Scout for Fusarium Head Blight (Scab) symptoms (Cropland Diseases)
Description:

Several samples with Fusarium Head Blight (FHB), also known as Scab, have come through the Schutter Diagnostic Lab this past week. FHB is an economically important disease affecting the heads and grain of wheat, barley, and durum, reducing yield and test weight and producing mycotoxins that impact human and animal health. While the window for infection and disease development, which is during flowering, has likely passed for most at-risk crops in the state, now is a good time to scout your crops for symptoms of the disease and develop a strategy for handling FHB diseased crops and grain. Read on for more information on this disease, management recommendations, and to find additional resources.

Quick Summary for Busy People

  • FHB is a disease of concern in wheat, barley, and durum. Moist and warm environments during and just after flowering promote the disease. Damage is caused through reduced grain yield and mycotoxin contaminations.
  • Look for for partially bleached heads between from soft to hard dough growth stage, sometimes highlighted by orange or pink spore masses on lower infected spikelets.
  • Important FHB risk factors include tight cereal rotation including corn, a history of the disease in a given field, and disease conducive conditions during flowering (irrigation, rain, dew).
  • Managing FHB infected crops: Stop irrigation upon detection of FHB. Smaller, lightweight diseased kernels can be removed from the seed lot by adjusting screen size and airflow of the combine. Cool down grain and store at low moisture. Test for mycotoxin concentrations before feeding grain to livestock.

Please don’t hesitate to email (uta.mckelvy@montana.edu) or call (406-994-557) if you have any questions. I’m here to help.

Best,

Uta McKelvy, Extension Field Crop Pathologist


Alert Period: 08/03/2022 - 05/31/2023
Submitted By: Uta McKelvy

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Elevated risk for white mold (Sclerotinia stem rot) in pulse crops (Cropland Diseases)
Description:

Recurrent rain events in the past couple of weeks have provided some moisture to boost crop growth but have also increased the risk for white mold in pulses. The risk is especially high in fields with a history of white mold. This fungal disease is most severe on chickpea, followed by lentil. The disease is of minor concern on pea. Although the focus of this AgAlert is on pulse crops, please note that white mold infects all broadleaf crops, including canola, dry beans, soybeans, etc. Read on for a description of white mold symptoms and information on the disease cycle and management recommendations.

Quick Summary for Busy People

  • White mold is favored by high humidity and temperatures of 50-78° Recent conditions in our state have been favorable for disease development.
  • Preventative fungicide sprays can suppress infection, but care needs to be taken to get the fungicides into the lower canopy.
  • Integrated management approaches are necessary for long-term management of this disease and include crop rotation, (broadleaf) weed control, sanitation, variety selection, and tillage.

Alert Period: 07/18/2022 - 05/31/2023
Submitted By: Uta McKelvy

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Ascochyta blight on chickpea detected in the state - monitor for disease symptoms (Cropland Diseases)
Description:

Happy July to you all! This Montana summer is in full swing, and I’ve been camping out in the Schutter Diagnostic Lab for the past few weeks … because it’s busy and samples are rolling in. Despite the ongoing drought conditions in many parts of the state, we have detected Ascochyta blight on chickpeas from Teton county (not yet on peas and lentils). This AgAlert discusses symptoms, disease development and management strategies (focused on chickpea).

Quick Summary for Busy People

  • Ascochyta blight can infect susceptible crops repeatedly throughout a season and at any stage during plant development.
  • Scout for gray to tan-brown lesions with brown to black halos, concentric rings, and brown to black dots in the lesion center.
  • Preventive applications of contact fungicides (chlorothalonil) before canopy closure/flowering are recommended. After canopy closure, applications of Triazole and Carboxamide systemic fungicides are required.
  • Strobilurin fungicides are not recommended for Ascochyta management due to resistance development. Rotate between fungicide modes of actions to prevent further resistance development.

Alert Period: 07/05/2022 - 05/31/2023
Submitted By: Uta McKelvy

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Winter Canola Research at Montana State University – Top 10 Questions and Answers by Perry Miller (Agri-Business/Cropland)
Description:

Decision time if fast approaching for winter canola seeding. Genetic technology has improved and some producers in Montana are having good success with winter canola, even in 2021’s severe drought year. Perry Miller, Cropping Systems Professor at MSU (pmiller@montana.edu; 406-994-5431), has been researching winter canola, mostly unfunded … so a bit piecemeal …, but shares his experience in managing this promising crop.

