[hamstring]

Straintester thanks for adding some info much appreciated I dug uo some more info i thoght was interesting. I hope the next time someone does a search on Leaf Spot they will have to go no futher than this thread.

Cherry Leaf Spot

III. Disease Cycle: There are two stages in the life cycle of this fungus, described as follows:

Primary cycle: The fungus overwinters in diseased leaves on the ground. In the spring, fruiting structures called apothecia develop on these leaves. Around bloom or shortly afterwards, ascospores are formed within these fruiting structures. During wet periods, ascospores are forcibly discharged from these leaves and are carried upward by wind and splashing rain to infect newly developing leaves. Sometimes the first sign of infection may be on suckers close to the ground. During this primary cycle, most spores are discharged from bloom to four to six weeks after petal fall. Infection early in the primary cycle is limited, for the new leaves are small and not as susceptible, and also because the stomata of these leaves are still immature. It is through these stomata that the fungus gains entry into the leaf. Another factor that limits infection are the low temperatures that usually occur in the early spring.

Once ascospores are ejected, they attach to the young leaves, germinate in a film of water, and penetrate through stomata on the underside of the leaf surface within a few hours. Small, purplish spots appear on the upper leaf surfaces in about 10 to 14 days after the first infections. The incubation period from the first infection to the appearance of spots varies with temperature and can occur in as little as five days. Temperatures of 60 to 68 F (16-20 C) are most favorable for disease development.

Secondary cycle: Eventually, the fungus produces conidia on the underside of the leaf. These conidia are responsible for the extensive spread of the disease. During wet periods, conidia appear as whitish-pink sticky masses of spores and are spread from leaf to leaf by water. If weather conditions for disease development are conducive, infection can become increasingly abundant as the season progresses. New infections can occur throughout the summer and fall due to the rapid increase and spread of the fungus during wet periods by means of repeated generations of conidia.


Three important fungal leaf spot diseases, tan spot, Stagonospora nodorum blotch (SNB) and Septoria tritici blotch (STB), commonly occur in North Dakota and can cause reduced test weights and yield losses of up to 50 percent. Among these, tan spot, caused by Pyrenophora tritici-repentis, is the most destructive leaf spot disease found in all wheat classes throughout the growing season across North Dakota. SNB and STB also are common in wheat in North Dakota each year, but symptoms generally appear after flag leaf emergence.


Tan Spot
Causal agent: Pyrenophora tritici-repentis

Eight races (often genetically and geographically distinct groups) of P. tritici-repentis have been identified on the basis of necrosis (browning) and/or chlorosis (yellowing) symptoms induced on a set of designated wheat cultivars. Among the races, race 1 is the most prevalent in North Dakota. These races produce different host-selective toxins (HSTs) on susceptible wheat varieties.

Symptoms and Signs
Leaves: The fungus produces oval or diamond-shaped to elongated irregular spots (1/8 to 1/2 inch long and 1/16 to 1/18 inch wide). These spots enlarge and turn tan with a yellow border and a small dark brown spot near the center (Figure 1). The dark spot is best observed by holding the leaf up to the light. This pattern of a tiny dark spot in a tan lesion and a narrow to broad yellow border produces an "eyespot" type of symptom, which is usually distinctive for the disease. Early in the season, tan spot lesions often have a very distinctive, large chlorotic (yellow) border
Disease cycle
The tan spot pathogen overwinters as black pinhead-sized fruiting structures (pseudothecia) that develop on last season's wheat stems (Figure 4). Pseudothecia release sexual spores (ascospores) in spring and early summer. Asexual spores (conidia) are produced on previous crop residue and leaf spots. Both spores are dispersed by wind, and germinate and infect wheat in a wide range of temperatures. During wet growing seasons, large numbers of conidia form in the disease spots and these conidia may be wind-borne to other wheat leaves to form new infections (Figure 5). Prolonged wet periods (24 hours or greater) can result in spore germination and infection on wheat leaves.

