Powdery Mildew of Cucurbits
Powdery mildew of cucurbits is caused by Podosphaera xanthii and Erysiphe cichoracearum, two prevalent fungal infections. It is hypothesized that airborne conidia spread from southern states or local areas with greenhouse-grown cucurbits serve as the disease’s major inoculum. All cucurbits are susceptible to infection by these fungal viruses. Powdery mildew attacks on cucurbits are more dangerous in the United States, India, Australia, and all over the world. Because of the high humidity, powdery mildew of cucurbit disease is most dangerous between 65 and 80 degrees Fahrenheit. Because of the dry and heated conditions, the disease became more widespread. Between the middle and end of summer, powdery mildew appears. The powdery mildew disease is more likely to infect the older leaves since they are more susceptible to it. The disease known as powdery mildew in cucurbits can therefore be prevented by using fungus.
Symptoms on cucurbits
The powdery mildew of cucurbits forms apparent pads of whitish mycelium on upper and lower leaf surfaces, petioles, and stems, making its symptoms frequently easier to detect than other diseases’ symptoms. During the growing season, the fungus produces hyphae and conidia, which are asexual spores, on the leaves. This disease may initially be detected on older leaves, which develop small, confined, reddish-brown circular spots. Currently, we must use a microscope to determine whether or not the characteristic conidia of powdery mildew are present. As hyphae and spores multiply, these spots finally turn white. Mycelium that resembles talcum powder forms rapidly in infected regions.
Severely infected plants exhibit a change in leaf color from dark green to pale yellow, then to brown, and finally to shriveling, which exposes cucurbit fruits to sunburn. Powdery mildew first appears on the older leaves and stems of cucurbits. Mycelium generates conidia in great quantity, and these spores are easily spread by wind or air currents to infect nearby and distant plant portions. This disease can rapidly and widely spread.
Powdery mildew on cucurbits is characterized by light yellow leaf spots; other symptoms include white spots on both upper and lower leaf surfaces that quickly progress to large blotches. The enormous blotches cover the whole leaf, petiole, and stem surfaces. Because at the point when powdery mildew taints most of the foliage, the plant becomes frail.
Powdery Mildew of Cucurbits is caused by
Powdery mildew of cucurbits, which is mostly caused by the fungus Podosphaera xanthii, infects all cucurbits, including melons, squash, cucumbers, gourds, watermelons, and pumpkins. Mildew contamination favors moist conditions between 65 and 82 degrees Fahrenheit. In warm and dry conditions, fresh spores form and successfully spread the disease. In Minnesota, the negative effects of fine mold become apparent in mid- to early autumn.
More mature leaves are defenseless against the powdery mildew of cucurbits, which infects them first. The wind transports spores delivered in leaf spots to contaminate different leaves. Under favorable conditions, the powdery mildew pathogen can rapidly spread and frequently cover the entire leaf surface. Despite the fact that powdery mildew primarily affects leaves and plants, infections can occasionally affect cucumber or melon natural goods. Powdery mildew does not directly contaminate squash products. On polluted plants, fewer and less modest organic items are produced. Reduced natural product quality is caused by increased sunscald, fragmented ripening, poor storage ability, and poor flavor.
Powdery Mildew of Cucurbits Disease Environment Factors
Diseases belonging to the class of powdery mildew that affects cucurbits can thrive in a number of environments. However, temperature, relative humidity, and light may all influence the development of this disease in cucurbits. Because the water vapor pressure deficit has such a dramatic effect on host-parasite interactions, both temperature and humidity must be considered concurrently. Without precipitation, conditions such as high temperatures (75–85 °F) and high humidity (80–95%) are ideal for the spread of this disease. In periods of heavy dew on leaf surfaces, the severity of powdery mildew increases, yet excessive water on the leaves can actually impede the disease’s progression.
In contrast, if the inoculum level of spores from nearby infected plants is high enough, the fungus that causes powdery mildew can infect under relatively dry conditions. When precipitation is rare and the weather is dry, as it frequently is throughout the winter and spring in Florida, the sickness can reach a deadly level. Powdery mildew on cucurbits is often more prevalent in partially shady locations than in completely sunny ones. Under their large, overlapping leaves, cucumbers and muskmelons are more susceptible to disease than beneath their younger, brighter foliage.
Powdery Mildew of Cucurbits Disease Management and Control
Powdery Mildew of Cucurbits Biological control
Baculovirus (parasitic wasp) bio fungicide is a fine-building parasitic hyperparasite (Ampelomyces quis-qualis). Baculovirus should be administered protectively with mineral oil or silicone surfactant as soon as possible in the morning or later in the evening for optimal results. When bacteriovirus is utilized for fine mold control, conventional fungicides such as EBDCs, sulfur, and strobilation should not be used.
Cultural Control
- Kill weeds in and around cucurbit fields.
- Use approved varieties of cucurbits.
- Use those varieties, that are resistant to powdery mildew disease.
The extensive availability of conidia and their propensity to germinate at low RH suggests that cultural practices such as crop rotation have little to no effect on the presence and growth of powdery mildew. However, powdery mildew is less likely to infect plants that are strong and robust and that have been cultivated using an appropriate nutritional program and proper sanitary conditions than plants that are under nutritional stress. Components of the following strategies might be used to produce an effective method for controlling powdery mildew on cucurbits: Utilize fungicides, biological agents, or chemical substances to induce systemic acquired resistance (SAR) in cucumber plants that are resistant to powdery mildew. These protective measures will be discussed in the following chapters.
Powdery Mildew of cucurbits Chemical Control
Fungicide controls vulnerable cucurbit cultivars best. Konstantinidou-Doltsinis attributes cucurbit fungicide use to powdery mildew control in cucurbit disease. To be effective, most powdery mildew fungicides must be applied before the fungus infects the plant. Powdery mildew fungus can also become fungicide-resistant. Flint® (trioxystrobin), Nova® (myclobutanil), Quadris® (azoxystrobin), and Pristine® (azoxystrobin) are Florida-approved powdery mildew fungicides (boscalid and pyraclostrobin). Handle, apply, and dispose of fungicides according to label instructions. The misuse of these fungicides increases environmental pollution and powdery mildew fungus resistance. Update registration, recommendations, and assistance with county extension agents.
Copper and sulfur, non-systemic fungicides, can reduce powdery mildew outbreaks. Sulfur controls the powdery mildew of cucurbits naturally. Sulfur hits many fungal targets without resistance. Microthiol Disperss®, a micronized, wettable sulfur compound, provides uniform dispersion over the plant surface and improves antifungal activity. Sulfur controls squash moderately, according to Mossler, Nesheim, and extension staff. Sulfur causes leaf scorch in various cucurbit species, especially muskmelons and honeydews. In this scenario, choose sulfur-tolerant melon types. Copper salt fungicides are less phytotoxic than sulfur but still damaging. Copper salts (Kocide® 2000, Microcop) are recommended for cucurbit powdery mildew control.