Scout for mid-summer chinch bugs in grain sorghum

Chinch bugs

Growers in southeast Nebraska should be checking for chinch bugs throughout their fields, not just the area bordering wheat or small grains. Chinch bugs feed at the base of the plant, but also may hide behind the leaf sheaths in the heat of the day.

According to KSU entomologists, “Unless spot treatment can be used, the size of the area infested must be compared to the cost of treating the entire field. Consider using field- wide treatment with ground-applied sprays for midsummer infestations in fields where infested spots (averaging about 50 bugs/plant where plant size is from about 1 foot in height through the flowering stages) are equivalent to about one acre infested in each seven acres of field size.” To think about this in terms of percentages, this is equivalent to the infested spots (as defined above) equaling 14% or more of the field.

A variety of foliar insecticides are labeled for control of chinch bugs in grain sorghum, including Sevin XLR (1-2 quarts per acre), Furadan 4 F (1 pint per acre), Warrior 1EC (2.56-3.84 fl oz per acre), Mustang (3.4-4.3 oz per acre), Baythroid 2EC (1.3-2.8 oz per acre) and Lorsban 4E (1-2 pints per acre). Higher spray volumes provide improved control because the sprays must penetrate the canopy to reach where chinch bugs feed on the lower part of the plant.

Grasshopper control with ATV-RAATs

These adjoining areas can be treated using the reduced agent and area treatment (RAAT) strategy of control. The RAAT method was developed to allow economical application of insecticides to reduce populations below a level that will cause economic damage in rangeland. This method can be modified for use in range, pasture, and non-crop areas adjoining cropland to prevent movement of grasshoppers from these areas when their food sources dry up.

Typical RAAT treatments are applied via air with lower chemical rates. Treatment is applied only to about 50% of the acreage by treating alternate swaths. This strategy also has been shown to be effective with an ATV sprayer applying narrow treatment swaths. Any sprayer could be used to treat the swaths, but an ATV will be able to cover rougher terrain. An advantage of this method is the use of narrow swaths that reduce the distance the grasshoppers need to move to enter a treated area.

Migratory grasshopper 4th instar nymph. The migratory is one of the four species of grasshoppers which commonly cause the most crop damage in Nebraska. See previous issues of CropWatch, 2003, in the Archives for information on scouting for these damaging species.

The RAATs strategy takes advantage of natural grasshopper behavior -- over time they will move from feeding zones into treated zones and be controlled. Also, natural enemies will survive in the untreated zones and continue to exert a controlling influence on the grasshopper population. The effectiveness of the RAATs strategy relies on several factors. First, and most importantly, the grasshoppers must be immature to enable better control. Third and fourth instars are the ideal stage to target. Next, the residual of the product used must be maximized to enable grasshoppers to move from the untreated zones into the treated zones to contact the insecticide. In addition, application techniques must be ideal to enable uniform application of the product in the treated zones. Control in a RAATs treated area will likely be slightly lower (5-15%) than a comparable blanket treatment area, but the much reduced cost makes the method a great benefit.

Three products are labeled for grasshopper control in range, pasture and non-cropland areas (carbaryl, malathion and diflubenzuron) and would be appropriate for treating these areas around cropland. The residual for malathion will be short, perhaps only a few days. Carbaryl (Sevin XLR+) will last longer and at higher application rates may last two to three weeks.

Diflubenzuron (Dimilin 2L) has a very long residual and will last 28 days or more at higher rates. The longer residual products have a better chance of success in the ATV-RAATs program. Techniques for ATV-RAATs application are quite different from those used in aerial RAATs.

Whereas application rates for aerial RAATs are reduced, recommendations for ATV-RAATs are to use the maximum labeled rate (1 oz/A Dimilin 2L, 32 oz/A Sevin XLR+). The RAATs strategy works by taking advantage of the movement behavior of the grasshoppers in that over time they will move into the treated zones and be controlled. Also, by leaving some areas untreated, natural enemies will survive and continue to exert an influence on the grasshopper population.

