Red Blotches on Leaves

[chrisfont23]

Newbie here. Can anyone tell me what this is and how to get rid of it (assuming it is bad).

 

[mgmarty]

Looks like scale to me. I've seen it on my citrus plants but never on grapes. Nasty stuff, but there's a spray for it. Check your local garden store. I use Fruit Tree Spray.

 

[BobR]

Check out this University of Minnesota website. The photo there looks like yours, but I know very little about grape growing and depend on this sites experts for my grape growing problems.

http://www.extension.umn.edu/gardeninfo/diagnostics/fruit/grape/leavespots.html

Black Rot
Guignardia bidwellii

Leaves have round tan spots with dark edges, tiny black pimples are often visible in the center of the spot

Black slightly sunken ovals or short streaks can be seen on Infected young green vines, leaf and flower stalks.

 

[chrisfont23]

Thanks guys. I sprayed it with fungicide a few weeks ago that was specifically meant to treat black rot. Oh well. Here's hoping the fruit is not destroyed too.

 

[mgmarty]

Is it a bump you can scrape off with your nail? Or is it a blotch in the leaf?

 

[chrisfont23]

It's a bump - through the leaf to the bottom. It's raised, red and then forms like a cone through the leaf on the other side.

 

[rob]

Pretty sure you have Phylloxera infestation

 

[rob]

You need to spray with a insecticide! If left long enough it can kill the vine

 

[ShawnDTurner]

Phylloxera

http://ohioline.osu.edu/hyg-fact/2000/2600.html

 

[chrisfont23]

This doesn't sound promising: Few chemicals are registered for control of foliar grape phylloxera. Thiodan (endosulfan) is the standard for commercial growers, but no compounds are registered for homeowner use against grape phylloxera. (Endosulfan does burn some cultivars.)

 

[rob]

If not to many try and pick the infested leaves off and bag them

 

[grapeman]

Hybrids can take a lot of phylloxera without treatment. It makes them look like heck but they keep growing. If just a few bad leaves, pick them off.

 

[MeadowCreek]

dont think its phylloxera and if it is, its only leaf. that can be treated with a miteocide and is not deadly to the vine. But I really think you have gullmakers on the leafs.

 

[rob]

Gullmakers? Can you explain what that is???

 

[MeadowCreek]

there original name was the tomato gall due to there round red spots, now they call them tumid galls. various fly species lay there eggs into the leaf, and the larvae hatch and enter the vine tissue. and as the larvae feeds the gall forms around them.

 

[rob]

there original name was the tomato gall due to there round red spots, now they call them tumid galls. various fly species lay there eggs into the leaf, and the larvae hatch and enter the vine tissue. and as the larvae feeds the gall forms around them.

Well ok but what you just described is Phylloxera....

 

[rob]

Looks like it is one of the same“Grape phylloxera is native to North America and occurs in many wild species of grapes in Florida as well as other areas of the Southeastern United States. The presence of grape phylloxera is easily recognized due to the characteristic galls that develop on the leaves. Leaf galls usually develop on the underside of vine leaves and are about 5-7 mm in diameter. Leaf (aerial) phylloxera does little harm and does not necessarily take up residence in all Florida vineyards. These galls also occur on the roots but they are not readily apparent. Root galls are small knots (enlarged areas) on the roots, which interfere with the roots ability to absorb water and mineral salts. An aphid-like insect is responsible for causing the symptoms of grape phylloxera. Many native American grapes are tolerant or resistant to root attack and are used as rootstocks for European grapes in other parts of the country.”

 

[MeadowCreek]

Is leaf infection deadly to the vine?

 

[MeadowCreek]

is infection deadly to the vine? And is spraying for it at bloom just a waist of time.

 

[grapeman]

No infection is not deadly and spraying that late is pretty much a waste of time and resources.