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Sunflower Downy Mildew (07/03/13)

Downy mildew is caused by a soil borne pathogen that can survive for many years in the soil. When frequent rains occur after planting, the pathogen produces swimming spores (zoospores) that infect roots and cause a systemic infection.

Sunflower Downy Mildew

Downy mildew is caused by a soil borne pathogen markell.1.healthy_and_downy_mildew_infected_sunflowers.pngthat can survive for many years in the soil.  When frequent rains occur after planting, the pathogen produces swimming spores (zoospores) that infect roots and cause a systemic infection.  Symptoms and signs include stunting of the plant (Figure 1), chlorosis along the veins on the upper side of the leaves (Figure 2), and a white cottony appearance on the underside of the leaves (Figure 3).  Infected plants will usually have no yield.  Yield loss can be significant if downy mildew occurs in large patches of the field, but when only localized infection occurs yield loss is generally low because neighboring plants will compensate.  No management tools are effective once downy mildew infection occurs.  However, genetic resistance and seed treatments may help manage downy mildew in future sunflower crops.  More information about downy mildew can be found at

http://www.ag.ndsu.edu/pubs/plantsci/rowcrops/pp1402.pdf

markell.2.downy_mildew_infected_plant_with_chlorotic_leaves.png

markell.3.downy_mildew_infected_leaf_with_white-cotony_sporulation_on_underside_of_leaf.png

Sam Markell

Extension Plant Pathologist

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Sclerotinia Stem Rot Risk Map And Calculator For Canola (07/03/13)

As canola enters bloom, the crop becomes susceptible to white mold. Fungicides are available that can help manage the disease, but the more important decision is whether or not the environment is favorable for infection and disease development.

Sclerotinia Stem Rot Risk Map And Calculator For Canola

As canola enters bloom, the crop becomes susceptible to white mold.   Fungicides are available that can help manage the disease, but the more important decision is whether or not the environment is favorable for infection and disease development.  The NDSU Sclerotinia stem rot (SSR) Risk Map for Canola, operated by NDSU Canola Pathologist Dr. Luis del Rio and funded by the Northern Canola Growers Association, is a very useful tool that can be used to help producers determine if a fungicide application may be warranted for management of the disease.  A brief description of white mold and the risk map is below.

                 White Mold.  The sclerotinia life-cycle begins when the overwintering structure, sclerotia, germinates and forms small mushroom-like structures called apothecia.  Apothecia release ascospores, which can utilize canola petals as a food source.  From those colonized petals, infection then progresses into branches and stems and can result in yield losses and lodging.  Because the infection begins on flower petals, canola is only at risk for SSR during flowering.  In general, 1-2 inches of rain within a week or two of flowering will provide a favorable environment for sclerotia germination and subsequent spore formation.  Moderate temperatures and long dew periods (or rain) during bloom will favor infection and disease development. 

                Risk Map.  Risk map are generated every three days by analyzing weather variables from NDAWN weather stations throughout the state.  When favorable environments exist for disease development, a ‘risk’ will be reported on the risk map.  Two words of caution: First, canola is only at risk in flowering so the risk map is only applicable to your field during (or possibly immediately prior) to bloom.   Secondly, disease development is driven by a combination of environmental conditions and availability of apothecia in the field.  This means the risk could be higher/lower than estimated depending on prior history of Sclerotinia problems and crop rotations.  To account for this, more accurate estimation of the risk for a particular field, use the “Risk Calculator” that is available at the same web site. 

                The risk map can be found at www.ag.ndsu.edu/sclerotinia or through the northern canola growers association website. Dr. Luis del Rio can be contacted directly at luis.delrio-mendoza@ndsu.edu

 

Sam Markell

Extension Plant Pathologist

 

Luis del Rio

Canola Pathologist

 

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Wheat Disease Update (07/03/13)

Risk of tan spot continues in some NDAWN locations in the northern tier of counties. However, the risk of FHB has diminished, due to warmer temperatures and dry conditions occurring now and predicted for the next few days.

