Rio Grande Basin Initiative

2007-08 Deliverables

Task 6 Extension
Principal Investigator(s): Mark Muegge

Task 6: Environment, Ecology and Water Quality Protection

  1. Maintain and monitor populations of the introduced leaf beetle, Diorhabda elongata, for biological control of saltcedar established at the Pecos, Imperial and Fort Stockton sites in TX.
  2. If populations are large enough, re-distribute the beetles from these sites to local landowners and land managers.
  3. Establish new populations of the Crete leaf beetle ecotype along the Rio Grande on a private ranch near Fort Hancock, TX and near Beals Creek in Midland County, TX.
  4. Continue efforts to determine feeding activity of Crete leaf beetle ecotype on Tamarix aphylla.
  5. Initiate study to determine effect of Crete leaf beetle ecotype feeding activity on longevity of seeding saltcedar.
  6. March-May. Collect data from overwintering study at Fort Stockton location. Maintain large field cages and establish cage sites at the El Paso and Martin county locations. Cut back saltcedar trees at new cage sites. Establish a large field cage at the feeding study site near Fort Stockton.
  7. April-July. Inspect large field cages at the Fort Stockton, Pecos and Imperial sites for emerging beetles. Establish transects at the Fort Stockton, Pecos and Imperial cage sites so that beetle movement can be monitored. Replant needed treatment trees for the beetle feeding study at the Fort Stockton site. Water test trees if and when needed.
  8. June-October. Inspect cages bimonthly and record the number of adult beetles and larvae observed at each cage site at the Fort Stockton, Pecos and Imperial sites. Monitor beetle movement from these sites every two weeks. Once the first generation of beetles is complete and beetle densities are relatively high, then sufficient beetles will be collected and transferred to new large field cages in El Paso and Martin counties, and to the large field cage at the feeding study site. Once beetles have completed one generation, beetles will be released at the feeding study site. Data will be collected at this site every week until first frost. Data collected will be number of beetles, egg masses and larvae found on each treatment tree in the experiment.
  9. Study to measure the impact of beetle feeding on seedling saltcedar during one and two generations will be initiated. Tentative protocol for this study is as follows: Select area large enough to contain 12 14 ft x 14 ft plots. Tests will be set up in a RCBD with 3 treatments and 4 blocks. Treatments:
    1. Caged Beetles
    2. Cage Only, no beetles
    3. No Cage-no beetles, the control.
  10. Procedure: Divide the 16 plots into four quadrants. Count the number of plants per quadrant in each cage. Then thin plants so all plots have the same number of plants. Randomly select 15 plants per quadrant (60 plants per cage). Tag and number each plant to obtain before and after data on same plant. Measure plant height, stem diameter at 6 inches above ground and volume of foliage. First Defoliation: Release 300 beetles into Treatment 1. Once larvae are 3rd instar, count the number of larvae per plant on each tagged plant. Once all larvae have fed and left the plant to pupate, remove cages from Treatment 1 and 2 to limit cage effect. Wait two weeks to allow adults to emerge from pupae and for damaged plants to die. Then sample all tagged plants again and record data as before. Second Generation: Repeat test by again applying treatments to same plots as before. Tag, number and measure new plants in the beetle treatment if the first tagged plants are dead. Measure these plants. Remove all cages. Mark corners of all plots. Be sure tags on each plant are weather proof. Leave plants until next spring and again measure number alive/dead.
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