LITHUANIAN UNIVERSITY OF AGRICULTURE LITHUANIAN INSTITUTE OF AGRICULTURE Remigijus matas MIGRATION ACTIVITY AND ABUNDANCE OF APHIDS (Aphididae) AND THRIPS (Thysanoptera) IN CEREALS AND THEIR CONTROL Summary of doctoral dissertacion Biomedical sciences, agronomy (06B) Akademija, 2006
This doctoral dissertation was prepared at the Lithuanian Institute of Agriculture in 2001 2005. Scientific supervisors: Dr. Habil Jonas urkus to 2004 (Lithuanian Institute of Agriculture, biomedical sciences, agronomy 06 B) Assoc. Prof. Dr. Vidmantas Pranas Juronis from 2004 (Kaunas Botanical Garden of Vytautas Magnus University, biomedical sciences, agronomy 06 B) This dissertation will be defended in the Council of Agronomy Sciences at the Lithuanian University of Agriculture: Chairperson: Dr. Irena Brazauskienė(Lithuanian Institute of Agriculture, biomedical sciences, agronomy 06 B) Members: Assoc. Prof. Dr. Vytautas Tamutis (Lithuanian University of Agriculture, biomedical sciences, agronomy 06 B) Dr. Roma Semakienė (Lithuanian Institute of Agriculture, biomedical sciences, agronomy 06 B) Dr. Habil. Juozas Benediktas Staniulis (Institute of Botany, biomedical sciences, biology 01 B) Dr. Elena Survilienė Institute of Horticulture, biomedical sciences, (Lithuanian agronomy 06 B) Oponents: Dr. Laimutis Raudonis (Lithuanian Institute of Horticulture, biomedical sciences, agronomy 06 B) Assoc. Prof. Dr. Algimantas Feliksas iogas (Lithuanian University of Agriculture, biomedical sciences, agronomy 06 B) Defense of doctoral dissertation will take place at the public meeting of the Council of Agronomy Science on the 28thof June, 2006 at 11 a.m. in the room No. 322, Central building of the Lithuanian University of Agriculture. Address: Lithuanian University of Agriculture, Studentųst. 11, LT-53361 Akademija, Kaunas d., Lithuania. e mail: email@example.com - The summary of the doctoral dissertation was distributed on the 27th of May, 2006. The doctoral dissertation is available in the libraries of the Lithuanian University of Agriculture and the Lithuanian Institute of Agriculture.
LIETUVOS EMĖSŪKIO UNIVERSITETAS LIETUVOS EMDIRBYSTĖS INSTITUTAS Remigijus matas AMARŲ(Aphididae) IR TRIPSŲ(Tyhaptersano) MIGRACIJOS AKTYVUMAS IR GAUSUMAS JAVUOSE BEI JŲKONTROLĖ Daktaro disertacijos santrauka Biomedicinos mokslai, agronomija (06B) Akademija, 2006
Disertacija rengta 2001 2005 metais Lietuvos emdirbystės institute. Moksliniai vadovai: Habil dr. Jonas urkus iki 2004 m. (Lietuvos emdirbystės institutas, biomedicinos mokslai, agronomija 06 B) Doc. dr. Vidmantas Pranas Juronis nuo 2004 m. (Vytauto Didiojo universiteto Kauno botanikos sodas, biomedicinos mokslai, agronomija 06 B) Disertacija ginama Lietuvos emėsūkio universiteto Agronomijos mokslo krypties taryboje: Pirmininkė: Dr. Irena Brazauskienė(Lietuvos emdirbystės institutas, biomedicinos mokslai, agronomija 06 B) Nariai: Doc. dr. Vytautas Tamutis (Lietuvos emėsūkio universitetas, biomedicinos mokslai, agronomija 06 B) Dr. Roma Semakienė(Lietuvos emdirbystė biomedicinoss institutas, mokslai, agronomija 06 B) Habil. dr. Juozas Benediktas Staniulis (Botanikos institutas, biomedicinos mokslai, biologija 01 B) Dr. Elena Survilienė(Lietuvos sodininkystės ir darininkystės institutas, biomedicinos mokslai, agronomija 06 B) Oponentai: Dr. Laimutis Raudonis (Lietuvos sodininkystės ir darininkystės institutas, biomedicinos mokslai, agronomija 06 B) Doc. dr. Algimantas Feliksas iogas (Lietuvos emėsūkio universitetas, biomedicinos mokslai, agronomija 06 B) Disertacija bus ginama vieame Agronomijos mokslo krypties tarybos posėdyje 2006 m. birelio mėn. 28 d. 11 val. Lietuvos emėsūkio universiteto centriniųrūmų322 auditorijoje. Adresas: Lietuvos emėsūkio universitetas, Studentųg. 11, LT-53361 Akademija, Kauno raj., Lietuva. e.patas: firstname.lastname@example.org Disertacijos santrauka isiuntinėta 2006 geguės mėn. 27 d. Disertacijągalima periūrėti Lietuvos emėsūkio universiteto ir Lietuvos emdirbystės instituto bibliotekose.