The amount of treated area with this program will vary depending on grasshopper density and grass forage coverage. The percent of the area treated should be equal to the grasshopper density with a minimum of 20% coverage. For example, if you have 30 grasshoppers per square yard in the areas to be treated, leave two untreated swaths for every swath that is sprayed (33% coverage). A second major factor that will impact optimum swath width is the density of foliage. Dense, lush foliage will slow grasshopper movement from the untreated to the treated strips. In these situations consider an increase in treated area (narrower skip swaths).

Mixing and application of these products is enhanced with the use of 8 oz/A crop oil to the mixture. Tests also have shown that canola oil may offer some advantages over crop oil in attracting grasshoppers into the treated areas. To maintain mixability, use at least 15% crop oil; for example 1.2 oz crop oil plus 7 oz canola oil.

Wheat being harvested east of Lincoln Thursday. Harvest is underway across most of the state now.

Randy Pryor, Extension Educator in Saline County: Wheat harvest is 95% complete with the highest yields I have seen since 1982. There are numerous reports of 60 and 70 bushel per acre farm averages on dryland wheat. Chinch bugs are causing problems in some areas of the county and border treatments are being used in adjacent corn and sorghum.

Leafhopper damage occurred in many alfalfa fields and most producers are harvesting low yields on second cutting alfalfa. Older alfalfa fields are under moisture stress and were damaged more by the leafhoppers. The rainbucket has been at zero for the last two weeks and dryland crops are hanging on but suffering, particularly in the dryest area south and southeast of Friend.

Gerald Hopp, Extension Educator in Richardson County: Wheat harvest is in full swing. Yields are astoundingly good with reports of top quality wheat at 70-80 bushels per acre. Corn tasseling started last week in many fields. It's not a usual practice in this area, but some farmers drilled oats this spring with the specific intent of using it as hay. That crop is being harvested now.

Paul Hay, Extension Educator in Gage County: The southeast Nebraska wheat crop was very good with yields in the range of 45-60 bushels per acre with good moisture condition and good test weights. Three fields with 0-25 bushel yields provide harsh reminders of the impact of disease and insects. If you plant wheat within two years of bromegrass pasture, take-all disease can be very real (10 bu/ac). In addition when common bunt or stinking smut aren't identified in the seed, the results can be disasterous and the wheat unhar-vestable.

When planting next year's wheat into soybean stubble, remember that this stubble can be dry and low in available nutrients so make sure your seeding depth is 1.25-1.5 inches. Use starter fertilizer to get the crop off to a quick start so it will be thick enough to thwart chinch bugs.

Karen DeBoer, Extension Educator in Cheyenne County: Wheat harvest started in the eastern part of the southern Panhandle late last week. Custom harvest crews were expected in the area this week. The recent hot, dry conditions have helped as the grain moisture content was 11% in one field cut on Sunday.

Drew J. Lyon, Extension Dryland Crops Specialist at the Panhandle REC: Hot, dry weather throughout most of the Nebraska Panhandle has moved winter wheat development along rapidly in the last few weeks. I anticipate wheat harvest to begin this week on the lighter soils and move into full gear this weekend and next week throughout the area.

What effect the recent weather will have on wheat yields and quality will soon be known. Spring rains resulted in the potential for an excellent wheat crop, but mostly dry conditions in June, along with some very warm temperatures the last few weeks certainly trimmed yield expectations. However, wheat never ceases to surprise, as exhibited by the surprisingly good yields last year given little or no precipitation from January through harvest in July of 2002.

Symptoms of fusarium head blight are most conspicuous after the soft dough stage on immature wheat. The fungus may attack the entire head or only part of it. Diseased heads appear to have ripened prematurely During warm, humid weather, infection produces a salmon orange to pink ring of mycelium and spores at the base of the spikelet or in the crease of the kernel. Infected spikelets take on a tan to brown color and are usually sterile or only partially filled. Infection of the young, developing grain results in shrunken kernels that have a dull, chalky, tombstone-like appearance. These kernels are easily crushed. A tuft of whitish pink mycelial growth may be seen on the seed.