  1. Winter canola is a fragile system that is a game-changer when all the pieces line up correctly. However, due to the fragility of the system, what works in one place and year may not work in the next place or year … and that’s just from experience within Gallatin Valley! As you read my experience below with this crop, please keep this statement in mind for farming wherever you are!
  2. In my plots near Bozeman, potential yield increase is 2.0X that of spring canola but average potential is maybe closer to 1.5X. Ostensibly, everything after the ‘.’ is profit. And with herbicide resistant types there is a real opportunity to manage problematic weeds in concert with crop competition. But if it doesn’t survive, then it’s 0.0X.
  3. Winter canola maturity is significantly more variable than spring canola, mostly due to variable overwinter stand injury, which can make harvesting very difficult. Over-ripe sections of field will be shattering while other areas are still too green to cut. Especially if stand is thin, swathing is not an option in wind-prone Montana. Shatter-resistant varieties are probably less than 5 years out, which will be a game changer (likely in both ease of harvest management AND increased seed cost). Current chemical desiccant and pod sealant options increase harvesting costs and reports from farmers state variable success with pod sealant products.
  4. Crop rotation? Early on in my research with winter canola, I learned that freshly harvested cereal stubble is the worst place to seed it due to too cool a microclimate in fall and early spring to produce strong seedlings. However, in 2021 at Moccasin, Pat Carr seeded into stripped wheat stubble in 3rd week of August after a big (and very unusual) rain, and had excellent canola survival. With that longer growth period, seedlings were likely less constrained by cool fall microclimate in stripped wheat stubble. Fragile system. My recent work targets chem fallow … managing canola as a very early fall-seeded (summer) crop. Chem fallow is more likely to have moisture reserve to prevent seedlings from germinating and then desiccating … we have tried several instances seeding winter canola on various crop/cover crop stubbles in summer and our most common experience is that IF get a big enough rain (~0.5”) to germinate canola, we can get seeds to germ … and then they quickly die when don’t get further rain for the next month. Canola that emerges in in fallow is much more likely to survive.
  5. Varieties? Improvement is being made. Seek out latest variety info that you think is relevant to your area. I remember being optimistic when DKW 225 RR (now called CP225WRR) as it was marketed as an improvement over the ‘100’ series of RR winter canola from same program. And it was. Then CP320WRR was released and it was even better. In a current variety trial at Bozeman sponsored by Kansas State University, 225 looks weak compared to just about every other RR winter canola entry in the trial … and 320 is in the bottom half … Point being: breeders in North American and Europe are steadily doing their part to create better adapted varieties.
  6. Seeding date? Mid to late August establishment is likely ideal in much of dryland Montana (MSU researchers are checking seeding dates in a new multi-site study at 4 locations in MT starting this fall) but how many years in 10 can you get dryland winter canola emerged in August? If get very far in September you may not have the heat units to get it to 4+lf stage (ideal minimum). If go in July (soil moisture permitting) the canola may get too large and require mowing/grazing, and have increased winter injury if crowns start to elevate off soil surface, as occurred in Bozeman this past winter with a July 19 seeding date in irrigated ground.
  7. Seed depth? I haven’t studied this but I am concerned about some of the unusual deep seeding recommendations I’m hearing, and I have heard similar concerns from some farmers. We aim to seed about ¼” deeper than we’d do spring canola in spring but I don’t know if that’s optimum. Needs research.
  8. Seed density? We looked at high (18/ft2) and medium (9/fts) seed densities with September seed dates in fresh crop stubbles and high densities established better. I can’t really say why … wasn’t simply a numbers game (If lose 50% of plants overwinter, maybe better to start with a bigger number) but that was certainly part of it. However, there is experience in central plains that suggests lower seed densities establish more vigorous ground-hugging cabbage. I see this as open research question that will be dependent on A) seeding date and B) seed cost.
  9. Fertilizer? Our 4-location seed date trial includes N and S fertilizer treatments also. Kansas State used to tell us to be wary of too much N during establishment phase as it would produce too vigorous growth in their environment which caused crowns to lift and increased winter kill. When we were focusing on recropping after wheat, we found that full N rates did not harm, and even helped with seedling establishment, partially because with that late seeding we were in a race to get seedlings big enough to survive winter … very different situation from Kansas.
  10. Insect Pests? And maybe this one should be at top of this list because it can be make or break. Beware of flea beetles (if was other canola nearby) and especially grasshoppers. If canola is emerging in late August it may be the only green thing for miles around … grasshoppers can damage seedlings very quickly. I have heard success out at Three Forks (Franck Groeneweg) with spraying field borders with insecticide … may limit grasshopper damage to the outside 20-30 ft of fields …

