance.
According to the Midwest Fruit Pest Management Guide, applications should be made from early bloom to petal fall. Another application may be done 3-4 weeks before harvest. Please note that symptoms will not be visible to the naked eye at the times of these applications.
Effective organic fungicide options for brown rot are limited, and all growers, including organic growers, should employ good canopy management, air circulation, and spotted wing Drosophila management to reduce introduction of American brown rot to the fruit.
Below are four of the fruit-related questions that I received this week from growers in Minnesota, with my responses. I hope that these are helpful to growers who are encountering similar issues. Please let me know if you like this format, as I am working out the best way to give weekly fruit updates throughout the growing season.
1) Some of my grapevines still have not gone through bud break. Will the buds pull through?
 |
| This new vine did not pull through after its first year. The cause is currently unknown. Photo: Annie Klodd. |
At this point, most grapevines in Minnesota are past bud break and are somewhere between 2-5 inch shoots. Buds that have not swollen at this point, or have swollen but look yellowed or brown, may be dead. Another possible but less likely scenario is that some buds may have been delayed due to environmental conditions and could put out secondary or tertiary buds later. The best way to tell is to cut into some of the buds and see if they are green on the inside. Green inside the buds indicates live tissue.
If a large percentage of the tested buds are dead, then it is time to consider the possibility that the above-ground part of the vines will not produce a crop this season. They are likely to still put up new suckers if the root system is healthy. However, if this problem has occurred multiple years in a row, evaluate the causes of the problem and then consider appropriate options to renovate the vineyard such as replacing vines, switching varieties, installing drainage tile, applying necessary soil amendments, or relocating the vineyard to a better site altogether.
2) The weather has been pretty dry this season. Do I still need to spray for fire blight on my apples if I had it last year?
Yes, I would still spray for fire blight this year, especially if you had it last year. While Minnesota has been below average precipitation for the last month, much of the state has still received rainfall events in the last week. More rain is expected this weekend for much of the state. If temperatures are warm, it just takes a few hours of wetness for fire blight to spread and infect plant tissue. It is slow, but active between 50-70 degrees F, and it spreads more rapidly between 70-85 degrees F. Read more about how fire blight spreads here.
Fire blight should be managed with appropriate fungicide applications at silver tip, bloom, and petal fall.
3) What products can be used for apple crop thinning?
A list of resources on apple fruit thinning can be found here on University of Wisconsin-Madison Extension's fruit website. You may also download a free pdf of the Midwest Fruit Pest Management Guide to read about fruit thinning options.
We will be recording a podcast episode on apple crop thinning today, and will have that posted in the next few days, in time for growers to purchase products for thinning. Please keep an eye out for this.
4) What can I spray to control brown rot on cherries, that is more sustainable than Indar?
 |
| Brown rot on sour cherries at the time of harvest. Much of the infection in this photo was introduced at SWD-associated injuries. Photo: Annie Klodd |
This question on the sustainability of Indar stems from data showing that American brown rot is establishing resistance to Indar in Michigan and the Northwest, where it is relied upon heavily for control of brown rot in cherries. Read more here.
Cherry growers should incorporate other options, and employ good canopy management, to eliminate or minimize reliance on Indar. Synthetic options with excellent control of American brown rot include strobilurins like Flint Extra, and Merivon/Luna Sensation, which are premixes of SDHI plus strobilurin. These should be mixed with Captan to help decrease risk of resistance.
According to the Midwest Fruit Pest Management Guide, applications should be made from early bloom to petal fall. Another application may be done 3-4 weeks before harvest. Please note that symptoms will not be visible to the naked eye at the times of these applications.
Effective organic fungicide options for brown rot are limited, and all growers, including organic growers, should employ good canopy management, air circulation, and spotted wing Drosophila management to reduce introduction of American brown rot to the fruit.
Comments
Post a Comment