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Diseases, Insects & Other Problems

Bacterial Wilt of Cucumbers Blossom End Rot of Tomatoes Cabbage Worms
Cucumber Beetles Cutworms Flea Beetles
Potato Bugs Powdery Mildew Rabbits
Root Maggots Slugs Tomato Blight

Tomato Leaf Roll

Bacterial Wilt in Cucumbers

What is Bacterial Wilt?

Bacterial wilt is a bacterial disease which plugs up the water-carrying vessels on the cucumber plants. As the vessels are plugged, the plant will wilt more and more each day until it completely dries up.

What can be done to control this condition?

Absolutely nothing can be done now, except to pull up the dying plants and throw them into the garbage. Bacterial wilt is spread from plant to plant by the cucumber beetle and the best method of controlling the disease is by controlling the cucumber beetle.

What is the best method of controlling the cucumber beetle?

Light, frequent applications of Sevin, Methoxychlor or Diazinon will control the cucumber beetle. Start spraying the beetles as soon as they appear in the spring.

Are other plants infected by Bacterial Wilt disease?

Yes, it can also be severe on melon plants and occasionally on squash and pumpkins.

Blossom End Rot of Tomatoes

What is blossom end rot?

Blossom end rot is a physiological condition which develops in tomatoes. Fruits are most commonly affected when a third to half grown but can be attacked at any stage.

What are the symptoms of blossom end rot?

The first signs of the disease is a water soaked spot near the blossom end of the fruit. This spot darkens and enlarges until it covers to the fruit. As it increase in size the tissues shrink and the surface of the spot becomes dark and leathery.

What causes this condition to occur?

Blossom end rot occurs commonly when the plants have grown rapidly during the early part of the season and them are subjected to dry weather at a time when the fruits are developing rapidly. Fluctuations in water supply are conducive to blossom end rot.

Can the condition be cured?

Once a tomato fruit has the condition it will continue to develop on that fruit, but other fruits on the same plant may not be affected.

Cabbage Worms

Do the white butterflies have any connection with the cabbage worms?

Yes, the white butterflies we commonly see flying around in the garden are the adult imported cabbage worm. The adult of the cabbage looper is a brown moth which is usually not active except at night.

How many different kinds of worms are called cabbage worms?

Usually the name cabbage worm is given collectively to the cabbage loopers and the imported cabbage worm. Both of these caterpillars are present on plants at the same time of the year and control measures are identical.

Does the bacterial insecticide Dipel control the cabbage worms?

Yes, Dipel will give good control of the worms and is not harmful to humans or pets.

Can other insecticides be used to control cabbage worms?

Yes, many of the common insecticides such as Sevin, Malathion and Diazinon all give good control. I've even had good luck using Garden Gard.

Cucumber Beetles

What type of damage is done by the cucumber beetles?

The cucumber beetles may attack the melons and cucumbers just as they come through the soil or any time later in the growing season. The beetles feed on the leaves, vines and fruits. They also transmit bacterial wilt and cucumber mosaic.

What do the beetles look like?

The adult cucumber beetle is about " in length with alternate black and yellow stripes on the back. They have 3 stripes on the back.

How can they be controlled?

Light dust or spray applications of Sevin or methoxychlor will control the beetles. Chemical control may have to be applied more than once but be careful not to apply any more chemical than necessary. Cucumbers and melons can be injured by applying excessive amounts of chemicals.

What is bacterial wilt disease?

It is a disease which plugs the water carrying vessels of the cucumber and melon plants. It is spread by the cucumber beetles and is always fatal.


Should something be done to prevent cutworm damage?

Yes, cutworms can really devastate your transplants. They come up at night and cut the tomato plants off at just above ground level. Use some type of mechanical barrier around the plants to keep the cutworm away. Tin cans or milk cartons with the ends cut out work well.

Flea Beetles

What type of damage is done by the flea beetles on the plants?

Flea beetles eat tiny holes in the leaves of many different garden plants. From a distance the plant leaves look like they have white spots on them, but if we look closely we can see the tiny holes.

Which plants are most commonly attacked by flea beetles?

They seem to prefer radishes, tomatoes, potatoes and allysum. I've been having a lot of problems with them on my cabbage, broccoli and cauliflower.

What can be done to control the flea beetles?

Garden insecticides are the only practical method of control. Dusts or sprays of Sevin, Methoxychlor or Diazinon will control them. Apply the insecticide liberally on the plants as well as on the ground between the plants.

Why would we want to spray on the ground?

When we move through the garden the flea beetles are disturbed and move from the plants to the ground. To get effective control we recommend spraying the ground as well as the vegetables themselves.

Potato Bugs

What do potato bugs look like?

The adults are about 3/8" long and 1/2" wide with alternate black and yellow stripes on their backs. The larvae are slightly smaller and reddish in color. When they feed their backs are arched into almost a semicircle.

Is it necessary to control them?

