BASIL

Fusarium Wilt

Pathogen - Fusarium oxysporum, a soil-borne fungus that can last in the soil for 8-12 years.

Host - Only sweet basils; specialty basils seem resistant.

Environment – Soils with high moisture and poor drainage have higher rates of presence.

Signs & Symptoms - Typical plant growth until 6-12 inches, then stunted growth, followed by wilting, brown streaks on stem, discoloration of internal stem tissue, crooked stems, and sudden leaf drop.

Controls - Buy disease-tested seed or resistant varieties. If soil is contaminated, avoid planting any members of the mint family in that plot for 8-12 years - mints will not display symptoms of disease, but will carry over the inoculum. Also spread through contaminated plant material, so careful handling and destruction (by burning) of the plants is necessary.

Basil Downy Mildew

A relatively new disease affecting the leaves of basil, making it unmarketable.

Pathogen - Peronospora belbahrii, a fungal-like pathogen spread from infected seed or wind-dispersed spores with high travel capabilities.

Host – Basil and other Lamiaceae family plants, including crops and ornamentals

Environment – Carried in by wind.

Signs & Symptoms – Slight yellowing of leaves, similar to nutrient deficiency or water stress, dark-grey fuzziness on underside of leaves.

Controls – Use disease-free certified seed or disease-resistant varieties. Several OMRI certified fungicides exist, but are most beneficial when applied before the disease shows up and will need to be applied to the underside of leaves, which can be difficult. Affected plants should be removed from the area to reduce the chance of spreading. Till in diseased plants or lay out on a sunny day for the pathogen to be killed by UV radiation.

Bacterial Leaf Spot

Pathogen - Pseudomonas cichorii, a bacteria spread by water splash or handling or by contaminated seed.

Host – wide host range

Environment – Thrives in hot, wet/humid conditions.

Signs & Symptoms – Blackening of leaves.

Controls – Use certified disease-free seed. Plant crop at a wider spacing to increase air circulation. Avoid the use of overhead watering systems. Remove diseased leaves to reduce spread.

BRASSICAS

There are many diseases that are common and  "bother" our brassicas as detailed below:

CLUB ROOT

Pathogen - Plasmodiophora brassicae, a soilborne slime mold-like parasite  

Host – most members of the brassica family

Environment – Cool, wet, acidic soils

Signs & Symptoms – Roots will be partially or totally swollen. If severe, water and nutrient uptake will be hindered and the plant will show symptoms similar to water and nutrient deficiency – wilting and yellowing of the leaves. Plants may also become stunted, show reduced head development, or die.

Controls – Awareness of disease presence in the past is important when developing a crop rotation. The parasite can survive in soil for up to 10 years. Ensure soils are well drained and at a proper pH. Select resistant varieties, when available. Remove infected crops from the field and burn them – do not bury or feed to livestock, as the organism will persist and be spread.

BLACK ROT

Pathogen – Xanthomonas campestris, a seedborne bacteria

Host – most members of the brassica family, particularly cabbage and cauliflower

Environment – wet and warm (80-86 degrees Fahrenheit) conditions

Signs & Symptoms – Initially, the plants will display V-shaped lesions at margins of leaves. Leaf veins will become blackened. Leaves will die off and drop. If the disease reaches the stems and affects the vascular system of the plant, the plant will wilt.

Controls -  A proper crop rotation of three years between brassicas and planting in areas of good soil drainage and aeration are important for prevention. Avoid overhead irrigation. If plants are infected, remove from the field. Use of copper may help prevent spread to healthy plants.

DOWNY MILDEW

Pathogen – Peronospora parasitica, a fungal-like organism

Host – many brassicas, including cabbages, cauliflowers, Brussels sprouts, radishes, swedes and turnips

Environment – favors cool, wet conditions

Signs & Symptoms – The disease starts with angular, yellow spots on upper leaf surface. Eventually, these spots will turn brown. Cotton-like spots will form on the underside of the leaves. Seedlings may also be affected and will be totally covered in the mildew.

Controls -  A proper crop rotation is a starting point. Grow resistant varieties or disease-free certified seeds. Ensure proper air circulation among plants. Remove infected leaves and burn. Copper may reduce spread of disease.

