RELATIONSHIP BETWEEN THE MAIZE PEST DIABROTICA VIRGIFERA VIRGIFERA LE CONTĖ AND THE CLIMATIC FACTORS, TROUGH MODERN STATISTICAL ANALYSIS ANOVA (BRAVAIS – PEARSON) IN THE WESTERN PART OF ROMANIA PUBLISHEDGheorghe Popescu, Floarea Adam, Ioana Grozea, Irina Oriol
The aggression of the new maize pest Diabrotica virgifera virgifera Le Conté was studied during the period 2006/2007, in Sagu, at S.C. Agrogil (Arad), from rhizotrophic (larvae), phylotrophic and stigmatrophic (adults) viewpoints, under conditions of connection to a trophic base represented by 8 „Pioneer” maize hybrids and under the climatic factors’ influence. The values of pest’s aggression - as dependent, resulting factor or as dependent variable and of the climatic factors – as independent, influencing factors or as independent variables are presented in table 1. The data was statistically processed, with the help of the software SPSS, ANOVA variance analysis, analysis of regression and of correlation. There is a moderate relationship (correlation) between the factors of influence (independent), namely the climatic ones and the resulting factor (dependent), actually the aggression (F%) of the new maize pest (Diabrotica); data regarding „relative humidity”, „wind” and „temperature” were homogeneous, and „rainfall”, „dew”, „nebulosity” and the dependent factor (F%) proved to be inhomogeneous. The method of exclusion, step by step, of the independent variables from the models designed proves that there is a very strong correlation between the climatic (influencing) factors and the rhizo-phylo-strigmatrophic aggression of the new pest Diabrotica, when the model includes all independent variables (temperature, RH, rainfall, wind, dew and nebulosity); this phenomenon is confirmed by the Pearson values (R=0.972), the „determination” values (R-Square=0.946), the values ensuring the results (Sig. F=0.052, namely over 5%) and by the concept Durbin-Watson. ANOVA variance analysis and the analyses of regression correlation lead us to the conclusion that the new maize pest (Diabrotica virgifera virgifera) is strongly influenced by humidity; rainfall and humidity have a negative influence (-0.9; -0.5), while „dew” is positive (0.9); „nebulosity”, like „dew”, is positive (0.90). The conclusions regarding „dew” and „nebulosity”, and the conclusion that „wind” is important only when is connected to the other independent variables, are original and represent a national premiere. The testing of the influencing factors excluded from data analysis (from models) signifies (only when the factor Sig.F., the one that ensures the results, is not below 5%) that the dependent factor F% may increase (positive influence, for example the temperature excluded would have increased F% with 0.664 units and nebulosity with 1.415 units) or decrease (negative influence, it would have decreased F% with 0.2-0.5 units). „Wind speed” (very important for dissemination of pathogens) did not assume the quality of accessible variable; it had reduced values, homogeneous or mild, despite the high values of maize pathogens’ aggression (Helminthosporium turcicum – 84.3%, Fusarium roseum – 46.7%). In this situation, our general conclusion, of national premiere, is that the new pest, beside other independent variables (positive), assumed the role of „dissemination” and „amplification” of their pathogenesis (it has a trophic attitude against leaf blight).
Diabrotica; aggression; rhizotrophic; phylotrophic and stigmatrophic aggression; statistic SPSS; ANOVA