Please reach out to Perry Miller by email (pmiller@montan.edu) or call (406-994-5431) with any questions on this AgAlert, canola production, and cropping systems.

Best,

Perry Miller, Professor Cropping Systems


Alert Period: 06/22/2022 - 06/30/2023
Submitted By: Uta McKelvy
Physiological Leaf Spots on winter wheat widespread – don’t confuse them with fungal leaf spots ! (Cropland Diseases)
Description:

Quick Summary for Busy People

  • Physiological leaf spots are caused by chloride deficiency. Fungicide applications are not effective, but chloride fertilizer can help.
  • Fungal leaf spots may occur where wet and cool weather is observed. Fungicide applications are effective but may not be necessary, depending on the crop growth stage.
  • Take the time to diagnose/get diagnosed the leaf spot cause before you make treatment decisions.

 

I’ve seen several winter wheat samples, mainly variety Bobcat, with tan spot-like symptoms in the Schutter Diagnostic Lab. These leaf spots turned out to be Physiological Leaf Spots (PLS). PLS are not caused by a (fungal) pathogen, which also means that fungicide applications will not be effective. Distinguishing between fungal leaf spots and PLS is difficult but important. This AgAlert discusses differentiation, characteristic symptoms, risk factors, and treatment options for PLS and fungal leaf spots on wheat and includes resources on fungicide applications.

 

Differentiation between Physiological and Fungal Leaf Spots – a “quick and dirty” key (by Mary Burrows)

  1. Physiological spots occur on all leaves, not just in the thicker, lower canopy.
  2. Physiological spots are more uniform than fungal spots (there aren’t more spots on lower leaves than upper leaves).
  3. Physiological spots are not highly associated with patches of residue in the field, it is more uniform across the field.
  4. Physiological spots have a very sharp edge to the lesion, whereas fungal spots are more fuzzy and continue to expand over time.
  5. Fungal spots, when left in a moist chamber 24-48 h, develop small black or brown spots that are fungal structures called Pycnidia. Physiological spots do not form pycnidia. You can see these under high humidity in the field with a 10-20x lens.
  6. Look on residue for black pycnidia – these are the source of fungal leaf spots. If there are none, it might be physiological.

 

View the full AgAlert for more details on Physiological and Fungal leaf spots (including some pictures) and treatment options.

Please don’t hesitate to email (uta.mckelvy@montana.edu) or call (406-994-557) if you have any questions. I’m here to help.

Best,

Uta McKelvy, Extension Field Crop Pathologist


Alert Period: 05/31/2022 - 07/31/2023
Submitted By: Uta McKelvy

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Cold spring causes cold injury and nutrient deficiency symptoms in field crops (Cropland Diseases)
Description:

Crop samples are starting to come into the Schutter Diagnostic Clinic and my phone is buzzing a lot more these days. Thank you all for reaching out! This year’s cold spring is giving our crops a slow start and a lot of what I see in the diagnostic lab is related to cold temperatures and nutrient deficiencies. This AgAlert includes a summary of what to look out for these days.

Quick Summary for Busy People

  • This spring has been unusually cold, which is slowing plant growth. Be patient.
  • Color banding is a common symptom of freeze injury in spring-sown seedlings. Burned leaf tips and bleached, wilted-looking leaves (or leaf sections) are also typical. Depending on the crop growth stage, temperature low and duration of low temperatures, the damage from cold/freeze injury may range from cosmetical to yield-limiting.
  • Cold soils limit nutrient uptake. We’ve seen symptoms of nitrogen, iron, and zinc deficiency. Nutrient deficiency could further be compounded by root rot issues.

