Prevention of solidification cracking during pulsed laser beam welding

We present a mathematical model to describe laser beam welding based on the heat equation. Since the material coeff cients depend on the temperature, this leads to a quasi-linear parabolic partial differential equation. It is our goal to prevent solidif cation cracking. We address this problem by means of optimal control. It is the intensity prof le of the laser beam which acts as the control function. The main challenge is the formulation of a suitable objective function. In particular, high velocities of the solidif cation interface need to be properly penalized in order to deal with and avoid cracking phenomena

The effect of foliar fertilizers on the occurrence of apple scab [Venturia inaequalis Cooke Aderh.]

Apple scab caused by Venturia inaequalis is the most serious fungal disease of apple in Poland. The strategy for apple scab control relies mostly on multiple applications of fungicides, usually 8 to 15 times each gr owing season. Because of the reduction in the range of fungicides and the problem with resistance, alternative methods are being searched for to help control this disease. The objective of this work was to study the effect of different foliar fertilizers f rom Intermag Co., commonly used in apple orchards, against apple scab. Experiments were conducted in 2008 and 2009 on apple trees cv. McIntosh, very susceptible to V. inaequalis . In both seasons, which were favourable to apple scab infections, a significan t reduction in the occurrence of the disease was observed after the applications of a mixture of Chelat Cu 12 Forte + Bormax + Chelat Zn 14 Forte, Alkalin KB + Si, and Alkalin PK. These fertilizers reduced disease severity by more than 80% when used at the highest of the tested concentrations (2%), and by 60% when used at lower concentrations. Two products, Alkalin KB + Si used at 2% and a 1.0% copper solution were phytotoxic to both the leaves and fruits. The results obtained showed that some of the common ly used foliar fertilizers can be useful for controlling apple scab because they cause a reduction in disease intensity (by approx. 70%

Increase in the occurrence of Venturia inaequalis [Cooke] Aderh. resistance to strobilurin fungicides in Polish apple orchards

Monitoring of the occurrence of V. inaequalis resistance to strobilurins (QoI - Quinone outside Inhibitors) was conducted in selected orchards in Poland in 2004 - 2009. During the first years of monitoring (2004 - 2007), a high level of resistance to strobilurins was observed in 54.7% of the orchards, with only some resistant forms or no resistance noted in the others. Monitoring carried out in the two last years, 2008 and 2009, indicated a significant spread and increase in the frequency of occurrence of resistant forms of V. inaequalis. The problem of resistance affected 79.7% of the monitored orchards and only in 20.3% the level of resistance was low. The results showe that in Polish orchards the resistance to strobilurins has increased strongly. It has happened in spite of the reduction in strobilurins use recommended by FRAC

Studies on the susceptibility of selected strawberry genotypes to some economically important fungi diseases of leaves

Polową ocenę wrażliwości 18 odmian i klonów truskawki hodowli Instytutu Sadownictwa i Kwiaciarstwa w Skierniewicach (ISK) na trzy najważniejsze gospodarczo choroby grzybowe liści (białą i czerwoną plamistość liści oraz mączniaka prawdziwego truskawki) przeprowadzono w latach 2000 i 2001 w ISK. Oceniane genotypy charakteryzowały się zróżnicowaną wrażliwością na ważne gospodarczo choroby liści. Żaden z badanych genotypów nie był odporny na wszystkie choroby. Klony K-1254, K-1278, K-1283 i K-1565 oraz odmiany 'Heros' i 'Vikať wyróżniały się najmniejszą podatnością na białą i czerwoną plamistość liści truskawki. W warunkach sprzyjających rozwojowi mączniaka prawdziwego truskawki większość genotypów wykazała wysoką wrażliwość na porażenie przez S. macularis. Całkowitą odpornością na mączniaka prawdziwego truskawki charakteryzowała się jedynie odmiana 'Karel'.Susceptibility of 18 strawberry cultivars and clones to three economically important diseases (leaf spot, leaf scorch and powdery mildew) was evaluated under field conditions in 2000 and 2001 in the Research Institute of Pomology and Floriculture at Skierniewice, Poland. Tested genotypes showed different susceptibility to three economically important leaf diseases. None of the collection genotypes was immune to all diseases. Clones K-1254, K-1278, K-1283 and K-1565, and cultivars 'Heros' and 'Vikať were distinguished by the least susceptibility to leaf spot and leaf scorch. Under favourable conditions to develop the powdery mildew most of tested genotypes were strongly affected by Sphaerotheca macularis. Only 'Karel' cultivar showed high resistance to powdery mildew

The effect of some endogenic substances contained in the cortical parenchyma of apple trees on growth in vitro of the fungus Phytophthora cactorum (Leb. of Cohn) Schroeter

Gel filtration of an alkaline extract of the cortical parenchyma yielded four fractions of which two had activity in vitro on the growth of Phytophthora cactorum. Fraction I was stimulatory and fraction IV inhibitory; one of the inhibitors in fraction IV was identified as phloridzin. When the extraction solvent contained sodium sulphite in addition to sodium hydroxide, fraction II showed inhibitory activity