Spots on pepper leaves

Treating Plant Diseases Naturally

Plants, like people and animals, can develop a number of diseases. Whether you see it in your houseplants or out in the garden, diseases can destroy your greenery quickly if not treated, prevented, or destroyed. It’s probably not the end of the world if you lose a houseplant to a disease, but if you rely on your vegetable garden for food, it can be a major problem.

There are a number of diseases that could be affecting your plants. Some may occur on any type of plant, while others will be specific to certain plants. Some of the most common issues are mildew, leaf spot, and fungal infections. These and other plant diseases can often be treated with a natural remedy. In most cases, there is no need to get a harsh chemical from the gardening store that could harm you or your family.

Before you try the remedies, however, be sure that you have a good understanding of the diseases and what they look like. Especially if a plant is very important to you, be careful that you are treating the disease accurately. Read up on plant diseases to learn what the signs of various problems and pests are. Choose a treatment that suits your needs but that is also convenient. There are several treatments that work on the same disease, so pick one based on the ingredients you happen to have on hand.

Natural Remedies

Many of these treatments involve making and using a spray. It is best to use the spray in the early morning or in the evening. Do not spray when it is too hot, or it may burn your plant’s leaves. Before trying any spray, you would be wise to test it on one leaf first. Observe the leaf twenty-four hours later to see if there was an adverse reaction. Only spray the part of the plant that is diseased. Protect yourself while spraying. Some of the ingredients may be irritating to your eyes, nose, or skin.

  • Apple cider vinegar. Dilute one tablespoon of vinegar in one gallon of water and use to treat fungal infection on any type of plant. It can also help treat black spot on aspen trees and on roses.
  • Baking soda. Another fungicidal spray is made with baking soda. Mix one tablespoon of soda with two and a half tablespoons of vegetable oil and add to a gallon of water. Shake the mixture well and add to it one half teaspoon of castile soap. Shake the spray bottle regularly while you are using it to keep the ingredients together. They tend to separate out. When using this spray to treat powdery mildew, first spray down the affected leaves with water. This can help to loosen up spores. You can also use the baking soda spray to treat early tomato blight, leaf blight, and anthracnose.
  • Chive spray. This mixture is useful for treating downy mildew on vegetables like pumpkins, squash, and cucumber. To make it, steep a large bunch of chopped chives in boiling water. Strain the chives out and use the liquid to treat the vegetables. It can also help prevent apple scab.
  • Garlic and corn spray. To prevent fungal infections in any plants that you feel are susceptible to them, you can use this effective spray. To make it, you need corn leaves, clematis leaves, and the papery outer covering of garlic. Chop them up together in a blender or food processor with water. Strain the liquid and use it as a spray.
  • Elder leaf spray. Elder leaves are known to be fungicidal. If you have a shrub on your property, collect several of the leaves and simmer in water for about thirty minutes. Use about two times as much water as leaves. Strain out the leaves and add a tablespoon of castile soap per sixteen ounces of solution. Spray on your affected plants.
  • Horseradish spray. Horseradish is a potent substance, as anyone who has eaten it can tell you. That spicy flavor indicates a potent cleanser that is an excellent way to prevent fungal infections and particularly, brown rot in apple trees. Process one cup of horseradish roots in a blender or food processor and mix with two cups of water. Let it sit for twenty-four hours and strain out the roots. Dilute this liquid with two quarts of water.
  • Milk spray. A milk spray has several uses. It can treat common mildews that occur on tomato, squash, asters, and cucumbers, as well as mosaic disease in cucumbers, tomatoes, and lettuce. The milk changes the pH on leaves, making it a poor environment for the growth of the disease. To make it, mix one part milk to nine parts water. Spray plants thoroughly every three to four days when mildew has already formed, or just once a week as a preventative measure.
  • Chamomile tea. Chamomile tea is a good fungicide. Spray tea on the seedlings and on the soil to treat damping off disease, especially if you see fuzzy white growths.
  • Seaweed spray. To make it, steep about two-thirds of a cup of kelp in a gallon of water, and spray it on plants to prevent and treat damping off disease.
  • Cinnamon. Perhaps the simplest remedy for preventing damping off disease is to sprinkle a little cinnamon over your seedlings and surrounding soil. It will not harm the sprouts, but will kill fungi.
  • Hydrogen peroxide. Right out of your medicine cabinet, three percent hydrogen peroxide can be sprayed directly on leaves to prevent both fungal and bacterial infections. It will not harm the plants, but do not use it on seedlings. It can also help to treat infections that are already present.