Wheat Disease Update

Risk of tan spot continues in some NDAWN locations in the northern tier of counties.  However, the risk of FHB has diminished, due to warmer temperatures and dry conditions occurring now and predicted for the next few days.  Wheat is at many different growth stages across the state, with early planted spring wheat headed out, but other fields in flag leaf stage.  Continued monitoring of the NDSU forecasting site is warranted, as scattered thunderstorms can change disease risk rapidly in a given area, and crop stages are variable, with many fields still approaching heading to flowering.

 

Sam Markell

Extension Plant Pathologist

 

Marcia McMullen
Professor Emeritus, Cereal Crops

 

 

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Impacts Of Flooding/Waterlogging On Crop Development (07/03/13)

This article is a rework of an article I wrote a couple of years ago. I also addressed this topic briefly earlier this season. Nevertheless, with the extensive flooding/ponding this past week, I have decided to provide this information again.

Impacts Of Flooding/Waterlogging On Crop Development

This article is a rework of an article I wrote a couple of years ago. I also addressed this topic briefly earlier this season. Nevertheless, with the extensive flooding/ponding this past week, I have decided to provide this information again.

Waterlogging (flooded/ponded/saturated soils) affects a number of biological and chemical processes in plants and soils that can impact crop growth in both the short and long term.  The primary cause of waterlogging in crop plants is oxygen deprivation or anoxia as excess water itself does not react chemically with the plant.  Plants need oxygen for cell division, growth and the uptake and transport of nutrients.  Since oxygen diffuses through undisturbed water much more slowly than a well-drained soil, oxygen requirements rapidly exceed that which is available when soils are saturated.  The rate of oxygen depletion in a saturated soil is impacted by temperature and the rate of biological activity in the soil.  Faster oxygen depletion occurs when temperatures are higher and when soils are actively metabolizing organic matter.

The relatively warm weather this past week has accentuated the adverse effects of waterlogging on any emerged crops.  Generally, the oxygen level in a saturated soil reaches the point that is harmful to plant growth after about 48-96 hours. In an effort to survive, tissues growing under reduced oxygen levels use alternate metabolic pathways that produce by-products, some of which are toxic at elevated levels.  Germinating seeds/emerging seedlings are very sensitive to waterlogging as their level of metabolism is high. Late planted crops look much worse than earlier planted crops after the most recent rain events. Crops like small grains and corn tend ransom.Waterlogging_impacts_corn_and_soybean_2013.pngto be more sensitive to waterlogging when their growing point is still below the surface of the soil (before the 5-6 leaf stage). Fortunately, the early planted corn and small grains are beyond these most sensitive stages. Young crops can be killed if soils are saturated beyond 48 hours when soil temperatures exceed 65 degrees.

Crops can differ in their tolerance to waterlogging.  Although I was not able to find definitive information on the relative tolerance of crops to waterlogging, data from differing sources suggest a possible ranking of waterlogging tolerance as follows (most tolerant to most susceptible): rice, soybean, oats, wheat, corn, barley, canola, peas, dry beans and lentils.  Growth stage and variety can impact this ranking. This was a list I compiled a few years ago. Based on our experience this past week, it is pretty obvious that soybean was much more sensitive to the ponding events in one our research sites (see image 1), than either corn or wheat; perhaps because the soybean plants were shorter and had less access to oxygen.

Waterlogged conditions also reduce root growth and can predispose the plant to root rots, so the ultimate effect of excess moisture may not be known until late in the season. It is common to observe plants that have experienced waterlogging to be especially sensitive to hot temperatures and to display nitrogen and phosphorus deficiencies later in the season due to restricted root development.  Yield losses can occur even if these obvious visible symptoms are not observed.

