Spring planting conditions for corn varied from field to field and even within fields. Farmers planted into soils that were too wet and later the same day planted into other fields where soils were so dry that a miracle would be needed for emergence to occur (a 1.5 inch rain also would do nicely).

Many pivot irrigation systems were used to help insure adequate stands and to activate herbicides. If timely rains do not occur on gravity-irrigated or non-irrigated fields, corn stands may be marginal. In addition, insect feeding, early-season frost or hail also may reduce plant populations early in the season.

To decide whether early season replanting of corn is beneficial, consider the following:

1. Determine the remaining plant population. Calculate the plant population in several "random" areas of the field to help estimate the potential yield assuming every thing else goes right during the growing season. Random does not mean that you go to the best area of the field and start counting, ignoring the bad areas. Likewise it does not mean that you sample only the bad areas. Sample them both; the idea is to characterize the field as well as you can.

   To estimate stands, count plants in at least three places in affected fields. Count plants in an area equal to at least 1/100 of an acre. Use Table 1 to determine the length of row necessary to achieve 1/100 of an acre. Divide that number by the number of sampling locations to determine how many feet of plants to count in each sampling location. (You also could sample 10 areas within a field, each representing 1/1000 of an acre.) The total linear feet of row necessary to end up with 1/100th of an acre in different row spacings is shown in Table 1. Now determine why the plants are missing in the "skip" areas. Was it because of dry soil and the seed will germinate and grow with moisture or was it due to an insect, disease, frost, hail, etc? If plants are missing due to dry soil conditions and the seed is still viable and will emerge given enough moisture, read the following in No. 2. If skips are not due to dry soil, proceed to No. 3.

2. Consider plant emergence uniformity.
   • If uneven emergence is row to row, that is, most rows are emerged but some are not, replanting will probably not increase yield.
   • If the delay in emergence is less than two weeks between the early and late emerging plants, replanting may increase yields, but by only 5% or less. This is probably not economical.
   • If one-half or more of the plants in the stand emerge three weeks later than the initial plant emergence, replanting may increase yields by 10% or so. If this is the situation, go to No. 5.
   • If the seed or plant is missing due to insects, hail, etc. and the seed is not viable and will not emerge, read No. 3.

3. Calculate expected yield from the remaining original stand. The original planting date plus the remaining plant population is used to estimate the yield potential of the field as it stands. Table 2 summarizes planting date and plant population relationships. Use this table to estimate expected yield from the original stand using long-term yield averages from the same field. For example, if the original planting date was April 30, a population of 30,000 seeds/acre would be expected to provide maximum yield, based on Table 2. If the population is only 20,000 plants/acre because of poor emergence, yield potential is still 92%. If the long-term yield of this field was 200 bushels/acre, the estimated yield is 184 bushels/acre. If several 4- to 6-foot gaps occur within the row, yields will be reduced an additional 5% relative to a uniform stand. Likewise, stand gaps of 16 to 33 inches will penalize yields by 2%.

4. Estimate replant yield. Expected planting date and target plant population are used to estimate the yield potential of the replanted field. Use Table 2 for this too. Planting on May 19 at 30,000 seeds/acre would result in about 91% of maximum yield. Multiply this by the field's long-term yield to obtain the estimated replant yield. If this actually was the situation, and the original crop was planted on April 30 at 30,000 seeds/acre and now had 20,000 plants/acre as in the example in No. 3, there would be no point in replanting. Expected yields are similar, 91% versus 92% of maximum. Remember: there is no guarantee of getting a good stand with replanting.

5. Estimate replanting costs. The cost of replanting a field is often the deciding factor. Costs include tillage, seed, fuel (for tillage and planting), additional pesticides, labor, additional dryer fuel for drying the crop in the fall, etc. Make sure to check with your seed dealer to see what hybrid seed is available and if there is any rebate or price reduction for replant situations.

