Adaptation of Salt Cedar Biocontrol Beetles to Shorter Critical Daylengths
* Do the beetles imported from Fukang, China, and resident at Pueblo, Colorado, for eight years show a measurable difference in critical daylength from Fukang beetles at native latitudes?
* Could these beetles be used at latitudes more southern than Pueblo?
Need and Benefit
Salt cedar clogs waterways and consumes up to three times more water than native vegetation. One of the biggest factors in the high amount of water used is its ability to tap deeper water tables far back from riparian zones. This enables it to grow in larger numbers and farther away from riparian zones than native vegetation. It has invaded most riparian areas (approximately 1.6 million acres) of the arid Western United States, causing an annual water loss estimated to be as great as 2,500,000 acre-feet. The annual dollar value of lost irrigation water is estimated to be as high as $121,000,000, and the annual dollar value of lost power generation along the Colorado River alone is as great as $43,600,000 million. Total losses are set at $291,000,000 annually (Zavaleta 2000).
Costs for use of traditional methods of salt cedar control were estimated in the above article and by Reclamation weed managers and researchers to average about $2,000/acre (for root plowing or cut stump herbicide application). Equipment, supplies, and labor for these methods are costly.
Biocontrol insects, once developed, provide a less expensive option. Biocontrol methods would assist Reclamation to deliver water savings at lower monetary and environmental costs. Several groups have been attempting to establish beetles in southern latitudes, but there have been fewer successes than in northern sites, both in terms of permitting and beetle establishment.
As we have found in general, and in attempting to establish a few other ecotypes of _Diorhabda_, insect supply is frequently the bottleneck in biocontrol programs. If it does prove possible to move the Pueblo-adapted Fukang beetles to more southern latitudes, we would have a very good supply with which to establish new populations quickly. This ecotype of beetle has also met with fewer regulatory hurdles, especially with regard to host-specificity to _Frankenia spp._ and _athel_ salt cedar. It would also mean we would spend less time and money investigating the biology and behaviors of a new ecotype.
Zavaleta E., 2000. The Economic Value of Controlling an Invasive Shrub. Ambio vol.29 number 8, pages 462-467.
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