Corn rootworm egg hatch detected; begin scouting for larvae, feeding damage

Larval corn rootworms (Jim Kalisch, UNL Department of Entomology)

Corn rootworm egg hatch was detected June 2 at UNL's Agricultural Research and Development Center near Ithaca and on June 3 at the South Central Ag Lab near Clay Center, but may have begun over the weekend. This is within the normal range of occurrence. Hatch will occur later in northeastern and western Nebraska.

Initial hatch is very hard to detect in the field, as newly hatched rootworms are very small. One method to detect hatch is to dig up corn plants, carefully shake off soil from the roots and put roots over a coffee can containing water. A coarse wire screen platform can be placed over the top of the can to hold corn roots. As the roots dry out, rootworm larvae will fall out and drop into the water where they can be more easily seen.

After hatch occurs begin scouting continuous corn fields for corn rootworm larvae and damage, regardless of whether a soil insecticide was applied at planting. This will help determine whether an insecticide is needed, if one was not used at planting, and provide a check of the effectiveness of planting time insecticide applications. In case of poor control, this will allow you to apply a rescue treatment before too much damage occurs.

On the positive side, precipitation in the Panhandle is running from slightly below normal to above normal. Row crops are well established and should have adequate soil water for the next couple of weeks. This week's temperatures in the mid 80s have allowed plants to grow without having to endure the high temperature stress likely to occur as summer progresses. With a little bit of additional precipitation most row crops in the North Platte Valley should be okay until water comes into the canals and is available for irrigation.

This is not to say everything is in good shape. A significant amount of winter wheat was planted in the valley last fall as a precaution against not having a full water supply this year. Most of the winter wheat crop will not be irrigated in order to save water for other crops. For the most part alfalfa growers have used up winter and spring soil water in producing the first cutting of hay. To get the second cutting growing, most alfalfa fields will need irrigation when water in the canals is released.

Conservation was and will be the key word this year and next. North Platte Valley growers will likely use any stored water this year and will be in the same predicament next year being totally dependent on snow pack in the Colorado and Wyoming mountains. As can be seen this year, with average snow pack and no water carried over from the previous year, irrigation demands cannot be met.

Saving water through irrigation, tillage, residue and crop selection will likely be a key factor again next year.

1. calculating what portion of the irrigated land’s purchase price constituted the additional value represented by the underlying ground water, and
2. calculating the annual amount of ground water depletion (if any).

For example: Value of ground water = land purchase price less value of improvements less dryland value of land when purchased. E.g., if 100 acres cost $12,000, improvements were worth $2000 and dryland value was $6000, value of ground water equals $4000. If the aquifer (ground water supply) beneath this tract of land were 160 feet thick when the land was purchased, the water is worth $25 per foot.

If in 1980 the ground water level fell 10 feet, the irrigator would have 10 feet of allowable depletion or a $250 deduction (annual depletion times value of water per foot or 10 feet times $25/foot). If the ground water level fell 20 feet in 1981, the irrigator would have 20 feet of allowable depletion or a $500 deduction. If the ground water level rose 10 feet in 1982, the irrigator would have no allowable depletion for 1982, and no depletion deduction. If the ground water level fell 15 feet in 1983, the irrigator would have allowable depletion of 5 feet and a $125 depletion deduction. The allowable depletion is 5 feet because the 1982 ground water rise of 10 feet would be netted with the 1983 ground water level drop of 15 feet for a net drop of 5 feet.

One factor to realize is that the purchase price of the land will be very important in determining the cost of the water subject to depletion. If land was inherited that originally was homesteaded, the land will have a low cost basis if any; thus there will be little water value to be claimed as a depletion deduction. If land was purchased at a high price, e.g. during the late 1970s, then the depletion deduction may be more significant. Because ground water depletion rates in Nebraska generally are slow relative to other Plains states, the cost of the ground water will be important in determining the amount of any ground water depletion deduction. For more information regarding the ground water depletion deduction, consult your income tax advisor.

See Table of postemergence herbicides for soybeans

Producers who used a preemergence herbicide this year may have more flexibility in their postemergence weed management strategy. Generally they'll be able to wait longer before applying postemergence herbicides or cultivating.

Several other strategies include the use of an early postemergence herbicide with residual such as Roundup + Pursuit (or Extreme) tank mix, a timely postemergence application followed by cultivation or two separate postemergence applications timed roughly 20-30 days apart, letting the weed growth stage dictate application timing.

Regardless of which strategy you use, timing of weed removal is critical. An article in the June 6 CropWatch explained why soybeans should be kept free of weed competition from the 2nd trifoliate to beginning bloom. The weed management strategy you choose should keep this in mind and yet be flexible enough to allow for removal during this critical time. Management strategies will largely be based on the time constraints of individual producers. Selecting a strategy that fits into your schedule will help you maintain optimum weed management in fields this year.

Growers should consider several issues when choosing a postemer-gence herbicide, including safety. Many soybean herbicides utilized for broadleaf control are cell membrane disrupters. Herbicides such as Blazer, Cobra, Resource, and Flexstar will do well on many broadleaf weeds, especially waterhemp, but also will cause some burning on the soybean leaves. Research has shown there is little to no yield impact from this burn in early growth stages of soybeans. Once soybeans begin blooming avoid spraying these cell membrane disrupter herbicides.

Grass control is not a problem with soybeans as herbicides such as Poast, Fusion, Fusilade, and Select will easily control annual grasses. One slight problem, however, is that these grass herbicides require crop oil and when tank mixed with cell membrane disrupters for broadleaf control, things can really heat up. In addition, grass control will often be slightly reduced when one of these grass products is tank mixed with a broadleaf herbicide.