INTRODUCTION Relevance of the subject.thrips are known worldwide as important pests ofAphids and cultivated crops. They damage plants directly by sucking plant sap, as well as indirectly by spreading viruses. Aphids contaminate plant surface by secreting honeydew, and thrips are mentioned as passive vectors of bacteria and fungi spores. Due to thrips damage, leaf sheaths and leaves usually turn silvery white, later brown, ears emerge deformed, with twisted awns, with very few or no grain at the top. Thrips were first described in 1744, and their importance in agriculture has been increasing over the last 40 years (Xenou-Kokoletsi, Christians 2001; Fereres et al. 1988; Parella, Lewis 1997; Reitzel, Jakobsen 1980; Ananthakrishnan 1980; Vappula 1965; Lewis 1997c; Childers 1997; Gonzales et al. 1982; Pickett et al. 1988). Cereals are mainly attacked by the three aphid species -Sitobion avenae (Fabricius, 1775), Rhopalosiphum padi (Linnaeus, 1758) irMetopolophium dirhodum (Walker, 1894) (Schepers 1989; Wiktelius et al. 1988; Hansen 1991; Özder 2002; Bennewicz 2001; Vappula 1965; Ma et al. 2004; De Barro 1992; Pons 1993). Different thrips species occur in cereals in different localities. In our neighbouring countries the most common thrips species that occur in cereals are:Limothrips denticornis(Haliday, 1836),Frankliniella tenuicornis(Uzel, 1895) and Haplothrips aculeatus 1803) (Lewis 1973; Larsson 1995; Larsson 2005; Zawirska, (Fabricius, Wałkowski 2000; Kąkol, Kucharczyk 2004; Kobro et al. 2000; Köpä 1970). Host plant is a decisive factor for the prolificacy of pests. The prolificacy of aphids is largely dependent on the age and growth stage of a host plant. Aphids attack all species of cereal crops. Thrips are most often mentioned as pests of winter cereals, however, they also occur on spring cereals (Mound 1997; Awmak, Leather 2002; Leather, Dixon 1981a; Larsson 2005). Temperature is a very important factor for the development of pests. The lowest temperature at whichS. avenaecan develop is 5.9oC, andR. padi 3.3oC. Thrips become active when the air temperature in spring reaches 5oC. Some authors report that heavy rain reduces feeding intensity of aphids. Air temperature, light (minimal light intensity for thrips flight is 1000 lux) and wind speed play an important role in thrips migration (Kieckhefer et al. 1989; Lykouressis 1985; Ma et al. 2004; Bannewicz, Krasicka-Korczyńska 2004; Broadbent, Hollings 1980; Acreman, Dixon 1989; Kirk 1997; Jańczak et al. 2004; Lewis, 1963). Research on thrips occurrence in cereals in Lithuania is scarce. There is shortage of more comprehensive investigations on species composition of aphids, and especially thrips, and peculiarities of their occurrence in cereals. No research has been done in Lithuania before to estimate the activity of aphids migration using a suction trap and to compare the activity of aphids migration with aphids abundance in cereal crops. Research on thrips harmfulness for winter rye is also insufficient. There are only limited data on the damage done by aphids and thrips to winter cereals as well as on the efficacy of means intended to reduce the damage done by these pests. As a result, more comprehensive research on species composition of aphids and thrips and variation of their abundance, as well as investigation on the means designed for the reduction of damage done by these pests, are relevant. Hypothesis.Environmental factors exert a great effect on the occurrence of aphids and thrips, their abundance and damage done in cereal crops, as well as the time of appearance of these pests in the crops, timing of their control and means used. By involving a suction trap in the experimental design we expected to be able to forecast the trends of aphids spread, their appearance time in cereal crops and to estimate the expedience of the use of pest control means. We also expect to specify thresholds of harmfulness of aphids and thrips in cereals and to verify and validate the recommendations for their control. Experimental objectives and tasks.The objectives of the present study were to identify species diversity of aphids and thrips occurring in cereal crops, to study the peculiarities of aphids and thrips occurrence in relation to environmental factors, to estimate the activity of aphids migration using a suction trap and to compare with aphid abundance in cereal crops, to determine thrips