6. Determine whether the costs of replanting are offset by increased yield from the replant.

Acknowledgments

Since black cutworms do not overwinter in Nebraska, they are dependent on spring weather conditions, primarily prevailing southerly winds, to bring them into our state. Nebraska is on the western edge of the black cutworm's area of influence, and they are rarely found west of the 100th meridian. Because of their cutting habits and the possibility that large numbers can be transported to Nebraska if favorable weather conditions occur, they have the most potential to cause a widespread problem. Light traps and pheromone traps are used to monitor the flight patterns and populations of black cutworms. Remember, the presence of moths in a trap only indicates potential problems and is no guarantee that extensive damage will occur. Trap counts are more useful in alerting growers and consultants as to when to begin scouting efforts.

The last couple of months have been dominated by cool fronts moving in from the north and northwest. This is NOT favorable for black cutworm establishment. Light trap counts have been extremely low up to this time. From here on out, corn planted after the rain delay into heavy residue or fields with winter annuals, or fields planted into spring killed alfalfa (that may attract egg-laying moths) have a slightly higher potential for cutworms. When weeds are destroyed mechanically or by herbicides, the cutworms will feed on the newly emerging corn. Because most cutworm damage occurs in the first two weeks after emergence, growers should be on the lookout.

Cutworms that overwinter as larvae generally prefer to lay eggs in the fall in green vegetation such as small grain stubble, legumes, rye, and pasture. The eggs hatch and the larvae feed on the vegetation present before overwintering. In spring, after the previous crop is removed and the corn emerges, the cutworms will transfer their feeding activity to the corn. Recent experience has been that corn planted into alfalfa that has been killed in the spring has a greater potential for cutworm problems.

Tillage has minimal effect on cutworm populations. If fields are tilled before black cutworm migration, it may limit egg laying in those fields. Cutworms already in the field may suffer some mortality by mechanical action, but there is no guarantee that tillage by itself will eliminate cutworm problems. Many cutworm problems have occurred in fields that have been tilled.

It is extremely rare to experience cutworm problems in continuous corn. Corn stubble is not a preferred egg-laying site. Potential problems in continuous corn may be the result of a previous year's late season flush of weeds, an interseeding of a fall cover crop such as rye, or a flush of winter annuals this spring, which possibly attract egg laying moths.

Managing cutworms in corn

Several options exist for the grower who wants to manage cutworms in corn. Since a vast majority of corn is not affected by cutworms, the most economically sound practice is to scout for cutworm damage as soon as corn emerges and apply a rescue treatment if necessary. Early detection of a problem is essential because most of the cutting occurs within seven days of plant emergence. Generally, a rescue treatment should be considered if 5% or more cutting (an average of one plant or more in a set of 20) is observed and the worms are one inch or less in length.

As we are moving toward more reliance on pre and post emergence herbicides, it is becoming more common to apply a liquid insecticide with the herbicide as an "insurance" treatment. With competition driving down the price of some insecticides, some treatments can be applied for as little as $3 an acre. While this option may be attractive, it will be a money loser in the vast majority of cases. Three dollars an acre to control something that isn't there is still $3 an acre lost. Another unfortunate occurrence of price competition is the overstating of insecticide properties in regard to efficacy or residual activity. In some areas of the state certain insecticides are being touted as providing a 30-day residual. Since most cutworm treatments are surface applied and not incorporated, sunlight, heat and water will begin to break down these chemicals immediately after they are applied. Expect no more than five to seven days of killing activity even under the best of conditions.

Last frost may still be around the corner

During the last 30 days, rainfall and snow have contributed to a broad area of above normal precipitation north and east of a Valentine- O'Neill-Norfolk-Fairbury line. Precipitation totals have been in the range of 100%-120% of normal. A small area east of a line from Yankton, S.D. to Omaha has received 120%-140% of normal precipitation.

On the down side, precipitation continues to be disappointing for western Nebraska. The worst hit area of the state during the last 30 days falls west of a line from Chadron - North Platte - Kearney - Red Cloud. Precipitation totals in this area are 20%-60% of normal. The remainder of the state is 60%-100% of normal.

