Ivelina Nikolova

OTIORRHYNCHUS LIGUSTICI L. (COLEOPTERA: CURCULIONIDAE) I. COMPARATIVE STUDY OF THE RESISTANCE OF ALFALFA VARIETIES

From studies carried out during the period 2006–2009 in the experimental field of the IFC–Pleven with 8 alfalfa varieties included in the Official variety catalog of Bulgaria (2005): Europe (France), Prista 2 (Obraztsov Chiflik, Rouse), Prista 3 (Obraztsov Chiflik, Rouse), Prista 4 (Exemplary Chiflik, Rouse), Obnova 10 (EFC, Pleven), Pleven 6 (EFC, Pleven), Dara (EFC, Pleven) and Multifoliate (Obraztsov Chiflik, Rousse) it was found that in the year of the establishment of the stand there was partial damage from Otiorrhynchus ligustici. It was found that surface of caused damage was a major sign to determination of the degree of infestation from the insect pest as it increased from second to fourth year on average from 5.6 to 42.1 cm. Varieties of Multifoliate, Europe and Prista 2 were the least preferred and with low values of surface of damage, number and length of the gnawed furrows. These varieties can be used as sources of germplasm resistant to Otiorrhynchus ligustici.

Development and reproduction of spider mites Tetranychus turkestani (Acari: Tetranychidae) under water deficit condition in soybeans

SUMMARY One of the major pests of soybeans in Bulgaria is the spider mite Tetranychus turkestani Ug et Nik (Acari: Tetranychidae) and different results have been reported about the impact of water stress on its development and reproduction. Soybean plants exposed to natural infestation by spider mites, water deficit and treatment with imidacloprid were examined under greenhouse conditions at the Institute of Forage Crops, Pleven, Bulgaria, over the period 2011-2012. The development of mites and their eggs was faster when plants were exposed to water deficit, which created favorable conditions for high density and reproduction of T. turkestani. There was a vertical distribution of protonymphs, deutonymphs and adults as their numbers and egg counts were significantly higher under conditions of water deficit on the upper and middle plant parts, compared with their bottom parts, and imidacloprid treatment had a stronger and more prolonged activity against mites, compared to its influence on well-watered plants. Spider mites on water-stressed plants caused a 24.8% reduction in the contents of plastid pigments, and carotenoids, and 21.5% decrease on well-watered plants.

DENSITY AND REDUCTION OF THE STAND AT ALFALFA VARIETIES (MEDICAGO SATIVA L.)

With purpose to study the density and reduction of stand at 9 alfalfa varieties (Europe, Prista 2, Prista 3, Prista 4, Obnova 10, Pleven 6, Dara, Multifoliate and Dama) during 2006–2009 period in IFC–Pleven is carried out an experimental activity. The average density of stand at studied alfalfa varieties during the first year of development was 1313 plants/m. The reduction during next three years was disproportionately and was the strongest pronounced during the second year–by 58.3% to the density of the stand in the previous year. During the third experimental year the reduction of alfalfa was still strong pronounced albeit with a lower value (51.1%) and during the fourth year it was 5 times less than that during the previous two years at average value of 10.6%. In the end of four–year experimental period the reduction at different varieties was in limits from 68.6% (Obnova10) to 85.7% (Dara) at average value for the species of 81.8%. It is established correlations with high negative value among the stand density and root mass weigh/plant (r=–0.811) and diameter of root collar (r=–0.692), and a correlation with medium negative value between the stand density and number of stems/plant (r=–0.488)