harmfulness in rye, to identify means for the reduction of damage done by aphids and thrips in winter cereals. The following tasks were set: ¾ to identify species diversity of aphids and thrips in winter rye, triticale, wheat and spring barley ¾ to determine the variation of aphids and thrips species abundance in mentioned crops in relation to crop growth stages and environmental factors (accumulated effective temperatures) ¾ by using a suction trap and toto assess migration activity of different aphid species compare with aphid abundance in cereal crops ¾ to measure thrips harmfulness in winter rye ¾ to identify means for the reduction of damage done by aphids and thrips in winter cereals (rye, triticale, and wheat) Novelty of the research work.Species diversity of aphids and thrips in winter rye, triticale, wheat, and spring barley was identified. Variation of the abundance of the main species of aphids and thrips in the mentioned crops was determined in relation to crop growth stages and environmental factors. For the first time in Lithuania we estimated migration activity ofR. padi andS. avenaeusing a suction trap and compared with the abundance of these aphid species in cereal crops. Practical significance.The experimental data obtained in this study enables assessment of damage done by aphids and thrips in winter rye, triticale and wheat crops and estimation of expedience of the application of aphids and thrips control measures. Thrips threshold of harmfulness at which it is expedient to apply control measures was identified in winter rye. Approval of the work.Experimental results were presented in the PhD students research conferences The youth seek for progress (Kaunas, 2001 and 2003, oral presentations), international conference Research for rural development (Jelgava, 2002, oral presentation), international conference "Plant protection in the Baltic region in the EU integration context" (Kaunas, 2002, poster presentation), international conference Optimizing agricultural output production: theory and praxis (Jelgava, 2005, two poster presentations), Lithuanian Institute of Agricultures completed research projects conference (2006, two oral presentations). The main experimental findings were published in three research articles in refereed publications. The volume of work.The dissertation is written in Lithuanian. It includes 142 pages, 25 figures, and 51 tables, 293 references were used. MATERIALS AND METHODS Experiments were conducted at the Lithuanian Institute of Agriculture, Department of Plant Pathology and Protection during the period 2001 2005. Investigations on the variation of species diversity and abundance of aphids and thrips were carried out in winter rye, triticale, and spring barley during 2002-2004, and in winter wheat during 2002-2003. Five observation sites 25 m2in size (10 m x 2.5 m) were marked in each crop. No pest control products were applied in these sites. Assessments of the abundance of aphids and thrips in winter cereals were started at the beginning of cereal tillering stage (BBCH 21), in spring barley at leaf development stage (BBCH 11) and were continued until complete maturity stage (BBCH 89). The assessments were done three times a week (on Mondays, Wednesdays and Fridays). Ten randomly selected main stems were cut at the base per each observation site and were immediately placed into jars with turpentine (Evans, 1933; Lewis, 1960; Patrzich, 1984). After 24 hours storage in the laboratory the stems were taken out of the jars, the remaining aphids and thrips were collected from the jars walls, stems, and ear surface by a pair of pincers as well as the thrips remaining in the leaf sheathes. The collected pests were preserved in 70 % alcohol.