ALTERNARIA LEAF SPOT

Pathogen – Alternaria brassicae & A. brassicicola, seedborne pathogens easily spread by wind

Host – most brassicas

Environment – warm (77-86 degrees Fahrenheit), wet weather

Signs & Symptoms – Leaf spots start as pinpoint yellow areas, expanding to up to 5cm in diameter. As these spots enlarge, the centers display dark concentric rings. Browning of the heads in broccoli and cauliflower may also be seen.

Controls – A proper crop rotation is a good start. Use disease-free seed. Avoid overhead irrigation.

References:

http://nu-distance.unl.edu/homer/disease/hort/crucifer/CrClbRoot.html

http://www.cals.ncsu.edu/plantpath/people/faculty/cubeta/Publications_%20Links/Keinath2006.pdf

http://en.wikipedia.org/wiki/Clubroot (for image)

http://www.cals.ncsu.edu/plantpath/extension/commodities/colecrops-crucifers.html

http://www.ipm.iastate.edu/ipm/hortnews/1999/8-13-1999/blackrotcab.html

http://vegetablemdonline.ppath.cornell.edu/PhotoPages/Crucifers/BlkRot_Cruc/BR_CrucFS5.htm (image)

http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=105

http://extension.umass.edu/vegetable/diseases/broccoli-downy-mildew (image)

http://www.avrdc.org/LC/cabbage/alternaria.html

http://plant-clinic.bpp.oregonstate.edu/content/10-1160 (image)

RADISHES

We noticed Scab on the radishes at the college farm a couple of weeks ago.  Areas highlighted reference symptoms and controls in particular to radishes:

Potato scab is a common tuber disease that occurs throughout the potato growing regions of the world. Although scab does not usually affect total yields, significant economic losses result from reduced marketability of the tubers. Economic losses are greatest when tubers intended for table stock are infected, since appearance is important for this market. While superficial scab lesions do not greatly affect the marketability of processing potatoes, deep-pitted lesions, however, do increase peeling losses and detract from the appearance of the processed product. The occurrence of scab and its severity varies by season and from field to field. Cropping history, soil moisture, and soil texture are largely responsible for this variability. Potato scab lesions can be confused with powdery scab, a disease caused by an entirely different pathogen, the fungus Spongospora subterranea (see Cornell Cooperative Extension Information Bulletin 205: Detection of Potato Tuber Diseases and Defects).

Symptoms and Signs

Potato scab lesions are quite variable and distinctions have been made between russet (superficial corky tissue), erumpent (a raised corky area), and pitted (a shallow-to-deep hole) scab  All of these can be caused by the same pathogen, Streptomyces scabies; however, the type of lesion probably is determined by host resistance, aggressiveness of the pathogen strain, time of infection, and environmental conditions.

Individual scab lesions are circular but may coalesce into large scabby areas. Insects may be involved in creating deep pitted lesions. The term "common scab" generally refers to the response of the disease to soil pH. Common scab is controlled or greatly suppressed at soil pH levels of 5.2 or lower. Common scab is widespread and is caused by S. scabies. "Acid scab" seems to have a more limited distribution, but has been found in several states in the Northeast. This disease occurs in soils below pH 5.2, as well as at higher levels. The causal agent, S. acidiscabies, is closely related to the common scab pathogen and can grow in soils as low as pH 4.0. Acid scab is controlled by crop rotation, but can be a problem when seed is produced in contaminated soils. Acid scab lesions are similar, if not identical, to those caused by S. scabies.

Disease Cycle

Most if not all potato soils have a resident population of S. scabies which will increase with successive potato or other host crops. Scab-susceptible potato varieties appear to increase soil populations faster than scab-resistant varieties. Rotation with grains or other nonhosts eventually reduces but does not eliminate the S. scabies population. This pathogen is a good saprophyte and probably reproduces to some extent on organic material in the soil. Given the right environmental conditions and a scab-susceptible potato variety, scab can occur in afield that has been out of potatoes for several years.

