File Name: cabbage pests and diseases .zip
Black rot Xanthomonas campestris pathovar campestris symptoms are yellow, V-shaped lesions that appear along the tips of the leaves with the point of the V directed toward a vein.
- Identify, Prevent, and Treat Common Cabbage Diseases
- Cabbage and Cauliflower Insect pests
- Cabbage Pests
- Cabbage, Broccoli & Other Cole Crop Insect Pests
It is distributed worldwide infesting cruciferous plants of Brassica spp. Brachymeria spp. Eriborus spp.
Cabbage comprising several cultivars of Brassica oleracea is a leafy green, red purple , or white pale green biennial plant grown as an annual vegetable crop for its dense-leaved heads. It is descended from the wild cabbage B. Smooth-leafed, firm-headed green cabbages are the most common, with smooth-leafed purple cabbages and crinkle-leafed savoy cabbages of both colours being rarer. Under conditions of long sunny days, such as those found at high northern latitudes in summer, cabbages can grow quite large.
Identify, Prevent, and Treat Common Cabbage Diseases
Cabbages can fall victim to an array of diseases from all of the major classes of pathogens — fungi, water molds, bacteria, and viruses. The infections can range in severity from the unsightly but not usually fatal, such as powdery mildew , to the almost uniformly fatal bacterial soft rot.
Some of these pathogens live in the soil where they can readily attack the roots of your crop, and many others lurk in the cruciferous weeds growing nearby. Read on to learn about the many diseases that can affect your cabbage crop, and steps you can take to prevent or control them.
Alternaria leaf spot is caused by two species of fungi, Alternaria brassicicola and A. Both species are well known for causing leaf spots to develop on older tissue, but these fungi can also infect the base of the developing heads.
As the tissue dies, the centers may fall out, resulting in holes in the foliage. As the disease develops, the spots join together to form large areas of dead tissue. Controls for Alternaria leaf spot start with good cultural practices. These include the use of drip irrigation, sanitizing your gardening tools, rotating your crops, and removing all dead plant material at the end of the growing season.
Biopesticides that may prove effective in the case of an outbreak include Bacillus amyloliquefaciens and Bacillus subtilis. There are two different species of bacteria that can cause bacterial leaf spot in cabbage, Pseudomonas syringae pv. It causes spots to form on the leaves that start out small, becoming dark brown or purple as they increase in size. These spots can join together to form angular lesions, which make the leaves look ragged.
In the case of a severe infection, the foliage can die. Unfortunately, this form of bacterial leaf spot is readily spread by splashing water, including irrigation water, and by insects.
This disease is most prevalent during periods of cool, wet weather. In contrast, X. Initial symptoms include dark flecks on the leaves that spread into lesions. The centers often degrade with time, resulting in circular holes in the foliage. Prevention and control efforts range from planting heat-treated seed to irrigation practices that minimize the amount of moisture that comes in contact with the foliage.
Crop rotation is also critical in subsequent seasons, as the bacteria can overwinter in the soil. Bacterial soft rot is caused by the the bacteria Pectobacterium spp. The first signs of infection are small lesions that appear water soaked. They quickly enlarge, and infected plant tissue turns brown and mushy. The bacteria that cause soft rot infect plants most readily in warm, humid conditions. Plants are easily infected, because the bacteria live in the soil.
Even if temperatures are cool and less conducive to infection, the bacteria can still infect through wounds in plant tissue, including those caused by insect damage. The bacteria is spread by splashing water, gardening tools, and insects like cabbage maggots.
In addition, plants that are already diseased with blackleg or black rot can contract soft rot as a secondary infection. There are a number of steps you can take to minimize the chances of your cabbages being infected, ranging from avoiding harvesting crops in wet conditions to removing any soil with a dry cloth before you store the heads. Read more about bacterial soft rot here. Blackleg is caused by a fungus, Phoma lingam , and it destroys the roots of many types of crops.
Young seedlings may develop pale, irregular spots on their leaves or stems, which can become circular or oval with gray centers. As the symptoms spread, spots can develop on the underside of the leaves. In the case of a severe infection, the immature cabbages will be stunted and plants will often wilt, although the leaves remain attached.
Initial symptoms of blackleg — such as light brown, sunken cankers — can be seen at the base of the stems. If infected cabbages are harvested and put in storage, dark brown or black spots can develop on the leaves. Infected seeds can be a source of this fungus, and it can survive in crop debris.
Cruciferous weeds can also serve as hosts. If the levels of seed infection are low but the weather is favorable for disease, severe losses can still occur. The pathogen can spread by splashing water from rain or irrigation, and it can also be transmitted on gardening tools. In addition, spores on infected plants can be blown for miles in the wind. And to make things worse, secondary infections frequently follow cases of blackleg. These can include white mold and bacterial soft rot.
Remove any cruciferous weeds, like wild radish, yellow cress, or wild mustard. Start with seed from a reputable source that has been shown to be free of the pathogen. Space plants widely in the garden, so adequate airflow is readily available, and they will quickly dry after rain or dew. Remove infected crop debris from the garden as soon as possible. Dispose of it in the garbage, rather than on your compost pile. Rotate crops for three to four years, and avoid planting other brassicas near where you plan to grow your cabbage.
Black rot, caused by the bacterium Xanthomonas campestris pv. The first symptoms involve yellowing of the leaf margins, which then spread to the center of the leaf. Next, the vascular system turns black, and the infection then spreads throughout the whole plant.