Severe drought has encroached upon the western Panhandle and the extreme southwestern corner of the state. The remaining western two-thirds of the state is experiencing moderate drought. Conditions in several areas, including Kearney and Red Cloud, make them prime candidates for upgrades to severe drought status.

An active storm track is forecast to continue across the central United States during the next two weeks; however, the best chances for above normal precipitation are in the eastern third of the state. It has become apparent that a sharp delineation continues between areas receiving above normal and below normal precipitation. This is likely to persist during the next two weeks. Models indicate intrusions of cold air with each successive precipitation event. These systems need to be closely monitored for possible freezing temperatures, since below normal temperatures are projected to occur after each of these systems pass through Nebraska. Although the models are not projecting freezing temperatures at this time, the intensity of cold air associated with systems passing through the state recently have been stronger than was initially projected by forecast models.

Producers across the Panhandle, Sandhills, and areas north of I-80 from North Platte to Grand Island are most vulnerable to freezing temperatures during the next two weeks.

Keep a close eye on weather reports and refrain from cultivation activities if the forecast indicates the possibility of lows dropping into the thirties within the next 24 hours. Cultivation will allow air to penetrate beneath the soil surface and increase vulnerability to plant freeze damage. Enough heat is stored in the soil surface (top 4 inches) to protect the infiltration of cold air below the surface if it is not cultivated. Corn seedling growing points are typically below the soil surface until the six-leaf stage. Although freezing temperatures will burn the corn leaves above the surface, the growing point will typically survive in an uncultivated environment.

Depending on how much Gulf of Mexico moisture is tapped by systems moving across the state over the next 14 days, it is entirely possible that some planting delays will occur. At this time, wet field conditions exist in pockets across east central and southeast Nebraska. Models are projecting an average frequency of three to four days between systems, so field drying time may be limited.

Wheat streak mosaic is probably the most threatening disease this season in western and southwestern Nebraska. The extended fall allowed for greater movement of the wheat curl mite and thus greater spread of the virus. We will be doing a wheat survey of the Panhandle next week and should have a better idea of the incidence and severity of that disease at that time. No rust, either leaf or stripe, has been observed in Nebraska at this time. However, both rusts are active in the southern Great Plains, which means we could see rust development within the next two to three weeks. The cool, wet weather has been favorable for stripe rust so growers should scout fields for its presence. Stripe rust was our most predominant and damaging foliar disease last season.

Fortunately, many of the varieties grown in Nebraska appeared to have some level of resistance compared to the varieties Lakin and 2137. We will continue to monitor the progress of rust development in the states to the south of Nebraska. Should they be necessary, there are fungicides available for rust control. They include Tilt (Syngenta), PropiMax EC (Dow AgroSciences) and Stratego (Bayer), which must be applied at or before flag leaf emergence.

Quadris (Syngenta), unlike Tilt, PropiMax and Stratego, can legally be applied up to flowering in Nebraska. With any of these products, a single application is sufficient. Mancozeb, of which there are several product brands, is a contact fungicide that requires two applications to be effective. The first must be made before any infection of the flag leaf to be effective followed by a second treatment in about 10 days.

Generally, fungicide treatment is not needed on dry land production fields in Nebraska, but occasionally it is justified. If rust is detected in mid-May followed by wet weather, the rusts can develop rapidly on susceptible varieties. Know you variety's level of resistance to leaf rust before deciding to make an application and pay attention to the progress of rust in Kansas and the weather forecasts.

Alfalfa weevil scouting This map shows accumulated growing degree days base 48 as of May 6. Most of the state has passed the 350 GDD threshold and scouting should be underway for alfalfa weevils. Keith Jarvi, Extension entomologist at the Northeast REC, reminds producers to not let down their guard. Recent cool weather has slowed insect development and their appearance may be a little delayed in some areas, leading to an unwelcome surprise if scouting stops short. (Map prepared by Al Dutcher, state climatologist, NU School of Natural Resource Sciences.)

