ALLIUMS (Onions, Garlic,and Leeks)

SCLEROTIM CEPIVORUM-also known as ALLIUM ROOT ROT 

Plant pathogen-Sclerotium Cepivorum FUNGUS

Host- alliums, Onions, garlic, leeks; Occurs all around the world where alliums are grown.  

Ideal growing conditions- The fungus thrives in cool weather and is found in the soil as small round structures called Sclerotia, These can live in the soil for decades and affect any allium planted there. 

Symptoms: One of the first things you will notice in the Allium is the foliage lacking luster.  The leaves will appear stunted and starting to yellow; eventually the older leaves will die.  In cool weather mycelium  growth will appear around the base plate and eventually covering the entire bulb, it looks white and fluffy.  The fungus can create very small hardened fungal bodies, sclerotium bodies, these will appear in the fluffy white growth.  Mycelium can grow outwards from the roots of one plant to the roots of a neighboring plant, and it is by this method that the pathogen can move down a planted row.  

Prevention: The most effective controls for white rot are avoidance and sanitation. Once a field is infected, chemical treatments are necessary to produce onion or garlic crops.  If S. Cepivorum is found in soil do not plant Alliums there for over ten years. Possible sifting methods to remove mycelium but seems extremely labor intensive.  On garlic, the disease is commonly introduced into the field on seed cloves. The best way to prevent disease from gettin onto your land is to only buy seeds from a trusted seed seller.  However, the fungus is vulnerable at temperatures above 115°F, thus dipping seed garlic in hot water will greatly reduce the amount of pathogen and is a good preventative measure, although it may not completely eradicate the fungus. Also, temperatures above 120°F may kill the garlic, so careful temperature control is essential.  

BOTRYTIS LEAF BLIGHT

Host- alliums, Onions, garlic, leeks at early bullbing stages

Pathogen- fungi Botrytis squamosa

Symptoms: First occur on oldest leaves, atiny oval white or yellow spot, Blight, Slighty sunken into the leaf and surrounded by a silver halo.  If you slice the leaf open you can find the lesion goes all the way though the leaf.  Botrytis can easily be confused with Leaf fleck, ozone injury and leaftip dieback. 

Environment-   favorable environmental conditions, high rainfall, extended periods of leaf wetness, high relative humidity, and moderately warm temperatures 50 F-75 F, can result in reduced onion bulb growth and yield.  The Squamosa fungi, compacted as sclerotic bodies,  can live in debris piles and lay dorment for a long period of time, idea conditions for spore production include wet with low winds.  Debris piles should be properly disposed of to prevent spreading. 

Prevention: proper two year crop rotation practices, and healthy seeds. To reduce the incidence and severity of botrytis leaf blight, cull piles should be destroyed, seed fields should be planned well apart from commercial onion production fields, and volunteer onions should be rogued. At harvest, severed onion tops should be removed from the field and destroyed. Fungicides are used instantly in commercial farms. 

Soft Rot:

Caused by the bacteria: Erwinia carotovora.

Symptoms:  At first the bacteria accesses the allium tissues through the bulb neck as the plant becomes mature, it becomes water logged; later becoming a decomposing slimy mess. It infects and rots certain scales or layers of the allium bulb flesh and emits a foul odor, remember> stink=bacteria.   

Environment: Alliums stored in a warm environment can become affect by E. carotovara.  Plants that have been damaged or bruised can also be affected.  These affected plants can easily spread infection by contact with other alliums.  

Management: Cultural controls. 

STRAWBERRIES

ANTHRACNOSE OF STRAWBERRY:

Symptoms:  The fungus can attack fruit, runners, petioles, and the crown of the plant. Dark elongated lesions develop on   petioles and runner stems. Affected petioles and stems are sometimes girdled by le­sions causing individual leaves or entire daughter plants to wilt and die. Under warm, humid conditions, salmon-colored masses of spores may form on the lesion surface. If the crown tissue is infected, crown rot may develop and the entire plant may wilt and die. When infected crowns are sectioned, internal tissue is firm and reddish-brown to dark-brown in color (Figure 1). Crown tissue may be uniformly discolored or streaked with brown.  Whitish, tan, or light-brown water-soaked lesions up to 3 mm in diameter initially develop on fruit. The lesions eventually turn brown or dark-brown, are sunken, and enlarge within two to three days to cover most of the fruit (Figure 2). Lesions are covered with pale-orange or salmon-colored spore masses. Under moist conditions, the fungus may grow out around the edge of the lesion or through the lesion, giving a fuzzy appearance. Infected fruit eventually dry down to form hard, black, shriveled mummies. Fruit can be infected at any stage of development.

