What's wrong with these leaves?

[EricW]

Hello, I am very new at growing grapes. I am growing petite sirah and lots of the leaves are turning yellow. They seem to be infested with aphids but I am not sure. Can anyone recommend any pesticide this close to harvest time? The only thing that has been sprayed on the vines is sulfur. Any help is appreciated. Thanks.

 

[TOMMARIANI22]

Soil deffinency and you can use paraffinic oil or any horticulture oil it smother and kill them

 

[EricW]

Soil deffinency and you can use paraffinic oil or any horticulture oil it smother and kill them

How would you recommend fixing the soil deficiency? Can I apply oil this close to harvest? Thank you so much!

 

[TOMMARIANI22]

Depending on where you want to be with brix you can use oil at a lower one percent solution.. it should effect sugar accumulation too much .. also.weather dependent as well.. you can also use a insecticide known as mustang Max and harvest the same day it does a really good job.. for your soil deffinency problem you should take a lab sample and send it in. If i had to guess it looks close to low potassium possibly magnesium with yellowing on the bottom, but the only sure.way to know I'd by lab results.

 

[EricW]

Depending on where you want to be with brix you can use oil at a lower one percent solution.. it should effect sugar accumulation too much .. also.weather dependent as well.. you can also use a insecticide known as mustang Max and harvest the same day it does a really good job.. for your soil deffinency problem you should take a lab sample and send it in. If i had to guess it looks close to low potassium possibly magnesium with yellowing on the bottom, but the only sure.way to know I'd by lab results.

Okay, that you very much for your help.

 

[TOMMARIANI22]

No problem. Good Luck!

 

[Dennis Griffith]

Double A Vineyards offers a testing service designed for grape growers. And a viticulturist will give you recommendations on what you need to do.

 

[EricW]

Double A Vineyards offers a testing service designed for grape growers. And a viticulturist will give you recommendations on what you need to do.

Okay thank you. I am going to have the leaves tested for nutrient deficiencies.

 

[Dennis Griffith]

It will be the petioles (stems) that you need to harvest for testing. Make sure they are clean and dry.

 

[EricW]

It will be the petioles (stems) that you need to harvest for testing. Make sure they are clean and dry.

Okay, thanks!

 

[EricW]

Here are the results from the petiole testing. It looks like Nitrate is low but everything else is on the verge of being excessive. Can anyone make sense of this for me? Thanks

 

[EricW]

I found out the bugs are grape leafhoppers. They don't seem to cause reddening of the leaf ends though.

 

[TOMMARIANI22]

You might be a victim to grape leaf roll disease... Your soil should deffinetly be amended with a simple compost, or you can you use a derived amonium nitrate addition at a low solution. If it is leaf roll virus then it is disrupting the passage way for nutrients to reach the vine and produce leaves that are able to photosynthesize correctly. There really is nothing you can do for the disease ... There is another test that they can do to tell you if it is.

 

[balatonwine]

You might be a victim to grape leaf roll disease...

From the photos, I would not think this is a high probability. There is a real obvious "roll" to the leaves with this virus on the entire plant, that is not really obvious here just from a few photos of leaves (which may just be desiccated for other reasons). But only an official test will confirm it.

Looks more like generic late season pest damage to me. So I would first ask, what fungicide/insecticide was applied, on what schedule?

 

[EricW]

From the photos, I would not think this is a high probability. There is a real obvious "roll" to the leaves with this virus on the entire plant, that is not really obvious here just from a few photos of leaves (which may just be desiccated for other reasons). But only an official test will confirm it.

Looks more like generic late season pest damage to me. So I would first ask, what fungicide/insecticide was applied, on what schedule?

The vines were neglected and only dusted a couple times with sulfur. I just started getting involved with managing the vineyard and creating an ipm program.

 

[Dennis Griffith]

Here are the results from the petiole testing. It looks like Nitrate is low but everything else is on the verge of being excessive. Can anyone make sense of this for me? Thanks

I notice that they didn't test Boron. This is an important element for vine growth and fruit set. Nitrogen can be corrected with adjusting your fertilizer application, but only early in the season. Did you get the soil tested at the same time?

 

[EricW]

I notice that they didn't test Boron. This is an important element for vine growth and fruit set. Nitrogen can be corrected with adjusting your fertilizer application, but only early in the season. Did you get the soil tested at the same time?

Thank you for the info. I will definitely add boron to the list for the next tests. It was an extra cost and I didn't realize how important it is. Would you recommend doing the soil testing right now or before adding fertilizer next season?

 

[Dennis Griffith]

Right now before you add anything,.

 

[EricW]

Right now before you add anything,.

Okay sounds good, I'll have boron tested too. Thanks for the advice.

 

[pdq250]

Hello, I am very new at growing grapes. I am growing petite sirah and lots of the leaves are turning yellow. They seem to be infested with aphids but I am not sure. Can anyone recommend any pesticide this close to harvest time? The only thing that has been sprayed on the vines is sulfur. Any help is appreciated. Thanks.

The little white bugs are Grape vine leaf hoppers. A few are ok, but they can kill a lot of leafs if not taken care of. The grapes will not ripen if to meany leafs die.