Waterlogging can also indirectly impact cereal growth by affecting the availability of nitrogen in the soil. Excessive water can leach nitrate nitrogen beyond the rooting zone of the developing plant, particularly in well-drained lighter textured soils. In heavier soils, nitrate nitrogen can be lost through denitrification. The amount of loss depends on the amount of nitrate in the soil (most fertilizer applied N is probably in the nitrate form now), soil temperature, and the length of time that the soil is saturated. Research conducted in other states found losses from denitrification between 1 and 5% for each day that the soil remains saturated. Corn is still young enough in its development that you may consider side-dressing with some additional nitrogen if your appears to have survived the deluge and starts to show some N deficiency symptoms. Additions of N to small grains that are in the boot stage or later will not be responsive to additional N as far as yield is concerned, but additional N may have a beneficial effect on protein.

 

Joel Ransom

Extension Agronomist for Cereal Crops

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Cover Crops (07/03/13)

Excessive rainfall and regional local flooding has resulted in many fields that have not been planted with the intended crop.

Cover Crops

Excessive rainfall and regional local flooding has resulted in many fields that have not been planted with the intended crop. Producers may want to explore the benefits of planting a cover crop. Some cover crops have the ability to fix nitrogen. Other potential benefits of a cover crop growing in the field include: build organic matter, suppress weeds, reduce water and wind erosion, utilize some of the excess moisture and/or improve soil quality during the remainder of the growing season. From a biological stand point it is important to have green vegetation growing on fields. These different cover crop benefits may help increase the yield potential of the subsequent main crops. 

The cover crop to be used will depend greatly on the main objective. If nitrogen fixation is the main factor a legume needs to be used. The seed cost of legumes tends to be a little higher than a non-legume small grain.

In areas where the salt concentration in the top soil is relatively high kandel.radish_in_cover_crop_cocktail.pngproducers will want to consider types of crops with more tolerance to salinity. For instance barley would be more tolerant to salt when compared to some of the legume crops. Salt tolerant alfalfa or grass species might also be considered. However, if the salt concentration is too high even the so called salt tolerant crops may not establish.

If fertilizer for the main crop was already applied a brassica or grass (small grain), or brassica and grass mix can be utilized. These crops can scavenge residual N or pre-plant applied nutrients from the soil. When the cover crop is incorporated into the soil at the end of the season some of the nutrients will be availability for the subsequent main crop.

Cover crop selection and management should focus on maximizing both above and below-ground biomass and encouraging nutrient cycling.  Selection of a cover crop can include a “cocktail mixture” of various crops and may include turnips, radishes, sugarbeets, sunflower, legumes, small grains, sorghum or other grains.  These cocktail mixtures can be used as cover crop or for forage or grazing.  If acreage is reported as ‘Prevent Plant,’ haying or grazing of the cover crops may not occur until November first. Cover crop plant guides are available from NRCS with information about rye, clover, brassica species, pea, and sorghum.

One of the challenges of mid-summer seeding is sufficient soil moisture or timeliness of rainfall after seeding for germination of the cover crop.  Drilling seed will provide better seed to soil contact than broadcasted seeding followed by a harrowing.

                Resources:

                Prevented Planting Options.

                Cover Crop Chart (Info about various cover crops).

                North Dakota Report: Cover crops as a source of nitrogen for bioenergy crops, forage for hay and

                fall grazing, salinity management, and prevented planting.

 

Hans Kandel

Extension Agronomist Broadleaf Crops

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Protect Our Pollinators When Using Pesticides (07/03/13)

Agricultural production is in full swing in North Dakota, and flowering field crops or weeds in the field are important food sources of many species of pollinators, including honey bees and native bees.

Protect Our Pollinators When Using Pesticides

Agricultural production is in full swing in North Dakota, and flowering field knodel.honey_bee_foraging.pngcrops or weeds in the field are important food sources of many species of pollinators, including honey bees and native bees. Bees are attracted to blooming field crops, such as canola and sunflowers, and even weeds, such as dandelions, wild mustard, white clover and goldenrod, in the field for nectar and/or pollen. Remember if you need to spray a flowering crop with insecticide or any other pesticide, please read, understand and follow the label and protect our pollinators against pesticide poisoning or spray drift. North Dakota leads the nation in honey production and our honey bees are a valuable and needed resource! The value of bee pollination is estimated at 14.6 billion dollars in the United States. With the reduction in number of domestic and wild bee colonies due to colony collapse disorder and other diseases, the value of honeybees and native bees for pollination has increased. This increases the importance of protecting bees from pesticide poisoning. Let’s try to avoid any pollinator kills like the example below.

