# Alternaria Black Spot (_Alternaria brassicae_) Infection Severity on Cruciferous Oilseed Crops
## 3 Results
### Development of Alternaria Black Spot Disease  
The weather conditions were very favorable for Alternaria black spot development and assessments on both observation years. In 2010, the first occurrence of Alternaria black spot infection was found on 7 July on _B. juncea_ and _B. napus_ plants, but the infection level was very low (Figure 1a). Five days later, on 12 July, the degree of infection was 7.6 \(\pm\) 0.3% (average \(\pm\) SE) on _B. napus_ and 10.9 \(\pm\) 4.5% on _B. juncea_, whereas the degree of infection was already 33.0 \(\pm\) 2.3% on _B. nigra_ plants (Figure 1a). _S. alba_ plants were also infected (4.9 \(\pm\) 4.2%). After 26 July, Alternaria black spot development progressed on _B. nigra_, _B. juncea_, _S. alba_ and _B. napus_, being the most severe on plants of _B. nigra_ (49.2 \(\pm\) 3.8%) and _B. juncea_ (27.2 \(\pm\) 5.4%) plots (F\({}_{5,12}\) = 16.38, \(p\) < 0.001 for comparison between species). On 26 July, the infection was also observed on _E. sativa_ plants with 0.5 \(\pm\) 0.3% and on _R. sativus_ with 8.2 \(\pm\) 1.5% (Figure 1a). By the end of the observation period, 83.2 \(\pm\) 2.9% of foliage \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Month**} & \multirow{2}{*}{
\begin{tabular}{c} **Ten-Day** \\ **Period** \\ \end{tabular} } & \multicolumn{4}{c}{**Temperature (\({}^{\circ}\)C)**} & \multicolumn{4}{c}{**Rainfall (mm)**} & \multicolumn{4}{c}{**Relative Humidity (\%)**} \\ \cline{3-10}  & & **2010** & **2011** & **1964–2011** & **2010** & **2011** & **1964–2011** & **2010** & **2011** & **1964–2011** \\ \hline \multirow{3}{*}{May} & I 1 & 7.8 & 8.0 & 9.7 & 36.2 & 0.2 & 12.9 & 76.0 & 56.1 & 65.5 \\  & II & 17.3 & 11.8 & 11.4 & 10.4 & 46.6 & 20.9 & 70.5 & 73.3 & 66.3 \\  & III & 12.8 & 13.0 & 12.8 & 14.8 & 11.6 & 22.8 & 71.1 & 67.8 & 66.9 \\  & I & 13.6 & 19.7 & 14.9 & 25.8 & 0.0 & 20.9 & 72.2 & 54.4 & 67.5 \\  & III & 14.0 & 15.9 & 15.1 & 8.6 & 24.8 & 26.9 & 71.5 & 69.7 & 70.9 \\  & III & 16.1 & 16.2 & 16.2 & 38.2 & 10.4 & 28.0 & 71.9 & 70.1 & 72.9 \\  & I & 20.2 & 20.0 & 17.3 & 10.6 & 9.2 & 19.3 & 69.5 & 72.6 & 72.9 \\  & II & 23.3 & 18.6 & 17.4 & 8.0 & 30.4 & 24.8 & 65.7 & 70.2 & 74.7 \\  & III & 23.0 & 21.0 & 17.8 & 17.4 & 8.6 & 26.5 & 69.5 & 72.4 & 75.8 \\  & I & 21.4 & 16.1 & 17.6 & 13.4 & 16.2 & 33.3 & 75.4 & 66.2 & 76.3 \\  & I–III & 16.9 & 16.0 & 14.6 & 183.4 & 158.0 & 236.3 & 71.3 & 67.3 & 71.0 \\ \hline \hline \end{tabular}  
* Period of 10 days.  
\end{table} 
Table 3: Average monthly temperature (\({}^{\circ}\)C), precipitation (mm) and relative humidity (%) in Eerika experimental field during the vegetation period and the corresponding long-term averages (1964–2011). of _B. nigra_ plants (BBCH 81-83) and 60.2 \(\pm\) 6.8% of foliage of _S. alba_ plants (BBCH 83-86) were infected. These percentages are significantly higher compared to other cruciferous species (F\({}_{5,12}\) = 23.84, \(p\) \(<\) 0.001) (Figure 1a). At the end of the observation period, the lowest Alternaria black spot infection severities were observed on _E. sativa_ plants with 17.2 \(\pm\) 8.7% and on _R. sativus_ plants with 20.8 \(\pm\) 4.1% (Figure 1a). In 2011, the first Alternaria black spot symptoms were recorded on 8 July on _B. napus_ and _B. nigra_ plants (Figure 1b). A week later, on 15 July, low-level infection was observed on _E. sativa_ and _B. juncea_ plants (Figure 1b). At that date, the disease infection on _B. napus_ had increased to 15.7 \(\pm\) 4.5% and on _B. nigra_ plants to 12.7 \(\pm\) 4.4% (Figure 1b). From 29 July, the disease infection rapidly progressed on _B. napus_, _B. nigra_ and _E. sativa_ and culminated on _B. napus_ (BBCH 78-81) with 79.8 \(\pm\) 4.1%, on _B. nigra_ (BBCH 82-85) with 72.5 \(\pm\) 4.0% and on _E. sativa_ (BBCH 74-74) with 46.5 \(\pm\) 14.9% (F\({}_{5,12}\) = 6.91, \(p\) \(<\) 0.01). At the end of the observation period, low infection severity was recorded only on _S. alba_ plants with 5.2 \(\pm\) 1.9% and on _R. sativus_ plants with 14.7 \(\pm\) 2.4% (Figure 1b).