S. scabies infects young developing tubers through the lenticels and occasionally through wounds. Initial infections result in superficial reddish-brown spots on the surface of tubers. As the tubers grow, lesions expand, becoming corky and necrotic. The pathogen sporulates in the lesion, and some of these spores are shed into the soil or reinfest soil when cull potatoes are left in the field. The pathogen survives in lesions on tubers in storage, but the disease does not spread or increase in severity. Inoculum from infected seed tubers can produce disease on progeny tubers the next season.

The disease cycle of S. acidiscabies is similar to that of S. scabies, but the acid scab pathogen does not survive in soil as well as common scab. Inoculum on seed tubers, even those without visible lesions, seems to be important in disease outbreaks in New York.

Factors Influencing Disease Severity

• Varietal resistance. Though the mechanism of resistance to scab is not well understood, varieties with different levels of resistance have been identified through field screening programs. Using resistant varieties is an effective tool for management of scab. Resistant varieties are not immune, however, and will become infected given high inoculum densities and favorable environmental conditions. The limited information available indicates that there is a good correlation between resistance to common scab and to acid scab among potato varieties. Consult potato disease-control recommendations for current information on potato varieties with resistance to scab.

• Soil acidity. Severity of common scab is significantly reduced in soils with pH levels of 5.2 and below, but losses can rapidly increase with small increases in pH above 5.2. Potatoes are commonly grown in soils with a pH of 5.0 to 5.2 for control of common scab. As mentioned, S. acidiscabies ("acid scab") causes scab in low-pH soils. This species does not compete well with other soilborne microbes, however, and can usually be controlled with seed treatments and crop rotation.

While low-pH soils provide good control of common scab, there are disadvantages associated with this management strategy. Plant nutrients are most available at soil pH levels near 6.5. Since acid soils are unfavorable for most vegetable and field crops, the number of them that can be grown in rotation with potatoes is limited. Maintaining soils near pH 5.0 reduces both fertilizer efficiency and minor element availability, and may result in phytotoxic levels of some minor elements. Potatoes grown in soils near pH 6.5 produce higher yields with less fertilizer. Lack of crop rotation aggravates many pest problems, especially the Colorado potato beetle.

• Soil moisture. Soil moisture during tuberization has a dramatic effect on common scab infection. Maintaining soil at moisture levels above -0.4 bars (near field capacity) during the 2 to 6 weeks following tuber initiation will inhibit infection by S. scabies. Bacteria that flourish at high soil moisture appear to outcompete S. scabies on the tuber surface. However, maintaining high soil moisture may be difficult in some soils, and it is possible that other disease problems may be aggravated by excessive irrigation.

• Soil type and soil amendments. Light-textured soils and those with high levels of organic matter are favorable to scab infection.Streptomyces are generally involved in the decomposition of soil organic matter, and therefore thought to be stimulated by its presence. Applying manure to potato fields can cause an increase in scab infection. Coarse-textured soils are conducive to scab, probably because of their moisture-holding capacity; thus, gravelly or eroded areas of fields that tend to dry out rapidly are often sites of heavy scab infection.

• Crop rotation. Crop rotation reduces the inoculum levels in potato fields, but S. scabies can survive for many years in the absence of potato. This may be due to saprophytic activity or an ability of S. scabies to infect other plants. Infection of seedlings of many vegetables and fleshy roots of beet, cabbage, carrot, radish, spinach, turnips and other plants has been reported. Rotation with small grains, corn, or alfalfa appears to reduce disease in subsequent potato crops. Red clover, however, stimulates problems with common scab and should not be used in fields where scab has been a problem. S. acidiscabies appears to have a host range similar to that of S. scabies but does not survive well in the presence of nonhost crops.

Recommended Disease-control Strategies

1. Use resistant varieties in fields where scab is a problem

2. Use scab-free seed and seed treatments to prevent introduction of the pathogen into fields. Seed treatments do not eliminate the pathogen but will provide some suppression of disease. Consult current potato disease-control recommendations for appropriate seed treatments.

3. Rotate heavily infested fields away from potatoes and alternate hosts such as radish, beets, and carrots. Use small grains, corn, or alfalfa in rotations; avoid red clover.

4. Maintain soil pH levels between 5.0 and 5.2 by using acid-producing fertilizers such as ammonium sulphate. Avoid or limit the use of such alkaline-producing amendments as lime and manure.