Last week, the EPA notified the Office of Pest Management Policy regarding a large bumble bee kill in Oregon involving a landscaper using an insecticide (Safari, IRAC Group 4A, neonicotinoids) to control aphids in linden trees at a Target parking lot. EPA has been notified that as of last night (8 pm ET), the State of Oregon has issued a 180 day “don’t use” moratorium on the product. The investigation is ongoing. This event indicates a need to remind users of pesticides about the absolute importance of reading and following the label – and to pay particular attention to WARNINGS. While this was not a result of an agricultural application and was an urban use, the EPA has asked if OPMP can work thru the land grant system to get the word out through extension and education offices to reinforce this very important message to the agricultural community. (Source:  David Epstein, USDA Office of Pest Management Policy)

Use of any pesticide in any way that is not consistent with label directions and precautions is illegal. It may also be ineffective and dangerous. The environmental hazard section of labels may include specific restrictions that protect bees. Language that describe bee pesticide restrictions are while “actively visiting (foraging in field)” and “visiting (flying through a field).”

Bees are actively foraging when there is daylight and temperatures are above 60 F. Because bees forage up to two and half miles or more from their hive, all beekeepers within two to three miles of the area to be treated with insecticide should be notified several days before the insecticide is to be applied. The names of beekeepers can be obtained by going to the North Dakota Department of Agriculture’s bee website.

The basic steps in reducing pesticide risks for pollinators are:

  • Know and communicate with beekeepers about hive locations.
  • Use economic thresholds and other IPM strategies. Economic thresholds ensure that pesticides are used only when crop losses prevented by pesticide use are greater than the cost of the pesticide and the application.
  • Use pesticides with low toxicity and low residual to bees. For example, avoid using dusts or wettable powder insecticide formulations because they generally are more toxic to bees.
  • Evening or early morning applications are the least harmful to bees, because fewer bees are foraging.

Never apply pesticides outdoors on a windy day (winds higher than 10 mph) which could cause spray drift problems.

 

Janet J. Knodel

Extension Entomologist

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Wheat Midge Levels Dropped To Record Lows For 2013 (07/03/13)

Soil samples collected by the NDSU Extension Ag Agents in North Dakota indicated low levels of overwintering wheat midge larvae (cocoons) for the 2013 season. With the majority of soil samples statewide being low risk for wheat midge infestation, minimal insecticides should be needed for controlling wheat midge in most of the state in 2013.

Wheat Midge Levels Dropped To Record Lows For 2013

Soil samples collected by the NDSU Extension Ag Agents in North Dakota indicated low levels of overwintering wheat midge larvae (cocoons) for the 2013 season. With the majority of soil samples statewide being low risk for wheat midge infestation, minimal insecticides should be needed for controlling wheat midge in most of the state in 2013. However, we still recommend field scouting for wheat midge even with low populations to ensure that wheat midge will not reduce wheat yields, grade and quality.knodel.wheat_midge_larval_survey.png

A total of 199 soil samples were collected from 21 counties to estimate the regional risk for wheat midge. The distribution of wheat midge in the 2013 forecast map is based on unparasitized cocoons found in the soil samples collected in the fall of 2012. The southeastern area of Mountrail County and southeastern area of Ward County are the only two pockets of moderate risk that need to be monitored closely for wheat midge. The decrease in wheat midge can be attributed to the drought, which may have prevented wheat midge larvae from dropping out of the wheat heads in late summer. Moisture (rain or dew) triggers mature larvae to drop to the soil surface, where they burrow in and form overwintering cocoons. If larvae did drop out of the head, they encountered hard, dry soils, which may have prevented them from moving down into the soil and exposed them to predators. This would decrease the overall number of overwintering wheat midge cocoons as indicated by the results of the wheat midge soil survey.

