How to deal with powdery mildew and other diseases in your garden (Wally Richards)

This is the time of the year that the disease called Powdery Mildew will attack a number of plants in your garden.

Powdery mildew is a common fungus that affects a wide variety of plants. It is easily identified and appears as light grey or white powdery spots usually found on infected leaves, but can also be found underneath, or on stems, flowers, fruit or vegetables.

Powdery mildew, mainly caused by the fungus Podosphaera xanthii, infects all cucurbits, including zucchini, squash, cucumbers, gourds, watermelons and pumpkins.

Powdery mildew infections favor humid conditions with temperatures around 20-27° C so recent rains and warm temperatures have been the cause of what we now see in our gardens.

A little early this season as it more often appears with the autumn rains in March and April. Being early means a problem in obtaining the maturity of some crops such as pumpkins.

Unlike some other diseases, powdery mildew spores do not live in the soil, but rather are transferred from plant to plant by the wind …

If possible, plant cultivars that are resistant to powdery mildew and be sure to rotate crops in your vegetable garden.

I always describe diseases and insect pests as the cleaners of Nature, helping to take out the weak plants and contributing to their demise at the end of the season.

But when a disease such as powdery mildew strikes before the end of the season it means you may not get the best out of infected plants before they fail completely.

Pumpkins and zucchini will stop growing as they cannot gather energy from the sun when their leaves are covered with the powder.

That means their fruit may not mature and thus be wasted.

My easy solution is to spray the affected foliage with Wallys Super Neem Tree Oil; it instantly turns the leaf back to green and allows the plants to carry on for a while longer.

Only spray at the end of the day when the sun is off the plants as oil and sun/UV become a weed killer and you would burn the leaves.

One reader this week from up Auckland way asked about when he could spray his peaches for brown rot as he has been spraying the fruit every week with Wallys Super Neem Oil and Raingard for preventing the guava moth maggots from entering the fruit. An interesting dilemma as the oil will have an adverse reaction with the sprays needed to control brown rot in stone fruit.

My recipe for brown rot is a combination of Wallys Liquid Copper, potassium permanganate, spray-able sulphur with Raingard added.

If you have brown rot problems then that spray program should be started after the fruit have formed and reached about half their full size.

No need to spray the tree just the fruit to protect them as they head to maturity. Spray two-weekly till harvest.

One gardener that reported back to me about 2 years ago said that he was able to obtain about 90% of his crop from using the program.

He also thought that because he missed one 2 weekly spray in the middle because he had to go away, it may otherwise have been 100% successful.

The previous season all his fruit was lost which is a good indication how successful the combined sprays are.

Another disease that could be appearing on the trunks of your tomato plants at this time is a fungus growth, grayish in colour, that is going to kill your plants.

The cause of the disease is the insect pest, tomato/potato psyllid.

The nymphs when feeding on the foliage inject a toxin into the plant which will cause the fruit to be smaller, the leaves to turn yellow and drop and the death of the plants.

There is only one solution that is 100% effective for all plants which are hosts to the psyllid and that is Wallys Cell Strengthening spray/drench program.

Three components ; Wallys Silicon and Boron soil drench which is applied prior to or at planting time and again two weeks later.

By the way some gardeners have told me that they have use the drench on other plants which has resulted in very healthy strong plants.

This is likely due to the boron aspect as well as the silicon and boron deficient soils will prevent some plants from preforming as well as they could. Avocados and cauliflowers are two that come to mind.

There is on our mail order website a natural slow release boron you can use in your gardens every couple of years or so. The Cell Strengthening spray with the Super Spreader that drives the former into the plant should be applied weekly while the plants are growing.

If your tomatoes are failing and you can get some Russian Red seedlings plant them out with the strengthening products as it is not too late to get them going for some late cropping.

Feed them with Wallys Secret Tomato food with Neem granules and add the Magic Botanic Liquid to the Cell Strengthening sprays.

Happy Gardening.

Photo: Sweetaholic @ pixabay.com

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