Fungal Disease: Powdery Mildews and Their Hosts
Powdery mildew is a type of fungal disease caused by various genera, such as Erysiphe, Sphaerotheca, and Uncinula, which are commonly known as powdery mildews. Each type of powdery mildew infects specific plants, usually those belonging to the same or closely related plant families. The disease thrives in environments with moderate to high humidity and low light intensity, commonly found in lower parts of plants or dense foliage.
Powdery mildews can affect a range of plants, including tomatoes, potatoes, capsicum, carrots, peas, cucurbits, citrus fruits, mangoes, onions, and members of the wheat family, among others.
Typically, powdery mildews are identifiable by the presence of white to gray powdery spots or large blotches on the leaves, stems, and fruits of the infected plants. This white powdery growth consists of the fungal mycelium (a network of fungal threads) and asexual reproductive spores.
Initially, the powdery white fungal growth appears on the oldest leaves but eventually spreads to cover all surfaces of the leaves. The disease is spread through airborne spores, carried by wind or pests that land on the leaves and germinate. Although powdery mildews require plant tissues to grow, they do not directly kill the host plant. Instead, they feed on the plant’s cells. As a result, the infected foliage becomes brittle and distorted, while the petioles (leaf stalks) turn brown and wither. This can reduce the yield of the plant, and the breakage of petioles can hinder mechanical harvesting.
There are several methods to control powdery mildew:
1. Cultural Control
Planting resistant varieties that are less susceptible to powdery mildew.
Removing crop debris from the field after harvest, as the fungi can survive on plant remnants.
2. Chemical Control
Utilizing appropriate chemical products to manage the disease.
It is important to follow recommended guidelines and regulations when using chemical control methods to ensure their effectiveness and minimize any potential negative impacts on the environment.
Effective management of powdery mildew involves employing a rotation strategy with the aforementioned products, as they contain distinct active ingredients. This alternating approach is also recommended as a strategic method to prevent the development of disease resistance.