Nutrient Status of Cucumber Plants Affects Powdery Mildew (Podosphaera xanthii)

Yigal Elad; Dor Barnea; Dalia Rav-David; Uri Yermiyahu

doi:10.3390/plants10102216

Nutrient Status of Cucumber Plants Affects Powdery Mildew (Podosphaera xanthii)

Plants (Basel). 2021 Oct 19;10(10):2216. doi: 10.3390/plants10102216.

Authors

Yigal Elad¹, Dor Barnea^{1

2

3}, Dalia Rav-David¹, Uri Yermiyahu³

Affiliations

¹ Department Plant Pathology and Weed Research, Agricultural Research Organization, The Volcani Center, 68 Hamakabim Rd, Rishon LeZion 7534509, Israel.
² The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
³ Agricultural Research Organization, Gilat Research Center, D.N. Negev 2, Bet Dagan 85280, Israel.

Abstract

We examined the effects of applications of N, P, K, Mg, and Ca through an irrigation solution and spraying K, Ca, and Mg salts on cucumber powdery mildew (CPM, Podosphaera xanthii) in potted plants and under commercial-like conditions. Spraying CaCl₂ and MgCl₂, or KCl and K₂SO₄, decreased CPM. There were significant negative correlations between the anion-related molar concentrations of the salts and disease severity. Among the sprayed treatments, NaCl provided significantly less CPM control when applied at a low (0.05 M) concentration, as compared with CaCl₂ and MgCl₂. When sprayed applications of Mg and K salts were analyzed separately from the untreated control, the Cl^- salts were found to be more effective than the SO₄^-2 salts. High N and Mg concentrations in the irrigation water delivered to young, fruit-less cucumber plants reduced CPM, whereas more CPM was observed when the irrigation solution contained a medium amount of P and a high amount of K. In contrast, mature, fruit-bearing plants had less severe CPM at higher N, lower P, and higher K levels. Spraying mature plants with monopotassium phosphate, polyhalite (K₂Ca₂Mg(SO₄)₄·2H₂O), and the salts mentioned above over an entire growing season suppressed CPM. CPM severity was also reduced by spray applications of Ca, Mg, and KSO₄^-2 and Cl^- salts. Spray applications provided better CPM control than fertigation treatments. Induced resistance is probably involved in the effects of nutrients on CPM.

Keywords: Cucumis sativus; agrotechnical control; calcium; cultural control; integrated management; magnesium; plant disease; potassium; powdery mildew.