Vol.12_No.2 - Pesticide Alternatives Lab - Michigan State University

Spring 2003 Resistant Pest Management Newsletter Vol. 12, No.2then bioassayed as young adults (M. sanguinipes) or4th instar larvae (the two lepidopterans) with thefungus.From the Annual Meeting of the EntomologicalSociety of America, Nov. 17-21, 2002, Ft. LauderdaleFL.P. AveryLee AcademyLee, ME 04455S. T. JaronskiUSDA ARS NPARLSidney, MT 59270Kit for the Detection of Echinochloa colona andIschaemum rugosum Susceptibility Status to theHerbicide Fenoxaprop-p-ethylA kit for the detection of the status ofsusceptibility of Echinochloa colona and Ischaemumrugosum to the herbicide fenoxaprop-p-ethyl is a newtool that allows verification of the loss of susceptibilityfrom these two grass weeds to the herbicide in areliable, quick, and simple way. The kit is the result ofseveral years of research in two different laboratoriesworking simultaneously: the Laboratory of Herbicidesof "La Tupia" Bayer Crop Science ExperimentalStation located at Cauca Valley-Colombia and theWeed Science Laboratory of the Agronomy Faculty-National University of Colombia, Bogotá. Previous andexperimental work included more than 60 experimentsand kit validation under field conditions. Initially,different techniques were evaluated by dose-responsebioassays considering seeds, meristems, seedlings(shoots) growing in nutrient solutions, and foliartreatment with a microsyringe, compared with thetraditional methodology of herbicide treatment in awide dose range to plants growing in pots. Twostandards (purified biotypes) - one sensitive and oneresistant - of each one of the two weed species wereconsidered in all experiments. "Seedling (shoots) test"showed the best performance and is therefore the oneon which this kit has been based. To develop the kit,the following were determined: flask size, plant state,time of activity of the herbicide solutions onceprepared, optimal date of visual fitotoxicity testing,DG50, discriminatory dose (dose that marks thebiggest difference between the sensitive standard andthe resistant one), and optimal population sample size.DG50 was calculated by a log-logistic model. The kitmanual instruction explains in a simple and practicalway the procedure of gathering the plants in the field,of seedling assembly in the flasks, and of evaluatingherbicide fitotoxicity. This kit will not be marketed. Itwill have restricted use for the technical staff of BayerCrop Science in Colombia and in any other country.Cilia L. FuentesNational University of ColombiaAgronomy Faculty-BogotáSantiago Montoya, Bernard Jacqmin & NorbertoHernándezBayer Crop ScienceColombiaRelative Susceptibility in Open and GreenhousePopulations of Two-Spotted Spider Mite,Tetranychus urticae Koch, on Rose to DicofolDicofol is a very commonly used acaricide for themanagement of spider mites. Development ofresistance to miticides in spider mites (Tetranychidae)is often so rapid that effective spider mite managementis difficult in many agricultural systems (Jeppson et al.,1975). There are extensive reports worldwide regardingresistance of the two-spotted spider mite, Tetranychusurticae Koch, to different groups of chemicals.However, there is no information available regardingrelative susceptibility of T. urticae to dicofol from openand greenhouse populations from India. In response toan increasing number of treatment failures of dicofolagainst T. urticae on rose, as expressed by farmers inand around Bangalore, this study was taken up.Bioassays were carried out during April-May 2002 toassess the relative susceptibility of open andgreenhouse populations of this mite on rose to dicofol18.5 EC (Kelthane) at the Indian Institute ofHorticultural Research (IIHR), Bangalore. Leaf residuemethod was used for the bioassays as described byFAO (1980). Each concentration was replicated threetimes. Mite mortality was observed 24 h after releaseof mites to the insecticide treated leaves of differentconcentrations. The LC50 values of dicofol to T.urticae were recorded as 0.0404 % for greenhousepopulations and 0.0195 % for open field populations.Thus, greenhouse population of T. urticae haddeveloped 2.1fold resistance to dicofol when comparedto the open field. Relatively more tolerance ofgreenhouse populations of the mite to dicofol might beattributed to more number of generations of mitessubjected to acaricidal sprays when compared to opencultivated roses. The development of cross resistanceto different chemicals frequently used on this cropneeds to be further studied.REFERENCESFAO 1980. Revised method for spider mites and their eggs.FAO MethodNo.10a In: plant production and Protection Paper 21:49-53.Jeppson, L.R., Keifer, H.H. and. Baker. E.W. 1975. Mites injurious toeconomic plants. University of California Press.V. Sridhar and B. Jhansi RaniDepartment of Entomology and NematologyIndian Institute of Horticultural ResearchHessaraghatta LakeP.O., Bangalore-560 089India83