Agave problems may be result of tunneling weevils

     By Bob Morris
     View columnist
      The following are typical questions our Master Gardeners deal with 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 4 p.m. Monday through Friday. There is also a gardening Web site at http://www. intermind.net/mgarden/.
     
      Thanks to all of you who helped make the plant sale at the University's Center for Urban Water Conservation a success. Watch for a second sale this fall.
      Learn how to convert your water-guzzling, water-wasting yard into a low water-use, efficient and attractive landscape. Our Landscape Retrofit (remodeling) class is a hands-on design class offered from 6:30 to 9 p.m. Thursday evenings, Sept. 16 through Oct. 28 at the Community College of Southern Nevada's Charleston Avenue campus.
      The class is being taught by the University of Nevada Master Gardeners. Class space is limited so sign up early by calling the Master Gardener hot line at 257-5555. Weekly homework will result in a finished design that you will be able to put to use and enjoy.
      Brown spots on lawns are still a big problem. If these areas are spreading then I would consult with a nursery and garden center supplier for fungicides.
      Lawn areas that have died can be reseeded this fall with the appropriate lawn grass seed. Be sure to use a seed comparable to the one already in your lawn. Tall fescue seed such as Kentucky 31 (this is a popular one because of its price) will give you a much more coarse looking lawn than improved fescues which are more expensive.
      We will be seeing sap oozing from some trees such as African sumac and some stone fruit trees. This may be in response to the heat. Just because sap is coming from a tree does not automatically mean it has a borer. Check to see if the bark is peeling and if there are signs of borer activity.
      Borer activity include loose and shedding bark, sawdust coming from the holes or under loose bark and holes in the stem or trunk or tunneling just under the bark.
      This year we have seen more damage from elm leaf beetle than we have in the past few years. This insect causes the leaves to appear skeletonized by June. Damage is done by the immature form which clings to the leaf as it eats the surface.
      A few years ago this pest was very damaging to many elms in the area. As with many pests, they come in cycles and it appears that this pest has been building again in the past couple of years.
      The same is true with the cicadas. The Apache cicada, which is native to Southern Nevada, may follow a two to four year cycle so their populations may build to a peak in these intervals. These are the insects causing all the noise when it gets hot outside.
      Question: My agave died this past month and when I dug it out I saw that the roots were rotten and had holes all through it. What happened?
      Answer: This may have been due to the agave weevil, which tunnels into the base and roots of the plant. Adults chew into the lower leaves of agave and introduce a bacterial rot that appears to be necessary for larval development. They lay eggs into these holes and the larvae burrow into the plant carrying the bacterial rot with them.
      Agaves first show signs of yellowing like they are getting too much or too little water. Later these plants die during late summer as a result of bacterial rot.
      Adults are dusty black weevils about an inch long, with a long snout. They do not have wings. Larvae are whitish grubs without legs. The adults may be seen earlier in the summer on the ground and plant early in the summer.
      To prevent, apply diazinon granules to soil around the base of agaves every two weeks mid-May through June. Remove and destroy infected plants as soon as damage is evident. Remove larvae and adults from soil around the area where the plant was removed.
      If an agave is yellow in midsummer, the plant is receiving regular waterings and the soil has good drainage, you might assume you have an infestation of agave weevils.
      Q: I have this large green insect flying and dive bombing my family and me. I had it last year and I know it was damaging fruit on our fruit trees. What is it?
      A: If you had the green June beetle last year and you had fruit trees then I'm sure you did have problems with your fruit.
      Why it's called a June beetle is beyond me. It should be called a July and August beetle instead. They cause damage to peaches, plums, figs, apricots, grapes and tomatoes during July and August. Damage is done by the adults which can scrape a hole in the fruit and feed on the flesh inside.
      Their excrement stains and taints the skin and flesh of the fruit. The green June beetle or fruit beetle is more than an inch long, metallic green in color with a brownish yellow band around the edge of the wings.
      They can be aggressive toward humans and animals which come near their places of activity.
      The head has a short hornlike extension on the front. Larvae are soil dwelling and feed on organic matter on the soil surface or in compost piles.
      The larvae may be 2 inches long when mature. Mature larvae form hollow cells in the soil and pupate there.
      These insects can be attracted to traps where they can be caught and destroyed. Traps can be made with attractants such as very ripe fruit or fruit juice. Remove leaf litter and other organic matter from the soil surface in spring to starve larvae. Also, allow the soil surface to dry out and harden to imprison the adults before they emerge.
      Q: My sago palm or cycad has yellow leaves. What could be the problem?
      A: The usual reasons for yellowing are planting in locations with too much direct sun, over watering or poor drainage. They are tough plants. The sago palm, also called cycad, is a bit out of place in the desert. However, they will grow very well here if we are careful where they are planted, how they are planted and how they are maintained.
      They shouldn't be planted in full shade and they shouldn't be planted in hot locations in full sun. They prefer light shade or a few hours of direct sunlight in the morning or early afternoon.
      Avoid direct, late afternoon sun next to hot walls. When they are planted, amend the soil heavily with organic matter particularly those amendments that produce acid such as peat moss or home-made, well-rotted compost if you have it.
      Use sulfur in the backfill along with a good starter fertilizer. Make sure that the irrigation system is watering the entire root zone when it is operating and that the planting hole is draining.
      It should be on an irrigation valve that is watering other plants that need frequent irrigations other than the lawn. Cycads do well in flower beds. Do not water from overhead if at all possible or at least do it infrequently.
     
     Bob Morris is a horticulture specialist with Nevada Cooperative Extension.