The dissertation theoretically generalizes and practically solves an important scientific problem of establishing a pathogenic complex of cucumber plants for growing in film greenhouses with constant use of soils: determined the species composition of pathogens by phases of plant ontogenesis, establishing the harmfulness of the dominant ones; the means of development control are substantiated, the role of plant growth regulators on the basis of humic and biologically active substances and microfertilizers as inducers of resistance to plant pathogens is investigated.
During the spring-summer crop rotation, cucumber plants are affected by pathogens of fungal etiology – F. oxysporum f. sp. sucumerinum J.H. Owen, F. solani (Mart) App. et Wr., F. culmorum (W.G.Sm) Sacc., Sclerotinia sclerotiorum (Lib.) de Bary, Pseudoperonospora cubensis Rostowz., Erysiphe cichoracearum DC; bacterial – Pseudomonas lachrymans Smith et Bryan and viral – Сucumber green mottle mosaic tobamovirus.
The intensity of development of the main diseases of cucumber plants in the conditions of film greenhouses during 2016–2018 was: root rot – 24,3–38,7 %, fusarium wilt – up to 15,1 %, white rot – 12,3–24,1 %, downy mildew – 82,1–88,1 %, powdery mildew – up to 0,4 %; bacterial diseases – 0,2–12,2 %, viral diseases – 2,2–5,5 %.
The dominant role in the pathological complex of cucumber belonged to diseases of fungal etiology – 84 %; pathogens of bacterial and viral diseases occupy 13 and 3 %, respectively, and were not of significant economic importance.
Harmfulness of cucumber diseases by phases of ontogenesis was manifested: in seedling culture – root rot developed; at the beginning of flowering - the vegetative mass was affected by viral and bacterial diseases; the fruiting phase was dominated by fusarium wilt, white rot, downy mildew, powdery mildew. In the first half of the growing season, root rot can cause significant damage, the harmfulness of which is manifested in an increase in the number of gap after planting seedlings in the greenhouse. Yield losses are significant – 1,2–2,3 kg / m2.
In the second half of the growing season, the main losses of cucumber fruits are caused by downy mildew, which in recent years has acquired an epiphytic nature. The analytical dependence of yield on the degree of plant damage by downy mildew was established: Y = 28,16 – 0,17X.
High resistance (score 7) to downy mildew showed samples: Golubchik F1, Zircon F1 Kitajskij pletistyj F1, Gollandskij F1 and lines L Golub-18 and L Park-18. It is recommended to involve them in the selection process. A close inverse correlation (r = – 0,90) was found between the intensity of the development of downy mildew and peroxidase activity in healthy cucumber leaves. It is confirmed that this indicator can be considered as an additional marker during the selection of the source material for the selection of cucumber for resistance to downy mildew.
There is a direct correlation between the indicators of the intensity of downy mildew and yield (r = 0,99), and the fruiting period (r = 0,71), the inverse – between the duration of the period from mass germination to the beginning of fruiting , 87), the content of dry matter in the fruit (r = – 0,80) and the average weight of the fruit (r = – 0,83), which indicates a strong relationship between the studied characteristic.
Pre-sowing treatment of cucumber seeds with PGRs and microfertilizer increased the energy of seed germination by 4,5–14,7%, laboratory germination – by 2.9–6.6%, hypocotyl length – by 0,5–1,5 cm. Among PGRs on the basis of biologically active substances the greatest stimulating influence on these indicators was shown by Epin extra and salicylic acid, on the basis of humic substances – Gulliver Stimulus and Vimpel Maxi.
Salicylic acid, Epine Extra and succinic acid inhibited the development of the mycelium of the fungus Fusarium solani (Mart) App. et Wr in vitro. Their inhibitory activity was 56,7, 36,7 and 33,3 %, respectively. The tendency to increase the level of peroxidase activity in cucumber plants by 1,2–2,2 times, or 14,3–54,6 % after their treatment with plant growth regulators and complex microfertilizer.
Against root rot was the most effective microfertilizer KompleMet – 60 %; among growth regulators – Vimpel Maxi, salicylic acid, Epin extra with biological efficiency of 56, 55, 52 % respectively.
The increase in yield due to the action of PGRs and complex microfertilizer KompleMet was 1,70–2,50 kg/m2. The highest rate (2,50 kg/m2) was provided by the use of complex microfertilizer KompleMet. Among м on the basis of biologically active substances the best were Epine extra (2,30 kg / m2); based on humic substances – Vimpel Maxi (1,70 kg/m2).
The economic efficiency of the developed element of protection of cucumber plants was: reduction of production costs – by 10,0–14,4%, obtaining profit of 28,92–32,75 UAH/m2, increasing the profitability of production – by 16,0–25,0.