There were no areas where the cocoon populations exceeded 1,200 per square meter, which would have indicated a high risk for a wheat midge infestation. Areas of moderate risk (populations of 501 to 1,200 midge larvae per square meter) accounted for only 1 percent of the samples (southeastern Mountrail County and southeastern Ward County). Field monitoring is recommended for areas at moderate risk. In most of the remaining counties, 27 percent of the samples had one to 500 larvae per square meter (low risk) and 72 percent had zero larvae per square meter.

Although most areas of North Dakota have low levels of midge larvae (one to 500 midge larvae per square meter), it is always good practice to scout fields to determine if an action threshold population level exists, especially since weather conditions are favoring wheat midge emergence and development in 2013. Weather conditions prior to and during adult knodel.accumulated_midge_degree_days.pngwheat midge emergence will play an important role in determining the amount of economic damage. So far, we have had high soil moisture in late June and warm temperatures, which will favor midge development and localized outbreaks.

A degree day model is a good predictor of wheat midge emergence and can help time field scouting. It is available on the NDSU North Dakota Agricultural Weather Network (NDAWN) website, select ‘Applications,’ ‘Wheat’ and then ‘Midge Degree Days’. The current DD map indicates that wheat midge emergence will be starting soon (1,300 – 1,600 growing degree days) in the northern tier of counties.

Scouting should be conducted at night when temperatures are greater than 59 degrees and winds are calm (less than 6 miles per hour) during the heading to early flowering crop stages. The critical spray timing is from late heading to early flowering when wheat is most susceptible to wheat midge infestation.

With the high price of wheat this year, the action threshold for durum wheat is recommended also for spring wheat - one midge per seven to eight heads. Organophosphate (OP) insecticides, such as chlorpyrifos, are recommended over pyrethroids since OPs can kill the eggs, larvae and adults. Most insecticides labeled for wheat midge control can be tank-mixed with a fungicide if scab is also a potential problem. A late insecticide application should be avoided to minimize negative impacts on the parasitoids that naturally control wheat midge. A listing of insecticides registered for wheat midge control in ND is available from the ND Field Crop Insect Management Guide 2013, E1143, NDSU Extension Service. For more information, consult the IPM of the Wheat Midge in North Dakota, E1330 extension publication. 

The wheat midge survey is supported by the North Dakota Wheat Commission, and soil samples are collected by the Ag County Extension Agents of the NDSU Extension Service.

 

Janet J. Knodel

Extension Entomologist

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Soybean Aphids Slowly Increasing (07/03/13)

Our IPM Scouts are picking up low numbers of soybean aphids (< 80 aphids per plant) in Cass and Richland Counties. Soybean aphids are typically concentrated in the upper trifoliates until flowering.

Soybean Aphids Slowly Increasing

Our IPM Scouts are picking up low numbers of soybean aphids (< 80 aphids per plant) in Cass and Richland Counties. Soybean aphids are typically concentrated in the upper trifoliates until flowering.

Avoid early insecticide applications to allow natural enemies to reduce aphid populations, to reduce secondary insect pest outbreaks, such as spider mites, and to reduce the risk of soybean aphids developing insecticide resistance.

If you spray early, you kill the natural enemies of soybean aphids and insecticide residual is too short to provide protection throughout the growing season. So, soybean aphid will most likely re-infest the field later in the season and a second insecticide application will be needed.

Take action when the aphid population averages 250 aphids per plants on 80 percent of more of the plants, and an increasing aphid population from R1 (beginning of bloom) through R5 (beginning seed) stage soybeans. Positive yield responses have been recorded when insecticides are applied at the Economic Threshold Level.

Janet J. Knodel

Extension Entomologist

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Scout For Barley Thrips (07/03/13)

Barley thrips have been found in Ward, Cass, and Linton Counties and central ND near Rugby. Some fields have high numbers of barley thrips (>5 thrips per stem) while other fields are still low in numbers (0-3 thrips per stem).