5. Avoid moisture stress during the 2 to 6 weeks following tuberization.

SOLANACEOUS (Tomatoes, Peppers, Eggplant, Potatoes)

BLOSSOM END ROT:

Blossom End Rot is a physiological disorder which looks like rot on the side of the fruit opposite the stem and is associated with low concentrations of Calcium in the fruit.  Rot is induced in life stages such as fruit ripening when the demand for Calcium for the fruit walls is high enough to exceed supply.  It can also be induced by high levels of competing cations, drought stress, and excessive soil moisture fluctuations - all of which affect the uptake of Calcium ions.  Additionally, over fertilization that causes rapid growth can cause blossom end rot because the plant won't have enough time to uptake Calcium as the fruit is developing so quickly.

This rot can be managed by maintaining the soil around 6.5.  Liming to do this both supplies dissolved calcium ions and reduces the levels of competing cations.  Using nitrate as a Nitrogen source as opposed to ammonia which reduces Calcium uptake.  It is also important to avoid over-fertilization during fruiting.  To avoid drought stress and fluctuations in soil moisture, mulch and consistent irrigation should be used.

EARLY BLIGHT:

Early Blight is a fungal pathogen spread when alternaria spores land on a leaf surface.  The spores then germinate and penetrate the leaf tissue.  The fungal mycelia grow and expand to produce a characteristic brown, circular lesion on the infected tissue with dark concentric rings.  The spores can be spread by the wind, contaminated tools, and running water and their germination is encouraged on wet leaf surfaces and in temperatures between 65 and 85 degrees Fahrenheit. Tomatoes are most susceptible when their fruit is aging because this is when nutrient demands are highest and therefore nutrient concentrations in tissue where the spores can grow are highest.  The fungus generally moves up the plant to the younger leaves.

Management recommendations include a three year or greater crop rotation, removing all potentially infected crop debris and plants as soon as they're discovered, and avoid standing water on leaves and fruit (especially during fruit maturation)

SOUTHERN STEM BLIGHT:

Southern Stem Blight is a fungal pathogen which results in wilting and eventual plant death in infected plants.  Sun scald can occur as a result of the wilting or dead foliage.  Plant death is accompanied by a characteristic white ring of cottony mold at the soil line punctuated by brown spots (sclerotia) which develop in late stages of infection.  Infection patterns begin with a single plant or hot spot and move outward to infect nearby plants creating infection zones in the field.

The blight can be avoided by staying away from fields with a history of disease and immediately removing roots and stem debris when discovered.  Incorporate covers early to ensure that the debris has rotted well before transplanting tomatoes and peppers.  Good weed and grass control through cultivation, mulching, etc. will also help to avoid fungi living in debris.

PHYTOPHTHORA CROWN:

Phytophthoro crown is a soil born pathogen that primarily attacks seedlings of peppers, tomatoes, and eggplants.  When the soil is saturates, phytophthora produces zoospores which can travel through water filled pores to infect the plant tissue.  It can also produce chlamydospores and oospores which can survive up to three years in the soil.  The infection generally occurs in cool to moderate temperatures and causes brown discoloration in plant tissue.  Specifically, it initially causes stunting and small leaves but plant collapse occurs later.  When the dead plant tissue is cut open, brown discoloration in the crown vascular tissue can be seen.  The same species can also attack roots causing brown or black rot.

It can be managed by controlling water flow strictly in the field.  Raised beds reduce the amount of standing water as does preparing the beds carefully  for good drainage.  It is imperative to buy resistant cultivars if there is a history of phytophthora in the field but buying certified transplants or seed is important no matter what.  Drip irrigation should be used and monitored carefully to avoid standing water on the leaves.  Also, runoff water should not be used on or near other plants.  To avoid runoff water which might inadvertently reach your solanaceous plants, make sure to account for slope in your crop rotation.

VERTICILIUM WILT:

Verticilium is a wilt that affects tomatoes, peppers, eggplant and tomato equally and can live in the soil and in weeds as alternate hosts for years.  The symptoms may be confused with Alternaria/ early blight but the spots are less definite and have no concentric rings.  Specifically, verticilium wilt causes yellow blotches on the lower leaves until brown veins appear followed by chocolate brown spots immediately prior to plant death.