New Natural Fertilizer Doubles Garden Production!


Why not prevent the diseases from forming in the first place? Certainly, you can’t anticipate and stop every problem that may arise, but there are some steps you can take while your plants are healthy to avoid the onset of diseases.

  • Disinfect your tools before working. When making cuttings, trimming, or shaping, disinfect your tools with bleach between each use. Be sure to rinse the bleach off thoroughly before using the tools on a plant. Keeping your tools clean can help remove any parasites and fungi before they get a chance to infect your plants.
  • Use new or disinfected containers. When transplanting or starting seeds, use containers that are either new or have been disinfected. As with the tools, this can prevent the spread of any diseases that might be lingering in a well-used pot.
  • Allow plenty of space between plants. Having adequate space allows air to flow between the plants. Fungal diseases in particular thrive in the close, damp environment that develops when plants are too close together. Putting plants too close together also makes it easier for disease to spread if one plant happens to get infected.
  • Take care of your plants. Healthy plants will be less susceptible to infection, so take care to give your plants everything they need: organic matter, sunlight, and adequate (but not too much)water.
  • Stick with local plants. As much as you can, grow plants that are native to your local environment. A plant that evolved to live in the tropics is going to be more likely to become diseased when grown in rural Oregon than a native plant.
  • Be observant. The sooner you notice and begin to treat a disease, the more likely you will be able to cure it with a treatment. Check your plants every day and make sure there are no signs of disease.
  • Watch out for damping off disease. Damping off affects seedlings and can potentially destroy your little sprouts if you start your garden from seeds. Being careful about the soil you use is a good way to prevent damping off, but you can also try sprays for extra protection.
  • Rotate your crops. When growing vegetables, rotating crops each year will help prevent diseases from building up in the soil.

Your plants, especially those in your vegetable garden, are an important part of your lifestyle. If you rely on growing your own food, you need to be very careful when it comes to plant diseases. Take precautions and take care to set your garden up for success. When that fails, try some natural treatments to eradicate the infections.

©2012 Off the Grid News

How to Manage Pests

UC Pest Management Guidelines

| All peppers pests | All crops | About guidelines |


Bacterial Spot

Scientific name: Xanthomonas campestris pv. vesicatoria

(Reviewed 12/09, updated 12/09)

In this Guideline:

  • Symptoms and signs
  • Comments on the disease
  • Management
  • Publication
  • Glossary


Bacterial spot appears as spots that form on leaves, stems, and fruit. Leaf spots first appear as small, angular spots on the undersurface of the leaf. The spots, which are about 0.25 inch in diameter, are initially water-soaked and later turn brown. Elongated raised cankers form on the stems. Fruit spots are circular, brown, and raised with a cracked, roughened, and wartlike surface.


The bacterium is seedborne and can occur within the seed or on the seed surface. The pathogen is disseminated with seed or on transplants. Bacterial spot is a relatively minor disease that is favored by high relative humidity and free moisture on the surface of the plant. Symptoms develop 5 to 15 days after inoculation and develop most rapidly at temperatures of 68°F or above. The bacteria do not survive in soil after the infected plant residue decomposes. Some strains of the bacteria favor pepper, others favor tomato, and others are equally pathogenic on both tomato and pepper.


Use indexed pathogen-negative seed, treated seed, or disease-free transplants. Rotate out of peppers for at least 1 year. Use furrow or drip irrigation instead of overhead irrigation. Treatment with copper spray is justified only under high pressure as might occur with sprinkler irrigations. Resistance to copper is known to occur in California populations of this pathogen.


UC IPM Pest Management Guidelines: Peppers
UC ANR Publication 3460

Acknowledgment for contributions to Diseases:

B. W. Falk, Plant Pathology, UC Davis

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Integrated Pest Management

Fact Sheets > Vegetables > Crop Specific Articles > Peppers

Bacterial Leaf Spot of Peppers

The University of Connecticut Cooperative Extension System started to develop and deliver a full-season IPM training program to commercial pepper growers in 1989. The program helps farmers recognize and successfully manage most of the important pests that influence the economics of producing this crop. By far, the most destructive pest of peppers in Connecticut, New England, and the throughout the East Coast during the past seven years has been bacterial leaf spot (BLS). Since 1989, BLS has been observed on 90% of Connecticut’s pepper plantings. Up to 91% of the acreage enrolled in the IPM program has been infected with this disease in any given year. Ironically, only 24% of the IPM growers identified BLS as a significant pepper problem in pre-program surveys. Before pepper production can be profitable, New England growers must learn to recognize this disease and minimize its occurrence and destruction.

