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Two species of leaf beetle (Oulema spp.) – Oulema melanopus (Linnaeus 1758) and Oulema gallaeciana (Heyden 1870) are classified as the pests of cereals of economicalimportance in Poland. Determination of the optimalperiod of their control is very difficult due to extended time of laying eggs and brood of larvae. Mass brood of larvae of both species takes place at the time when larvae hatched from first laid eggs reached ca. 4 mm length of both species. Both developmental stages indicate an optimal term of leaf beetle control. To improve short-term forecasting and warning system the data on developmental cycles of both species from an egg to larva (ca. 4 mm size), the studies were carried out in the field trails in the Wielkopolska region and some in an environmental growth chamber.
One of common cereal pests in Poland are flies of the Agromyzidae family. The larvae of these flies is the stage which is harmful. Leaf miner larvae feeding on the leaf parenchyma cause characteristic damage (mines). Their widespread occurrence contributes to a reduction in leaf assimilation surface. Leaf miner larvae mostly damage first-flag and second leaves. Their damage has a negative effect on the yield parameters. Locally they cause losses of economic significance. The flight of leaf miner imagines coincides with the development of leaf beetles (Oulema spp.), another dangerous cereal crop pest. The aim of the conducted research was to determine the optimum time for chemical treatment of leaf mining flies and leaf beetles as part of integrated cereal protection. To achieve that aim, field experiments were conducted in the years 2008–2009 at the Research Station for Variety Testing in Słupia Wielka (the county of Środa Wielkopolska) using winter wheat of the Bogatka variety. Values monitored included the dynamics of flight for leaf mining flies along with the speed of leaf beetle development. The accuracy of the suggested dates was measured by the quantity of the yield obtained. Additionally, the species composition of Agromyzidae damaging winter wheat was also analyzed. During the years of the research, the biggest yields were obtained when both pest species were chemically treated during the period when the leaf mining flies were abundant and when the oldest leaf beetle larvae reached the size of about 2 mm (in the year 2008) and about 4 mm (in the year 2009). It was also determined that the species composition of Agromyzidae damaging winter wheat changes between particular years.
The oats were observed to be the species mostly damaged by Oulema ssp. phytophages which is represented by the highest damage indexes of the plant in all the objects researched. The two other species: barley and spring triticale are much less sensitive to feeding of the pest. The initial damage which was due to the complementary feeding was hidden due to the compensation capabilities of the cereals. Spring barley, which tillers most, compensated for the damage most considerably. The economic harmfulness of the Oulema feeding may be estimated only in shooting phase, when also the larvae start skeleting of leaf blades. In barley and spring triticale a considerably lower larvae feeding was observed when compared with leaf beetles. The co-ordinate cultivation of the researched species with fodder pea and in two-ingredient cereal mixtures enhances the damage reduction caused by Oulema feeding.
The cereal leaf beetles Oulema melanopus L. and Oulema gallaeciana Heyden (Chrysomelidae) are common pests in European and North American cereal fields. Here we report infestation rates by Oulema spp. and yield loss of winter wheat and barley in Northern Poland (1995 to 1997) and show that both Oulema species might be of significant economic importance. Oulema melanopus was in all the three study years more abundant than Oulema gallaeciana. Larval densities ranged from 22 to 26 larvae per 100 stalks for winter wheat and 29 to 36 larvae per 100 stalks for barley. From these data we estimate yield losses of 0.5 to 4% for winter wheat and 3 to 8% for barley. The significant negative correlation between beetle abundances and the hydrothermic index indicates that higher precipitation and/or lower temperature had a negative effect on the activity of O. melanopus and O. gallaeciana.
Two species of leaf beetles from Chrysomelidae family i.e. the cereal leaf beetle Oulema melanopus (Linnaeus 1758) and the blue leaf beetle Oulema gallaeciana (Heyden 1970) can cause considerable damage to cereal crops. Improvement of short-term forecasting was focused on determination of optimal time of control of these pests that takes place at mass larval hatching. Thus long term studies were carried out to evaluate a correlation between duration of egg incubation, temperature and air humidity. The length of egg incubation was examined at temperatures of 16°C, 20°C and 25°C and air humidity 60% in a growth chamber and under field conditions. Based on linear and curvilinear multinomial regression analyses the influence and significance of such independent variable (x) as: sum of temperatures (sums of mean daily temperatures), mean air humidity, sum of effective temperatures and mean effective temperature versus duration of egg incubation of O. melanopus and O. gallaeciana (dependent variable – y) were evaluated. Analyses of 32 interactions (x, y) showed that only four were insignificant i.e. mean air humidity in the growth chamber at 20°C had no effect on the length of egg incubation of O. melanopus and at 25°C on the length of egg incubation of O. gallaeciana. Also under field conditions sums of effective temperatures showed no effect on duration of egg incubation of both species.
Badania przeprowadzono w latach 2004 i 2005 w Pracowni Doświadczalnictwa Polowego w Winnej Górze, należącej do Instytutu Ochrony Roślin. Zboża uprawiane były w dwugatunkowych mieszankach (50% + 50%) oraz w siewach czystych. Analizę zachwaszczenia przeprowadzono dwukrotnie w ciągu okresu wegetacji - dwa i trzy miesiące po siewie zbóż. Ocenę nasilenia występowania szkodników, do których zaliczały się skrzypionki (Oulema spp.) i wciornastki (Thysanoptera), wykonywano jednokrotnie w sezonie wegetacyjnym. Najbardziej konkurencyjną w stosunku do chwastów okazała się mieszanka jęczmienia jarego z owsem - podczas pierwszej obserwacji zanotowano spadek zarówno liczby chwastów, jak i ich świeżej masy, w drugiej obserwacji natomiast świeżej masy w stosunku do siewu czystego samego owsa. Wzrost świeżej masy chwastów w drugiej obserwacji nie miał wpływu na wysokość plonów wymienionej mieszanki, które były wyższe od plonów pozostałych mieszanek i średnich plonów z siewów czystych. Redukcja liczebności skrzypionek wystąpiła w mieszankach pszenicy jarej z jęczmieniem jarym i pszenicy jarej z owsem. Pszenica jara była również najsłabiej zaatakowanym przez skrzypionki zbożem w siewie czystym. W mieszance jęczmienia jarego z owsem nie odnotowano wystąpienia redukcji liczebności skrzypionek w stosunku do siewów czystych. Nie zanotowano redukcji średniej liczby wciornastków w badanych mieszankach. Uzyskane wyniki poddano analizie statystycznej.
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