Most new varieties have good resistance to wilt pathogens, Phytophthora root rot, and anthracnose. Make sure to select varieties with a high level or good rating for these diseases. Moderate to low ratings will not be sufficient to keep these diseases in check. Always take a careful look at seed company information so that you're sure the scale is not switched around from company to company. For additional information on selecting alfalfa varieties, check the UNL Extension publication, "Selecting Alfalfa Varieties for Nebraska 2002," (EC 02-153).

The main diseases for which alfalfa varieties are rated include wilt pathogens, phytophthora, anthracnose, and stem nematode. Bacterial wilt has been a problem in Nebraska and most varieties have good bacterial wilt resistance. There are different degrees of resistance within varieties classified as bacterial wilt-resistant. Anthracnose is a fungal disease that often occurs in irrigated alfalfa or high moisture conditions. Varieties will vary in anthracnose resistance. Phytophthora root rot can be a significant disease problem. Phytophthora is mostly a problem on poorly drained soils, compacted areas, or high clay content soils. This is often the case in fields with stand establishment problems. Other wilt pathogens and stem nematodes have not been a consistent problem in Nebraska alfalfa fields. Common leafspot, lepto leafspot and blackstem are foliar diseases that cause leaf loss and reduce total alfalfa yield and quality. Varieties will vary in susceptibility to these diseases.

Most alfalfa seed is treated with metalaxyl or mefenoxam, which are active against Phytophthora and Pythium seedling blights. With the current wet weather, these definitely would be good treatments since both of these fungi are favored by high moisture. If you buy untreated seed, consider treating it as a good measure of insurance. If you're planting into a field with a history of stand establishment problems, a seed treatment would be especially beneficial.

Being able to successfully inoculate the seed after planting depends on two things. First, get enough inoculant and place it into the soil where the roots are quickly. Direct sunlight can kill bacteria in the inoculant. Second, get it there under cool, moist conditions. High temperatures also can kill the bacteria, and nodules do not form well when soils are dry.

Inoculating after planting takes much more inoculant than if it had been added to the seed originally. I recommend applying 1.5 lbs of peat inoculant per acre. One good way to get this into the soil is with a drill. You will need to attach this inoculant to some type of carrier, such as pel-lime or killed small grains. Time your drilling to occur just prior to some rain showers, or sprinkler irrigate right after drilling.

Sometimes you might be able to apply inoculant through a broadcast sprayer or the irrigation system. If you use this method, be sure to watch for clogged nozzles and screens. Apply late in the day so sunlight won't harm the bacterial and, as with drilling, rain or irrigation right after the application will increase the chance of success.

Inoculating the seed is your best option, but if it's too late for that, you can still improve the situation by applying inoculant now.

Readers report adjusting practices with RR beans

Nebraska’s plastic pesticide container and crop protection drum recycling program is entering its 11th year, having collected nearly 400 tons of agricultural pesticide containers, said NU Extension Pesticide Coordinator Larry Schulze.

Schulze coordinates the recycling program with the help of extension educators across the state. The program, which has earned national attention and been used as a model by other states, recycles the containers into products including shipping pallets, drain tile, dimension lumber and parking lot tire bumpers.

The program accepts pressure-rinsed or triple-rinsed 1- and 2.5-gallon plastic pesticide containers. They must be dry and clean, inside and out. Caps, labels and slip-cover plastic labels must be removed since they cannot be recycled as part of the program.

Nineteen of the 43 collection sites accept 15 and 30-gallon plastic crop protection chemical, crop oil and adjuvant drums. These drums must be thoroughly rinsed before delivery to collection sites and should not be cut or opened in any way. Mini-bulk, saddle tanks and nurse tanks, which can be made of fiberglass or plastics not compatible with the recycling program, are not accepted.

Before delivering containers to a collection site, pesticide applicators should: clean, rinse and drain containers and drums and put the rinsate back in the spray tank; remove and properly dispose of booklets and caps from containers; and remove and properly dispose of plastic shrink-wraps from containers. Glued-on paper labels can be left on the container.

At collection sites, containers are inspected. They cannot have any pesticide residue that can be rubbed off by a chemical-resistant gloved hand. Stained, but clean, containers are acceptable. Containers not meeting these requirements must be re-rinsed before being accepted for recycling.

