Compost Tea and Milk to Suppress Powdery Mildew (Podosphaera xanthii) on Pumpkins

Matthew DeBacco

Open Access Open Access


Compost tea and milk to suppress powdery mildew (Podosphaera xanthii) on pumpkins


Powdery mildew (caused by Podosphaera xanthii) a common problem for vegetable growers, and the cost of controlling the disease with fungicides to the growers and the environment is high. An alternative approach for control using methods approved for organic production are sprays based on teas made from compost, both actively aerated (ACT) and non-aerated (NCT) compost teas, and sprays made from diluted milk. We evaluated these sprays for control of powdery mildew on pumpkins in field trials in Connecticut in 2008 and 2009, and in greenhouse trials in 2009. We also evaluated the compost teas and milk in the greenhouse in 2009, as well as additives, like liquid seaweed and humic acid, used to enhance the effectiveness of compost teas. Applications were applied to the leaves before disease symptoms were noticed and visual assessments of the plants were made on a weekly basis. In 2008 both the ACT and NCT treatments applied in combination with a milk spray significantly reduced the incidence of powdery mildew compared with compost tea applied without the additional milk spray. In 2009 the treatments were changed to evaluate the effect of milk applied alone, and the compost teas were evaluated without the additional milk application. In both locations the compost teas provided no control of powdery mildew when compared to the untreated control plots. The milk treatment provided significantly less disease than the untreated control, and the chemical treatment had equal or significantly less disease than the milk. In greenhouse trials the milk treatment was as effective as the chemical control, and the enhancer products, liquid seaweed and humic acid, were as effective as the compost teas at suppressing powdery mildew with all treatments reducing disease when compared with the untreated control. These results suggest that enhancers added to compost teas may provide as much control as the teas, and milk may be an effective control for powdery mildew on pumpkins. Both organic and conventional growers could benefit from using milk in place of the fungicides typically sprayed to control powdery mildew.