Use insecticides cautiously to avoid killing honeybees

      The following are typical questions our Master Gardeners answer daily at the Nevada Cooperative Extension. If you have gardening questions, call the Master Gardeners' hot line at 257-5555 between 9 a.m. and noon Monday through Friday.
     
      Many plants are beginning to bloom again now that the weather has warmed. Be careful with the use of pesticides and the killing of bees. Our bee populations are small in numbers without accidentally killing honeybees through the application of insecticides on or near plants in bloom.
      Those yellow-flowered weeds in bloom now in weak lawns and flower beds are in the mustard family. Crush the leaves and smell them. They are winter annuals and germinated last fall.
      The seeds produced by these yellow flowers will drop to the ground in a couple of weeks where they will lie dormant through the hot summer. Next fall they will germinate and remain dormant through the winter as a plant with a low-growing rosette of leaves.
      Pull or cut the flowers off to keep the plant from producing seeds for next spring's crop. They won't even get started if you thicken the lawn or mulch the flower beds. These weeds are poor competitors.
      This week some aerial galls were brought into the office for identification. These are tumor-like growths on branches. The owner claimed that they were all over their tree's branches. Bacterial galls can be spread by pruners that are laid on soil which carries the bacterium that causes the gall to form.
      I was present at a pruning demonstration outside of Las Vegas recently. I noticed that the people pruning were carrying shears, loppers and a saw. Because their hands were busy, they laid the tools they were not using on the ground. When they needed a different tool, they picked up the tool from the ground, made their cut and laid the tool on the ground again.
      Do not lay saws, pruners or loppers on the ground when pruning. Contaminated soil is everywhere and laying these tools on the soil will contaminate them. The disease can then be spread to the tree where it will cause gall formations.
      Protect trees and shrubs from being damaged above the soil line during planting. If the damaged part of a plant comes in contact with contaminated soil, a disease called crown gall can occur. This same disease can cause the aerial galls mentioned above.
      Question: How can I make my own soil for a raised bed garden?
      Answer: Generally, soils for raised beds should have good drainage and be friable. A soil which is friable should be easily worked with a garden trowel or by hand.
      Ideally, the soil could be made from one-third soil, one-third sand and one-third compost. The soil mentioned in the above mix could come from your garden but native, raw desert soil would be a mistake to use. Even at one-third of the mix, the native desert soil might contain high levels of salts that damage plants and may take a long time to remove.
      In the meantime, plants sensitive to salts such as beans and beets would suffer. A soil with a history known to support garden plants would be best to use.
      The sand used should not be "reject" sand. Reject sand will plug the pore spaces in your garden soil so that drainage will be slow. The sand used should have good drainage properties and be free of natural toxic chemicals such as boron.
      A natural substitute for sand would be a mineral such as zeolite, which has become more available from suppliers in recent years. Zeolite has better properties than sand.
      Zeolite holds fertilizers like a clay but does not cause the problems of clay soils. It's lightweight compared to sand. Zeolite is absorbent and therefore, unlike a sand, retains water. The zeolite used should not be "reject" zeolite.
      That is, it should be screened to remove the extremely fine particles. If money is not a problem, then perlite or vermiculite can be substituted for sand as well.
      Q: I tried to start seeds indoors but they came up and died. Why?
      A: Seeds started indoors must be planted in clean soil. If soil used to start vegetable or flower seed was used for other plants and not sterilized, the young seedlings may be subjected to diseases such as "damping off."
      This disease is very common and can be caused by at least five different organisms. If your soil was used previously, then the soil must be heated to 130 degrees for 30 minutes to kill these types of disease organisms. Don't use your oven to heat the soil.
      The soil will smell up the whole house when it is "baked." Soil purchased from garden stores is sterilized. Using this soil would not be a concern.
      Use solar heating to sterilize soil. The soil can be spread on a plastic sheet on the ground, sprinkled with water, covered with clear plastic and "baked" in full sun. Two or three good, "hot" days will do the trick.
      Q: I was digging a hole for a tree in my landscape and the soil from the planting hole smelled like a sewer. Is there something wrong with my soil? Is it contaminated with chemicals?
      A: The gas you are smelling is probably hydrogen sulfide. It's a natural gas made in soils that are anaerobic, that is, they don't contain enough oxygen. Oftentimes, this smell results because the soil is waterlogged due to overwatering and poor drainage. Usually this soil is grayish or black in color.
      Our soils contain quite a bit of sulfur in the form of gypsum and other minerals. Organic matter can contain quite a bit of sulfur as well. This, combined with poor drainage, may be the source of the sulfur smell.
      Plant roots cannot live under these conditions. Improving the drainage of the soil will get rid of the problem. If you still have drainage problems, plant the tree on a berm or mound instead of in a hole.
     
     Bob Morris is a horticulture specialist with Nevada Cooperative Extension.