All Dr Dendros - Cottonwoods in CO

[jrizman]

Wondering if we cant put our heads together on determining the issues with some cottonwoods (3"Dia) that were planted ( in a riparian zone in the front range of CO in close proximity to large cottonwoods) this spring. they are in a natural area and have drywater tubes.

-- decline is present in approximately 60% of them

-- many of them are showing yellowing of the leaves (between veins not the veins). some are in turn showing leaf spot due to stress (IMO). i have not gotten the soil test done yet, but should have something soon.

-- There is also a boring insect present in the main trunk. in turn some woodpeckers have done some pretty good damage.

-- also, looks like a defoliator is eating leaves at the top, but they had a pretty bad hail storm there and that could have done the damage as well, im leaning towards insect damage...


Im thinking there may be some soil issue as these trees attempt to establish. What about the boring insect damage?
Ideas?
Thanks!

 

[S Mc]

Were these trees field dug, container plants, balled in burlap? Normally with this species you can take a finger size cutting and stick it in the ground and you are good to go, however, as with most trees, the larger the caliper the more issues you will have with establishment. The more likely of physical damage to occur in digging, transporting and planting. If they are planted amongst mature cottonwoods they are going into an area with a lot of competition. Not only with the resources available below and above ground, but the mature trees are already going to be a natural host for a variety of insects and pathogens that will not be hesitant to check out new stressed trees.

The symptoms you describe of chlorotic leaves and defoliated top could be caused by some borer activity such as the Agrilus liragus.

Woodpeckers are the primary predator for borers in natural settings and so if there are borers it would not be surprising to find woodpecker damage.

As you know, stressed trees are more susceptible to the successful invasion of insects and pathogens. Healthy trees being able to fend them off more successfully.

Could you post pictures? And do you know what kind of cottonwoods these are? I'm not sure that matters all that much as they hybridize like crazy and the number of insects that go for them (which are numerous) tend to cross over.

Sylvia

 

[jrizman]

they say they are native cottonwoods, my guess is they are a deltoides variety. they were nursery grown, B&B

i agree, about using bigger trees, but thats what was selected and im curious if they maybe just need some additonal fert from growing up in the plush nursery setting (dont get me into that!) and now being stressed, ill make a decision after a quick soil test this week. we did bucket water the other day. i also want to recommend getting the bush hog in there to cut down the ridiculous thistles that are just insane!

my camera is shot and i wasnt able to get pics. but the yellowing is very typical to what youd see

Were these trees field dug, container plants, balled in burlap? Normally with this species you can take a finger size cutting and stick it in the ground and you are good to go, however, as with most trees, the larger the caliper the more issues you will have with establishment. The more likely of physical damage to occur in digging, transporting and planting. If they are planted amongst mature cottonwoods they are going into an area with a lot of competition. Not only with the resources available below and above ground, but the mature trees are already going to be a natural host for a variety of insects and pathogens that will not be hesitant to check out new stressed trees.

The symptoms you describe of chlorotic leaves and defoliated top could be caused by some borer activity such as the Agrilus liragus.

Woodpeckers are the primary predator for borers in natural settings and so if there are borers it would not be surprising to find woodpecker damage.

As you know, stressed trees are more susceptible to the successful invasion of insects and pathogens. Healthy trees being able to fend them off more successfully.

Could you post pictures? And do you know what kind of cottonwoods these are? I'm not sure that matters all that much as they hybridize like crazy and the number of insects that go for them (which are numerous) tend to cross over.

Sylvia

 

[S Mc]

Are the native cottonwoods around these trees stressed in the same manner as the young trees? If not, I would think the appropriate nutrients are available in the soil.

Remembering that balled and burlap trees lose 75 to 90% of their roots during the transplanting process it is not surprising that these are showing stress. As stated, stressed trees are ripe for insect invasion.

Fertilization can push new growth, which may or may not be in the trees' best interest. Many insects enjoy the fresh, succulent growth as well, so you can end up enhancing a problem.

Proper irrigation of establishing trees is the primary cause of success and the lack thereof of failure. From your description, it sounds that adequate water may perhaps have been lacking.

Sylvia

 

[treeseer]

Click Buying and Planting and Mulching in the link below. Sounds like the problem is in the roots, and could be correctable by proper planting methods.

Dendro can't do much if he can't see the tree.