The following recommendations address management strategies for some particularly difficult weeds postemergence in soybeans.

Black nightshade
Problematic in many soybean stands mid to late season, black nightshade usually can be controlled with Pheonix at 8-12.5 oz/a, UltraBlazer at 1-1.5 pt/a, Reflex/Flexstar at 1 pt/a, Pursuit DG at 1.44 oz, a, Raptor at 5 oz/a and Roundup WeatherMax in RR soybeans at 22 oz/a or glyphosate at 32 oz/a. Because nightshade moves in late in the season, cell membrane disrupters may not be a feasible treatment, especially during blooming.

Kochia
Roundup WeatherMax in RR soybeans at 22 oz/a or glyphosate at 32 oz/a. Herbicides offering less control, in the 80% range, include Basagran at 2 pt/a, Pursuit DG at 1.44 oz/a, Raptor at 5 oz/a, and Synchrony in STS soybeans at 0.5 oz/a. Remember that many areas have ALS- resistant kochia, meaning herbicides such as Synchrony, Pursuit, and Raptor will not provide control.

Velvetleaf
Control can be had with cell membrane disrupters including UltraBlazer at 1-1.5 pt/a, Pheonix at 8-12.5 oz/a, Reflex/Flexstar at 1 pt/a, as well as Basagran at 2 pt/a, Classic at 0.5-0.75 oz/a, Pursuit DG at 1.44 oz/a, Raptor at 5 oz/a, Resource at 4 oz for velvetleaf <4 inches, Synchrony in STS soybeans at 0.5 oz/a, Roundup WeatherMax in RR soybeans at 22 oz/a or 32 oz/a of glyphosate, and Stellar at 6 oz/a.

Waterhemp
Waterhemp can be difficult to manage so strive for control before it's 6-8 inches tall. No herbicides work well on 12- to 18-inch waterhemp. Because much of the waterhemp is ALS-resistant, only a few herbicides pro-vide satisfactory control. These include cell membrane disrupters such as UltraBlazer/Status at 1-1.5 pt/a, Pheonix at 10-12 oz/a, Reflex/Flexstar at 1 pt/a, Stellar at 6 oz/a and Roundup WeatherMax at 22 oz/a or glyphosate at 32 oz/a in RR soybeans.

When comparing glyphosate products, first examine the formulation. This is presented in terms of active ingredient and acid equivalent. Glyphosate is an acid formulated as a salt to improve performance and handling. Two formulations may contain the same amount of acid equivalent but different amounts of active ingredients because the salts are of different weights. Four salts of glyphosate are being marketed: isopropyl amine, potatssium salt, and ammonium and di-ammonium salt.

Drew Lyon, Extension dryland crops specialist at the Panhandle REC, said many fields could still go either way, depending on weather conditions in the next few weeks. Wheat condition is deteriorating in some areas but at a slower rate than last week.

Bob Klein, Extension crops specialist at the West Central REC, agreed, reporting that in southwest Nebraska the winter wheat is highly variable ranging from poor to good. Some fields have already run out of moisture and yields will be minimal to nonexistant, he said. In other fields, wheat condition is fair to good, depending on recent rain and disease and insect pressures. Localized wheat streak mosaic, wheat stem maggot, and winter injury will limit yields. Moisture continues to be the most determining factor for most wheat in southwest Nebraska.

Statewide, wheat is faring better than last year. Based on June 1 conditions, the crop is forecast at 72.6 million bushels, up 49% from last year and 16% above last month's forecast, according to USDA's NASS.

Projected costs and potential benefits of the new law, known as COOL, are at the center of debate over what must be done to make the new law work in an increasingly competitive business climate.

Darrell Mark, University of Nebraska Cooperative Extension agribusiness management specialist, will analyze the issues on NU's "Market Journal Extra" program, which is presented by extension and the University of Nebraska-Lincoln's Department of Agricultural Economics.

Mark's analysis of the country of origin labeling debate brings into focus several provisions of the law that have yet to be clarified. At a U.S. Department of Agriculture listening session last month in Kearney, Mark asked William Sessions, the USDA official charged with oversight of COOL, what producers should do to verify country of origin for animals that will be harvested after mandatory labeling takes effective Sept. 30, 2004. Could there be a new provision attached to the law that would exempt those animals?

"At this time, we don't envision a grandfather clause. The law is very specific," said Sessions. "There's a whole other world out there of areas for them (producers) to market their animals to food service and other sectors that don't require country of origin labeling. They can be marketed in that manner."

Mark also talked with Rod Johnson, Nebraska Pork Producers Association executive director; Mike Briggs, Seward cattle feeder; and Wendy Umberger, a Colorado State University ag economist who has studied consumer interest in country of origin labeling. Mark's interviews with Sessions, Johnson, Briggs and Umberger, which provide a balanced look at opinions and concerns about COOL, will be shown in their entirety.

"Market Journal Extra" will be broadcast June 20 on the Dish Network's University House Channel (NAUHS) 9411, at 1:30 p.m. Central Time.

Heavy rains on Monday night, June 9, should have killed many 1st and 2nd instar grasshoppers.

We treated several thousand acres of rangeland for grasshoppers and continue to monitor the situation in rangeland. Along roadsides and in rangeland, we're starting to see grasshoppers other than the banded wing grasshoppers that USDA APHIS is treating. Most of these spur grasshoppers are still small (less than 3rd instar) and could be fairly easily controlled. While wheat and pastures appear to be growing well, the soil probe indicates that there is little reserve moisture in many dryland fields. Fertilizer application and weed control are the main field work concerns of producers this week.