For more information and some symptom pictures, see the full AgAlert by pushing the button below.

Please don’t hesitate to email (uta.mckelvy@montana.edu) or call (406-994-557) if you have any questions. I’m here to help. If you’re unsure about the symptoms you are observing, bring a sample to your local Extension agent or submit one to the Schutter Diagnostic Lab.

Best,

Uta McKelvy, Extension Field Crop Pathologist

Phone: (406) 994-5572

Email: uta.mckelvy@montana.edu


Alert Period: 05/27/2022 - 05/31/2023
Submitted By: Uta McKelvy

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Drought and Wildife Resources (General)
Description:

Hello all,

As we enter the 2022 growing season, keep in mind the MSU Extension Wildfire and Drought Taskforce has made substantial changes to our web page with new information and updates to existing information.  Much of Montana's dryland production areas are still experienceing moderate to extreme drought.  Consult our web page for timely and relevant information and as always, reach out to us with suggestions. 

MSU Wildfire and Drought web page: http://aboutus.msuextension.org/wildfiredrought/

 


Alert Period: 05/16/2022 - 09/30/2022
Submitted By: Hayes Goosey
Prime conditions for Pythium seed and seedling rot - Use seed treatments for crops not yet planted! (Cropland Diseases)
Description:

Quick Summary for Busy People

  • We observe prime conditions for Pythium seed and seedling rot: high soil moisture and cool soil temperatures.
  • Use fungicide seed treatments with mixed modes of action including Metalaxyl, Mefenoxam, or Ethaboxam for spring crops not yet planted.
  • Delay planting of highly susceptible crops, especially Kabuli-type chickpeas, until soils have warmed up to above 50 F. Use disease-free seed with maximum vigor.

Spring has sprung and planting is in full swing. The snowstorms and rain events in the past days and weeks brought some much-needed moisture to the state. But the newly received soil moisture in combination with still cool soil temperatures create prime conditions for seed and seedling rot caused by Pythium. Pulse crops are at high risk.

What is Pythium rot?

Favorable Conditions: Pythium is a soilborne water mold (Oomycete) that causes seed rot and pre- and post-emergence damping-off on a wide range of host plants. Pulse crops are at high risk. The pathogen is favored by high soil moisture and low to moderate soil temperatures (50 to 75 F). The risk of seedling damping-off is especially high when soils are saturated for one or more days after planting and before emergence. Low-lying areas in the field, where water accumulates, are likely disease hot spots. High residue cover, that keeps soil temperatures cool, also favors the disease.

Symptoms: Poor stand establishment and yellow seedlings are initial indicators of seedling damping-off. These symptoms often occur in circular patches in the field and may be more noticeable in low-lying areas. The root system of affected seedlings is poorly developed with a lack of fine root hairs. Roots often show brown discoloration and have a gelatinous texture. The root cortex (outer layer of the root) can easily be stripped away, exposing the root core (see pictures).

Susceptible crops: Pythium has a wide host range, including small grain crops, alfalfa, and many weed species. Pulse crops are very sensitive to seed, seedling, and root rot diseases caused by this pathogen. Pythium is the most frequently reported cause of seed and seedling rot in peas. Kabuli-type chickpeas are much more susceptible than the Desi-type. Low-tannin cultivars of lentil with light-colored seeds are more susceptible than dark-colored seed cultivars.

How can I manage Pythium root rot?

Fungicide seed treatments are strongly recommended for pulse crops. Choose a seed treatment product with mixed modes of action to achieve broad-spectrum protection against a variety of soilborne seed and seedling pathogens. Fungicides active ingredients with efficacy against Pythium (Oomycete, not a true fungus) include Metalaxyl, Mefenoxam, and Ethaboxam. At least one of these active ingredients should be included in your fungicide treatment to provide protection against Pythium. VibranceMaxx Pulses is one suitable product with efficacy against Pythium and other seed- and soilborne diseases. I have updated the Fungicide Seed Treatment Table for Pulse Crops for the 2022 growing season which provides an overview of suitable seed treatment options. You may also refer to the North Dakota Field Crop Plant Disease Management Guide for seed treatment options in pulses and other crops.