Figure 4. Fungal structures of the tan spot fungus and Stagonsopora nodorum on wheat straw. (Photos by Carl Bradley, previously with NDSU Extension Service) (49KB)

Figure 5. Disease cycle of tan spot on wheat. (20KB)


Stagonospora Nodorum Blotch (SNB)
Causal agent: Stagonospora nodorum (previously named Septoria nodorum)

Symptoms and Signs
Leaves: Stagonospora nodorum initially causes water-soaked and small chlorotic lesions on the lower leaves of the plant. The lesions become yellow and eventually red-brown. Mature lesions are generally lens-shaped without the distinct yellow border typical of tan spot lesions (Figure 6). As the disease progresses, the lesions develop an ashen gray-brown center containing brown specks (pycnidia), which are sometimes difficult to see in brown lesions. Pycnidia are the asexual reproducing structure of the fungus and are diagnostic of this disease.

Figure 6. Lens-shaped lesions with ashen gray centers, typical of infections by SNB. (Some scattered leaf rust pustules also are present on leaf.) (16KB)

Grain head and kernels: After flowering, wet weather can lead to lesion development on the glumes, often starting at the tip, but whole areas of the glumes may be covered with dark brown to dark purple with ash gray areas. This phase of the disease is called "glume blotch" (Figure 7). Severe leaf blotch or glume blotch infections may result in lightweight, shriveled kernels (Figure 8).

Figure 7. Glume blotch symptoms caused by SNB infections. Note browning of glumes and brown infected spots on awns. (15KB)

Figure 8. Shriveled durum kernels (left) caused by SNB infections and normal durum kernels (right). (27KB)

Disease cycle
The life cycle for SNB is very similar to that observed for tan spot (Figure 5). The overwintering reproductive structures (pseudothecia) or asexual structures (pycnidia) are similar in appearance to those of the tan spot fungus, but they are smaller in size (Figure 4). The fungus survives in wheat straw, infested seed or an overwintering crop. Ascospores released from the pseudothecia generally cause the first lesions. Pycnidia release conidia, which are water-splash dispersed. Stagonospora nodorum blotch spores generally require 12 to18 hours of leaf wetness for infection, and the disease develops most rapidly between 68 and 81 degrees Fahrenheit.


Septoria Leaf Blotch (STB)
Causal agent: Septoria tritici

Symptoms and Signs
Leaves: Initial symptoms of STB develop on the lower leaves as chlorotic flecks and expand into irregular brown lesions (Figure 9). The lesions are restricted to the leaf veins, giving the appearance of parallel sides. More importantly, lesions are associated with the presence of visible pycnidia that are sphere or ball-shaped, gelatinous and gray-brown. The white to cream masses of spores can be seen oozing from matured pycnidia (Figure 9 close-up) and are reliable diagnostic signs for distinguishing Septoria leaf blotch infection from Stagonospora nodorum blotch.

Figure 9. (20KB)

Disease cycle
Septoria tritici can survive for several years in the form of vegetative strands (mycelium), pycnidia and perthecia in wheat residues. Sexual spores (ascospores) from perithecia and asexual spores (pycnidiospores) from pycnidia are released and dispersed by either wind or splash rain during the wheat-growing season and can initiate infections under favorable environmental conditions. S. tritici requires more than 24 hours of wetness and is most destructive between 50 and 68 F.


Disease Management for Tan Spot, SNB and STB
Integrated disease management is the best approach to reduce losses due to fungal leaf spot diseases in wheat. These include a combination of host plant resistance, seed quality, crop rotations and fungicide methods.

Host Plant Resistance
Some spring wheat and durum cultivars have good resistance to these fungal leaf spot pathogens, but other cultivars may range in response from susceptible to moderately resistant. New spring wheat and durum cultivars are released each year and growers are advised to consult the most recent reports of their nearest NDSU Research Extension Centers or the NDSU Extension variety trial publications for current information about cultivar response to fungal leaf spot diseases in North Dakota. Use of a resistant cultivar reduces the risk of yield and quality losses.

