Zucchini plants are stupidly easy to grow. All they need is sun, water and some love. They grow fast and produce squash like crazy . . . when they're healthy, that is. Within ten days time my plants went from this to this with absolutely no maintenance . . . we were on vacation and we came home to enormous plants starting to bear fruit.
My poor zucchini plants have been the abused by pests every year that we've had our garden. First come the squash and cucumber beetles followed inevitably by powdery mildew. Both will greatly diminish the output of the plant at best and destroy the plant at worst.
Fortunately, both the these problems are easily eradicated by chemical means or controlled by organic measures. I'll give you both options for both methods that I've had varying degrees of success with.
My plot is in a community garden where we are only allowed to use organic products. However, in the past, I have used Sevin for pest control and Daconil as a fungicide . . . both with exceptional results.
One simple thing is to lay a mat of tin foil around the base of the plants. Most of these pests prefer the shady underside of the leaves; which is also where they lay their nasty little eggs. The idea is either to confuse them by reflecting a light underneath the plant or to cook the eggs to an uncomfortable temperature. It also helps to prevent bugs like squash borers from coming up from under the soil from emerging and climbing up the plant.
There are plenty of organic fungicides and pesticides available commercially, but I haven't tried them. I use homemade organic concoctions for pest and fungus control. They're really quick and easy to make . . . not to mention inexpensive.
For pest control I make an orange oil insecticide. Simply combine 1 tablespoon of orange essential oil with 1 quart of water in a spray bottle. Then add 1 teaspoon of cayenne pepper to the mixture and shake the bottle to mix the oil with the water. Spray the orange oil pesticide on the stems, undersides of the leaves and the vegetables themselves to protect them. Store the pesticide away from heat and direct sunlight. Shake the bottle before each use.
Believe it or not, milk makes a great fungicide. It's so easy to make a milk based fungicide, too! It is believed that the antibiotic qualities of pasteurized milk impede the germination of powdery mildew spores and also provides nutrients to the plant. All you need to do is dilute one part organic cows milk with between five to ten parts water. Spray the solution during the cool of the morning to reduce the risk of foliage being burned in intense sunshine before it dries. Wet both sides of leaves and stems until it begins to drip off. Reapply after rain or irrigation. It is most effective when applied in the early stages of infection.
Proper watering is also important to make your plants as productive as they can be. First of all, they like a LOT of water . . . the zucchini fruit is mostly water. If the soil is dry make sure you give them a good drink.
Generally speaking but especially once the plants start flowering you should watering only the bottom of the plant near the roots. The first reason is the plants are susceptible to diseases when wet, so you should make sure to avoid watering the leaves and stems of your zucchini plants, if possible.
The second reason is as simple as the birds and the bees . . . well, the bees mostly. Zucchini plants need the bees to pollinate the female flowers in order to make the squash. You don't want to water the from the top because you will wash the pollen from the flowers.
Take care of your plants . . . protect them, water them . . . and they will give you more zucchini than you can possibly consume.