The effect of different pre-crops on Rhizoctonia solani complex in potato

R. Simson¹,*, L. Tartlan², E. Loit³ and V. Eremeev³

¹ Estonian Crop Research Institute, Department of Plant Biotechnology, Aamisepa 1, EE48309 Jõgeva, Estonia
² Estonian Research Institute of Agriculture, Department of Plant Sciences, Teaduse 13, EE75501 Saku, Estonia
³Estonian University of Life Sciences, Department of Field Crop and Grassland Husbandry, Kreutzwaldi 1, EE51014 Tartu, Estonia
*Correspondence: reijo.simson@etki.ee

Abstract:

Rhizoctonia disease in potato is widely distributed in Estonia. Field experiments with cv. ‘Red Fantasy’ were undertaken with seven pre-crop treatments at the Estonian Research Institute of Agriculture in 2009 and 2010. Monocropped potato, spring barley, spring barley underseeded with red clover, spring wheat, grain pea, spring oil seed rape and oil seed radish were involved in the study as pre-crops. Growing conditions on both years were rather optimal for potato growth but year 2010 was drier at early bulking stage. The effect of different pre-crops on Rhizoctonia solani complex was studied (i.e. incidence and severity of stem and stolon canker and black scurf) at 15, 30, 45, 60, 90 and 120 days after planting. Results indicated that pathogenfree
seed tubers are of primary importance in the disease control and no pre-crop was suppressive to disease if seed tubers had sufficient amount of inoculum. However, to achieve consistent reduction in disease development, inoculum-free seed tubers and crop rotation with non-host crops should be considered.

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