Field evaluation of entomopathogenic nematodes applied via remotely activated sprayer for eradication of southern cattle fever ticks on nilgai

Authors: Goolsby, John; BAUMGARDT, JEREMY - Texas A&M University; DE YOUNG, RANDY - Texas A&M University; ORTEGA, ALFONSO - Texas A&M University; HEWITT, DAVID - Texas A&M University; Shapiro Ilan, David; Perez De Leon, Adalberto - Beto

Submitted to: Subtropical Agriculture and Environments
Publication Type: Abstract Only
Publication Acceptance Date: 12/12/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary: Cattle fever ticks (CFT), Rhipicephalus (Boophilus) microplus and Rhipicephalus annulatus, are invasive livestock pests endemic to Mexico and invasive along the Texas – Mexico border. Acaricide resistance, alternate wildlife hosts, and pathogenic landscape forming weeds present challenges for sustainable eradication of this pest in the U.S. CFT are the vectors for the microbes that cause bovine babesiosis, which is a disease causing high mortality particularly in susceptible European breeds of cattle that severely impacts the profitability of the beef cattle industry. CFT were eradicated from the United States; however, a permanent quarantine zone (PQZ) is maintained at the U.S. border with Mexico in south Texas to prevent incursions of CFT from wildlife and stray cattle. In recent years, there has been an increase in CFT infestations outside of the PQZ in Texas. An alternate wildlife hosts for CFT in South Texas is the nilgai (Boselaphus tragocamelus), an exotic Asian antelope. Nilgai are highly mobile with large home ranges and are implicated in the spread of CFT through the landscape. Currently, there are no methods for control of CFT on nilgai other than culling. Insect and tick killing parasitic round worms (entomopathogenic nematodes) native to Cameron County and the treatment area are under field evaluation for eradication of CFT on nilgai. Nematodes were applied as a water-based spray to nilgai as they move through fence crossings. A remotely activated field sprayer was developed for application of nematodes on CFT infested nilgai. The nilgai sprayer was tested in a field trial on private ranches in Cameron Co. TX. Counts of ticks on nilgai, including CFT, before and after treatment with nematodes showed they were effective. To confirm these results, the field test will be repeated in the Spring of 2020.

Technical Abstract: Nilgai antelope Boselaphus tragocamelus (Pallas) are implicated in the long-range dispersal and cycling of southern cattle fever ticks, Rhipicephalus microplus Canestrini (Acari: Ixodidae) in the environment, especially in Cameron and Willacy Counties. Treatment methods for nilgai are needed to support the Cattle Fever Tick Eradication Program. Remotely activated sprayers developed for application of entomopathogenic nematodes at fence crossings were tested in the summer of 2019 at private ranches in Cameron Co., TX. Sprayers are activated by ultra-sonic sensors as nilgai transit through fence crossings. Nilgai are treated directly with Steinernema riobrave entomopathogenic nematodes (Nemasys-R, BASF) and passively as they contact wetted foliage and soil. Satellite collars and game cameras were used to determine movements of nilgai through established fence crossings and within the treated and untreated ranches. Pre and post treatment counts of R. microplus and other tick species on the satellite collared nilgai in the study areas showed a significant treatment effect. These methods show promise for eradication of R. microplus on nilgai and the study will be refined and repeated in 2020.