In total, 44234 aphids and 62801 thrips were collected and identified during the experimental years. The species of aphids were identified using Heie (1986), Taylor et al. (1984) descriptors. The species of adult thrips were identified using Strasen (2003), Moritz (1994) descriptors. Larvae, nymphs and pronymphs of thrips were identified using Nakahara (1993) descriptor. The weather data during the study period were obtained from the Dotnuva weather station, situated at a 500- meter distance from the experimental field. To identify the activity of aphids migrationduring the 2002-2004 period, we used a suction trap 12.2 m in height. This type of trap is manufactured in England and is designed to measure the abundance of pests in the air and the variation of the pest abundance in relation to the height from the soil surface (Macaulay et al., 1988). In each experimental year the suction trap was turned on at the end of April beginning of May, taking into account the weather conditions and beginning of pest migration. Upon completion of insect migration the suction trap was switched off (end of November). Samples of insects were taken from the trap three times a week (on Mondays, Wednesdays, and Fridays), at the same time 8:00-8:30 a.m. On the same day the insect samples were preserved in 70% alcohol and later analysed in the laboratory. During the 2002-2004 experimental period there were caught and analysed 31859 aphids. Field experimentsperiod 20012004 in the LIA Plant Pathology andwere conducted during the Protection Departments crop rotation: in winter rye cv. Duoniai, winter triticale cv. Tornado, winter wheat (in 2001 cv. irvinta, in 20022004 cv. Zentos). The cereals were cultivated following the crop cultivation technologies approved by LIA. Plant growth stages were identified according to the BBCH scale (Growth stages of, 1997). Winter rye, triticale, and wheat grain yield was combine-harvested by a Sampo 500 harvester, each plot separately. The grain yield per plot was weighed, moisture content was measured by a hygrometer Multi-grain, and 1.5 kg grain samples were taken for laboratory analyses. Grain yield data are presented in t ha-1, adjusted to 15 % moisture content. One thousand grain weight (g) was measured by a seed counter Contador and electronic balance Explorer Ohaus. Investigations on thrips harmfulnessin winter rye were done in 2001, 2003 and 2004 according to the experimental design: unsprayed, the other three treatments were sprayed with thiamethoxam 15 g ha-1, when the number of thrips per stem was on average 1-2, 3-4 and 5 and more. In 2004, when aphids appeared, all experimental plots were sprayed with aficide triazamat 14 g ha-1. Research on the reduction of the damage done by aphids and thripsin winter rye, triticale and wheat was done according to the same experimental design: treatment 1 unsprayed; treatments 2 and 3 sprayed when 1-2 thrips per stem were found; treatments 4 and 5-sprayed when on average 5-10 aphids per stem were identified. In the experiments devoted to the testing of products used for the reduction of damage done by aphids and thrips we used insecticides of two different modes of action contact insecticide (treatments 2 and 4) lambda-cihalotrin 10 g ha-1and systemic insecticide (treatments 3 and 5) thiamethoxam 15 g ha-1. In the trials designed to study thrips harmfulness in winter rye, prior to insecticide spray application average abundance of thrips was determined, and in the trials devoted to the studies of the reduction of damage done by aphids and thrips, the abundance of aphids