ECONOMIC EVALUATION OF FORAGE PEA ORGANIC PRODUCTION

The presented evaluation provides an opportunity to be compared the economic results at different variants of forage pea organic production. From the recommended indicators in economic literature in the current evaluation are calculated following ones: total production (€/da), production costs (€/da), cost price (€/kg), net income (€/da) and rentability (%). In the organic production are used four products: foliar fertilizer Biofа, growth regulator and fungicide Polyversum, bioinsecticides Pyrethrum and NeemAzal which are applied alone and in combination. Comparisons are chemicals (regulator Flordimex, insecticide Nurelle D) that are used in the standard conventional technology. All variants of organic production are cost–effective and enable the realization of good economic results. With the highest economic effect is the application of organic fertilizer Biofa in combination with bioinsecticide Polyversum. In the production of hay, this combination provides profitability of 79.30 %, exceeding the profitability of the standard variant in conventional production (75.00 %); the profitability in grain production (137.05 %) is somewhat lower than that of the conventional variant (140.00 %). Overall, the profitability in different variants of pea organic production for grain and hay is with average values of 109.91 % and 51.67 %, as values for the conventional production are 128.905 and 68.43 %, respectively. Although the result of the economic evaluation is chosen a certain optimal variant of pea organic production, open to future studies remain questions concerning the effectiveness of various organic products in different forms of production organization. Keyword: economic evaluation, rentability, organic production, pea.

NUTRITIVE VALUE OF FORAGE OF VETCH CULTIVARS (Vicia sativa L., Vicia villosa ROTH.)

The chemical composition, plant cell–wall fiber components content, in vitro enzyme digestibility, potential protein and energy feeding value of forage of seven vetch cultivars were evaluated. Vicia sativa L. (cultivars Liya, Lorina, Vilena, Moldovskaya, Obrazets 666) and Vicia villosa Roth. (cultivars Violeta and Viola) were planted at the experimental field of the Institute of Forage Crops, Pleven (Bulgaria) during 2012–2014 period. The origin of Obrazets 666 is Bulgaria and of the rest six cultivars–Moldova. Vicia villosa cultivars revealed a greater content of CP and fiber components, measured as NDF, ADF and ADL (211.4, 451.9, 378.5, 74.0 g kg DM respectively) in comparison with Vicia sativa cultivars (189.5, 409.2, 352.4, 67.9 g kg DM respectively). Quality of the herbage in terms of digestibility was 63.9% IVDMD for Vicia sativa and 52.9 % IVDMD for Vicia villosa. The nutritive value based on arithmetical rank sum of all studied parameters (chemical composition, in vitro enzyme digestibility, protein and energy feeding value) showed better forage quality of V. sativa compared to V. villosa. With the highest nutritive value was distinguished cultivars Liya, Vilena and Moldovskaya, which could be used as germplasm in future breeding programmes for quality improvement. Keyword: fiber, digestibility, vetch, feeding value.

VARIABILITY IN SPRING PEA (Pisum sativum L.) VARIETIES FOR TOLERANCE TO Bruchus pisorum L. (COLEOPTERA: BRUCHIDAE)

During the 2012–2014 period in the experimental field of the Institute of Forage Crops, Pleven, Bulgaria, a study was conducted on tolerance of 5 spring pea varieties to Bruchus pisorum L. (Coleoptera: Bruchidae): Glyans, Modus; Kamerton and Svit (Ukrainian varieties) and Pleven 4 (Bulgarian variety). It was found that the duration of flowering and pods development stages in spring pea varieties affected the seasonal dynamics of B. pisorum. Modus variety had the shortest duration of flowering and pods development stages and the lowest density of the pea weevil. The tolerance of Modus was related to earliness of the variety. The resistance to bruchids in spring pea may be related to length of pods, affecting oviposition. Modus had the shortest length of pods, the lowest proportion of infected pods and number of laid eggs per pod. Use of different markers for resistance as discrepancy between the phenological development of the host plant and the life cycle of the phytophagous insects, a length of pods etc. in the creation of new pea varieties may be effective methods for defense and control against B. pisorum. Keyword: pea weevil, pea varieties, tolerance

OM NeemAzal–T/S AND Pyrethrum AND THEIR EFFECT ON THE PEA PESTS AND SEED QUALITY

A study was conducted on the influence of biological insecticides (NeemAzal and Pyrethrum, applied alone and in combinations with organic products) to Bruchus pisorum L. (Coleoptera: Chrysomelidae) population density and rate of damaged seeds. The change of chemical composition in damaged by pea weevil and Cydia nigricana Fabr. (Lepidoptera: Tortricidae) seeds was found. The treatments were performed in budding and budding and flowering stages. The toxic effect of biological insecticides Pyrethrum and NeemAzal after treatment in budding and flowering stages was considerably higher in comparison to the single use. The weevil density was decreased at the greatest rate after treatment with Pyrethrum + Biofa (37.5%) among biological treatments. The biological and synthetic products use had positively influence on the crude protein, crude fiber and phosphorus content. The treatment in budding and flowering stages led to a stronger increase in the crude protein and phosphorus content to a single treatment. Keyword: NeemAzal, Pyrethrum, organic products, Bruchus pisorum, crude protein, phosphorus.

