You’ve got your garden planted, everything is growing beautifully and one day you go out to check on progress and you notice a couple of chewed leaves. Or a sticky film on a plant stem. Or all off a sudden a young squash plant has yellow spots and the leaves are turning brown. What’s going on?
Lots. A garden environment changes daily due to many conditions. After all, there’s not much about nature that you can control. Heat, water stress (too much AND too little), soil and weather conditions are just a few things that invite pest and fungus issues. Healthy plants and viable soil are better able to withstand the attention of caterpillars, leafminers, thrips, aphids, squash bugs, etc.
Ask any gardener and they’ll tell you that you can do everything right and still get pests. The next question is what to do. With some things, like an early infestation of tomato hornworms, you can pick them off and dispose of them. Or you can use Bt (Bacillus thuringiensis), an organic insecticide that will control leaf eating caterpillars.
Biological insecticides and fungicides are actual living organisms or the toxins produced by them. Examples include viruses, bacteria, fungi, and nematodes.The chief benefit of using biological, or microbial, insecticides is their low toxicity to humans and non-target insects. Some of these insecticides are so selective that they affect only one part of the life cycle of the insect, such as the caterpillar (larva) stage of moths and butterflies. The low toxicity also means less risk to groundwater and surface water.
But there are drawbacks. Biological insecticides do not have as long a shelf life as conventional pesticides, so proper storage is critical. In addition, certain microbial pesticides can lose their effectiveness rapidly if exposed to heat and ultraviolet radiation, or when they dry out. For this reason, proper timing and application procedures are extremely important.
Here’s a rundown of OMRI listed controls that can help with most of the pests and fungus you may find in your garden. OMRI means that this product is has been listed by the Organic Materials Review Institution as an organic product and can be used by certified organic growers as well as the general homeowner who wants an organic method of disease control. There are pros and cons with any control, so we’ve linked each product to its label information if you’d like more details.
You’ll also notice that some of these controls overlap, in that they work on the same pests. You’ll want to consider your plant type and pest type before choosing any control.
We carry all of the following products at Southwest Gardener and are happy to talk with you more about them.
Bacillus thuringiensis, often abbreviated as Bt, is a naturally-occurring bacteria that makes pests sick when they eat it. There are two strains commonly used as natural pesticides. Bacillus thuringiensis kurstaki (Btk) gives excellent control of leaf-eating caterpillars such as cabbage worms and tomato hornworms, but has no activity against insects that do not eat treated leaves. After the insects eat the bacteria, their guts rupture and they die. Bt is therefore one of the safest natural pesticides you can use in terms of controlling caterpillar pests of vegetables or fruits without harming beneficial insects.
Most caterpillars seen eating leaves can be controlled by Bt when applied at the proper time. In vegetable gardens, cabbage worms, diamondback moths, melon worms, corn earworms, tomato hornworms and grapeleaf skeltonizers are candidates for treatment with Bt.
Bt is best applied in indirect light, such as dusk.
Neem oil is a naturally occurring pesticide found in seeds from the neem tree. It is yellow to brown, has a bitter taste, and a garlic/sulfur smell. It has been used for hundreds of years to control pests and diseases. Components of neem oil can be found in many products today. Azadirachtin is the most active component for repelling and killing pests and can be extracted from neem oil. The portion left over is called clarified hydrophobic neem oil.
We carry a neem oil spray that acts as a fungicide, insecticide and miticide. It is most effective when applied to young plant growth. The insecticide works as a systemic so that once it is in the plant’s vascular system, insects intake it during feeding. The compound causes insects to reduce or cease feeding, can prevent larvae from maturing and reduces or interrupts mating behavior.
Use neem oil to manage more than 200 other species of chewing or sucking insects according to product information, including: aphids, mealybugs, scale, spider mites and whiteflies.
Neem oil fungicide is useful against fungi, mildews and rusts. It works especially well on black spot and powdery mildew. It’s best to test neem oil on a small area of the plant and wait 24 hours to see if there is any leaf damage. It can burn so shouldn’t be used in hot weather and is best applied in indirect light, such as dusk.
This Garden Insect Spray biological insecticide controls worms and caterpillars on fruits, vegetables, ornamentals, and shade trees as well as thrips, spider mites, ants and leafminers. It contains Spinosad, a natural substance derived through fermentation of a naturally occurring soil bacterium. Spinosad controls caterpillars, thrips, codling moth, leafminers, borers, fruit flies, fire ants, and more. It works on the insect’s nervous system, causing paralysis and then death in 1-2 days. Since the insects are paralyzed, they may stay on the plants and be mistaken for live insects; always check for Spinosad’s effect 2-3 days after spraying to evaluate control in the insect population.
This is safe to use with the following beneficials: minute pirate bug, ladybird beetles (lady bugs), green lacewing, and mite predators. However, it is toxic to bees, so apply it in the late evening and on plants that are not blooming, pollen-shedding, or nectar-producing.
Bi-Carb Fungicide is a preventative and contact fungicide for the control of powdery mildew based on potassium bicarbonate. It is called “Old Fashioned” because if your grandmother wanted to control powdery mildew on her roses she would mix up a solution of baking soda (sodium bicarbonate) and use it as a spray. In fact, many organic growers use this method today. In the commercial versions, the sodium is replaced with potassium since it is safer on the plant and breaks down into an essential plant nutrient for the same results.
Bi-carb old fashioned fungicide is a contact fungicide and works by disrupting the potassium ion balance in the fungus cell, causing it to collapse and die. Plants that are highly susceptible to getting powdery mildew include ornamentals such as roses and vegetables such as squash, melons and cucumbers.