Squash Powdery Mildew Treatment: Effective Solutions for Sustainable Disease Control

Powdery mildew is a common fungal disease of squash in worldwide agriculture. It's capable of quickly infecting leaves and causing considerable losses if not controlled – and inducing general weakening of plants. Powdery mildew on squash leaves can be a problem in the field or home garden and often is characterized by white powdery patches on leaves on warm, humid nights.

Today with increasing disease pressure, most growers are shifting towards biologic disease management in order to improve sustainable crop production. Utilization of beneficial microorganisms via products to minimize pathogen population and protect beneficial microorganisms and to reduce the need for chemicals is yet another new means in the IPM toolbox.

The guide covers the causes of powdery mildew, early detection of the disease, how to treat powdery mildew on squash and the use of biological control methods like Novobac FloraEgis, which contains Trichoderma harzianum, to provide long-term disease control.

Powdery mildew is the name used to describe the fungus, Sphaerotheca blight, which attacks cucurbs

Powdery mildew of cucumber is a fungal disease which occurs on squash and is mainly caused by Podosphaera xanthii, the most frequent pathogen of cucurbit crops. Mimicked by disease on leaves, stems and occasionally petioles resulting in poor photosynthetic efficiency and fruit production.

Unlike many other fungal diseases, powdery mildew need not have free water for germination, it can be caused at relative humidities of approximately 70% at warm temperatures. This will enable rapid spread of infection throughout the squash crop during the season.

Long before large areas of the canopy are affected, it is important to institute disease management to achieve crop recovery.

What causes powdery mildew of squash?

There are several factors associated with disease development relating to the environment and crop management. Daytime temperatures and relatively high humidity levels (20°C - 30°C) are conducive to fungi growth during the day during cool nights. Spores spread rapidly from plant to plant in denser crop canopies that don't have much air circulation.

Culture of the crop on a continuous (greenhouse) system, volunteer plants and infected crop residues are also important as they can provide a seasonal reservoir of fungal spores and thus contribute to disease pressure. Control of such diseases will minimize the effects of this disease before substantial damage is done to the crop. Powdery Mildew is also a problem in the field on squash leaves with early signs appearing

Powdery Mildew is also a problem in the field on squash leaves with early signs appearing

Early diagnosis greatly involves the management of the disease.

Powdery Mildew usually first spots on squash leaves are small, white circular patches on older leaves. When these patches develop, they spread and merge together with time covering larger and larger areas with a white powdery deposit on the leaf surface.

These are also other symptoms that may be present:

•  Yellowing foliage
•  Premature leaf aging
•  Curling leaf edges
•  Reduced photosynthesis
•  Poor fruit development
•  Premature defoliation

As leaves become less efficient in capturing the sunlight, fruit size, sugar gain and yield starts to decrease.

What impact does the powdery mildew have on the squash crop?

The above ground parts of a squash plant are also the main organs that produce food to give the plant the energy it needs. Photosynthesis is greatly cut back if the leaves contract powdery mildew on squash leave, and so are not able to produce enough carbohydrates for flowering or fruit filling.

With heavy infections, your doctor may find that you have:

•  Smaller fruits
•  Lower fruit quality
•  Damage from sun exposure resulting from depletion of canopy.
•  Reduced harvest duration
•  Lower marketable yields

However, repeated fungicide for powdery mildew on squash applications may be required if the disease becomes prevalent which could cause an extra cost to commercial growers.

How to get rid of powdery mildew on squash naturally?

A question often posed by many growers is how to control powdery mildew on the squash without 100% chemical powdery mildew control fungicide use.

The best way is to monitor the disease early and by using disease management (cultural method) and biological method. Recommendations for management address plant spacing to allow more air flow, removal of heavily infested leaves, avoid excessive nitrogen fertilization, cropping rotation (no host crop) and field sanitation after harvest. Preventative use of biological products in early stages of disease development will generally give increased lasting control than squash powdery mildew treatment when the disease is established. The key point to a successful squash powdery mildew treatment program is to minimize the disease pressure before the fungus is able to get into the canopy. 

If powdery mildew is likely to occur on squash, follow the spray recommendation for the fungicide

Knowing how to deal with powdery mildew on squash (prevent the problem) will save cents over extensive powdery mildew problems.
Preventative management starts with careful selection of healthy seed (pre-control), balanced fertility and improving drainage (pre-control). Growers need to conduct regular field scouting and keep an eye on weather which creates the opportunity for crop disease.

Space between plants ensures good air movement are adequate, and don't irrigate too much overhead which is not desirable in a plant. Biologicals can also be used for preventive Disease Management applications to further enhance disease management programs, as well as protecting the leaf surfaces prior to heavy infestation.

How to get rid of white powdery mildew on squash?

