Pests and Diseases in the Vegetable Garden: A Closer Look at Problems Encountered in Gardens

There are many things that can go wrong when growing a vegetable garden. Plant diseases and insects can wreak havoc in the vegetable patch. Below are a few things which can affect the health of plants and the amount of produce can be expected from each crop grown.

Producing healthy vegetables starts with healthy soil. This is probably the single most important part of gardening. Diseases and insects live in unhealthy soil.

This is one method of using insects to control pests in the garden. Biological pest control is a natural, nonchemical method of controlling pests and disease in the garden.

Monilinia fructicola is a common fungus found on stone fruits. *Look for disease resistant trees when purchasing orchard stock.

A crucial nutrient needed in plants to promote strong cells. It can be found in the root system of growing plants and stored in fruits as well.

When plants are nutrient-deficient, the leaves will turn yellow and may become diseased. This is referred to as chlorosis because of the lack of chlorophyll in the leaves.

Plasmodiophora brassicae is a fungus which infects the roots of Brassica plants such as kale, mustards, cabbage and others. The infection causes roots to swell which makes them unable to draw in the water and nutrients they need to thrive. Plants will die. The infection spreads by spores which enter the soil and can infect roots of other plants.

Combining plants in the vegetable or flower garden and orchard that work together for instance, French Marigolds (Tagetes patula) attract nematodes and when planted in the garden draw these away from vegetable plants.

A disease caused by bacteria (Erwinia amylovora) which first attacks the flowers and twigs then the branches of fruit trees. This disease often strikes fruit trees.

An insect, Drosophila melanogaster, which lays eggs on or beneath the surface of fruits and when the larvae hatch they begin to eat the fruit. This fills the fruit with holes and causes it to rot.

Cover crops, such as clover, which is grown to improve nitrogen level in the soil.

Much like it sounds, honeydew is sticky and sugary. It can be found on plants where aphids and some scale insects have deposited it. Ants can be found dining on honeydew.

These are the elements used in large amounts by plants and must be found in or added to soil for healthy productive plants. They include the primary nutrients nitrogen (N), phosphorus (P), and potassium (K). The secondary nutrients are calcium (Ca), magnesium (Mg), and sulfur (S).

A tea made by soaking manure in water and then pouring the liquid through a thin fabric or wire sieve into a container. This liquid makes a good organic fertilizer.

A scale insect found most often in humid areas. They feed on plants by sucking the sap.

These elements are sometimes called trace elements. Plants need these in smaller quantities than macro-nutrients. They are boron (B), chloride (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo) and zinc (Zn).

Many pests in the garden can be controlled by using their natural enemies against them. For instance, to control aphids it is a good idea to invite insects such as; lacewings, ladybugs, damsel bugs and others.

Thread-like or a worm-like parasitic organism that attacks the roots of plants, others attack the bark of trees such as pine and still others cause disease in grapes by spreading viruses.

Nitrogen is a nutrient which promotes healthy growth and dark green foliage in plants.

Powdery mildew is a fungal disease typically seen on plants in humid climates, although it can grow in other environment. Infected plants are easy to spot because white powder-like spots on the leaves and stems are obvious.

Also known as sun-scald, leaf-scald is caused by prolonged periods of very hot sunlight directly on plant leaves.

Scale is caused by insects such as aphids sucking the sap from foliage. This can cause severe damage.

Anything added to soil which improves its texture by either adding or allowing it to retain nutrients.

Aphids and other insects release a sticky substance called 'honeydew' on plants where a fungus (mold) can begin to grow. This mold is called sooty mold.

Sterilizing soil helps to kill bacteria, dormant weeds and other hidden organisms in the soil. Heating the soil to above 180 F sterilizes it.

Spotted and striped (Acalymma vittata) cucumber beetles cause bacterial wilt in cucurbits such as cucumbers and melons

Bugs commonly found on pumpkins and squash. They attack all members of the cucurbit family of plants

The list above covers a few pests and diseases gardeners deal with during the growing season and beyond. Also included are a few things which help plants to remain healthy.

The copyright of the article Pests and Diseases in the Vegetable Garden in Garden Pests & Diseases is owned by Jacqueline Cross. Permission to republish Pests and Diseases in the Vegetable Garden in print or online must be granted by the author in writing.

Jun 20, 2009 8:44 AM

Guest :

I would like to find out what would eat marigold leaves, onion tops, spinach leaves, young zinnia leaves..........etc.

Jun 20, 2009 11:07 AM

Jacqueline Cross :

Slugs & snails are most likely eating your leaves. Look for slimy trails on the plant leaves to verify. They hide in the mulch, under rocks or other things laying on the ground during the day and come out at night to feed on plants. You might want to try and catch them by pouring a can of beer into a low container (or containers) & setting it out in the garden. Scoop out a trowel of soil so the top of the container sits at ground level. The little pests will be drawn to the beer and fall right in.
You can also hand pick these pests from plants early in the morning & late in the evening. Have a bucket of soapy water nearby to drop them into once you've picked them off.

It could also be Cabbage Loopers or Leaf Miners doing the damage. I am seeing a lot of damage from these pests this year. It does not take them long to destroy plants once they set their sites on them.