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Fungicides
Fungicides are available for both early season control of tan spot and for later season control of all three leaf spot diseases. NDSU research has shown modest (2- to 6-bushel) yield responses with application of reduced rates of fungicide to wheat for control of early season tan spot when: 1) wheat was planted into wheat residue, 2) a susceptible to moderately susceptible variety was grown and 3) when spring rains favored disease development. Early season application is not recommended as a standard practice in the absence of disease or favorable environment, and reduced-rate applications are not recommended in other crops.

Protectant fungicides, such as those containing mancozeb (Dithane products, Manzate 200, Manex II, Penncozeb products, Manzate 75, etc.), copper (Kocide, Champ) or combination products of mancozeb + copper (ManKocide) provide a layer of protection against infection if they are present prior to the spores landing on the leaf surface. They need to be in place before infection occurs. Protectant fungicides generally are effective only from seven to 10 days because they degrade with rain and sunlight. Two applications of protectants may be needed for longer season protection, and they generally need the addition of a spreader/sticker product.

Locally systemic fungicides, such as triazoles and strobilurins, have very good to excellent activity against the leaf spot diseases of wheat. Products with mixtures of these two classes of chemistry also are available. For some, half the full label rates have been used for early season tan spot control, generally applied at the four- to five-leaf stage, but this is a practice only recommended for tan spot of wheat under certain environmental conditions: i.e. wet weather, susceptible variety and some wheat residue present. Check fungicide and/or herbicide labels for allowed tank mixes for this early season use. Full label rates of fungicides generally are applied to protect the flag leaf from boot stage (Feekes 10) to flowering (Feekes 10.51). The flag leaf is an important source of nutrients transmitted to kernels for grain fill.

The following table provides information on the newer fungicide chemistries available in North Dakota for fungal leaf spot control in wheat and durum. Please consult the most current edition of PP-622, "North Dakota Field Crop Fungicide Guide," for updated information on registered fungicides.


Newer fungicide chemistries for fungal leaf spot control
in spring and durum wheat

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Class* Active Ingredient Product Full Label
Rate/A
Fl oz Harvest
restrictions

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Strobilurins
(Class 11) Azoxystrobin 22.9% Quadris 2.08 SC 6.2 - 10.8 45 days
Pyraclostrobin 3.6% Headline 2.09 EC 6 - 9 Feekes 10.5

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Triazoles
(Class 3) Metconazole 8.6% Caramba 10 - 17 30 days

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Propiconazole 41.8% Tilt 3.6 Ec 4 40 days
PropiMax 3.6 EC
Bumper 41.8 EC

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Prothioconazole 41% Proline 480 SC 5 - 5.7 30 days

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Tebuconazole 38.7% Folicur 3.6 F 4 30 days
Embrace 3.6 L
Monsoon
Muscle 3.6 F
Orius 3.6 F
Tebucon 3.6 F
Tebustar 3.6F
Tebuzol
Tegrol
Toledo, others

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Prothioconazole 19% Prosaro 421 SC 6.5 - 8.5 30 days
Tebuconazole 19%

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Mixtures of
triazoles +
strobilurins
(Classes 3 and 11) Metconazole 7.4% Multiva or TwinLine 6 - 11 Feekes 10.5
Pyraclostrobin 12%

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Propiconazole 11.7% Quilt 200 SC 14 45 days
Asozystrobin 7.0%

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Propiconazole 11.4% Stratego 250 EC 5 - 10 35 days
Trifloxystrobin 11.4%

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* Class indicates class of chemistry and fungicide resistance group.

Please check individual labels for further information on recommendations for use of spreader stickers, tank mixes allowed, timing of application, and possible grazing or feeding restrictions.Above table derived from one prepared by the North Central Regional Committee on Management of Small Grain Diseases, NCERA-184.