As the disease progresses to the head some white powdery mildew of squash may also appear on the leaves and stems, but many growers still ask: How do I deal with white powdery mildew in squash when it first appears on the leaves and stems?

After being a severe infector it is not usually possible to eradicate completely. Disease management is designed, instead, to reduce the growth of disease causing organisms, conserving the healthy plant tissue, and maintaining yield potential. Healthy leaves can be removed, which will decrease the amount of spores in the environment for dissemination. Timely use of a ffungicide for powdery mildew on squash when required in conjunction with a biological disease management programme can help to maintain the production life of a crop and protect the new leaves from disease.

Early intervention always surpasses the attempt to control the spread of the infections later in the season.

Why is Organic Disease Management Gaining Popularity?

As growers become increasingly interested in environmentally responsible methods which reduce chemical inputs, they want results with effective disease control.

The use of powdery mildew squash organics solutions to control powdery mildew helps maintain healthy soil biology, minimizes chemical pesticide residue and does not create resistance problems like a been-on-it mindset through fungicide application.

While most fungicide products inhibit a single biochemical pathway, often biological control products have more than one mode of action, reducing the likelihood of the pests becoming resistant.

The above have established biological disease management as an important part of modern Integrated Pest Management (IPM) programs.

Evidence to validate Trichoderma harzianum

Trichoderma harzianum, organic treatment for powdery mildew on squash, is one of the microorganisms used for disease management which has been studied in detail.

This fungus is beneficial and invades the surface of the plants, thereby competing for space and nutrients with disease-causing fungi. It is also a source of enzymes breaking cell walls of pathogens, secretes metabolites that are antimicrobial and triggers the defense mechanisms of plants induced by systemic resistance.

It is effective in controlling powdery mildew pathogens, which is supported by research.

Podosphaera xanthii is the fungus that causes powdery mildew in squash, and Hafez et al. (2018) showed an effective reduction in the incidence of this fungus using biological control methods and using Trichoderma species in a study published in Egyptian Journal of Biological Pest Control. The study also revealed that the squash plants' natural resistance against pathogens has also increased, expressed through higher levels of natural defense enzymes.

The results emphasize the importance of the consideration of biological disease management in sustainable crop protection.

How to treat powdery mildew on squash with Novobac FloraEgis 

How to prevent powdery mildew on squash​? Novobac has a strong emphasis on biological crop protection, microbial technologies and solutions for plant development that enable growers to control plant diseases for sustainable development and environmental protection. 

Novobac FloraEgis (organic treatment for powdery mildew on squash) is a formulation of biological foliar fungicide with Trichoderma harzianum used for promoting the biological control of foliar fungal diseases also in cucurbit vegetables, such as powdery mildew disease. 

Following application, the beneficial fungus infects the leaf gutters, suppresses disease causing pathogens, produces fungal metabolites and enhances plant resistance. A multi-mechanism activity to help lower disease pressure and encourage healthier foliage over the growing season.

Growers around the world, including Canada, the USA, Mexico, Europe, India and Southeast Asia, have integrated FloraEgis into their disease management program to give them more flexibility in their use of chemical fungicide for powdery mildew on squash.

The wrong fungicide strategy will kill the crop

When selecting a fungicide to control powdery mildew on squash leaves, disease pressure, environmental conditions and a long-term approach to resistance management are important factors to take into account.

Biological products are used alongside conventional powdery mildew control fungicide in many instances, by the grower, to maximize the number of modes of action in use and lessen the selection pressure for fungal populations.

Integrated programs are the use of a combination of biological protection measures, cultural control, field monitoring and appropriate interventions to ensure more effective long-term disease control rather than use of a single powdery mildew control fungicide.

This method also helps to increase sustainable and environmentally friendly production, as residues of chemicals are minimised without sacrificing disease control.

Creating a Sustainable Powdery Mildew Management Programme

Preventing the plant from getting the disease starts very early. Healthy crop establishment, appropriate plant spacing, fertility balance, regular scouting, biological crop protection and integrated programmes against the disease form a resilient production system which helps to protect yield potential whilst reducing the spread of disease.

With the increased use of organic farming methods in both agriculture and aquaculture, organic control of powdery mildew of squash is gaining importance in crop management considerations. Responsible powdery mildew management, combined with sound agronomic practices, can be achieved using biological products like Novobac FloraEgis which contributes to healthy plants, more productive crops and environmentally sustainable agriculture.

Reference: 

• Hafez, Yaser M., et al. "Biological control of Podosphaera xanthii the causal agent of squash powdery mildew disease by upregulation of defense-related enzymes." Egyptian Journal of Biological Pest Control 28.1 (2018): 57.
• Elsisi, Ahmed A. "Evaluation of biological control agents for managing squash powdery mildew under greenhouse conditions." Egyptian Journal of Biological Pest Control 29.1 (2019): 89.