A 4-5 year rotation is necessary to manage verticilium wilt if it shows up in a field.  Well-drained soils and raised beds also prevent transmission and, in general, soil moisture should be kept as a minmum to avoid transfer within the soil water.  If verticilium has been a serious issue in the past, the soil can be solarized prior to planting to control the populations of the pathogen.

FUSARIUM WILT:

Fusarium wilt is often confused with verticilium wilt in its early and has similar causative agents which mean that is is managed in the same way.  However, in later wilt stages, fusarium can cause cankers and brown streaks.  Also, fusarium doesn't affect the whole plant uniformly.  Symptoms also vary by species.  See the attached table for details on how the symptoms present in each plant.  See the above section on verticilium wilt for management strategies.

BACTERIAL SPOT & SPECK:

Bacterial spot and speck are both bacterial pathogens introduced to a field by contaminated seed or transplants and spread by splashing rain or by equipment during cultivation.  Outbreaks are favored by excessive overhead irrigation, frequent warm, driving rains, and long dew periods.  The only differences between the two are the size of the necrotic spots and the optimal temperatures under which they flourish. Bacterial spot is common in soil temperatures of 75 to 85 degree weather while speck is favored in 65 to 75 degree temperatures.

Bacterial infections can be managed by ensuring that you buy certified seeds or transplants as well as buying resistant varieties if you have had issues historically or in nearby fields. Having a minimum of three year rotation can control the bacterial community.  Avoiding excessive Nitrogen fertilization in which the bacteria can breed is important.  Avoiding irrigation or handling the plants while they're wet also helps to avoid spread in your fields.  Remove field debris as soon as speck or spot is observed but it's not imperative to remove the infected plant immediately unless runoff will touch the fruit and infect other plants downslope.

ROOT KNOT NEMATODES:

Root knot nematodes are microscopic roundworms that live in the soil and attack the roots of young plants.  The nematodes reduce the root volume which, in turn, affects the nutrient and water absorption capacity of the plant.  The optimal soil temperature for nematode population growth is 70 to 80 degrees Fahrenheit.

To manage nematode populations, it is important first to determine the nematode density prior to planting by sending a soil sample to a nearby extension agent.  Cover crop between planting with hairy indigo, American jointvetch, or sorghum.   The field can also be fallowed for a year to starve the nematodes if the cover crop will not establish quickly enough to smother all other nematode hosts (including weeds).  Mulching with organic matter that has balanced microbial populations can also be beneficial because these populations can outcompete the root knot nematodes.  Soil solarization can decrease the nematode populations.  Resistant cultivars exist.

COMMON SCAB:

Common scab is a tuber disease that affect potatoes exclusively in the solanaceous family.  It impacts marketability but not necessarily the yield of potatoes.  Different types of scab can present, though all including circles of corky or scabbed tissue on the tubers and are caused by the same species of bacteria.  The type of scab is determined by the host resistance, the aggressiveness of the infection, the strain of both bacteria and plant, etc.

The bacteria populations which cause common scab will always be present in fields but the populations can be suppressed at highly acidic pHs (below 5.2).  Rotations with non-hosts (such as small grains, corn, or alfalfa directly after a potato crop) also reduces populations. Planting radishes, beets, carrots, or crimson clover prior to potato crops encourages growth in the bacterial populations.  Consistent soil moisture should be provided to avoid scab during the 2-6 weeks following tuber initiation because the bacteria in the water outcompete the scab.  Thick applications of alkaline producing organic matter should also be avoided.

TOMATO SPOTTED WILT VIRUS:

Tomatos Spotted Wilt Virus is a virus transmitted by thrips that affects a wide variety of plant species.  In the South, it generally only presents in greenhouses.  Symptoms differ by plant species but generally include yellowing and/or necrotic spots on leaf tissue as well as characteristic necrotic rings on fruit.

TSWV can be managed by testing for thrips in the greenhouse regularly and throwing out or submerging transplants when discovered to get rid of them.  Also avoid mowing weeds or cover that might be alternate hosts for thrips while the transplants in the greenhouse are being aired.  Stock the greenhouse with yellow sticky traps.  Blue traps catch more thrips but the yellow ones are more universal.

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.