Foliar fungicides may be applied with aerial or ground equipment. Five gallons of water per acre are recommended for air; ground application generally requires 10 to 20 gallons of water per acre.

[D.S. Toker. MD]

Ill be spraying the liquid copper today. Thank goodness were having a cool spell,(only85degrees) so im going to start. Ive read a lot about the Liquid copper and it has the potential for causing phytotoxicity so i'm goint to start by spraying 2 white widows that are going to die anyway if something isnt done. Im going to use the lightest dose possible. Im intend to drench one plant fully and only lightly spray the other. I think im going to leave the infected leaves on the plant to see it there is any change.


With regaurds to applying chemicals to your plants: i use sevin, pyrethrins, Rootenone and other fairly toxic substances on my plants because guerilla plants can encounter some tough bugs and tough deseases that make applications of products like neem inpracticle. This fungus is a case in point.

Keep in mind that as long as a product is water soluble, you can spray it on your plants and then water cure, which will remove any residue that might remain on the plant. Water curing is very simple. Before hanging the buds up to dry, i fill a small tupperware tub with tepid water. I take an amount of manicured bud that would fill a jar and put it in the water. 30 min later, i remove the buds and dry normally just as i would if i had skipped the soaking step. This doesnt impact potency at all but it does remove any remaining chemicals, along with the dirt/grime and bug poop that is on the bud. I'll l keep track of every plant i treat with liquid copper and will water cure that bud before jarring it, so that im assured that no chemical residue remains. Watercuring allows you to use chemicals that you wouldnt want to use.

[ghost of sage]

I ordered the liquid copper DS.Are you saying that if you treat with the liquid copper you have to water cure your buds or is that not 100% necessary?I have never done that and am gonna have more than I have ever had this year so its gonna be a big enuff job for me to just manicure and dry normally.i do however wanna stop this damn disease!!!

[straintester]

*****

[Dorje113]

Seeing the pics in the book I had leaf Septoria on one of my plants (indoors).

Serenade stinks but has held it at bay with one application. Going to do a 2nd 7 days later.

[plhkarma]

Will neem oil do any good with the leaf spot? If so, then how often can we spray? Are their any low cost treatments for this as we are on a fixed disability income?
Thanks so much for this thread, we had posted pics asking for help but the pics from the book are exactly what's wrong with our poor little girls Brand new 1st time outdoor grow.
The info on this thread is invaluable







Peace, Love, and Harmony

[D.S. Toker. MD]

Just a little heads up for anyone hoping to battle this shit with neem oil or greencure.
This young lady was hit hard witrh Gcure, 4 days later another heavy dose- nothing. 4days later, neem oil. 3days after the neem,here you go. They're as effective as high quality turd polish






Your only hope is this stuff. Ive used a concentration of 1oz per gallon and litterally drenched the plant and all surfaces. It seems to be working. Its approved for organic gardening/OMRI listed
I havent seen any signs of phytotoxicity, I'll keep you posted

[D.S. Toker. MD]

One other point.

Look over the top of the plant in the foreground. Do you see the dead as fuck plant behind it? Thats the difference between strains. Biddy early is dead, Great white shark is hardly effected.

[straintester]

You rule D.S. Toker
Thats perfect
You even added a picture of the diseased plant with the product
....along with the dirty socks

certified organic even....right on

I'm really glad you got something that works for you and came back to inform us. I wouldn't have recommended neem oil as a solution either BUT if it is all you have until you can get something then might as well use it right away as it does help.

Good job!

[Xare]

D.S. Toker, those plants are dying from a soil borne root infection not a Foliar disease.

They needed a soil drench with a Fungicide to prevent root rot, not a foliar applicated fungicide like greencure or copper spray.

To fight these kind of infections effectively you have to be able to diagnose them correctly.

All that wilting you see happening overnight is because fungal slime like pythium or fusariam are building up on the roots and suffocating it.

Dig up the roots to one of those infected plants and you will be able to find it. You may even notice a dead rotting plant death smell. Get your nose down by the roots and sniff.