Weird weather wreaks havoc on grass, plant leaves

     By Bob Morris
     View columnist
      The weather has been quite peculiar over the past several weeks. We have seen a lot of wind damage on plant leaves that are soft and succulent. This damage makes the leaves appear tattered and ripped. It can appear like insect damage.
      The sudden change in temperatures and wind has caused some plant leaves to brown around the edges. Turfgrass has been caught off guard and there has been a sudden increase in watering.
      Look for smoky-grey patches in the lawn which indicates dry areas. If these areas persist, aerate the lawn. Any fertilizer applications on fescues should be light; about half the label rate or less.
      This will help in disease prevention. Lawn fertilizers used now should contain plenty of potassium for the heat.
      Aphids are still quite a problem on many plants. This is unusual since by this time it's usually hot and aphids don't like hot weather. The alternating warm followed by cool weather has given these insects an unusually long spring season.
      This may have given some gardeners some trouble in controlling these insects with organic controls such as insecticidal soaps.
      Traditional pesticides for controlling aphids may be required for good control.
      Watch for caterpillars that cause webbing in mesquite leaves. This can be followed later with spider mites. Spider mites are the worst of the two problems since they are much more long lasting and more difficult to control.
      The only biological controls available for mites are washing the leaves with water to remove dirt and the use of horticultural oils. Dirt can interfere with natural controls, such as beneficial mites.
      Oils are an excellent pest control method that are safe to use, provided the air temperatures are not too high. Read the label before using. Oils work well on mites, aphids and scale insects.
      Look for tobacco budworm damage on flowering plants. Damage from tobacco budworm usually is a decrease in flowering. Look for them on petunias, geraniums and other bedding plants. Sprays of Bt (Dipel and Thuricide) will work well.
      Question: I have noticed webbing that holds the leaves of mesquite trees together. When I pull the leaves apart there is a small worm on the inside. Why is this?
      Answer: This insect is very common on mesquite. We see it every year since so many mesquites were planted in the valley in the last 10 years.
      These caterpillars feed on the leaves of the mesquite and can cause significant damage, if enough are present, by reducing the number of leaves on the tree. The bacterium spray containing Bt does an excellent job controlling these insects and is safe to use, provided you aren't worrying about other caterpillars that you might be trying not to kill.
      Q: My tomatoes and peppers from my garden have brown spots on the bottom. How do I prevent this?
      A: This is most likely blossom end rot and is caused by irregular waterings. The real cause is a poor availability of calcium during fruit formation but is aggravated by irregular watering. I would mulch plants with an organic mulch covering the surface of the soil on top of the root area.
      This slows evaporation from the soil and helps to cool the roots. Just a half-inch of mulch is adequate such as a top dressing of compost or bagged commercial compost. Don't let the plant roots go through alternate dry and wet cycles but try to maintain a moist soil during fruit production.
      Q: My cucumber plant is flowering and then not producing fruit or the fruit it produces is shriveling.
      A: Some of the older cucumber varieties first produce male flowers followed by the female flowers that set fruit. Since the first flowers are male they will appear but will not produce any fruit. When picking a variety of cucumber to grow, select one that produces fruit with the first flowers.
      These are called gynecious hybrids and will be designated as such on the package or in the seed catalog. If the female flowers are not pollinated, they may set fruit that shrivels on the vine when small.
      This may be because of poor bee activity or bad weather during blossoming. Remember that many of the garden pesticides will kill bees and never apply a pesticide to a plant in bloom.
      Q: My grapes are getting these worms eating at the leaf surface. What are these things and how do I get rid of them?
      A: These are grape leaf skeletonizers, a nasty moth that really doesn't look like one. The adults are black, fly around the vine and lay their eggs on the leaf surface.
      The eggs hatch and these caterpillars cling on the leaf surface, eating the surface layer. The veins of the leaves are generally left untouched, leaving the leaf "skeletonized."
      The safest spray to use is the Bt or bacterial sprays like Dipel or Thuricide, which won't kill them immediately but will stop feeding within 24 hours and finally die. Be careful of these caterpillars. If they fall on your skin they burn, feeling like a matchhead. We used to recommend diazinon and it will work but it isn't as safe to use on humans as the Bt spray.
      The Bt's are still a pesticide and you should follow the directions on the label. These bacteria are safe for humans and other animals that might come in contact with the spray.
      Q: I have yellow daisies with black bugs under the flowers. They are giving off a sticky sap. What are they and how do I control them?
      A: This is most likely aphids on your daisies. Wash them off with a hose. Follow this with an insecticidal soap. Repeat applications of the soap will be necessary. If you choose a traditional pesticide, insecticides to use include diazinon and soil applied systemics.
      The soil applied systemics work the best but can also be the most dangerous to use. If it's not too hot, try oils or soaps, and follow label directions.
     
     Bob Morris is a horticulture specialist with Nevada Cooperative Extension.