Delay seeding dates of highly susceptible crops and cultivars, especially if fungicide seed treatments are not a management option for you. This concerns especially Kabuli-type chickpeas which are highly susceptible to Pythium seed and seedling rot. Delay seeding until soil temperatures have increase above 50 F.

Plant disease-free seed with maximum vigor to ensure rapid germination and emergence. This will reduce the window of susceptibility for infection, because older seedlings are less susceptible to Pythium (lignification of the root system provides a physical barrier to infection).

 

Picture Captions

Figure 1. Pea seedlings affected by Pythium spp. with dark-brown lesions of the upper root and stem and secondary root rot on lateral root buds.

Figure 2. Circular patches of poor emergence and stand establishment caused by seed and seedling rot.

Figure 3. Roots infected with Pythium often have a gelatinous texture and the root cortex (outer layer of the root) easily strips off exposing the root steele (root core).

 

Please don’t hesitate to email (uta.mckelvy@montana.edu) or call (406-994-557) if you have any questions. I’m here to help.

Best,

Uta McKelvy, Extension Field Crop Pathologist


Alert Period: 05/04/2022 - 05/31/2023
Submitted By: Uta McKelvy
Prime conditions for Pythium seed and seedling rot - Use seed treatments for crops not yet planted! (Cropland Diseases)
Description:

Quick Summary for Busy People

  • We observe prime conditions for Pythium seed and seedling rot: high soil moisture and cool soil temperatures.
  • Use fungicide seed treatments with mixed modes of action including Metalaxyl, Mefenoxam, or Ethaboxam for spring crops not yet planted.
  • Delay planting of highly susceptible crops, especially Kabuli-type chickpeas, until soils have warmed up to above 50 F. Use disease-free seed with maximum vigor.

Spring has sprung and planting is in full swing. The snowstorms and rain events in the past days and weeks brought some much-needed moisture to the state. But the newly received soil moisture in combination with still cool soil temperatures create prime conditions for seed and seedling rot caused by Pythium. Pulse crops are at high risk.

What is Pythium rot?

Favorable Conditions: Pythium is a soilborne water mold (Oomycete) that causes seed rot and pre- and post-emergence damping-off on a wide range of host plants. Pulse crops are at high risk. The pathogen is favored by high soil moisture and low to moderate soil temperatures (50 to 75 F). The risk of seedling damping-off is especially high when soils are saturated for one or more days after planting and before emergence. Low-lying areas in the field, where water accumulates, are likely disease hot spots. High residue cover, that keeps soil temperatures cool, also favors the disease.

Symptoms: Poor stand establishment and yellow seedlings are initial indicators of seedling damping-off. These symptoms often occur in circular patches in the field and may be more noticeable in low-lying areas. The root system of affected seedlings is poorly developed with a lack of fine root hairs. Roots often show brown discoloration and have a gelatinous texture. The root cortex (outer layer of the root) can easily be stripped away, exposing the root core (see pictures).

Susceptible crops: Pythium has a wide host range, including small grain crops, alfalfa, and many weed species. Pulse crops are very sensitive to seed, seedling, and root rot diseases caused by this pathogen. Pythium is the most frequently reported cause of seed and seedling rot in peas. Kabuli-type chickpeas are much more susceptible than the Desi-type. Low-tannin cultivars of lentil with light-colored seeds are more susceptible than dark-colored seed cultivars.

How can I manage Pythium root rot?

Fungicide seed treatments are strongly recommended for pulse crops. Choose a seed treatment product with mixed modes of action to achieve broad-spectrum protection against a variety of soilborne seed and seedling pathogens. Fungicides active ingredients with efficacy against Pythium (Oomycete, not a true fungus) include Metalaxyl, Mefenoxam, and Ethaboxam. At least one of these active ingredients should be included in your fungicide treatment to provide protection against Pythium. VibranceMaxx Pulses is one suitable product with efficacy against Pythium and other seed- and soilborne diseases. I have updated the Fungicide Seed Treatment Table for Pulse Crops for the 2022 growing season which provides an overview of suitable seed treatment options. You may also refer to the North Dakota Field Crop Plant Disease Management Guide for seed treatment options in pulses and other crops.