If a wheat field appears to be infected, harvest it last and keep the grain separated from non-infected grain. Increasing the air on the combine will have a tendency to separate and blow out a lot of the lighter, diseased kernels.

Pinkish tint typical of fusarium blight.

Fusarium head blight can produce toxins harmful to animals. If scab-infected grain is to be used for feed, the grain should be tested for vomitoxin and zearalenone. If it is to be fed to horses, include a fumonisin test. Fumonisins can cause equine leukoencepha-lomalacia in horses. Straw from nonharvested, scab-infected fields should not be used for bedding for swine or horses without being screened for mycotoxins.

Regular scouting of rootworm beetles during late July and August, which corresponds with their egg-laying period, provides information on the potential for damage in that field if it is planted to corn next year.

Be aware that rootworm beetles emerging before silks are available will feed on the corn leaf surface by scraping away the green surface tissue, producing a window-pane appearance on the leaf. This is not an economic concern.

Two corn hybrids with different types of Bt toxin were used in the experiment. Two plantings of these hybrids were grown in greenhouse pots. Ammonium nitrate was blended into the potting mixture prior to planting. Fertilizer rates used in the experiment represented zero, low, normal, and high amounts of nitrogen used to grow corn. Pots were carefully watered to avoid leaching of the fertilizer during the experiment. When the plants had five fully extended leaves, sample tissues were taken to determine the Bt and nitrogen concentrations of the plant.

The levels of Bt toxin and total nitrogen in the plant steadily increased as the amount of nitrogen fertilizer increased. Both Bt hybrids responded the same to increasing levels of nitrogen fertilizer. Increasing available nitrogen is known to increase protein levels in most plant specices, especially in vegetative cells. Much of this increase is in the form of enzymes. The authors suggest that as nitrogen levels increase, more Bt d-endotoxin synthesizing enzymes are likely produced, which could result in more of the Bt protein being synthesized.

"The effectiveness of Bt hybrids to avoid insect damage may be dependent on the amount of nitrogen fertilizer applied to the crop early in the growing season. Further research will be necessary to determine if similar effects to Bt concentrations can be found in more mature corn. These findings could affect the way we manage nitrogen fertilizer applications to Bt hybrid corns," Bruns said.

Based on the results from this one-year greenhouse study, researchers are now conducting multi-year, full-season field trials. Nitrogen rates ranging from 0 to 300 lbs per acre were applied to help determine how different rates may affect the extent of the nitrogen advantage over a longer term. In the preliminary study, plant tissue samples were taken at the five-six leaf stage; however, in the field studies, plant tissue samples will be taken at silking and analyzed for Bt content.

These early results indicate that adequate levels of nitrogen are essential to get the effect of Bt that you desire, Bruns said. General timing of the application may not be as critical as ensuring that the nitrogen is available when the plant needs it.

"If you're investing that kind of money [in Bt corn], you want to get the maximum benefit from it," Bruns said.

In the Agronomy Journal, the authors suggested that further research also would be needed to "determine if the Bt protein remains intact after synthesis or if it can be degraded and translocated and the nitrogen utilized in developing tissue, thus rendering the plant susceptible to insect attack."

Ascochyta blight, caused by the fungal pathogen, Ascochyta rabiei, is the most serious and widespread disease of chickpeas in the world. A severe epidemic of this disease occurred in Box Butte County in 2001, causing complete crop failure in those fields that were not treated. Disease development is most rapid at temperatures of 68^o-70^oF, and high relative humidity (leaf wetness periods of more than six hours).

Symptoms on leaves and pods consist of circular lesions with dark brown concentric rings of pycnidia (spore-bearing structures). Petioles and stems contain elongate lesions. The pathogen is seedborne. Early in the season infected plants will appear scattered in fields and can serve as foci for further disease spread under conducive conditions.

This disease has been identified at numerous locations in Box Butte County and from Keith County, near Ogalalla.