Over 2/3 of the pesticide applied to peppers by Connecticut growers was targeted at controlling this disease, yet nine out of 10 producers still lost a substantial portion of their yield and profits to BLS. Although most IPM participants have yield increases after program involvement, there is a lot of room for improvement in managing this disease. Why is BLS so difficult to control? Bacterial diseases on most crops are notoriously hard to control, especially in places with humid, wet climates that favor disease infection and spread. Bacteria multiply rapidly, and can be spread throughout the field within a week’s time by any mechanical means you can imagine: on worker’s hands, by splashing rain drops or irrigation water or by machinery such as cultivators. Many of the strains of the Xanthomonas campestris pv. vesicatoria bacteria that cause BLS are completely or partially resistant to copper and antibiotics; the only two pesticides capable of partially “controlling” the disease. If weather conditions favor disease development and spread, pesticides are ineffective at stopping even susceptible strains of the bacteria. Low foliar nitrogen and potassium, and high magnesium and calcium levels have also been associated with increased crop susceptibility to BLS.

Some studies have shown that high-pressure mist blowers or airblast sprayers actually increased BLS incidence on plants in rows close to the nozzles by forcing bacteria present on the surface of foliage into the leaf. Such high pressure is also thought to increase the number of entry sites for infection because of broken leaf hairs and abrasion from windblown particles. High-pressure sprayers may also help spread the bacteria across rows on contaminated water droplets and crop residue.

Disease Symptoms and Development

Bell types are particularly vulnerable to this disease, although under favorable conditions for BLS spread, more tolerant varieties of hot or sweet peppers may show varying degrees of susceptibility. The X. campestris bacteria can be introduced on infected seed or arrive on transplants. It cannot survive in the soil for extended periods, but will live through the winter on the residue of solanaceous crops (especially peppers and tomatoes), on weeds in the nightshade family and on the roots of wheat. There are three known races of the leaf spot bacteria and they differ in their ability to infect various breeding lines of peppers (varieties) and the symptoms that they produce.

The bacteria may enter leaves through natural openings (i.e. stomates) or through abrasions or broken leaf hairs. The presence of water on the leaf surface is important in the infection process and thus, the first symptoms usually occur on the margins or tips of leaves where droplets accumulate. Once inside the plant, the bacteria reproduce rapidly and move through the vascular system, congesting and killing tissue. Symptoms may develop in as little as five days or not show up for six or more weeks.

BLS affects all aboveground parts of the plant. Spots on leaves appear as chocolate-brown irregular-shaped areas of dead leaf tissue. These spots start out less than 1/4 inch in diameter, grow in size and accumulate in number until the infected leaves drop off. In a severe outbreak, plants will drop 50 to 100% of their foliage, leaving the fruit exposed to the sun and vulnerable to sunscald. Plant stems and branches develop elongated, raised, light-brown cankers, less than 1/4 inch long. Fruit may develop light-colored, raised, wart-like spots that eventually darken to brown or black. BLS spreads rapidly up the crop row after canopy closure and can usually be distinguished from fertilizer burn or other problems because several adjacent plants will share similar symptoms.

Disease development is favored by relative humidity above 85%, extended periods of leaf wetness and heat waves, especially when night temperatures remain above 70 degrees F. Short periods (three days or more) below 40% relative humidity will reduce disease severity and delay development. Extended periods (three weeks) of low humidity irreversibly halt disease spread and development, even if favorable conditions return later. In addition, night temperatures below 61 degrees F suppress disease development. Typically in New England, both our humidity levels and our night temperatures begin to drop dramatically by mid-August. Depending upon the late summer weather in a given year, chemical controls may be safely dropped without fear of further disease spread. In 1995, all pepper growers on the Connecticut IPM program stopped spraying for BLS in mid-August, and experienced no increase in disease severity.