Scout For Barley Thrips

Barley thrips have been found in Ward, Cass, and Linton Counties and central ND near Rugby. Some fields have high numbers of barley thrips (>5 thrips per stem) while other fields are still low in numbers (0-3 thrips per stem).  Typically, hot dry weather conditions favor barley thrips development that may result in crop losses.knodel.beauzay.adult_barley_thrips.png

Barley thrips are small dark brown to black insects about 1-2 mm long. Females have feathery wings while males are wingless. Immature larvae are wingless, pale yellow, white or green with red eyespots. Larvae are difficult to see due to their light, almost transparent color and extremely small size. Adult and immature thrips have a long, narrow body shape.

Female thrips overwinter as adults in debris in fields and shelterbelts. Thrips emerge in late May and early June and move into winter wheat/rye and eventually to early seeded barley (preferred host). Occasionally, barley thrips will feed on hard red spring wheat and durum as well. There is one generation per year.

Adult and immature thrips cause damage by feeding on succulent plant tissues (puncturing plant cells and sucking out the contents). Feeding injury symptoms are a whitened or bleached appearance with gooseneck-shaped stems and heads under severe pressures. Intensive feeding at the beginning of head formation produces small, shriveled grains. Often there is no seed development at the top and bottom of the head and intermediate grains are shriveled. When thrips feeding is severe on the flag leaf, kernels do not fill properly and seed weight is reduced.knodel.barley_thrips_injury-bleached_stem_and_head.png

Scout for barley thrips from flag leaf to heading. Barley thrips can be found by unrolling the flag leaf away from the stem. Remember, populations will probably be higher at the field edges.

Economic Threshold: Cost of control ÷ Expected value per bushel ($)

0.4

 Using the cost of control as $8-12/acres (insecticide + application cost) and $4.50/bu of barley (low price range for feed barley), the economic threshold is 5-7 barley thrips per stem before the crop is fully headed. Using the cost of control as $8-12/acres (insecticide + application cost) and $6.00/bu of barley (high price range for malting barley), the economic threshold is 3-5 barley thrips per stem before the crop is fully headed.

One thrips per stem results in a 0.4 bushel per acre loss! Once the barley heads the insect damage is done and NO insecticide treatment is advised. The only registered insecticide for barley thrips control in North Dakota is methyl parathion 4 EC at 0.5-1.5 pt per acre (do not enter treated fields within 48 hours after application). EPA is phasing out methyl parathion with no product sale after 8/31/2013 with no product use after 12/31/2013. Other insecticides approved for use on barley but do NOT have barley thrips listed on the label include: Warrior II (lambda-cyhalothrin), Baythroid (beta-cyfluthrin), malathion, Lannate (methomyl), and Penncap-M (methyl parathion). It is legal to apply an insecticide if it is labeled for use in the crop; however, if the target pest is not listed for that crop, efficacy is not implied by the manufacturer and growers who choose to use the product assume their own liability for any unsatisfactory performance. We are testing a new insecticide against barley thrips this year. We definitely need a replacement insecticide for this economic insect pest in barley.

Although many growers want to wait to tank-mix the insecticide with a fungicide for scab control at Feekes 10.5 (head fully emerged), NDSU Extension Entomology does NOT recommend waiting for the insecticide application to coincide with the optimal timing of a fungicide application for scab control. This is too late for effective barley thrips control and the damage/yield loss is already done by then.

Please be aware of any bee hives located near your barley fields as insecticides, especially methyl parathion, are extremely toxic to honey bees. Notify your local beekeepers if you intend to spray, so the bee hive can be moved to another area before spraying. A list of honey beekeepers in North Dakota is available on the North Dakota Department of Agriculture website.

Janet J. Knodel

Extension Entomologist

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Weather and Crop Phenology Maps (06/27/13)

Maps detailing corn accumulated daily growing days, percent normal rainfall, departure from normal average air temperature, and accumulated wheat growing degree days.

corn

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Temperature.png

Wheat.png

F. Adnan Akyuz, Ph.D.

Assistant Professor of Climatology

North Dakota State Climatologist

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