The tuber necrotic strain of Potato virus Y (PVYNTN) causes widespread disease and has severe negative effects on the growth and yields of plants, especially those of the Solanaceae family. The consequences of residual toxicity and non-biodegradation of synthetic chemicals and pollution of the environment has led to investigations into new non-toxic and biological treatments to control plant viral diseases. Ethanolic extracts of Bowiea volubilis (bulbs), Cotyledon orbiculata (leaves), Gomphocarpus fruticosus (leaves), Merwilla plumbea (dry and fresh bulbs), Nerium oleander (leaves), and the fruits and leaves of Strophanthus speciosus, were evaluated against PVYNTN in vivo and in vitro. At a concentration of 20 mg · ml−1, ethanolic extracts of Strophanthus speciosus (leaves) and fruits (50 mg · ml−1) significantly reduced the expression of PVYNTN symptoms on tobacco plants in vitro without affecting the normal growth and development of the plant. Similarly, at 50 mg · ml−1, N. oleander, C. orbiculata and B. volubilis (fresh bulbs) and S. speciousus leaves at 20 mg · ml−1 extracts showed significant differences in PVYNTN symptoms in the in vivo experiment. Strophanthus speciosus leaf and fruit extracts showed significant inhibition in the in vitro and in vivo assays and demonstrated that S. speciosus has potential to be used as an antiphytoviral treatment.

In the spring of 2019, many plants, mainly winter wheat, were observed to have dwarfism and leaf yellowing symptoms. These plants from several regions of Poland were collected and sent to the Plant Disease Clinic of the Institute of Plant Protection – National Research Institute in Poznań to test for the presence of viral diseases. Double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) results showed numerous cases of Wheat dwarf virus (WDV) and a few cases of plant infections caused by Barley yellow dwarf viruses (BYDVs). WDV was detected in 163 out of 236 tested winter wheat plants (69.1%), in 10 out of 27 tested winter barley plants (37%) and in 6 out of 7 triticale plants (85.7%) while BYDVs were found, respectively, in 9.7% (23 out of 236) and in 18.5% (5 out of 27) of tested winter forms of wheat and barley plants. Infected plants came mainly from the regions of Lower Silesia and Greater Poland. Furthermore, individual cases of infections were also confirmed in the following districts: Lubusz, Opole, Silesia, Kuyavia-Pomerania and Warmia-Masuria. Results of Duplex-immunocapture-polymerase chain reaction (Duplex-IC-PCR) indicated the dominance of WDV-W form in wheat and WDV-B form in barley plants. Moreover, results of reverse transcription – polymerase chain reaction (RT-PCR) connected with restriction fragment length polymorphism (RFLP) analysis, performed for 17 BYDVs samples, revealed 8 BYDV-PAS, 4 BYDV-MAV and 2 BYDVPAV as well as the presence of two mixed infections of BYDV-MAV/-PAS and one case of BYDV-MAV/-PAV. Next, RT-PCR reactions confirmed single BYDV-GAV infection and the common presence of BYDV-SGV. To the best of our knowledge, in 2020 the viruses were not a big threat to cereal crops in Poland.