Integrated Disease Management

Once BLS arrives on your farm, it will claim at least some of your yields and profits, even if chemical control is “successful.” Too many times, I have seen it destroy 80-100% of a grower’s peppers, taking several years-worth of profits at once. If inoculum (bacteria) levels are high enough, with the right environmental conditions, even “resistant” varieties may be hurt or succumb to this disease. Good sanitation and preventative practices are essential to minimize the risk of initial infection and reduce the amount of bacteria present early in the disease cycle. Delaying the spread of this disease for a week or more early in its development, may add weeks to your harvesting time and translate directly into higher profits.

Start by washing and disinfecting used bench tops, flats and cell trays and sterilizing soil for seedling production or using synthetic media. Do not accept transplants from other farms unless proper sanitary practices are followed. Relocate or fumigate seedbeds annually. Choose fields that have been free of solanaceous crops or weeds and wheat for at least two years. Choose sites that hasten the drying of foliage after rain or irrigation and avoid excessively foggy areas. Use trickle irrigation instead of overhead. Scout fields at least weekly to detect the presence of BLS as soon as possible. If detected in the early stages, when just a few localized plants show symptoms, remove or bury all diseased specimens and symptomless plants for 10 or more feet in all directions. Always work in infected sections of pepper fields last and disinfect machinery after completing the job. Deep plow crop residues after final harvest to speed decomposition of infected tissues.

Soils amended with dolomitic lime (high in magnesium) have been shown to produce a higher incidence of BLS on pepper plants than when the soil was adjusted with Cal limestone (CaCo3). If possible, switch to calcium carbonate (Cal limestone) several years before planting peppers in a field. Maintain proper nutrient levels, especially nitrogen, by sidedressing with ammonium nitrate or urea several times during the season.

Seed Treatments

Companies take many preventative measures to reduce the spread of BLS, including; inspecting production fields, testing 10-30,000 seeds per lot for bacterium or using chemical treatments, such as sodium hypochlorite, to disinfect the surface of the seed. Some companies offer hot-water seed treatment for a small fee. Research has shown that hot-water treatment can penetrate the seed sufficiently to eradicate bacteria inside the seed. Since every plant in a field can eventually become infected with BLS from a single infected seed, hot-water treatment is highly recommended. It is easier, cheaper and more effective than trying to combat BLS in the field with chemicals, but there is a risk of reducing germination. Seed crops grown under stressful conditions may not tolerate the treatment as well as seed from plants that were not stressed.

Once you hot water treat, all seed company liability and guarantees are null and void, therefore, the following precautions and recommendations should be observed. It is important that the water be maintained at a uniform temperature throughout the vessel; use a stirring hot plate not a stove. Use a laboratory thermometer to assure that the water temperature does not rise above 122 degrees F, and treat for 25 minutes only, no longer. Watch the temperature throughout the duration of the procedure.

Conduct a greenhouse germination test before exposing all your pepper seeds to the high temperature bath. Treat a 100 seed sample of each variety and lot number and plant alongside of an equal number of untreated seed in the same growing media that you plan to use for your transplant production. If the test gives acceptable germination rates, treat as much seed as you expect to plant this year, carefully using the same procedure. Apply a fungicide according to the manufacturer’s directions for protection against soil-borne rot organisms.

We tried this to make sure it is safe when done correctly. In the spring of 1995, germination tests were conducted on five new lots (varieties) of pepper seed and one lot which was a year old. The hot water treated seed had an average germination rate of 95% compared to 94% for the untreated seeds when planted the day after treatment. Ten weeks after the hot-water treatment a second planting was made, and again, there was no reduction in germination for treated seed.

For more details see ‘Preventing Bacterial Diseases of Vegetables with Hot Water Seed Treatment’ by Jude Boucher, Ruth Hazzard and Robert Wick. Contact Jude Boucher at UConn’s Vernon Cooperative Extension office.

Pesticides and Sprayers

Some states recommend the use of streptomycin on seedlings before transplanting, but this often produces unsatisfactory results due to the prevalence of resistance to antibiotics. Growers on the IPM program apply copper plus Manex every seven to 10 days once the disease is detected through weekly field scouting. The fungicide Manex has no direct effect on the bacteria but has been shown to double the amount of copper that goes into solution when the two materials are mixed. The copper in solution increases fourfold within an hour and sevenfold in four hours, if the mixture is allowed to age before application. Manex is one of the few maneb type products still labeled for use on peppers and contains zinc, which has been shown to suppress copper resistant strains of the bacteria.

