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ISSUE 8  June 21, 2001

 

PREVENTED PLANTING GUIDELINES-CLARIFICATION

In the June 7 issue of the NDSU Crop and Pest Report No. 6, I indicated that cover crops on prevented planting acres can be hayed and grazed "only" by the producer or farm operator. New information from the Risk Management Agency-USDA indicates that the cover crop cut for hay can be sold and the cover crops can also be leased for grazing. Again it must be stressed that the prevented planting acreage be certified and verified that the intended cash crop could not be planted because of wet saturated soil conditions at a certain date before cover crops are sown for whatever use. All producers are encouraged to check with their local crop insurance agent and the FSA office to insure that they are in total compliance before planting cover crops.

Duane R. Berglund
Extension Agronomist
dberglun@ndsuext.nodak.edu

 

WILL YOUR CORN BE KNEE-HIGH BY THE FOURTH OF JULY?

Early planted corn should be ahead of the expected growth for the season this year. Corn planted within the first week of May that has not had any replanting problems should be looking good and well above knee-high. Low insect pressure this year in corn has helped in preserving crop health (even on late-planted and replanted fields) and reports from the Midwest suggest low levels of corn borer are being seen.

From germination to the four-leaf stage, corn normally is at risk from sod webworms, slugs, stalk borers, true armyworms, billbugs, flea beetles and corn root aphids on the plant with wireworms, white grubs, black cutworms, seed corn beetles and seed corn maggots still having the potential for a go at the root of the seedlings. Once into corn's fifth-leaf stage, the insects to watch for through silking include: European corn borer, corn rootworm, true armyworm, fall army worm with still some potential damage from stalk borer, sod webworm, black cutworm, white grub and wireworm if numbers increase beyond what we have seen during spring.

Besides insects, other reasons to carefully monitor your corn fields from knee-high to tasseling include:

Any severe wilting or death of plants may be due to lightning (usually a circular pattern in the field) or with dieback of the leaves (wilting, drying up of leaf tissue beginning at the leaf tips) the problem may be molybdenum deficiency (younger leaves also twist) .

Corn plants that become discolored may be revealing some production problems such as yellowing of the plants (beginning with the lower leaves) due to nitrogen deficiency, drought conditions or ponded conditions (standing water can produce nitrogen deficiency). Yellowing of leaves beginning at the tips may harold potassium deficiency. Purpling or reddening of leaves from the tip back and affecting the lower leaves first may show phosphorus deficiency. Yellow to white interveinal striping on corn leaves may just be genetic or may be magnesium deficiency or if the leaves have white spots that graduate to striping, boron may be deficient. Pale green to white striping shows iron deficiency (some is being seen this year due to the ample moisture) or with this symptom along with the lower leaves very dark (almost olive) colored, magnesium deficiency may be a problem.

Stunting or very fine chlorotic stripes in the whorl leaves will suggest that the plants be checked for maize dwarf mosaic or maize dwarf chlorotic disease. Individual stunted, tillered plants with twisting and rolled leaves probably indicates isolated plants with crazy top fungal disease (possible this year due to the very wet spring).

Plants that have top leaves fused so leaves have difficulty emerging ("rat-tailed" plants) may have been exposed to some growth regulator herbicide or may be mechanically injured during a cultivation or sprayer pass. Corn leaves that are very tightly rolled and very erect show symptoms of growth regulator injury or can simply be exhibiting drought stress. Lodged plants or plants showing "sledrunner" or "goosenecked" shapes may have problems with corn rootworm larvae, corn nematode feeding (usually not a problem in ND), an earlier herbicide damage residual symptom (from a dinitroaniline or a growth regulator herbicide), simple mechanical injury or from hot, dry weather with winds which prevents normal brace root development.

Corn stalks that show a brown, soft rot on the lower internode with some stalks twisting and lodging will probably be pythium stalk rot or bacterial stalk rot, or heavy European corn borer or stalk borer damage which has weakened the stalks.

Fused brace roots, as they emerge on the plant, will be due to growth regulator herbicide injury from an application which was applied after the corn was taller than eight inches.

Appearance of soft, glistening white galls that soon become black and dusty on corn stalks, leaves and later the ear or tassel will be from common smut (a possibility this year, from the early, wet spring affect on the early planted corn).

Ragged plant tissue due to shredding or tearing of leaves in fields may be due to hail damage, wind damage, Western corn rootworm beetles (the green upper layer of leaf tissue is stripped) or corn blotch leafminers (window effect, interior leaf is eaten out). Whole leaf or large chunks of leaf removed may be due to armyworms, grasshoppers, fall armyworms or browsing livestock or wildlife. Holes bored into the stalks are due to European corn borers or stalk borers.

