Host range of the European leaf sheath mining midge, Lasioptera donacis Coutin, a biological control of giant reed, Arundo donax

Authors: Goolsby, John; VACEK, ANN - University Of Texas Rio Grande Valley; SALINAS, CRYSTAL - University Of Texas Rio Grande Valley; RACELIS, ALEX - University Of Texas Rio Grande Valley; Moran, Patrick; KIRK, ALAN - Retired ARS Employee

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2017
Publication Date: 6/23/2017
Citation: Goolsby, J., Vacek, A.T., Salinas, C., Racelis, A.E., Moran, P.J. 2017. Host range of the European leaf sheath mining midge, Lasioptera donacis Coutin, a biological control of giant reed, Arundo donax. Biocontrol Science and Technology. 27(6):781-795.

Interpretive Summary: Biological control of A. donax with insects may be the best long-term option for managing this highly invasive weed, because it is low cost, sustainable, and suitable for use of large areas such as the RGB. A bi-national biological control program was initiated in 2009. Two specialist, insect biological control agents from the native range of A. donax in Spain, the arundo wasp, Tetramesa romana Walker (Hymenoptera: Eurytomidae) and the arundo scale, Rhizaspidiotus donacis (Leonardi) (Homoptera: Diaspidae) have been released and established in Texas and Mexico, as well as in California. A third specialist insect, the arundo leafminer, Lasioptera donacis was evaluated for release in North America. This agent was found to be completely specific to A. donax and therefore, suitable for release. The arundo leafminer feeds on leaves causing early defoliation. Defoliation is expected to increase light penetration and therefore stimulate regrowth of native riverine plants. Transition of the riverine environment back to native vegetation conserves water, reduces risk of cattle fever tick invasion, and increase visibility of the international border for law enforcement. The arundo wasp lays eggs in arundo canes and side shoots, causing formation of galls (abnormal plant growth) which are fed on by the developing larvae, with adults emerging from the galls via characteristic exit holes. The wasp can complete its life cycle in 35-60 days and has now colonized A. donax along 600 river-miles or more of the Rio Grande and in several regions of Mexico. In 2016, six years after the release of T. romana, above ground biomass of A. donax had decreased on average by 32% along the Rio Grande. This change in biomass (above ground growth) was associated with damage caused by T. romana to main and lateral shoots. Declines in biomass, live shoot density and shoot lengths, especially from arundo wasp damage, appears to be leading to a consistent decline of A. donax all along the Rio Grande from Del Rio to Brownsville, TX. We have also documented significant changes in riverine plant biodiversity, with more than 54 native plant species recorded where there was once a solid monoculture of A. donax. Damage to stems and shoots of A. donax by the arundo wasp appears to be opening the once closed canopy to penetration of sunlight, which is stimulating the regrowth of understory vegetation. The arundo scale, R. donacis, feeds below ground on rhizomes and the bases of side shoots of A. donax. Females release tiny ‘crawlers’ which settle on suitable tissues, become immobile, and complete their life cycle in 5 to 6 months. In its native range in France and Spain, this scale reduces shoot growth and rhizome size by 50%. The arundo scale has been established at more than 50 sites along the Rio Grande in Texas and Mexico, and its impact in combination with the arundo wasp is being evaluated. A third biological control agent, Lasioptera donacis Coutin (Diptera: Cecidomyiidae), the arundo leaf miner, was recently permitted and releases along the Rio Grande are underway. The arundo leaf miner larvae feed and develop in the leaf sheath of A. donax. Damage to leaf sheaths by the leafminer ultimately leads to collapse and death of the entire leaf. This defoliation increases light penetration through the canopy, which may accelerate the recovery of the native riparian plant community along the Rio Grande. In addition, defoliation will make the environment less suitable for survival of cattle fever ticks, Rhipicephalus (=Boophilus) microplus and Rhipicephalus (B.) annulatus)); and increase within- stand visibility, which improves safety and effectiveness of law enforcement personnel and cattle fever tick personnel working along the international border in TX. Biological control has also been successfully integrated with mechanical topping of the cane. Topping cane at 3 f

Technical Abstract: The fundamental host range of the arundo leafminer, Lasioptera donacis a candidate agent for the invasive weed, Arundo donax was evaluated. Lasioptera donacis collects and inserts spores of a saprophytic fungus, Arthrinium arundinis, during oviposition. Larvae feed and develop in the decomposing leaf sheath channel tissue. Thirty six closely related and economic grass species along with several key habitat associates were evaluated in no-choice tests. Lasioptera donacis and its associated saprophyte completed development only on A. donax, in concurrence with published reports from its native range in Mediterranean Europe. The arundo leafminer feeding leads to premature defoliation, constituting a different mode of attack on the host plant as compared to two previously-released insects, the arundo wasp and arundo scale, which feed on shoot tips and rhizomes, respectively. Defoliation of A. donax is expected to increase light penetration into stands of A. donax which increases visibility for law enforcement, reduces the survival of cattle fever ticks, and enhance recovery of the native riparian vegetation along the Rio Grande and other habitats where this weed is invasive.