The disease is probably introduced into new plant­ings on infected plants. Recent research indicates that the fungus can grow and produce spores on the surface of apparently healthy leaves.  Once the disease is established in the field, the fungus can overwinter on infected plants and plant debris, such as old dead leaves and mummified fruit. Spore production, spore germination, and infection of strawberry fruits are favored by warm, humid weather and rainfall. In spring and early summer, spores are produced in abundance on previously infected plant debris. The spores are spread by splashing rain, wind-driven rain, and by people or equip­ment moving through the field. They are not airborne so they do not spread over long distances in the wind. Spores require free water on the plant surface in order to germinate and infect.

The optimum temperature for infection on both im­mature and mature fruit is between 77 and 86 degrees F. Under favorable conditions, the fungus produces second­ary spores on infected fruit. These spores are spread by rain and result in new infections throughout the growing season. Disease development can occur very rapidly. Up to 90 percent of the fruit can be infected within a week or less. Both immature and mature fruit are susceptible to infection; however, the disease is most common on ripening or mature fruit.

Control:  Use disease-free planting material as the disease is introduced to the field with infected plant material.  Although there are no nurseries that can certify plants to be free of fungal and bacterial plant pathogens, inspection of plants for the disease before planting is recommended.  If the field was previously infected, or the disease is present in the field, minimize the amount of overhead irrigation used. The fungus is spread by splashing water. Avoid the use of overhead irrigation and use drip irrigation if possible. Plastic mulch increases the level of splash dispersal of the pathogen. Mulching with straw is recommended in perennial matted row plantings to reduce water splash and disease spread.

Treatment:  Remove infected plant parts. Infected plant parts serve as a source of inoculum for the disease. Remove as much old, infected plant debris as possible. Try to remove infected berries from the planting during harvest.  Fungicide use. Once anthracnose fruit rot is established in a planting, it is difficult to control with fungicides. Fungicides for control of anthracnose fruit rot should be used in a protectant or preventative program. In order to obtain effective disease control, fungicides should be applied before the disease develops.

BOTRYTIS CROWN ROT OF STRAWBEERRIES:

 

Symptoms:  Usually begin in the upper part of the crown and spread downward. The youngest leaves wilt suddenly and often turn a bluish green. Wilting spreads quickly throughout the plant, and complete collapse occurs within days.   Collapse may be one sided, depending on the number of crowns infected. Infected plants will often break at the upper part of the crown when lifted from the soil. When cut lengthwise, the crown appears brown or sometimes rose pink throughout. Crown tissue will disintegrate with time.  Rot symptoms are most common between flowering and harvest when the plants are under stress. Warm, wet conditions and poorly drained soils favor infection. Symptom development is favored by high temperatures and low moisture conditions, factors that apparently stress the plant before harvest

Control:  Always plant healthy certified plant stock. Make sure growing site is well drained. If strawberry crown rot has set in remove infected plants. Apply a good layer of straw or other protective material to keep fruit off soil surface. Plant new crop far from the previous growing site. Provide adequate soil drainage (plant strawberries in raised beds)reducing the risk of plants developing strawberry crown rot.

PHYTOPHTHORA CROWN ROT:

 

Symptoms:  Initially, symptoms typically include plant stunting and small leaves. As the season progresses, plant collapse may occur rapidly or slowly. When infected plants are cut open, a brown discoloration can be seen in the crown vascular tissue or throughout the crown tissue. The same Phytophthora species also attack roots, causing a brown to black root rot.

Control:  Soil fumigation and good cultural practices provide adequate control of Phytophthora in production fields. Good cultural practices include the use of certified transplants, avoiding poorly drained soils, and preparing fields to provide good soil drainage during wet weather. Phytophthora can be moved in water that has drained from infested fields, so avoid using runoff water for irrigation or for wetting down field roads for dust control. In fields that are prone to Phytophthora problems, you may want to plant less susceptible cultivars. Even with tolerant cultivars, however, it is important to follow good cultural practices. As cultural controls, use raised beds and carefully managed drip irrigation; plant in noninfested soils that have good drainage. Also, use clean plant stock and consult your farm advisor about cultivar susceptibility. Soil solarization can also provide control.

WATERMELON

Anthracnose- Common disease caused by Colletotrichum lagenarium. Causes black brown spots on leafs and fruits. In wet weather  orange pink spores take over the center of larger leaf spots. If dry, the spots turn gray. Avoid soaking the seed and a minimum 5 year rotation is recommended.

Fusarium Wilt- Fusarium Wilt is soil born. It will wilt and die within several days. If you dig the soil around the plant you'll find the crown of the root rotted. The spores are white to pink.  Get rid of damaged plants and fruits immediately and have at least a 4 year rotation.

Gummy Stem Blight- Gummy Stem Blight is caused by seed born fungus Didymella bryoniae. Symptoms can be found on all parts of the plant except the roots. In the leaf lesions will appear that vary from dark yellow or reddish brown. If exposed to extended periods of rain the plants may collapse. Only the usual prevention strategies will work. 3-4 year crop rotation, clean equipment, etc.

---