Research On Occurrence Regularity And Comprehensive Prevention Of Mrdd

Maize rough dwarf disease (MRDD) is a viral disease caused by planthopper-borne, pathogenic bacteria of which is rice black-streaked dwarf virus(RBSDV). Currently it is the main prevalent disease in China's corn production area. There is more than 50000 acres of corn on the year basis in Chongming county. According to study on the historical data, the disease has not occurred in 2006, occurrence in 2007 reported as first time. In 2007, the disease broke out in parts of our county, with incidence rate around 50%, which caused serious losses.The writer conducted an extensive investigation on MRDD occurrence sympton by applying methods of fixed-point and general check-up between 2008 -2009 with research team, and carried out multi-point experiments on controlling laodelphax striatellus fallen by use of seed dressing and seedling spraying.Through research on occurrence sympton of MRDD,the imagoes move into corn fields from around May 15; move into peak period from May 20 to June 15; move into off-peak period from May 31 to June 3. Latent period from transmission to occurrence is about 20-25days. The symptoms of field disease firstly appeared in around June 5. June 15-25 and June 30-July 5 are two peak periods of symptom appearance, and the fisrst peak is greater than the second. Disease occurrence turns stable after July 10. Disease occurrence and symptoms are consistant with activities of transmission vector laodelphax striatellus fallen.Through the comprehensive research on MRDD, it has been put forward a comprehensive set of effective prevention techniques. First of all, agricultural control is the key measures in fight against MRDD and earlier sowing is the most important. Sowing advanced to 5th April, disease control effects can be achieved up to 90%; selecting disease–resistant varieties like Denghai 3622, Huyuno No.2 and 3 will reduce the occurrence rate of MRDD to some extent. Secondly, chemical control measures can be applied as supplementary aids of MRDD prevention. In the outbreak year, through the use of 10% imidacloprid with 6‰concentration for seed dressing; through the use of 20% pymetrozine 20 gram per mu for spraying; occurrence of MRDD can be controlled within a minimum range.