Low-pressure electrostatic sprayers or booms with drop nozzles will provide the best spray coverage and protection for many highly contagious diseases on short row crops.

Resistant Varieties

Many new resistant bell pepper varieties are now available. I advocate a complete shift to resistant varieties as soon as possible to minimize losses from BLS and maximize profits over the long haul. See ‘Disease Resistant Pepper Varieties’ in this publication for more details.

Putting It All Together

None of the above mentioned strategies if used alone will provide 100% protection of your crop when environmental conditions favor BLS and high levels of bacteria are present. There are no magic bullets! Only by integrating key components such as hot-water seed treatment, proper sanitation, resistant varieties, weekly scouting and chemical control (if necessary), can you grow peppers profitably each year.

More on BLS in Peppers

By: T. Jude Boucher, Vegetable Crops IPM Program Coordinator, University of Connecticut Cooperative Extension System, 24 Hyde Ave., Vernon, CT 06066. Reviewed 2012.

Published in: Proceedings. 1995 New England Vegetable and Berry Conference and Trade Show. December 12-14, 1995. Sturbridge Host Hotel, Sturbridge, MA. Pp.144-147

This information was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.

The information in this document is for educational purposes only. The recommendations contained are based on the best available knowledge at the time of publication. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension System does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available. The University of Connecticut, Cooperative Extension System, College of Agriculture and Natural Resources is an equal opportunity program provider and employer.

Black Spot Fungus: Getting Rid Of Black Leaf Spot

You’re strolling through your garden enjoying the lush growth the spring rains have produced. You stop to admire one particular specimen and you notice black spots on plant leaves. Closer inspection shows black spots on leaves throughout a whole section of your garden. This can’t be! You don’t have any roses. Unfortunately, you don’t need them. Your garden has been infected with black spot fungus.

What is Black Spot Fungus?

Don’t let the name fool you. Diplocarpon rosae, or black spot fungus, isn’t just a disease of roses. It can attack any plant with fleshy leaves and stems if the conditions are right. You’ve already taken the first step in treating black leaf spot. You’ve been inspecting your garden on a regular basis and you’ve caught it early.

Black spot fungus begins to develop in the spring when temperatures reach into the sixties and the garden has been continuously wet for six to nine hours. By the time temperatures reach into the seventies, the disease is running rampant and won’t slow down until the daytime temperatures rise above 85 F. (29 C.). It starts with tiny black spots on leaves, no bigger than a pinhead. As the fungus develops, those black spots on leaves are ringed with yellow. Soon the entire leaf turns yellow and falls.

Treating Black Leaf Spot Fungus

Getting rid of black leaf spot must be a two-pronged attack. Because its spores travel on the wind and plash from leaf to leaf during watering, treating black leaf spot should be first on your agenda.

There are several good fungicides on the market, several of which claim to be organic. They come in handy bottle sprayers, but if your garden is large, you might want to buy it as a concentrate to mix in your tank sprayer.

Neem oil is another alternative for treating black leaf spot. It’s an oil pressed from an evergreen tree. It’s all natural and has shown some remarkable results as an effective garden fungicide.

For those of you who prefer Grandma’s solutions to garden problems, try this: Mix one heaping tablespoon of bicarbonate of soda (baking soda) into a gallon of water for your sprayer. Add a dash of horticultural oil or horticultural soap and Voila! You have a method of treating black leaf spot that works by changing the pH on the leaf surface to one the fungus can’t survive. The oil or soap makes the solution stick and the cost is around four cents a gallon.

The next step in getting rid of black leaf spot is prevention and maintenance. The first, we already talked about. Inspect your garden regularly in the spring. Black spots on plant tissues will spread quickly. Start preventative spraying before the temperatures hit sixty. Read the label directions for the method you choose and follow it closely. For Grandma’s recipe, a light weekly dose should be sufficient. Continue spraying until temperatures are hot enough to get rid of black spot fungus without.

Avoid watering your plants on cloudy days. Bright sun and good air circulation are essential for getting rid of black leaf spot.

During an outbreak, all affected debris should be disposed of. It may not be ideal as far as looks go, but affected plants should be cut back, and in the fall every bit of garden debris should be thrown away or burned. The spores can overwinter on plant material, but can’t survive in bare soil.

The good news is that black spot fungus rarely kills the host plant. Getting rid of black leaf spot takes a lot of diligence, but in the end, the rewards are worth it.

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