General lesions, spots or color streaks initially on small areas can be Northern corn leaf spot, gray leaf spot, holcus bacterial spot, fungal leaf spots, Stewart's bacterial leaf blight, physoderma brown spot, or herbicide (contact) damage. Late-applied granular fertilizers or even air pollution can also cause spotting. Anthracnose leaf blight, bacterial leaf stripe, eyespot and common corn rust also cause lesions on plants that are very distinct in color and shape.

Carefully scout your corn fields through tasseling to determine production needs in order to optimize your corn yields.

 

WILL A NIP OF NITROGEN DO NICELY?

Many are now considering side-dressing nitrogen onto corn. The tillage system and fertilizer source affect proper placement of fertilizer nitrogen. With anhydrous ammonia, the most satisfactory way to apply is by injection in a band. Recent questions on how to place shanks for anhydrous injection and need for additional nitrogen at this time have been asked. Soil testing over in Minnesota has shown that some of the nitrogen has not been lost even with the multiple rains; however, other areas have experienced some denitrification or leaching and some cornfields have not had any fertilizer spread or injected this spring. If corn plants remain yellow after two to three days of good sunshine, you may need to check on nutrient needs. Research data on anhydrous injection has shown that an ammonia ban between every other pair of rows is generally satisfactory compared to injecting in the middle of every interrow. This saves on fuel for pulling the injector shanks through the field and limits any potential sidewall compaction in soils not perfectly dry throughout the injection surface. Rate of anhydrous (82% nitrogen) used will depend on needs for each field and residual nitrogen available. Remember with our early hybrids yield is limited, especially if planted late. Optimally, charts for the western Plains show a need for 1.3 pounds or so for each bushel of corn while more may be optimal toward the east. Carefully consider your needs at this point based on expected yield. Corn starts absorbing greater amounts of nutrients, including nitrogen, from the V6 to the V12 stages and beyond. Moisture or nutrient deficiencies will be readily revealed at the V12 to V13 stage when the ear is determining the potential number of seeds down the ear rows. Many of the corn roots are not extended much underground under the furrows due to saturated soils limiting root growth thus anhydrous shanks placed properly should not cut through and damage roots or contribute much to root burn. If injection can occur before the V8 stage in corn, less root pruning will occur. Depending on needs, only 20-100 pounds of anhydrous may be needed as a side-dress; hopefully, if some early nutrient applications occurred, the lower side-dress amounts will be all that is needed. Also remember that some nitrogen may still be available from earlier applications. Any ammonia that had been applied preplant diagonally may have corn showing a rolling color appearance across the field due only to the corn roots reaching the nitrogen bands at different times so wait for sunshine and heat units and possibly a quick soil test to confirm any additional side-dressing needed prior to corn reaching the critical V6 to V12 nutrient use stages.

 

SOYBEAN DIAGNOSTICS FOR VE TO V4

Good trouble-shooting diagnostics will help you manage your soybeans this year and will help in determining future needs and rotations. First, identify the growth stage of the crop. This will narrow down the types of problems that can occur in the crop. Next, determine if the problem you are seeing in the field occurred only one time or if it is continuous. Third, note the symptoms you are seeing on the soybeans. And fourth, if you cannot satisfactorily diagnose the problems in your soybeans take needed samples to the diagnostic lab, soil testing lab or germination lab here on campus at NDSU. Be sure to include information about the crop problem with the sample including weather history, field identification, cropping history, soil test results (if available), fertilizer and liming practices, pesticide applications, tillage and planting methods used on the field and any other pertinent management information.

Read the general symptoms and then select the affected soybean plant part to compare possible diagnostics:

Soybean plants emerged but are dead, dying or stunted in isolated or widespread areas of the field or the plants show the listed damage.

A. Roots

1. dry lesions on the roots or on the stem which is below the soil surface · soil-borne fungi or bacteria or disease carried on seed (Fusarium, Phytophthora, Pythium or Rhizoctonia)

2. lower stem and taproot are dark and rotted · charcoal rot · Phytophora rot

3. stubby, secondary roots on the plant appeared burned-off · nematodes ·fertilizer salt burn ·soil herbicide injury · soil compaction

4. roots or lower stem is chewed · wireworms · white grubs

5. little or no nodule development · molybdenum deficiency ·nitrogen deficiency ·soybean cyst nematode (not prevalent in ND) ·low soil pH ·calcium deficiency ·soil compaction

B. Stems

1. tunneling of stem at or near the soil line · lesser cornstalk borer · wireworms

2. stem girdled above the soil line · three-cornered alfalfa hopper ·cutworms

3. stem girdled at the soil line · lesser cornstalk borer · cutworms · high soil temperature · Rhizoctonia · Fusarium

4. stem girdled below the soil line · cutworms · lesser cornstalk borer · wireworms

5. stem snaps off near soil line · three-cornered alfalfa hopper · lesser cornstalk borer · soil-applied herbicide

6. upper part of the plant chewed or cut · wildlife or livestock feeding ·cutworms

