BEETLE - MANIA BIOLOGICAL CONTROL OF SALTCEDAR IN TEXAS

VOL. 5 NO. 1 2014

2014. 2012. After A aVery Slow Good Start, Year Leaf forBeetles : TamariskAgain Attack Leaf SaltcedarBeetles in in Texas Texas ! The saltcedar leaf beetle feeds only on After a slow start this past Rio Grande and Pecos sent from many sites. Beetle summer, saltcedar leaf beetle Rivers. The subtropical leaf numbers finally increased in saltcedar and athel. populations increased and beetle is well established in September and defoliated Athel is a closely defoliated saltcedar trees far west Texas on the Pecos trees at some locations. related species that again in many areas of Texas River and on the Rio Grande About 5-10% of the saltcedar grows along the Rio in 2014, further weakening from Big Bend National Park trees at these sites on the Rio trees defoliated in previous to El Paso. In 2013, this spe- Grande between Lajitas to Grande River in years. In areas where trees cies dispersed along these Candelaria appear to be dead Texas. have been defoliated for 3-4 two rivers into New Mexico. due to feeding by beetles. consecutive years, trees are However, it has not yet been Texas High Plains. The dying back and canopies are reported downriver from Big larger tamarisk beetles, origi- If saltcedar or thin and declining. There are Bend National Park. The spe- nally from Uzbekistan, is well athel trees are not now 3 species of leaf beetles cies got off to a slow start in established in the Texas High present, the larvae established in Texas. 2014, and beetles were ab- Plains and Rolling Plains and starve to death. adjacent areas in Oklahoma. In 2014, beetles defoliated large areas of saltcedar at Saltcedar beetles Palo Duro Canyon and along were first estab- the Prairie Dog Town Fork of the Red River and the Salt lished in Texas in Fork near Clarendon, TX. 2004 at Big Spring, Defoliation was also wide- TX. Since then, spread at Lake Meredith and there have been no on the Canadian River, but was more localized than in reports of beetles or 2013. The Uzbek beetle also larvae feeding on tracked the Canadian River any other plant. west and was reported for the first time in New Mexico except saltcedar when it was found at Ute and its close relative Lake, near Logan, N. M. athel (Tamarix Upper Colorado River. The third species, the Medi- aphylla). terranean leaf beetles, origi- Approximate distribution of the subtropical leaf beetle in the Trans nally from Crete, was found Pecos region (green area), the Mediterranean leaf beetle in the upper only in Howard and Martin Colorado River (brown area), and the larger leaf beetle in the High, Counties but again extensive- South and Rolling Plains of Texas (red). Beetles are not present ly defoliated large areas of throughout the shaded regions, but if not present, are likely to dis- perse in the future to new sites within the shaded region. saltcedar.

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2014 PAGE 2

Beetles Move on the Upper Brazos River.

A surprise find in 2014 was the presence per Brazos River Basin. This natural move- of leaf beetles defoliating saltcedar at Pos- ment apparently occurred during the fall of sum Kingdom Lake in late July. A survey of 2013 through the summer of 2014, and the Brazos River and its tributaries above represents a movement of more than 100 Possum Kingdom in August found beetles miles cross-country (Aspermont to Possum Larvae of the at Lake Graham and at four bridges cross- Kingdom Lake). Finally, leaf beetles were ing the Brazos in Young, Baylor and Knox found defoliating saltcedars at Lake Bridge- saltcedar leaf counties. At some sites, beetles had defoli- port, part of the Trinity River Basin, in beetle feed on ated up to 80% of the saltcedars. Leaf bee- Wise County in 2014. This is the now the tles were also present on the Double Mt. most easterly population of leaf beetles in saltcedar leaves Fork of the Brazos in Knox, Stonewall and Texas. Fisher Counties and the saltcedar trees More To Be Done. As of 2014, leaf and tender bark. visible from the HW 70 bridge north of beetles were present on an estimated 60% Rotan were heavily defoliated. of the saltcedar acreage in Texas. There Larvae feed for At Hubbard Creek Reservoir, near Bre- are still large infestations of saltcedar about 12-14 days kenridge, leaf beetles had defoliated several where leaf beetles are not yet present, areas of saltcedar growing near the lake including the Lake Spence and Lake Ivie during the shore. Leaf beetles were also found on the reservoirs on the Colorado river. Efforts Clear Fork of the Brazos River in Shackel- to establish beetles at these two reservoirs summer. Full ford and Jones County, at Lake Stamford in during the past 4 years have not been suc- Haskell County and Lake Fort Phantom Hill cessful and the Mediterranean beetles in grown larvae are north of Abilene. However, saltcedar trees the upper Colorado River have not moved about 1/3 inch were much less common and beetle num- down river. In the future, the larger tama- bers much lower at these sites. risk beetle from the north or the subtropi- long. Several The beetles found on the Upper Brazos cal beetles from the south may reach these are the larger tamarisk beetle, D. carinata, reservoirs. Also, the saltcedar infestations generations are originally collected from Uzbekistan. This the Lower Rio Grande Valley are distant species is widespread in the Texas High from any leaf beetles population. completed per Plains and northern Rolling Plains and in Thanks to Erin Jones, Jerry Michels, year. The adult late 2013 was found as far south as Asper- Anne Marie Hilscher, Chris Ritzi, Salvador mont (Stonewall County). The species nat- Vintanza, Mark Muegge, John Burch, Kenny stage overwinters urally dispersed from this area south to Gillespie and Carol Sutherland for sharing Abilene and southeast to Possum Kingdom information on beetle activity in their areas on the ground Lake and now is found throughout the Up- and to James Tracy for identifying leaf bee- under leaf litter

