Flea beetle (Coleoptera: Chrysomelidae) response to alkyl thiocyanates and alkyl isothiocyanates

I. Liblikas¹⋅², E. Mõttus¹, A.-K. Borg-Karlson², S. Kuusik¹, A. Ojarand¹, A. Kännaste¹ and J. Tanilsoo¹

¹Estonian Agricultural University, Kreutzwaldi 1, 51014 Tartu, Estonia
²The Royal Institute of Technology, Sweden, Dept of Chemistry, Organic Chemistry, Ecological Chemistry, KTH, S-100 44 Stockholm, Sweden

Abstract:

The attractivity of nine compounds, allyl isothiocyanate (allyl IT), benzyl isothiocyanate (benzyl ITC), 3-butenyl isothiocyanate (butenyl ITC), 3-butenyl thiocyanate (butenyl TC), butyl isothiocyanate (butyl ITC), butyl thiocyanate (butyl TC), 2-phenylethan-1-yl isothiocyanate (phenetyl ITC), 2-phenyleth-1-yl thiocyanate (phenetyl TC), and 2-phenylethan-1-ol, was compared to the beetle genera Phyllotreta species. Field tests were performed on fields of wild crucifer plants and on the edge of an oilseed rape field. Test places were at Juuru in Northern Estonia, at Valgeristi in the middle of Estonia and at Matsi in Southern Estonia. In our tests, Phyllotreta spp were most attracted to butenyl TC and butenyl ITC; allyl ITC and other tested alkyl-TC, alkyl-ITC, aryl-TC and aryl-ITC had lower attractivity. Cylindrical traps with a large clued area were tested and are recommended for practical usage, capillary polyethylene dispensers are recommended instead of sachet type dispensers. Emission of substances from sachet dispensers is described in the article.

Key words:

Specific composition of flea beetles (Phyllotreta spp ), the dynamics of their number on the summer rape (Brassica napus L. var. oleifera subvar. annua) Mascot

K. Hiiesaar¹, L. Metspalu¹, P. Lääniste² and K. Jõgar¹

¹Institute of Plant Protection, Estonian Agricultural University, Kreutzwaldi 64, 51014, Tartu, Estonia; e-mail: hkelli@eau.ee
²Institute of Field Crop Husbandry, Estonian Agricultural University, Kreutzwaldi 64, 51014, Tartu, Estonia

Abstract:

The specific composition of the flea beetle Phyllotreta spp (Coleoptera: Chrysomelidae), time of its appearance and dynamics of its number on the summer rape cultivar Mascot were determined. During the observation period, 6 species of flea beetles were found: Phyllotretaundulata Kutsch., Ph. nemorum L., Ph. vittata (Ph. striolata), Ph. nigripes F. Ph. atra and Ph. vittula. First flea beetles appeared at the time of the sprouting of rape plants. In the course of the entire observation period, the most numerous of these was the small striped flea beetle Ph. undulata. Proportion of the other species not often exceeded 10%. Very warm and dry weather following the sprouting of plants caused a rapid increase in the number of the pests and the maximum number was reached in a short time. A somewhat larger number of beetles was found on the edge plots. The field was sprayed three times, using Fastac (alphacypermethrin). Although after the first spraying the number of pests had decreased to almost zero, one week later the number of beetles began to rise again. Ten days after the spraying, the number of pests in the control and the sprayed variant had become equal, 2.0 and 2.2 individuals per plant. The second spraying lowered the number of pests again down to zero. At that time the plants were reaching the stage of 3-4 true leaves, the time when the growth rate is the fastest. The third spraying was primarily directed against pests damaging generative organs: pollen beetles and weevils, and at that time plants began to form secondary racemes, and primary racemes lengthened. For controlling of flea beetles spraying was no more necessary.

Key words:

chemical control, damage, flea beetles, summer rape