in the whole field was determined. The first assessment of thrips and aphids abundance was performed for each individual plot 3-4 days after the spray application, the other assessments were done weekly. Ten randomly selected main stems per each plot were used for assessments, aphids and thrips were counted on stems, leaves and ear, and thrips were also counted beneath leaf sheaths. The content of aphids and thrips-infested stems in per cent was calculated according to the formula: P = n / N x 100, where P content of pest-infested stems in per cent; n number of pest-infested stems in the selection; N number of inspected stems. The number of aphids and thrips per stem was calculated according to the formula: K =Σk / N, where K number of pests per stem;Σk total number of pests on inspected stems; N number of inspected stems. The
accumulated effective temperatures during the experimental period were calculated by adding up the mean daily temperatures of 5 ºC and above from the beginning of the year. The experimental data were processed by the analysis of variance. Data significance was estimated according to Fishers criterion (Доспеховthe data on aphids and thrips-, 1985). Prior to statistical analysis, infested stems were transformed byY=arcsinX% , and the data on the number of aphids and thrips per stem using logarithmic transformationY Log(X+ and Scarisbrick,1) (Clewer 2001). EXPERIMENTAL RESULTS Species diversity of aphids and thrips in winter rye, triticale, wheat, and spring barley.In the observed plants were identified three species of aphids belonging to thethere Aphididaefamily:Metopolophium dirhodum (Walker, 1849),Rhopalosiphum padi (Linnaeus, 1758) andSitobion avenae(Fabricius, 1775). Analysis of species composition of aphids in winter rye, triticale and wheat showed that S. avenaeandR. padi the dominant species, while in spring barley wereR. padi the most was prevalent species (Table 1). In winter ryeS. avenaeaccounted for 44.7 %,R. padifor 20.9 proc, whereasM. dirhodum in rye accounted for as little as 2.7 % from the total number of aphids found in rye. In triticale there was found a larger number ofR. padiaphids (4050) compared with rye,S. avenae accounted for 21.7 %, aphidsM. dirhodum for as little as 2.0 % from the total number of aphids found in triticale. In winter wheatS. avenae aphids accounted for the larger share of the total aphids found (35.0 %), whereasR. padi accounted for 23.6 % of the aphids total number of aphids found in wheat. In wheatM. dirhodumaphids were more prevalent than in rye and triticale. In spring barleyR. padilargest share (51.0 %) of allaphids accounted for the aphids found in barley, whileS. avenaeaccounted for 10.8 %,M. dirhodumfor as little as 1.4 %. In all crops assessed, first instar larvae accounted for nearly one third of the total number of aphids. The first instar larvae still do not have traits specific to one or another aphid species, therefore they were not attributed to any aphid species.S. avenaeandR. padiwere found to be the main aphid species to attack winter rye, triticale and wheat, whereasR. padi was the main species to attack spring barley. Table 1. diversity of aphids and their total number in winter rye, triticale, and spring Species barley (in 2002-2004) and in winter wheat (in 2002-2003) Dotnuva Total number of aphids found ecist Aphid spes Develaogpem ent nbu2emr0 -0W2.- r2y0e0 4% nbu2eWmr0. -0 t2ri-t2ic0a0l4%e nbue2mWr0 -0. 