Issue: October 28, 2000

• What caused the toa1stools
• Backfill soil over tree roots
• White fly problem

What caused the toadstools

The morning after a night of thunder, lightning and rain often produces toadstools on the lawn. What causes the toadstools to grow overnight? Is it the lightning or the rain?

It is important to understand that a toadstool (mushroom) is the fruiting structure of a large mass of fungus growing in the soil. When conditions are right for this (pre-existing) fungus to reproduce, it quickly produces the mushroom. The mushroom, the fruiting structure, then produces spores to reproduce the fungus.

The moisture provided by the rain storm is the factor for which the fungus waits.

Backfill soil over tree roots

We had a house reconstruction and added approximately 1-2 feet of dirt to level our back yard. We have two very big, old trees there. What needs to be done to make sure that the trees will not rot and will survive the added soil around them?

This is an important factor to consider. Most trees, especially old and well-established trees, do not grow well if the soil level over their roots is raised. The area just at the base of the tree is especially sensitive.

You should build a wall circling the base of the tree to keep the soil from collecting around the root collar of the tree. The diameter of this ring depends on the size of tree. Any soil already placed around the base of the tree should be removed to the level of the soil prior to construction. Many good arboriculture (tree care) and landscape architecture books show how this should be done. You can also contact your local Cooperative Extension Service agent for information.

White fly problem

What can I do to get rid of white fly? Everything in my (small) yard is infested, including marigolds, tomato plants, zinnias, snapdragons, etc. As soon as I start watering, a cloud of white flies rises from the plants being watered. There are trees in the area (Ash, Jacaranda, Mexican Elder, etc.) but not in my yard. I would appreciate any suggestions. Las Cruces, NM

There are several insecticides labeled for use in managing white fly infestations. Some white flies have developed resistance to some insecticides, so you might have to try several. Insecticidal soap will be effective but may do some damage to the plants. Horticultural oils may also be effective, but read the label to be certain that they may be used on the plants that are infested. Malathion(R), Diazinon(R) and other insecticides may also be tried. It is important that you read, understand, and follow the label direction for any product that you choose.

Send gardening questions to Southwest Yard and Garden, Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu or at https://www.facebook.com/DesertBloomsNM/. Please include your county Extension Agent (aces.nmsu.edu/county) and your county of residence with your question!

For more gardening information, visit the NMSU Extension Horticulture page: desertblooms@nmsu.edu.

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, office: 505-865-7340, ext. 113.