Complete: Insecticide resistance dynamics in aphid vectors of beet viruses

Timescale: 2005 - 2009
Project Lead: Dr Richard Harrington
Project Sponsor: Rothamsted Research and Broom's Barn

Project Summary

Sugar beet yellows is a disease caused by three viruses, Beet mild yellowing virus (BMYV), Beet chlorosis virus (BChV) and Beet yellows virus (BYV). BMYV and BChV are generally far more prevalent than BYV. Both viruses are transmitted by three species of aphid, Myzus persicae (peach–potato aphid), Macrosiphum euphorbiae (potato aphid) and, to a lesser extent, Aulacorthum solani (glasshouse and potato aphid). Myzus persicae commonly shows some resistance to a range of insecticides. Aphis fabae (black bean aphid) does not transmit the poleroviruses BMYV and BChV but can transmit BYV.

Main Objectives

The general objectives of the project were to optimise and sustain the use of insecticides against aphid pests on beet through monitoring resistance, evaluating potential alternative control strategies, and transferring relevant information to the industry.

Outcomes / Key Message For Growers And Industry

There are strong relationships between long-term aphid data from the Rothamsted Insect Survey's national suction trap network and long-term weather data. The timing and size of spring migrations of the two main vector aphids are correlated with temperature in January and February. In early March each year, forecasts of aphid activity and virus incidence were provided to the industry. These helped to determine control measures in crops not sown with insecticide-treated seed. 

Most M. persicae were susceptible or only moderately resistant (S+R1) to insecticides through having elevated levels of carboxylesterases. However, this resistance mechanism is no longer of much consequence as it is mainly to organophosphates. 39.3% of aphids tested (963 out of 2451) showed the more serious `MACE' mechanism, which confers strong resistance to pirimicarb and triazamate (the latter is no longer available as an aphicide for beet). This has risen dramatically from 10.6% in the previous four year period and 0.26% in the four year period before that. 56.3% of M. persicae tested (454 out of 807) did not have the kdr resistance mechanism that confers resistance to pyrethroids. The rest were heterozygotes showing partial resistance. None of the 220M. persicae tested had the super-kdr resistance mechanism.

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