The ergot fungus is a plant pathogen, but not a human pathogen. Sometimes people mention allergens, but they do not infect humans or plants ; they simply cause an allergic reaction for humans, not an infection.
One possible caveat to all this: how about our growing awareness of immune-compromised people, something the public became more aware of due to diseases such as AIDS or with the use of drugs to deliberately suppress the immune system when transplants are needed? There may be some case to be made that certain mold fungi that cause plant diseases can cause human infections of severely immune-compromised humans, but this is still at the edge of our scientific understanding thus far.
Rest assured, though, you will never get Dutch elm disease and elm trees will never catch the common cold! Their host ranges are simply not that broad. The fungus that causes this disease of humans is Sporothrix schenckii. So, is this not a case of both a human and a plant disease? No, Sporothrix schenckii is not a plant pathogen, it does not infect rose prickles or any other plant tissue, it is simply an occasional fellow traveler if splashed from soil onto prickles.
So at least for plants, this fungus does not join with plant pathogens that cause plant diseases, such as rose black spot, bacterial crown gall, or rose rosette virus disease. Never the twain shall meet on us humans. These kinds of distinctions can aid in our critical thinking as we learn more about infectious disease, certainly our topic du jour , and for many future days, weeks, months and years.
Pathogens and disease are ever with us: it is just one way that organisms naturally interact. Natural, but often to our despair and always a topic of our desire to manage. Especially if the person pricked by that rose has a compromised immune system. So, if you develop sporotrichosis from Sporothrix schenckii , and have symptoms of discolored lesions where prickles penetrated the skin, check with your physician. I do not have any of my own and try not to use too many images that are not mine; and 2.
They are rather gruesome. These two viruses can jump beyond their natural hosts and infect non-equid species with fatal consequences. The results of the study demonstrate a high prevalence of EHV-9 antibodies in healthy African rhinoceroses, suggesting that they are susceptible to EHV-9 infection and may serve as a natural and possibly definitive host or reservoir. Zebras, in contrast, had a lower prevalence of EHV-9 antibodies while having a much higher EHV-1 prevalence, consistent with other equid species such as domestic horses.
Interestingly, a higher prevalence of EHV-1 was observed in free-ranging zebras than in zoo kept zebras, suggesting captivity may reduce exposure to virus infection for EHV. The assay was applied to hundreds of samples collected from captive and wild animals representing 30 species in 12 families and five orders. The scientists proposed that EHV-1 and EHV-9 have evolved a broad host range among African mammals including distantly related perissodactyls.
Thus, EHV-1 and EHV-9 have a broad host range favoring African herbivores and may have acquired novel natural hosts in ecosystems where wild equids are common and are in close contact with animals such as zebras and rhinos. Several cases of fatal cross species transmission of EHVs have been documented recently, with the assumption that zebras or other equids were the source of infection.
Further study is needed to determine the role of these animals in EHV epidemiology in both captivity and the wild. Materials provided by Forschungsverbund Berlin e. Note: Content may be edited for style and length. TSWV in the Greenhouse. In recent years, tomato spotted wilt virus has caused symptoms and crop losses on a wide variety of greenhouse vegetable and ornamental plants across the United States and Canada. Tomato and gloxinia crops in particular have been devastated.
This upsurge in virus occurrence is attributed to the increased distribution of the western flower thrips which is commonly found in greenhouses in New York, other states, and Canadian provinces. Nearly every greenhouse ornamental is subject to TSWV; the only major crops that have not shown symptoms in the past two years are geranium, poinsettia, and rose.
Vegetatively propagated ornamentals are the most likely source for a TSWV infestation since the virus is not seedborne. Virus spread is rapid in a greenhouse with a western flower thrips population; some plants will develop symptoms within 5 days of feeding by infected thrips.
The western flower thrips, sometimes highly resistant to many currently registered pesticides, has typically been slow to be detected and identified when introduced to a greenhouse and difficult to control once its presence is known. TSWV has occurred in greenhouse crops previously but its impact is much greater now that a more widespread. TSWV in the Field. The natural occurrence of TSWV in the field is well documented and is a serious problem in many southern states. Infections on greenhouse bedding plants now present an additional threat to neighboring vegetable growers, to vegetable growers who acquire transplants from greenhouses, and to vegetable producers who grow a crop such as "hothouse" tomatoes to maturity.
Additionally, TSWV-infected tomato seedlings have been transplanted to the field, resulting in heavy losses in that crop and subsequently spreading to adjoining pepper and potato fields The common denominator in each case has been the innocent intermixing of virus-infected ornamentals with vegetable seedlings. The common practice of intermixing species to maximize available greenhouse space such as including hanging baskets above bench and floor plantings of vegetables adds to the potential for virus spread.
Growers should realize that growing plants from seeds in the same greenhouse with plants from cuttings poses a serious and unnecessary risk to seed crops. Wherever possible, vegetatively propagated crops should be grown in greenhouse units separate from seed crops of vegetables or ornamentals.
