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Title: Biology of the galling wasp, Tetramesa romana, a biological control agent of giant reed

item Moran, Patrick
item Goolsby, John

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2009
Publication Date: 3/15/2009
Citation: Moran, P.J., Goolsby, J. 2009. Biology of the galling wasp, Tetramesa romana, a biological control agent of giant reed. Biological Control. 49:169-179.

Interpretive Summary: Giant reed, also known as carrizo cane, is a grass species that can grow up to 5 meters (18 ft) tall and looks like bamboo, although it is not closely related to bamboo. Giant reed is not native to North America, and this giant grass has invaded river corridors and the banks of lakes along the Rio Grande and its tributaries in Texas and Mexico, as well as many other rivers and wet areas across the southern U.S., occupying over 100,000 acres. In dry areas stretching from South Texas to northern California, giant reed removes millions of dollars of water per year that is needed for agriculture and domestic use, and it threatens native plants and animals by pushing them aside and by increasing flood and wildfire damage along rivers. The objective of this study was to determine the development, reproduction, and survival of a wasp, collected from the native range of giant reed in Mediterranean Europe, that is capable of causing tumors or ‘galls’ on shoot tips of giant reed, interfering with plant growth and thus contributing to biological control of giant reed using natural enemies. Adult female wasps do not need to mate to reproduce. Females inject eggs into shoot tips, which hatch into larvae after 4 to 5 days and complete three wormlike ‘larval’ stages within 26 days of egg injection. The plant produces a gall and the larvae feed on the gall tissue. The fully-grown larva undergoes metamorphosis for about one week as a pupa, and then chews its way out of the gall to repeat the life cycle. The female wasp lives only 3 to 4 days, but in that time it can inject enough eggs to produce 20 to 55 offspring within one month of egg injection. About 65% of the wasps raised from a shipment from southern Spain produced offspring. Reproductively successful wasps spent more time probing or injecting giant reed stems than did unsuccessful wasps, and wasps spent more time probing in the afternoon than in the morning. The results of this study show that the wasp (Tetramesa romana) has biological characteristics that will help it succeed as a biological control agent against giant reed in the Rio Grande Basin and elsewhere in the U.S.

Technical Abstract: The biology of the gall-forming wasp, Tetramesa romana Walker (Hymenoptera: Eurytomidae), from southern France and Spain was studied for biological control of giant reed (Arundo donax L.), an exotic and invasive riparian weed in the U.S. Females developed eggs parthenogenetically and deposited them into shoot tips of A. donax. Eggs were 1.26 ± 0.08 mm long and hatched within five days of oviposition. Gall tissue developed around eggs and young larvae. The larvae completed three instars within 23-27 days of oviposition, with the first and second instars lasting 5 days each and the third instar lasting 12 days at 27°C. Larvae increased in length from 1.0 mm to 4.1 mm and in head capsule width from 0.14 to 0.47 mm between the first and last instars, respectively. The total generation time averaged 33 days. Adults were 6.8 mm long with antennae. Adults lived an average of 3.7 days. Spanish wasps lived 1.3 days longer than French wasps. French and Spanish females produced offspring 36% and 65% of the time, respectively. Individual Spanish wasps produced an average of 26 (up to 66) progeny, displaying an intrinsic capacity for increase of 0.081 and a population doubling time of 9.2 days. Reproductive wasps spent 15% more time probing stems than did wasps that failed to gall stems, and probing behavior was 13% more prevalent in the afternoon. The wasp T. romana has the potential to establish large populations on A. donax after field release.