and in bunch Leaf Beetles at Possum Kingdom Lake

grasses. Saltcedar has invaded the shoreline of Possum Kingdom Lake as lake levels have reced- ed in recent years. Beetles defoliated these young trees in 2014. Ants, which feed on leaf beetles, are uncommon in these sandy areas, and as a result, leaf beetles thrive. VOL. 5 NO. 1 P A G E 3 Impact of Beetle Feeding on Saltcedar Trees

Saltcedar is hard to kill. Leaf beetles season, food reserves again decline as several years, the tree declines further kill trees by slow starvation. Feeding by the tree tries to produce new leaves. until only a few green shoots are present larvae and adults removes the green During the winter, the tree survives on and some trees die. For seedling trees, foliage necessary to make food, the car- the stored carbohydrates and further death can be more rapid. While the pro- bohydrates, needed by the tree. Larvae depletes these reserves. With limited cess is slow, other plants begin to grow also feed on tender bark, causing food in the spring, the green canopy is as the open canopy allows sunlight to branches ends to die back. Saltcedar reduced as upper branches die back. reach the soil and without leaves during trees draw upon carbohydrate reserves Due to this stress, new leaves and much of the summer, water use is less. stored in the root crown to regrow new branches are small and deformed, a con- Leaf beetles will never eradicate saltce- leaves during the summer. However, if dition termed epicormic growth. As dar, but it should be less abundant trees are again defoliated by beetles that beetles continue to feed on trees for where beetle populations persist.

The Cactus Moth: A Biological Control Agent for Prickly Pear Becomes An Invasive Pest in North America The use of the cactus the next few years, the cactus moth Thus, in the US, the cactus moth is con- moth, Cactoblastis cactorum, as a biolog- destroyed the prickly pear infestation sidered an invasive pest and is under ical control agent for prickly pear cactus and the land was reclaimed for grazing federal quarantine regulations. in Australia is one of the most successful and agricultural use. From Florida, the cactus moth programs using an insect to control a The cactus moth was released to moved along the Gulf Coast as far west weed. Prickly pear was introduced into control prickly pear in some Carribea- as the coast of Louisiana. Control ef- Australia and cultivated to rear a small nean Islands in the 1950s. Unfortunate- forts are focused on removing prickly insect that feeds on this cactus. The ly, in 1989 the cactus moth was discov- pear plants along the Gulf coast and insect, cochineal, was then and is today ered in the Florida Keys. This discovery quarantine of cactus plants from infested collected from the pads and processed raised the alarm because the cactus areas. To-date, cactus moth has not to extract a bright red dye. The prickly moth feeds not only on prickly pear, but been reported from Texas. pear planted in Australia soon escaped on many of the other 60 species of cac- The caterpillar of the cactus moth is cultivation and became a very severe tus in the genus Opuntia that are found initially pink in color but becomes red- pest of grazing lands. By 1925, 60 million in the US. Many Opuntia species are not dish-orange with black dots that con- acres were infested and about 30 million weeds but play an important role in nect and form transverse bands. Cater- were so densely infested with prickly ecosystems. Some species are endan- pillars feed on the tender tissue inside pear that the land was nearly impenetra- gered. Also, if the cactus moth reached the prickly pear pad. The larvae eventu- ble by man or cattle. Mexico, it could be a serious pest of ally hollow out the pad which yellows Entomologists found the cactus prickly pear used as food for humans and dies. The mature caterpillar is about moth caterpillar feeding on prickly pear and livestock and valued at $80 million one inch long and several can feed to- in Argentina and it was collected and annually. The cactus moth could also gether within a pad. released into Australia in 1925. During threaten the ornamental cactus industry.

Cactus Moth Caterpillars and Pads Fed Upon by Cactus Moth Caterpillars. Photographs by Christine Miller, Univ. Florida. 2014 PAGE 4

Texas Panhandle. 2014. Saltcedar defoliated by beetles on ranch near Borger, TX. (photo E. Jones).

Rio Grande River near Presido, TX. Sept. 2014. Canopy dieback and tree death due to repeated feeding during five years by saltcedar beetles. (photo A. M. Hilscher). 2014 PAGE 5

Upper Colorado River, near Colorado City, TX. October, 2014. Canopy dieback. Beetles present here since 2009. (photo A. Knutson).

Allen Knutson Professor and Extension Entomologist Texas AgriLife Research and Extension 17360 Coit Road Dallas, TX 75252 For more information on Phone: 972-952-9222 biological control of saltcedar E-mail: [email protected] and other invasive weeds in

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