Growers in northeastern and north central regions of the country received infected seedlings from Georgia and were forced to reject the shipments, rogue fields already planted, or plow under many acres to destroy this additional inoculum source. Symptom Expression and Recognition. Symptoms for tomato spotted wilt virus infection are fairly unique to each of its many hosts.
Cultivars will also vary in their symptom expression. Common manifestations of TSWV are ringspots yellow or brown rings or other line patterns, black streaks on petioles or stems, necrotic leaf spots, or tip dieback.
Multiple strains of TSWV account for some of the differences in symptom type, severity. Plants are also more susceptible at certain times in their life cycles; gloxinia, cineraria, and calceolaria will be most profoundly affected when infected weeks after seeding Temperature may also exert a strong influence on symptom expression; affected cyclamen, gloxinia, cineraria, calceolaria, and New Guinea impatiens show the strongest symptoms during winter months.
In contrast, symptoms appear during the summer on marigold, calendula, salvia, and dahlia. Symptoms on Ornamentals. Browning of the new growth may be confused with the common crown rot caused by Phytophthora parasitica fig.
Plants infected at an older stage of growth may show yellow or brown leaf spotting, or brown oak-leaf patterns in the leaves, often accompanied by distortion of the normal outline fig. There is a wide variation among cultivars in response to the virus and in attractiveness to the thrips. The cultivar 'Polaris' is highly susceptible.
Black stem streaks, leaf scorch, and wilt are typical of TSWV-infected mums fig. Cyclamen infected with TSWV may have fairly subtle symptoms that are hard to identify. One common characteristic is the appearance of "thumbprints" on the leaves; e. Round brown necrotic spots may show on some leaves A brown necrosis of the petiole that bleeds into the leaf blade is typical on older leaves.
Impatiens sultan , the bedding plant impatiens, is stunted and shows black spots on the leaves, often surrounded by chlorotic zones. Sections of the stems may also be blackened fig. Double-flowered impatiens show dramatic leaf spotting. New Guinea impatiens. Again, cultivars respond differently; many are symptomless while others develop a black stem dieback and collapse entirely. Stunting, black discoloration at the base of the leaf, brown leaf spots, or distortion of leaves may occur fig.
Rieger begonias. Symptoms vary from brown vein necrosis to yellow mottle patterns on the leaf blade fig. Begonia semperflorens. Brown dead areas at the base of the leaf, extending into the petiole, are common. Symptoms of the disease on cineraria are black streaks on petioles fig. Symptoms on Vegetables.
Symptoms expressed on leaves, petioles, stems, and fruit will vary, depending on the stage plants are infected. Young leaves may show small, dark-brown spots and eventually die fig.
Dark brown streaks also appear on stems and leaf petioles. Growing tips are usually severely affected with systemic necrosis and greatly stunted growth fig. The plant may exhibit one-sided growth.
Tomato fruit set on severely infected plants will display very characteristic symptoms: immature fruit have mottled, light green rings with raised centers; the unique orange and red discoloration patterns on mature fruits make them unmarketable fig.
The virus may cause sudden yellowing and browning of young leaves which later become necrotic. Long necrotic streaks appear on stems extending to the growing tips.
Fruit formed after infection display large necrotic streaks and spots while younger fruit may be completely necrotic fig. Broad dark spots and necrotic ringspots, often with chlorotic halos, occur on both the lower and upper leaves of affected plants fig.
Verification of Diagnosis. Virus identification requires special laboratory techniques. Other procedures include mechanical inoculation to a series of diagnostic hosts and electron microscopy. Many cases have been noted where serological tests are negative, despite definite symptoms of TSWV on the sampled plant tissue. Verification of the virus' presence in symptomatic impatiens was particularly difficult until a new, more sensitive antiserum was recently developed at North Carolina State University.
Still, false negatives are possible. Until more reliable tests are developed, growers should consider that positive lab tests are indeed confirmation of the disease, but that negative lab tests may only reflect an inability to detect all strains of the TSWV under all circumstances. If symptoms suggestive of TSWV appear in the greenhouse at the same time that western flower thrips populations are heavy, it is quite possible that the virus is present despite negative lab test results.
Control measures should not be delayed while waiting for lab confirmation. Since there is no direct way to attack the virus other than roguing visibly infected plants, it is necessary to aim control efforts at its thrips vectors.
The primary greenhouse vector is the western flower thrips Resistance to specific organophosphates, carbamates, and synthetic pyrethroid insecticides is known in certain populations. Early detection of a thrips infestation is critical because the symptoms of their feeding are often not noticed until after the damage has occurred, and because small infestations are easier to control.
Yellow sticky cards provide an easy way to detect the onset of an infestation fig. Blue sticky cards catch more thrips, but since other insect pests e. Flowers can be checked for thrips by tapping a blossom over a sheet of paper, but it is more efficient to use sticky cards for detection and monitoring. Yellow or white flowers seem particularly attractive to thrips. Although effective thrips management can be difficult, adequate control can be achieved by a combination of physical, cultural, and chemical control measures.
Prevention is the obvious first step; it is easier to prevent an infestation than to manage an established one.
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