Delay seeding dates of highly susceptible crops and cultivars, especially if fungicide seed treatments are not a management option for you. This concerns especially Kabuli-type chickpeas which are highly susceptible to Pythium seed and seedling rot. Delay seeding until soil temperatures have increase above 50 F.

Plant disease-free seed with maximum vigor to ensure rapid germination and emergence. This will reduce the window of susceptibility for infection, because older seedlings are less susceptible to Pythium (lignification of the root system provides a physical barrier to infection).

 

Picture Captions

Figure 1. Pea seedlings affected by Pythium spp. with dark-brown lesions of the upper root and stem and secondary root rot on lateral root buds.

Figure 2. Circular patches of poor emergence and stand establishment caused by seed and seedling rot.

Figure 3. Roots infected with Pythium often have a gelatinous texture and the root cortex (outer layer of the root) easily strips off exposing the root steele (root core).

 

Please don’t hesitate to email (uta.mckelvy@montana.edu) or call (406-994-557) if you have any questions. I’m here to help.

Best,

Uta McKelvy, Extension Field Crop Pathologist


Alert Period: 05/04/2022 - 05/31/2023
Submitted By: Uta McKelvy
Updated Resources on Foliar Fungicides for Disease Control in Pulse Crops (General)
Description:

Greetings!

We have updated the Foliar Fungicides Table for Pulse Crops for the 2022 growing season. The table is available on the MSU Extension Plant Pathology website.

The table presents information on available fungicide products for the management of widespread fungal diseases of pulse crops (peas, lentils, and chickpeas) for use in the United States. Please be advised that consulting this resource does not substitute careful reading of the product label before an application is made.

To learn more about fungicides and other management strategies for diseases control in pulse crops contact your local extension agent or MSU Extension specialist Uta McKelvy


Alert Period: 04/07/2022 - 06/30/2023
Submitted By: Uta McKelvy
Updated Resources on Foliar Fungicides for Disease Control in Pulse Crops (General)
Description:

Greetings!

We have updated the Foliar Fungicides Table for Pulse Crops for the 2022 growing season. The table is available on the MSU Extension Plant Pathology website.

The table presents information on available fungicide products for the management of widespread fungal diseases of pulse crops (peas, lentils, and chickpeas) for use in the United States. Please be advised that consulting this resource does not substitute careful reading of the product label before an application is made.

To learn more about fungicides and other management strategies for diseases control in pulse crops contact your local extension agent or MSU Extension specialist Uta McKelvy


Alert Period: 04/07/2022 - 06/30/2023
Submitted By: Uta McKelvy
EPA Revokes Use of Chlorpyrifos on all Food / Feed Crops.. (Pesticides)
Description:

In August 2021, the Environmental Protection Agency (EPA) issued a final rule revoking all tolerances for pesticides containing chlorpyrifos. As a result, all tolerances of chlorpyrifos were revoked on February 28th, 2022. Chlorpyrifos is a common organophosphate active ingredient used in many pesticide products for managing insect pests in a wide array of agriculture and non-agriculture areas. Common Montana agriculture crops impacted include alfalfa, corn, soybeans, fruit/nut trees, and wheat. EPA’s decision was based on a response to the ninth circuit court’s order directing EPA to respond to a petition to revoke all tolerances of chlorpyrifos because they were not safe. EPA found that registered uses result in exposures exceeding safe levels of exposure due to the neurotoxic effects of chlorpyrifos and potential association of chlorpyrifos in neurodevelopmental effects in children.  