7. lower stem has cracks ·excessive rainfall · herbicide injury

8. lower stem is discolored · Phytophthora ·Rhizoctonia

C. Leaves

1. leaves discolored, dead or dropped · thrips (silvering of upper leaf surface) · herbicide injury ·soybean cyst nematode · spider mites

2. leaves wilted or dropping · lesser cornstalk borer · frost damage · three-cornered alfalfa hopper · wireworms ·white grubs

3. leaves wilted or dropped with plants dead in a circular pattern in the field · lightning

4. leaves torn with obvious physical damage · hail damage · grasshoppers · green cloverworm larvae · armyworms

5. leaves show spots with later necrotic areas · brown spot disease · bacterial pustule · bacterial blight · downy mildew (usually has fungal growth under the leaf surface) · powdery mildew (white powdery patches)

6. leaves appear sandblasted, speckled or burned and the plants may be stunted · thrips · spider mites · bean leaf beetle · herbicide injury · sunburn · air pollution

7. interveinal yellowing or along leaf margins · potassium deficiency · potato leaf hopper · rhizobia-induced chlorosis · soybean cyst nematode · herbicide injury · boron toxicity · manganese deficiency · iron chlorosis · magnesium deficiency · sulfur deficiency · nitrogen deficiency · molybdenum deficiency · water damage · wheat straw allelopathy · aluminum toxicity · low pH · zinc deficiency

8. leaves crinkled and possibly plants are stunted · herbicide injury · various plant viruses · manganese toxicity · boron toxicity

 

CORN AND SOYBEANS IN THE NEWS

Next year you won't be seeing the flat tech fee as a separate line item on your Roundup-Ready corn and soybeans. Monsanto has announced that the tech fee will be incorporated into the general seed cost and has made arrangements with other seed companies that use the technology. A similar fee across companies using the Monsanto technology for the transgenic seed will be charged to each company. On the transgenic line, the Starlink controversy appears to be just that rather than a confirmed allergy situation. Those individuals that complained about an allergic reaction and were tested through the CDC (centers for disease control) were found to not be allergic to the Cry9C. USDA continues, however, to negociate with seed companies affected by possible contamination of seed supplies. The "Chemical Market Reporter" has made a prediction that by 2010 insecticide use will decrease by 30% as more ingenuous transgenic crops are accepted. The herbicide market transfer to transgenics will be at 50%. The fungicide market may remain static unless new transgenics with disease prevention make it through to the market place. The current $700 million market for transgenic traits is expected to increase to $20 billion over the next ten years. In 1999, the plant biotech market amounted to only 3-4% worldwide. This may put traditional agrochemical business at risk as some of these companies have herbicides account for more than 50% of some total revenues. On another note, a recent article about Adventis SA and their partner Schering AG are now possibly considering a valuation for the Aventis Crop Science branch.

Denise McWilliams
Extension Crop Production Specialist
dmcwilli@ndsuext.nodak.edu

 

APPROACHING CRUCIAL SMALL GRAIN STAGES

Small grain crops around North Dakota are approaching critical development stages. While developmental covers a wide range of stages much of the crop, particularly the early planted portion, is jointing or early boot.

Two pests, scab and wheat midge, become problems during heading and flowering. From heading to flowering is when wheat is susceptible to the wheat midge. Once flowering is complete wheat midge no longer attack the developing heads. Wheat midge is not a problem on barley. Flowering is also when wheat is most susceptible to scab infection. Barley flowers in the boot and is most susceptible to scab once heading occurs. If current weather conditions persist following flowering the potential for scab will be high.

Monitoring heading in barley and wheat is extremely critical for effective control of either pest. The time required for both wheat and barley to go from mid boot to head emergence can range from three to five days. Obviously environmental conditions have a large impact on the developmental rate. Warm sunny days favor rapid development.

Growing degree days (GDD) can be used to predict when heading will occur (See May 20, 1999 Pest Report for an in-depth discussion on wheat GDD). Both wheat and barley will require about 140 GDD to go from mid boot to heading. Wheat will require about 270 GDD to go from mid boot to completion of flowering. The NDSU NDAWN system at  http://www.ext.nodak.edu/weather/ndawn/listgdd.shtml  provides GDD for several regions around the state.

Even though the past couple weeks have been quite cool early planted crops are developing rapidly. The important point is, if you plan on controlling wheat midge or scab with a pesticide application, timing application with development is crucial to success. Knowing the stage of a crop now and when it will head or flower is useful when planning for the pesticide application.

Control of scab with a fungicide depends on correct timing of the application. The optimum time for fungicide application on wheat is following heading when flowering has started in wheat and after heading is complete in barley. Fungicides only provide protection against scab on tissue that receive a direct application. Even though fungicides like Tilt and Folicur are systemic they do not move throughout the plant but remain in a localized area near the site of absorption. Applications before heading is complete in both wheat and barley will compromise control of scab.

Michael D. Peel
Small Grains Extension Agronomist
mpeel@ndsuext.nodak.edu


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