2w-2h0e0at3% nbue2mrS0 .0 b2-a2rl0e0y4 % -Metopolophium winged 3 5 0.1 11 0.1 22 0.3 0.1 dirhodum 0.2 14 0.1 53 0.8 11 0.1wingless 18 0.7 69 0.5 72 1.1 31 0.2nymphs 52 larvae 130 1.7 170 1.3 418 6.4 170 1.0 Total 203 2.7 264 2.0 565 8.6 217 1.4 Rhopalosiphum 73 1.1 162 1.0 1.2 111 0.8winged 92 padiwingless 225 2.9 546 4.1 230 3.5 843 5.0 1526 9.1 2.3 509 3.9 209 3.2nymphs 175 larvae 1109 14.5 2884 21.8 1027 15.8 6045 35.9 Total 1601 20.9 4050 30.6 1539 23.6 8576 51.0 Sitobion avenaewinged 66 0.9 50 0.4 29 0.4 52 0.3 wingless 335 4.4 233 1.8 213 3.3 176 1.1 nymphs 663 8.7 517 3.9 329 5.1 208 1.2 larvae 2354 30.7 2065 15.6 1710 26.2 1378 8.2 Total 3418 44.7 2865 21.7 2281 35.0 1814 10.8 First instar larvae 2438 31.8 6054 45.8 2135 32.8 6214 36.9 Total identified 7660 13233 6520 16821
In winter rye, triticale, wheat, and spring barley there were identified 16 thrips species and 2 genera that belonged to three thrips families:pidieaeAlotorh family comprisedAeolothrips intermedius (Bagnall, 1934),Thripidae - familyAnaphothrips obscurus 1776), (Müller, Aptinothrips rufus(Haliday, 1836),Aptinothrips stylifer(Trybom, 1894),Chirothrips manicatus (Haliday, 1836),Frankliniella intonsa 1895), (Trybom,Frankliniella tenuicornis (Uzel, 1895), Frankliniella spp.,Limothrips cerealium (Haliday, 1836),Limothrips denticornis(Haliday, 1836),Thrips angusticeps 1895), (Uzel,Thrips atratus (Haliday, 1836),Thrips fuscipennis (Haliday, 1836),Thrips physapus(Linnaeus, 1758),Thrips tabaci(Lindeman, 1888),Thrips sp., Phlaeothripidae - familyHaplothrips aculeatus 1803), (Fabricius,Haplothrips leucanthemi (Schrank, 1781). According to trophic status of the 16 thrips species found one (A. intermedius) belonged to zoophagous trophic status, the rest belonged to phytophagous. The largest number of adult thrips (13223) was found in winter rye, slightly less in winter triticale (8407). In winter wheat and spring barley the number of thrips found was markedly lower than in winter rye and triticale. The species diversity of thrips spread in winter rye and triticale was similar (Table 2). The most prevalent species in rye wasL. denticornis,which accounted for 79.3 % of the total adult thrips found in rye,H. aculeatus made up 15.2 %, F. tenuicornis 2.2 %. In triticale, like in rye, the dominating species wasL. denticornis(78.7 %), whileH. aculeatusandF. tenuicornisaccounted for 13.5 and 4.4 %, respectively of the total number of adult thrips found in triticale. In winter wheat the most prevalent species were L. denticornis(41.3 %),H. aculeatus(25.8 %) andF. tenuicornis(20.5 %). In spring barley the dominant species wereL. denticornis(62.0 %), whereasF. tenuicornisaccounted for 22.1 % of the total number of adult thrips found in barley. In all cereals observed there was identified A. intermediusspecies of thrips belonging to zoophagous trophic status. In cereals only sporadic individuals of this thrips species were found, therefore we think that they did not have any appreciable effect on the occurrence of other thrips species found. It was determined that the main species of thrips attacking winter rye and triticale areL. denticornisandH. aculeatus, the main species occurring on winter wheat areL. denticornis,H. aculeatusandF. tenuicornis, and the main species infesting barley areL. denticornisandF. tenuicornis. Table2.Species diversity of adult thrips and their total number in winter rye, triticale and spring barley (in 2002-2004) and in winter wheat (in 2002-2003) Total number of thrips found Thrips species or genus 2W0i0n2t-e2r 0ry0e4 Winter triticale Winter wheat Spring barl4ey 2002-2004 2002-2003 2002-200 number % number % number % number % Aeolothrips intermedius 0.11 0.1 5 0.1 2 0.1 3 Anaphothrips obscurus* 