ABSTRACT:In 2003 to 2005, Chrysomela populi L. gradated on yearly cut Populus nigra var. italica in street alleys in Brno and elsewhere. Imagoes occurred on trees from the end of April or from the beginning of May. In rearing, the chrysomelid consumed unwillingly leaves of 2-year shoots and laid on average 142 eggs. On leaves of shoots, imagoes damaged 100 to 200 cm 2 during 5 to 7 weeks, produced 480 to 900 frass pellets and laid on average 506 eggs. Oviposition was continual with breaks amounting to on average 2.6 days. Embryonal development took 6 to 8 (in the laboratory 5) days. Larvae of the 1 st generation occurred from mid-May to mid-July. In the course of 2 weeks (in the laboratory during 10 days) of life, they damaged about 20 cm 2 leaves and produced about 300 frass pallets. In the laboratory, prepupae took 2 days and pupae 4 days. Imagoes of the 1 st generation occurred from June to September. They damaged on average 113 cm 2 and produced on average 553 frass pellets and 653 eggs. At a temperature of 24 to 28°C, imagoes damaged on average 84 cm 2 during 2 to 3 weeks and diapaused until the next year. On growing up leaves, imagoes lived longer showing higher consumption of food and higher fecundity as against new fully-grown leaves. Larvae of the 2 nd generation destroyed on average 2 cm 2 smaller area than larvae of the 1 st generation. Part or all imagoes of the 2 nd generation diapaused. Imagoes of the 3 rd generation damaged 40 to 70 cm 2 leaves before departure to wintering grounds. In our natural conditions, the prospective 3 rd generation is always incomplete. Cleonice callida Meig. and Schizonotus sieboldi (Ratz.) rank among important enemies.
ABSTRACT:The paper deals with the occurrence, development and harmfulness of imported willow leaf beetle (Plagiodera versicolora Laich.) in riparian and accompanying stands of the Svratka and Svitava rivers in the region of Brno. Salix fragilis L. and S. × rubens Schr. are the most damaged species there. Imagoes leave wintering places usually at the beginning of May. During about a 60-day period, they damage ca. 23.3 cm 2 leaves of S. fragilis and lay 250 to 730 (on average 539) eggs. The whole egg-laying consists of 16 to 48 (on average 35.5) groups with 6 to 26 (on average 15.2) eggs. The fecundity of females hatched in the laboratory is minimally twice lower. Larvae hatch after 5 to 8 (in the laboratory after 4.3) days and damage about 282 mm 2 leaves. The development from laying eggs until hatching imagoes of the 1 st generation takes about 21 (in the laboratory about 15) days. Imagoes of the 1 st generation occur on trees from the end of May to mid-August and die after completing their reproduction. Plagiodera versicolora creates 3 to 4 (in the laboratory 4 to 6) generations during a year. The small part of imagoes of the 2 nd generation, predominant part (or all) imagoes of the 3 rd generation and under conditions of a tetravoltine development all imagoes of the 4 th generation enter a diapause. In the course of the growing season, the food consumption of imagoes and larvae decreases and fecundity of females markedly decreases. Schizonotus sieboldi (Ratz.), Medina melania (Meig.) and M. luctuosa (Meig.) rank among main enemies of Plagiodera versicolora.
Small-plot trials conducted in 2013–2015 studied the impact of longer vegetation periods (by means of earlier drilling and/or later harvest) on production results of two sugar beet cultivars – one nematode-tolerant cultivar and one cultivar without such tolerance. The trials took place at two sites with different Heterodera schachtii infestation levels. In all trial seasons, root yield was significantly higher in the earlier drilled plots. On average, prolongation of the vegetation period in spring by 13 days increased root yield by 10.9%. Therefore, each day by which drilling is postponed represents a 0.7–0.8% loss of yield. As to sugar content, no statistically significant benefit of vegetation period prolongation by early drilling was found. The spring gain was slightly higher for the non-tolerant cultivar than for the tolerant one on average over all trial seasons. This result confirms the theory that nematodes impact the crop mainly in later stages of vegetation, and early drilling can thus help eliminating, to a certain degree, the risk of nematode damage. In the autumn, root yield increased by 14.3% on average over 39 days. The autumn daily gain was about half of the rate found in the spring. The increase in sugar content was between 0.6% and 1% (abs.) on average. Autumn growth achieved at the non-infested site was much higher than at the infested site.
URBAN, J.: A contribution to the knowledge of biology and harmfulness of Deporaus betulae (L.) (Coleoptera, Attelabidae). Acta univ. agric. et silvic. Mendel. Brun., 2012, LX, No. 6, pp. 317-338 The paper deals with the occurrence, development and harmfulness of Deporaus betulae (L.). The majority of fi eld studies was carried out at Training Forest Enterprise (TFE) Masaryk Forest in Křtiny (District Brno-venkov) in 2010 and 2011. In addition to this, the species was studied in detail also in a laboratory. It occurred mostly on Betula pendula and Carpinus betulus. Rarely, the species was found on Alnus glutinosa and Corylus avellana and only sporadically on Fagus sylvatica, Quercus petraea, Tilia cordata and T. platyphyllos. In the studied area, larvae and pupae hibernate. Beetles occur on trees from the end of April to the beginning of July, sporadically later. Females lay on average 2.5 (in the laboratory 4.4) eggs into rolls on B. pendula, on C. betulus 2.2 eggs. During two months, they damage on average 5.3 cm 2 leaves creating 14 rolls and laying 35 eggs into the rolls. Larvae consume only 1.7 cm 2 leaf blade. The development of the species takes three to four months from egg laying to the departure of larvae into soil. On leaves of B. pendula of an average area of 14.2 cm 2 , females roll up the same area (about 11.2 cm 2 ) as on leaves of C. betulus of an area of 21.7 cm 2 . Into the rolls, they lay on average the same number of eggs. The average number of eggs in rolls increases with the increased area of B. pendula leaf blade. Trees partly compensate for the reduction of assimilatory area also by the growth of the area of neighbouring undamaged leaves (on average by 12.7 %).Deporaus betulae, Attelabidae, host plants, occurrence, creation of rolls, laying eggs, development, harmfulness 1 Birch leaf-roller (Deporaus betulae /L./) is a representative of the species-not very extensive but biologically exceedingly interesting family of leaf-rolling weevils (Attelabidae) (Curculionoidea). The majority of species of this family is characterized by the intensely developed instinct of mother care of off spring. In the course of reproduction, females make species-specifi c (or genus-specifi c) leaf rolls or develop in young shoots or fruits. At the same time, they generally disturb conducting tissues. As a consequence, plant organs or their parts gradually wilt and die back. They lay eggs into wilting tissues of plant organs or on the leaf surface into leaf bends, sporadically into leaf rolls of other species of leaf-rolling weevils. Larvae feed on dying tissues in plant organs prepared in this way. These remain joined with the plant during the growing season and sooner or later they fall to the soil surface where they rot. They pupate in the place of their development or in the soil layer. The species are characterized by univoltine or bivoltine development.The family of Attelabidae is created by representatives of three subfamilies (Rhynchitinae, Apoderinae and Attelabinae), which are sometimes con...
ABSTRACT:The paper summarizes results of the study of the occurrence, development and harmfulness of Phratora (= Phyllodecta) vitellinae (L.). The majority of studies was carried out in 1998 to 2005 in riparian and accompanying stands of the Svitava and Svratka rivers in the region of Brno and in a laboratory.
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