sweet gum problem

[SkwerI]

An old customer called me yesterday because his sweet gum tree seemed to be dying. 3/4 of the tree looks fine, but the lower 1/4 of the foliage is turning brown.

I went over this morning and looked at it. It appears to be some sort of aphid but I'm not sure what exactly to tell him. Here's a couple pictures of the foliage.

 

[NickfromWI]

What makes you say aphid? Did you see insects or the honeydew?

 

[Paul B]

in the second picture, at the top right where the leaf attaches to the petiole, I think I see some minute webbing, any chance of spider mites? If so your best offense is likely a dormant oil / lime sulphur application when it goes dormant. From what I see as damage though I would lean towards a viral infection, no halos on the spots and individual cells look depleted of chlorophyll hence the grey.

 

[Knotahippie]

Looks like it may be thrips to me, never seen it that bad though.

 

[Che]

Looks like spider mites to me. Get your magnifying glass out, touch a speck on the underside of the leaf with your fingernail and see if it moves.

 

[Paul B]

or takea leaf, bang it on a sheet of white paper and look for dust or slightly larger particles, if they move on their own, bingo!

 

[Wagnaw]

Has it been raining a lot near you this summer? ...powdery mildew.

 

[RIVERRAT]

Dont believe thats powdery midew.

I agree with the others mites or virul infection.

 

[treelooker]

late september leaf diseases are not usually a big issue.

that said i have seen a lot of sweetgums but nothing like that.

good advice re spider mites; good place to start.

 

[SkwerI]

Cool, guys. I'm taking all this in and will go look at it again tomorrow for more evidence of spider mites.

 

[Che]

Could you take a picture with a deeper depth of field? More would be in focus.

Or it could be Obama's or McDonald's fault. I see evidence of both on the underside of the leaf.


I swear it was only ONE glass of wine tonight..........

 

[SkwerI]

I am ashamed to say that I have no idea what 'depth of field' means. I took the pictures with my Canon digital on Macro mode so I could get up close, but I kept back far enough to get the entire leaf in the frame. Do you want a closer close up?


edit: I just looked closer at your picture.

 

[Che]

Ha!

Brian, Roger could certainly explain it in real terms...all I know is that with a deeper depth of field, more is in focus at one time.

If you're shooting it in 'macro mode', it's going to have a very shallow depth of field and it's hard to get everything in focus at the same time. If your subject is very flat, most everything will be in focus..but with your leaf, it's bowed so some is 'far' away and some is 'close'. I was just looking at some fuzzy little dealybobs up at the top of the upper right quadrant that looked more like chubby critters (aphids) than mites, but it's hard to tell.

 

[Strikermike]

to get more depth of field close the lens aperture down IE 5.6 instead of 2.8. The smaller the aperture the greater the depth of field. Larger depth of field means items at more variable distances from the lens will still be in focus. Suppose you were taking a picture of a group of people at a long table. A short depth of field would mean only the people closest to you would be in focus. To increase the depth of field and get all people in focus. You would stop down he aperture and compensate with a longer exposure. Hope this helps. Gerry could probably explain it better.

 

[Paul B]

does that mean we have to take the camera off the 'auto' setting?

 

[Strikermike]

aperture priority can be your friend.

 

[SkwerI]

Thanks for the help, guys. I went and grabbed another fresh leaf sample this morning and took it to my buddy at the nursery/ garden center and he confirmed it was spider mites. He gave me two containers of granular poison stuff to spread out around the root zone. I forgot the name but it's obviously a systemic insecticide/ miticide. Di-something.

Having this broad of a knowledge base to draw upon is a wonderful thing.

 

[Blinky]

I swear it was only ONE glass of wine tonight..........

I can totally see that and I haven't had a drop.

 

[Paul B]

all good RJS, hope it was the proper diagnosis and the miticide was right. was it Dimethoate?

 

[SkwerI]

Couldn't tell you, Paul. It was a rather strong smelling gray granular in a 3.5 lb yellow plastic jug with a shaker top. Just unscrew the top and shake it out, then water it in.

 

[Paul B]

aaaaaaaaaaaaaah! real names in the open forum... oh, hang on, mines not private....