Yes, very definitely, if they are not controlled they will strip your potato plants in a short time.

How is the best way to control potato bugs?

Chemical sprays or dust of Sevin or Methoxychlor will give some control, but don't get discouraged if one spray doesn't completely control the bugs.

Is it possible to control them without using chemicals?

Yes, but you must be diligent in picking the potato bugs off the plants every day or two. I can remember doing that many years back. We used to go out with a fruit jar every day or two and pick bugs.

Powdery Mildew

What type of symptoms are caused by powdery mildew?

Just as the name says, the disease causes a white powdery substance on the leaves and flowers. It may also cause the leaves to be twisted and distorted.

Which plants are affected?

Powdery mildew is common on garden peas and numerous other plants.

How is powdery mildew controlled on garden peas?

Flotox garden sulphur can be used on peas.


What can be done to keep the rabbits off the vegetables?

There are several ways to control rabbit damage. Rabbit proofing your yard with fencing is the most effective. Care must be taken to ensure that they can't crawl under. Repellents can also be used but with limited effect.

What type of repellents are available?

Local nurseries have commercial repellents which will give good control. It can be applied on the grass around the garden and directly on the vegetables. Dried blood and moth balls will also work but need to be replaced every time it rains.

I've heard you mention a home remedy with red pepper and glue. What are the exact proportions to use?

Yes, this remedy is very popular. The recipe is made up of 2 tblsp ground red pepper, 1 tblsp Elmer's white glue and a quart of water. Tabasco Sauce can be used as a substitute for the pepper.

Can this be used on vegetables such as tomatoes?

Yes, up to the point when fruit is set. The glue would make it tough to get the pepper or tabasco sauce off of something you want to eat.

Root Maggots

What can be done to keep the worms (root maggots) out of the radishes and onions?

Root maggots can be controlled in radishes by applying granular diazinon in the row with the seeds when planting. The same procedure can be used when planting onions and the cabbage type vegetables, but a repeat application will be needed later in the season for continuing control.


What can be done to keep the slugs under control?

Since they are not an insect the normal chemicals such as malathion, etc. won't work on them. There are several baits available which work well. Bug-geta liquid snail and slug killer is commonly available and does a good job. It gives off an odor which attracts the slugs. They eat it and proceed to die.

Can they be controlled without using a chemical?

Yes, but it's very difficult. Beer, put out in a partial buried pie tin just before dark, works as a good natural bait for slugs.

Which plants do the slugs feed on?

They really don't seem to be too particular about what they eat, but can really be a problem on ripening tomatoes.

How do slugs overwinter?

They overwinter in the soil or under litter and debris. Cleaning up the garden in the fall will reduce the overwintering population.

Tomato Blight

When should we start spraying for tomato blight?

Tomato blights usually become a problem when we get a period of warm rainy conditions. Watering with a sprinkler in the evening will also encourage the development of blight and other leaf diseases. When you notice the start of the disease on the bottom leaves it's time to start spraying with a fungicide.

How long is tomato blight a problem?

Tomato blight is a problem any time the leaves of the plant are wet, especially at night. Frequent rains or watering the plants in the late evening is very conducive to tomato blight.

What symptoms indicate a blight infection?

You'll first notice small brown spots on the lower leaves, followed by leaf yellowing and finally browning of the leaves. The disease progresses up the plant gradually killing the leaves. When the upper leaves are lost, the fruits will sunburn.

What chemicals should be used to control blight?

Ortho multi purpose fungicide (Daconil 2787) or any other product containing chlorothalonil can be used. It is a preventative spray and will keep the disease from spreading to more leaves.

Which tomato variety or varieties aren't affected by tomato blight?

Don't think there is such a variety. NDSU did some testing a few years back and all the varieties tested became infected. Just watch your plants and start spraying with a fungicide when you notice brown spots on the lower leaves.

Tomato Leaf Roll

What causes the tomato leaves to roll up, but not turn brown?

Leaf roll is a leaf disorder caused by excessive moisture, heavy applications of nitrogen fertilizer, root damage from close cultivation or by staking and pruning plants.

Will leaf roll effect the fruit production on the infected plants?

No, leaf roll usually doesn't have much effect on plant growth or fruit yield.

What causes the tomato leaves to become narrow, twisted and distorted?

It's probably the most common problem we have with tomatoes in this area. This is caused by using 2,4-D or a related weed killer to close to your tomatoes. Tomatoes are very susceptible to just traces of herbicide in the air. Herbicides should not be used when the temperature gets about 85 degrees and the wind is blowing.

Will plants recover from 2,4-D damage?

If the plants show only slight damage they should recover, particularly if growing conditions are good.  A good rule of thumb when pesticides have damaged your plant and you don't know what they were or the harvest interval is:  "When in doubt, throw it out."  It is better to not eat something that can make you sick (or worse) than to eat it.

Todd Weinmann, Extension Horticulturist & Master Gardener Coordinator
Phone: (701) 241-5707

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