41 0.5 41 3.0 49 1.8103 0.8 Anaphothrips obscurus 0 0 0 0 0 3 0.1** 0 Aptinothrips rufus 0 0 0.1 0 0 0 0 2 Aptinothrips stylifer 0 0.1 1 0.1 2 0.1 0 2 Chirothrips manicatus 6 0.2 42 0.3 28 0.3 10 0.7 Frankliniella intonsa 75 4.0 106 0.6 85 1.0 81 5.9 Frankliniella tenuicornis 22.1 20.5 592 2.2 370 4.4 283 289 Frankliniella 0.3 25 0.3 17 1.2 47 1.8spp. 34 Haplothrips aculeatus 15.2 1134 13.5 357 25.8 191 7.1 2011 Haplothrips leucanthemi 01 0.1 0 0.1 0 0 1 Limothrips cerealium 0 0 0 0.1 1 0.1 0 2 Limothrips denticornis 62.0 79.3 6614 78.7 571 41.3 1660 10491 Thrips angusticeps* 7 0.1 17 0.2 2 0.1 1 0.1 Thrips angusticeps** 24 0.2 15 0.2 0 0 1 0.1 Thrips atratus 0.1 2 0.1 0 1 0 0 0 Thrips fuscipennis 5 0 1 0.1 3 0.1 0 0.1 Thrips physapus 04 0.1 2 0.1 0 0 0 Thrips tabaci 64 0.8 13 0.9 16 0.6 130 2.0 Thrips sp. 0 0 0 0 01 0,1 0 Total 13223 8407 1382 2676 * macropterus form; ** micropterus form
Apart from adult thrips, we identified the larvae, pronymphs and nymphs of the thrips found. It was found that in winter rye the dominant genera wereLimothrips for (accounted 37.0 % of the total content of thrips larvae, pronymphs, and nymphs identified in rye) and Haplothrips(20.6 %) larvae (Table 3). In rye the number ofHaplothripspronymphs and nymphs was not high. Pronymphs and nymphs ofLimothripsand other genera made up 9.4 and 25.8 %, respectively. The data from the 2002-2004 period suggest that although the total amount of thrips larvae, pronymphs and nympths identified in triticale was by 1.7 times lower than that in rye, the ratio of larvae, nymphs and pronymphs from their total amount was very similar between these plant species. Larvae ofLimothrips larvae) and (4109ripslothHap larvae) genera (2756 dominated in triticale. The number of pronymphs and nymphs ofHaplothrips genus found in triticale was low, similar to that in rye. In winter wheat the number of thrips larvae, pronymphs and nymphs found in 2002-2003 period was markedly lower than in winter rye (8.0 times lower) and triticale (5.1 times lower). Thrips larvae prevailed, among which the most numerous were the larvae ofpsrihtolpaHand other genera (accordingly 34.3 and 26.2 % from the total number of larvae, pronymphs and nymphs identified in winter wheat). However, the number of Limothripslarvae found in wheat was relatively low (5.3 %). In spring barley, unlike in winter cereals (especially rye and triticale) the larvae of other unidentified genera prevailed. They accounted for 44.6 % of the total amount of thrips larvae, pronymphs and nymphs identified in barley. Only sporadic specimens ofHaplothrips and nymphs were identified in pronymphs barley, however, theLimothripsand other generas pronymphs and nymphs identified accounted for 5.9 and 25.3 % of the total amount of thrips larvae, pronymphs and nymphs. Table 3.Total number of thrips larvae, pronymphs and nymphs in winter rye, triticale and spring barley (in 2002-2004) and winter wheat (in 2002-2003) Dotnuva Total number of thrips larvae, pronymphs and nymphs identified Thrips genus Development 2W0i0n2t-e2r 0r0y4e W2in0t0e2r -t2ri0ti0c4a l e W2i0n0te2r- 2w0h0e3a t Sp2r0i0n2g- b20ar0l4ey stage um- nbuemr -% nber % nbuemr -% nbuemr -% Haplothrips 9.8 526 34.3 259 20.6 2756 22.2 4230spp. larvae pronymphs 163 0.8 128 1.0 11 0.7 3 0.1 nymphs 974 4.8 856 6.9 116 7.6 5 0.2 Limothrips 14.2 376 37.0 4109 33.1 7578 5.3 81spp. larvae (Outnhiedre ngteinfieerda) larvae 331 1.6 562 4.5 402 26.2 1182 44.6 Limothrips 896 7.2 102 6.7 156 5.9spp. and pronymphs 1929 9.4 other genera nymphs 5289 25.8 3127 25.2 295 19.2 671 25.3 Total 20494 