Effects of biological insecticides NeemAzal T/S and Pyrethrum FS EC and their interaction with organic products in treatments of pea aphid Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae) on Pisum sativum (L.)

The efficacy and effects of two biological insecticides, NeemAzal T/S® and Pyrethrum FS EC, applied individually and in combination with Polyversum (a biological growth regulator and fungicide) and Biofa (an organic foliar fertilizer), in controlling Acyrthosyphon pisum population density were studied. Nurelle D (a synthetic insecticide), applied alone and in combination with Flordimex 420 (a synthetic growth regulator), was used as a standard. The products were applied once (at budding stage) or twice (at budding and flowering stages). Twenty-four variants were studied. The interaction of Pyrethrum with Biofa was the most efficient variant of the biological products, causing a reduction in aphid density that reached 48.2% after double treatment, while Pyrethrum+Polyversum (42.5%) was the second most successful treatment. The combination of Pyrethrum with Biofa achieved the highest efficacy and synergism and their efficacy approached that of the synthetic insecticide.

Ovicidal effect of some insecticides on Bruchus pisorum L. (Coleoptera: Chrysomelidae) eggs.

It was studied the effect of insecticides Neonicotinoids: Mospilan 20 SP–300 g ha – 1 , Calypso 480 SC–300 ml ha –1 , Proteus 110 OD–700 ml ha –1 ; Pyrethroids: Duet 530 EC–500 ml ha –1 , Nurelle D–40 ml ha –1 and Fury 10 EC–100 ml ha –1 on Bruchus pisorum eggs under field conditions during 2011 and 2012. The insecticides were applied at the time of the first egg occurrence on lower pods. It was found that the females of B. pisorum laid more than 60% of the eggs in the form of two eggs clusters. The treatment with Mospilan, Fury, Proteus and Calypso significantly reduced the rate of pea weevil eggs survival compared to control. Mospilan 20 SP (300 g ha –1 dose) had the lowest level of B. pisorum eggs survival (37.7 %) and the highest ovicidal efficacy (51.63 %). From the comparison of the mean pea weevil eggs survival and efficacy, expressed separately for the group of pyrethroid and neonicotinoid insecticides, the neonicotinoid group emerged as significantly more effective. Keyword: Bruchus pisorum, egg, neonicotinoids, pyrethroids, ovicidal effect

STABILITY EVALUATION OF MIXTURES AMONG PREPARATIONS WITH DIFFERENT BIOLOGICAL EFFECT ON BASIS OF GRAIN YIELD IN SPRING FORAGE PEA

During the period 2007–2009 in IFC–Pleven is carried out three–factor field trial with purpose to evaluate the stability of mixtures among preparations with different biological effect on basis of the grain yield in spring forage pea. It is used the split plot method. Factor A includes the three years of the study. Factor B (preparations) includes 8 levels: untreated control, Atonic (growth stimulator), Masterblend (combined leaf fertilizer), Atonic + Masterblend, Confidor (insecticide), Confidor + Atonic, Confidor + Atonic + Masterblend, Confidor + Masterblend. Factor C (stages of treatment) includes 3 levels: budding, budding + flowering, flowering. In result of the held experiment is found that the preparations with different biological effect Atonic, Masterblend and Confidor used alone and in mixtures increase the productivity in the spring forage pea (from 101,9 to 129,0%). With highest stability is distinguished the triple mixture Confidor + Atonic + Masterblend (applied at budding stage), followed by mixtures Confidor + Atonic and Confidor + Masterblend (applied at flowering stage) and at alone use of preparations–the leaf fertilizer Masterblend (applied at flowering stage). Technologically the most valuable variants which match high stability and high productivity in the different years are appeared all of them with twofold treatment of the studied preparations and their mixtures as it is recommended the use of mixtures Confidor + Masterblend and Confidor + Atonic.