Buffalo: Kearney Recycling Center, Kearney, 7 a.m. to noon, 1 to 3 p.m. Monday through Friday; drums accepted.

Burt: Tekamah City Compactor, Tekamah, Tuesdays 2 to 5 p.m.; Thursdays 2 to 6 p.m.

Cuming: West Point Transfer Station, West Point, 8 a.m. to noon, 1 to 5 p.m. Monday through Friday; 8 a.m. to 4 p.m. Saturday; drums accepted.

Dawson: All Points Cooperative, Lexington and Overton, 7:30 a.m. to 5:30 p.m. Monday through Friday.

Dodge: Dodge County Extension Office, Fremont, by appointment only; phone (402)727-2775.

Lincoln: North Platte Transfer Station, North Platte, 7 a.m. to 4 p.m., Monday through Saturday.

Scotts Bluff: Gering Landfill, Gering, 7 a.m. to noon, 1 to 2:30 p.m. Monday through Friday; drums accepted.

Washington: Washington County Recycling Center, Blair, 8 a.m. to noon Saturday only; drums accepted.

Antelope: Central Farmers Cooperative, Clearwater, Elgin, Neligh and Tilden. Elgin site accepts drums.

Butler: Frontier Co-op (Yanka), David City.

Sarpy: Farmers Union Co-op, Gretna.

Saunders: Cedar Ridge Spraying, Ashland; Frontier Cooperative, Mead; and Otte Oil and Propane, Wahoo.

Adams: Heartland Cooperative, Juniata, 8 a.m. to 5 p.m. Aug. 16; drums accepted.

Antelope: Central Farmers Cooperative, Brunswick, 8 a.m. to 5 p.m. Aug. 1; drums accepted.

Clay: Fairfield Non-Stock Co-op, Fairfield, 8 a.m. to noon Saturdays, June through August.

Colfax: Husker Co-op Fertilizer, Schuyler, and Schuyler Cooperative, Richland; 8 a.m. to noon May 11, June 8, July 13 and Aug. 10; both sites accept drums.

Dakota: Northeast Cooperative, Emerson, 9:30 to 10:30 a.m. Wednesdays, June and July; Northeast Cooperative, South Sioux City, 11 a.m. to noon Wednesdays, June and July; both sites accept drums.

Dixon: Northeast Co-op, Allen and Ponca; and Precision Agronomy, Newcastle, 8 to 10 a.m. June 11 and 25, July 9 and 23; all sites accept drums.

Hamilton: Aurora Cooperative Elevator, Aurora, 8 a.m. to 5 p.m. Fridays through Aug. 16; Heartland Cooperative, Giltner, 8 a.m. to 5 p.m. Aug. 14; both sites accept drums.

Holt: Central Farmers Cooperative, O’Neill, 8 a.m. to noon June 22, July 26.

Kearney: Heartland Co-op, Minden, 8 a.m. to 5 p.m. Aug. 9, 8 a.m. to noon Aug. 10; drums accepted.

Lancaster: Farmers Cooperative., Bennet, 9 a.m. to 3 p.m. June 28; Firth Cooperative, Firth, 9 a.m. to 3 p.m. July 12; Farmers Cooperative, Waverly, 9 a.m. to 3 p.m. July 19.

Saunders: Otte Oil and Propane, Wahoo, 9 a.m. to 3 p.m. Sept. 13.

Stanton: Farmers Co-op of Pilger, Pilger, 9 to 11 a.m. Saturdays, May through July.

Thurston: Mother Earth Recycling Center, Macy, 10 a.m. to noon Wednesdays, June and July; drums accepted.

Wayne: Precision Agronomy, Wayne, 8 a.m. to noon June 25 and Aug. 6.

Brown: Ainsworth Transfer Station, Ainsworth, (402)387-2213; drums accepted.

Cedar: Hartington Recycling Center, Hartington, (402)254-6353.

Dakota: Boyer Valley Fertilizer, South Sioux City, (402)494-4261.

Knox: Precision Agronomy, Bloomfield, (402)373-4755.