12434 1533 2652 Variation of the abundance of aphids in winter rye, triticale, and wheat, and spring barley. In winter rye the abundance ofR. padiindividuals in different experimental years was diverse. The most intensiveR. padi migration was autumnrecorded in 2001, less intensive in 2003 and the least intensive in 2002. In the springs of the 2002-2004 period we identified the number ofR. padi that survived over winter on bird cherries that are initial feeders (host eggs plants) of this pest. Analysis has shown that after the intensive autumn migration, there were found more aphid eggs on bird cherry twigs in spring. The highestR. padiabundance in rye was identified in 2002, lower in 2004, whereas in 2003 experimental year during the whole rye growing season there was identified only one individual ofR. padi. The same trends ofR. padi abundance were determined in the other crops tested (winter triticale, wheat and spring barley). In all crops testedR. padiandS. avenaeaphids spread very weakly, therefore the data on their abundance are presented only from the years 2002 and 2004 when they spread more abundantly. The highest abundance ofR. padifemales, nymphs and larvae in rye crop in wingless 2002 and 2004 experimental years occurred at the beginning of grain filling stage (BBCH 71-
73), when accumulated effective temperatures had reached 982.1-998.2, 982.1-1027.0 and 944.9-1027.0°C, respectively (Table 4). Table 4. course of aphid development in cereals as affected by plant growth stages and The accumulated effective temperatures Dotnuva, 2002-2004. Aphid species Aphid The highest abundance determined in the crop evelopment 2002 2004 d stage BBCH AET BBCH AET Winter rye R. padi 71-73 winged 1099.0 944.9 73-75 1027.0 73 944.9larvae 71-73 wingless 73 982.1 71-73 998.2 nymphs 73 982.1 73 1027.0 S. avenae 71 951.1winged 73-75 1097.0 larvae 71-73 944.9 71-73 998.2 wingless 73 1015.0 73 1055.0 nymphs 73 1060.0 71 951.1 Winter triticale R. padi 944.9 77 1157.0 winged 71 larvae 71 944.9 71 951.1 wingless 71 944.9 73 1027.0 nymphs 71 944.9 75 1127.0 S. avenae 1097.0 73 1055.0winged 73 larvae 73 1060.0 71 951.1 wingless 73 1060.0 73 1055.0 nymphs 73 1060.0 73 1055.0 Winter wheat R. padi 65 winged n.a. n.a. 825.0 larvae 65 n.a. 825.0 n.a. wingless 65 825.0 n.a. n.a. nymphs 65 825.0 n.a. n.a. S. avenae n.a. 1196.0 n.a.winged 75 n.a. n.a. 1144.0larvae 73-75 wingless 73 1060.0 n.a. n.a. nymphs 73-75 1144.0 n.a. n.a. Spring barley R. padi 1099.0 71-73 winged 49 894.8 894.8 55 998.2larvae 49 wingless 49 860.4 55 998.2 nymphs 49 894.8 71-73 1127.0 S. avenae 55 998.2winged 53-55 1015.0 918.7 47-49 1060.0larvae 55 wingless 55-59 1097.0 55 998.2 nymphs 55 1060.0 71-73 1127.0 BBCH plant growth stage; AET accumulated effective temperatures; n.a. not assessed S. avenaein rye spread more abundantly thanR. padiaphids. During the 2002 and 2004 experimental years the highestS. avenae larvaeabundance in rye crop was recorded at the beginning of grain filling stage (BBCH 71-73), when the accumulated effective temperatures had reached 944.9-998.2°(Figure 1). The highest abundance of winglessC S. avenaefemales in the 2002 and 2004 experimental years was recorded at early milk maturity stage (BBCH 73), when the accumulated effective temperatures in separate experimental years had reached 1015.0-1055.0 °C. In 2002 in winter triticale the highest abundance ofR. padiwinged (0.26 specimens per stem), wingless females (1.90), nymphs (3.18) and larvae (10.34) was recorded at watery ripeness (BBCH 71), when the accumulated effective temperatures had reached 944.9°C. In