Growers in all production areas need to be alerted to this problem and be prepared to treat affected fields. It is important to remember to be particularly attentive to protecting young green foliage during pod fill.

Affected fields can be treated with fungicides, and several are currently labeled for chickpeas, including Bravo and Headline. To reduce pathogen survival, infected residue should be buried with tillage and volunteer plants controlled.

Exposure to sunlight is the most important factor for drying hay rapidly. Avoid bunching or mounding windrows up high. Instead, begin by making your swath loose and wide, at least half the width of the mown area for as much exposure as possible. If your soil is moist, though, leave enough ground uncovered so later you can turn hay onto some dried out soil.

Turning hay to speed drying so you don't lose many leaves takes skill and good judgement, especially when you have many acres to cover. Shortly after mowing, after the windrow has started to settle and top leaves are fairly dry, a tedder or fluffer can be used with little leaf loss to expose hay underneath to sunlight while maintaining a loose, spread out windrow.

But don't ted or fluff after hay gets too dry to retain leaves and don't rake too early unless you're able to gently flip the windrow upside down onto drier ground without losing leaves or roping the hay.

Final raking should occur when just the bottom of the windrow needs a little more drying and while humidity is high enough to help leaves on top stay attached to the stems.

It also provides good quality grazing similar to alfalfa before plants bloom heavily. After blooming, though, sweet clover gets stemmy and woody, reducing both feed value and palatability. Even young plants are quite bitter, so if other plants are available cattle will graze only limited amounts of sweet clover. This greatly reduces bloat hazards, which is a risk when sweet clover is abundant.

The biggest risk from sweet clover is in hay, specifically in moldy hay. Spoiled sweet clover produces a chemical called dicoumarin that interferes with metabolism and synthesis of vitamin K. Without vitamin K, blood will not clot properly after an injury and can even seep out of otherwise healthy blood vessels. That's why sweet clover poisoning also is called sweet clover bleeding disease.

Make sure hay containing sweet clover is extra dry before baling or storage to prevent mold. And remember -- mold can develop on perfectly dry bales if they get wet so avoid outdoor storage. If you must feed moldy sweet clover, alternate by feeding moldy hay for a week followed by alfalfa or other non-moldy forage for a week. This intermittent feeding is safer than mixing good and moldy hay together.

Corn condition declined and rated 1% very poor, 2% poor, 19% fair, 57% good, and 21% excellent, above last year and average. Irrigated corn rated 79% good and excellent while dryland rated 77%. Fields were beginning to silk in a few areas of the east and southwest, behind last year at 6% and average at 5%.

Soybean condition rated 2% poor, 21% fair, 61% good, and 16% excellent, above last year and average. Two percent of the fields were blooming, behind last year at 16% and average at 13%.

Oat condition rated 1% very poor, 1% poor, 19% fair, 57% good, and 22% excellent, well above last year and average. The crop was 98% headed, behind 100% last year and near 97% average. Harvest for grain was making a start with 3% combined, behind 26% last year and 10% average.

Sorghum condition rated 4% poor, 29% fair, 58% good, and 9% excellent, above last year and average.

Wheat condition rated 4% very poor, 10% poor, 25% fair, 48% good, and 13% excellent, well above last year and the five-year average. Wheat fields had turned color on 94% of the acreage, behind the 100% last year and 97% average. Forty percent of the acreage was ripe, well behind last year at 83% and average at 60%. Harvest made good progress with 15% completed, but was 10 days behind last year at 60% and a week behind average at 37%.

Dry bean condition rated 2% very poor, 5% poor, 24% fair, 57% good, and 12% excellent.

Alfalfa condition declined and rated 4% poor, 25% fair, 53% good, and 18% excellent, above last year and average. Second cutting activities progressed to 29% harvested, behind last year at 46% and average at 35%. Wild hay condition rated 1% very poor, 5% poor, 23% fair, 56% good, and 15% excellent.

Pasture and range condition rated 3% very poor, 11%, 34% fair, 43% good, and 9% excellent. With temperatures peaking above 100 degrees, extra care was being given to livestock in confined areas.

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