Alert Period: 03/18/2022 - 08/18/2022
Submitted By: Cecil Tharp

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EPA Revokes Use of Chlorpyrifos on all Food / Feed Crops.. (Pesticides)
Description:

In August 2021, the Environmental Protection Agency (EPA) issued a final rule revoking all tolerances for pesticides containing chlorpyrifos. As a result, all tolerances of chlorpyrifos were revoked on February 28th, 2022. Chlorpyrifos is a common organophosphate active ingredient used in many pesticide products for managing insect pests in a wide array of agriculture and non-agriculture areas. Common Montana agriculture crops impacted include alfalfa, corn, soybeans, fruit/nut trees, and wheat. EPA’s decision was based on a response to the ninth circuit court’s order directing EPA to respond to a petition to revoke all tolerances of chlorpyrifos because they were not safe. EPA found that registered uses result in exposures exceeding safe levels of exposure due to the neurotoxic effects of chlorpyrifos and potential association of chlorpyrifos in neurodevelopmental effects in children.  


Alert Period: 03/18/2022 - 08/18/2022
Submitted By: Cecil Tharp

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Powdery mildew showing up late in a sugar beet field in south central Montana (Cropland Diseases)
Description:

A sugar beet field with the majority of plants showing a dusty appearance on leaves was identified in south central Montana, near Billings, on September 9. Plants exhibited the symptoms both on the upper and underside of leaves at moderate to high levels of severity. Close observation of the symptoms suggested they corresponded to the disease known as powdery mildew, which is caused by the fungus Erysiphe polygoni. Leaf samples were taken to an MSU lab for microscopic observation and confirmation of the pathogen identity. Scattered, whitish mycelial mats were observed on both leaf surfaces containing abundant, cylindrical to elliptical conidia (asexual spores of the fungus) that originated singly from straight, short conidiophores. No chasmothecia (sexual stage of the fungus) were present in the observed leaves. Occurrence of the disease in this field coincides with a period of suitable weather conditions for disease development in this location, namely: warm, dry weather, and large diurnal temperature changes towards end of August-beginning of September. At this stage, since the crop in the scouted field is near harvest, a fungicide treatment is not justified. In situations where the disease is detected early in the season, a fungicide treatment would be recommended upon detection to reduce a potential rapid disease increase. Presence of the disease in this location constitutes a source of inoculum for healthy neighboring fields, though according to communication with the Yellowstone agriculture extension agent and area agronomists, no other fields with similar symptoms have been observed as yet. Disease presence in this location suggests future imminent risk for seasonal incursions of pathogen spores into the area from afar overwintering sites.

For questions and further discussion please contact Dr. Oscar Perez-Hernandez, MSU Extension Row Crop Pathologist (oscar.perezhernandez@montana.edu; 406-994-4091)

 


Alert Period: 09/17/2021 - 09/17/2022
Submitted By: Uta McKelvy

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Powdery mildew showing up late in a sugar beet field in south central Montana (Cropland Diseases)
Description:

A sugar beet field with the majority of plants showing a dusty appearance on leaves was identified in south central Montana, near Billings, on September 9. Plants exhibited the symptoms both on the upper and underside of leaves at moderate to high levels of severity. Close observation of the symptoms suggested they corresponded to the disease known as powdery mildew, which is caused by the fungus Erysiphe polygoni. Leaf samples were taken to an MSU lab for microscopic observation and confirmation of the pathogen identity. Scattered, whitish mycelial mats were observed on both leaf surfaces containing abundant, cylindrical to elliptical conidia (asexual spores of the fungus) that originated singly from straight, short conidiophores. No chasmothecia (sexual stage of the fungus) were present in the observed leaves. Occurrence of the disease in this field coincides with a period of suitable weather conditions for disease development in this location, namely: warm, dry weather, and large diurnal temperature changes towards end of August-beginning of September. At this stage, since the crop in the scouted field is near harvest, a fungicide treatment is not justified. In situations where the disease is detected early in the season, a fungicide treatment would be recommended upon detection to reduce a potential rapid disease increase. Presence of the disease in this location constitutes a source of inoculum for healthy neighboring fields, though according to communication with the Yellowstone agriculture extension agent and area agronomists, no other fields with similar symptoms have been observed as yet. Disease presence in this location suggests future imminent risk for seasonal incursions of pathogen spores into the area from afar overwintering sites.

For questions and further discussion please contact Dr. Oscar Perez-Hernandez, MSU Extension Row Crop Pathologist (oscar.perezhernandez@montana.edu; 406-994-4091)

 


Alert Period: 09/17/2021 - 09/17/2022
Submitted By: Uta McKelvy

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