These bacteria are easily spread in the field by insects, animals, irrigation, rain, and gardening equipment. Black rot can infect plants naturally through stomata at the leaf margins, or through mechanical injuries. Planting high-quality seed that does not contain X. You also have the option of planting varieties of cabbage that are resistant.
You can learn more about how to manage black rot in cabbage in this guide coming soon! A widespread soil-borne fungus, Rhizoctonia solani , is particularly destructive to cabbages. Plants can contract an infection from contaminated soil. The initial symptoms are tan or brown lesions on the outer leaves. Then the fungus invades the center of the head, which can rot completely within 10 days. Planting in raised beds will help to protect your crop, because the soil will typically drain better than it would if you were to plant directly in the ground.
Wherever you plant, well-draining soil is crucial. Keeping your crop healthy and providing the proper amount of fertilizer will also help to keep this disease at bay. See our guide to growing cabbage for more planting tips. Cabbages are particularly vulnerable to clubroot, a disease caused by Plasmodiophora brassicae , a water mold that can live in the soil for over 18 years after infecting a crop. This pernicious and long-lived disease can be hard to detect.
Older plants that are infected will wilt on hot days, but they can often appear to recover after the sun goes down. The pathogen enters the root hairs and then forms large club-like galls that can be as large as five or six inches wide. Infected seedlings take about three weeks to show signs of root swellings, and they will typically die. If they survive, yields can be greatly reduced because growth is stunted.
Infections occur when the plants are exposed to spores released from infected roots. Irrigation water, tools, or even footwear can spread these spores. Crucifers are more likely to become infected when they are growing in acidic soils with a pH of 6. Once a crop becomes infected, there are no effective control methods available. Since the most common source of infection is infected transplants, you should take care to use clean trays and seed starting media.
Do a soil test to check the pH of your soil, and amend the soil with lime as needed, to raise the pH to at least 7. Lime inhibits the development of this disease, but it will not prevent clubroot entirely if there are already a large number of spores present in the soil. Practice a long crop rotation if you have found an infection in your vegetable beds — wait to plant cabbage in the same location again for six years or more. Peronospora parasitica is a water mold oomycete , an organism previously classified as a fungus.
This serious disease starts out as lesions on the upper surfaces of the leaves, while the bottom surfaces have white to gray masses of fungal spores visible on them. If your seedlings are infected, the whole vascular system can turn black. You may not be able to eat your cabbages if they contract downy mildew. Fog, heavy dew, high humidity, and drizzling rains all favor the development and spread of downy mildew. Downy mildew is a particular problem in fall crops in areas with wet and mild winters, like Washington State.
The pathogen can continue infecting crops throughout the winter, and this can set the stage for severe infections in the spring if the conditions are right. To make matters worse, white rust can colonize host plants that have been weakened by downy mildew.
There are steps you can take to prevent downy mildew, such as eliminating cruciferous weeds, and giving plants plenty of space to grow rather than packing them too tightly together. Proper airflow will reduce humidity and make infections less likely to occur.
Read more about downy mildew here. While a number of different viruses can infect cabbage, you are most likely to encounter mosaic virus.
Unfortunately, there is no cure for the virulent pathogens that cause it, so taking steps to prevent the occurrence of this disease is your best bet. Controlling all cruciferous weeds will help to reduce the likelihood of your cabbage plants becoming infected. The most common viruses of this type to attack cabbage plants are cauliflower mosaic virus CaMV and turnip mosaic virus TuMV.
Infections can be difficult to observe early in the season. However, later on, the veins will appear clear. The first sign of this is often located at the base of a leaf.
Cabbage and Cauliflower Insect pests
Although there are many insect pests and diseases of brassicas aka crucifers , most can be prevented from damaging the crops by adhering to a few basic guidelines. In general, a preventative management approach involves a combination of the following practices:. Other methods can also be employed, but the above four are fundamental to management of the most common problems listed below. Crop rotation. Seedlings of direct-seeded crops are more vulnerable to damage — get a head start against flea beetles and other pests by using transplants. Weed control.
Cutworms, imported cabbageworm, cabbage looper, diamondback moth larvae, and cross-striped cabbage worm can be each cause substantial damage to cabbage. These pests can cause serious damage to young transplants as well as causing serious leaf feeding damage to older plants. Damage to the head or wrapper leaves often reduces marketability. Because many of these pests are much more difficult to control as large larvae, controls will always be most effective when directed toward small larvae. So early detection of economic infestations is critical to the management of these pests.
The Latin name is Pieris rapae , or Artogeia rapae. Do not be overly concerned if you see a hole in a leaf; plants can withstand much leaf loss without consequence. Cabbage worms are velvety green larvae.
Cabbage, Broccoli & Other Cole Crop Insect Pests
Cabbage red, white, Savoy. Content Content 1. Diseases - Fungal. Pests - Insects.
Two primary species of aphids plant lice attack cole crops: the cabbage aphid Brevicoryne brassicae and the turnip aphid Lipaphis erysimi. Because they are similar in life habits and response to treatments, they will be considered together. Plants in all stages of growth are frequently covered with dense clusters of whitish-green plant lice. Each is about the size of a pinhead. They suck plant sap from the leaf. The affected leaves curl and crinkle or form cups, completely lined with the aphids. In severe infestations, the plants wilt and die.
Alternaria leaf spot (Black spot, Gray spot) Alternaria brassicae. Anthracnose Colletotrichum higginsianum. Black rot Xanthomonas campestris. Clubroot Plasmodiophora brassicae. Damping-off (Wirestem, Head rot) Rhizoctonia solani. Powdery mildew Erysiphe cruciferarum. Sclerotinia stem rot (White mold) Sclerotinia.
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