Issue: November 18, 1996

Sick Chinese pistache

I have three Chinese pistache trees about 15 feet from each other. The leaves on the first one turned completely brown before we had any frost. Its limbs are still green, but they don't look as healthy as the limbs on the other two trees. The leaves on the second tree are beginning to turn brown like the those on the first tree did. The browning begins from the middle of the leaf cluster where the stem comes into the cluster. The leaves on the third tree have only slight browning on the inside of the leaf cluster. The trees all receive the same amount of water, not excessive. They are only between 10 to 15 feet in height and receive full sun. These symptoms have developed in the past month or so. By the way, something has also killed two of fifteen small shrubs. Can you help me or direct me to someone who can?

You have given me several clues which may be very useful. I can't be absolutely sure, but I am inclined to think that an herbicide has been applied to an area within about 50 feet of the trees. The most likely candidate would be one of the long persistence herbicides often called soil sterilants. These are often used in gravel driveways, cracks and crevices of driveways and sidewalks, and along fences and property lines. These chemicals may remain active in the soil for long periods of time until the tree roots grow into the area of treated soil. The roots then absorb the chemical and translocate it back to the tree.

The symptoms that make me consider herbicides as a cause are the progressive nature of the symptoms and the fact that the symptoms begin at the base of the leaflets. Salt damage, early frost damage, and wind desiccation usually affect the edge of the leaf, with symptoms moving from the edge to the base of the leaflet. These herbicide symptoms often develop first on one side of the tree and progress to the whole tree. However, if the herbicide was applied in locations on all sides of the tree, then the damage could show all around the tree.

Disease may also be a cause. To determine if a disease is a problem, call your local county Extension Service office and find out what kind of sample would be needed to determine the problem. They may already be familiar with the symptoms and advise you of the problem. Otherwise, with a proper sample sent to the Extension Service plant pathologist, causal diseases may be determined. Local nurseries are also a source of information, especially if they will send the sample to a plant pathologist for diagnosis.

The shrubs may have been affected by the same problem, or they may have a separate problem. Again, your local county Extension Service office or local nursery should be able to help you.

When applying herbicides, remember that tree and shrub roots do grow to extend a great distance beyond the ends of the branches and that they are nearer the surface than most people realize.

Drying gourds

How can I dry gourds without having them rot?

The first consideration is good air circulation. Place them in a place with good air circulation all around them. This air should be dry, but here in New Mexico that is the easy part.

Don't let the gourds touch each other while they are drying. This helps the air circulation and to prevent the spread of rot if some do begin to rot. The surface on which they rest should not hold moisture. A wire mesh surface would be the best, but a table top is also adequate. Turning them periodically helps them to dry and allows you to detect rot early and dispose of affected gourds.

Now the hard part. It can take six or more months for them to dry properly. Some people will drill pinholes at the ends of the fruit to speed the drying process, but even so, it takes many months. Be patient.

Be sure the gourds are mature before harvest. Leave them on the vines as long as possible to mature. Gourds harvested before they are sufficiently mature will be much more likely to rot before drying.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!