We are seeing yellow and stunted corn around Virginia du
e to many different factors that range from nutrient deficiencies to cool and wet growing conditions. Take a look at this article to give you a few reasons for this poor looking corn and different things to consider prior to making your sidedress nitrogen applications. Yellow_Corn_26May2016
Our overall mild winter and wet spring are the kinds of conditions that favor survivorship and early development of stink bug populations. Because of these conditions, this could be a summer when we see higher than normal stink bug infestations in a lot of crops including field corn, cotton and soybean. Brown stink bugs are already being found in small grain fields and areas of North Carolina are reporting pretty heavy stink bug pressure on seedling field corn. See this article by Dr. Dominic Reisig at the NCSU station on Plymouth for details https://entomology.ces.ncsu.edu/2016/05/how-to-avoid-a-stink-bug-disaster-in-corn-2/
We need to be thinking ‘stink bugs’ this summer and aligning our field scouting, sampling and threshold efforts in that direction as the summer progresses—and that applies to cotton and soybean fields as they mature.
It’s been many years since we’ve seen a true armyworm (see the attached image) infestation in our small grain crop, but one is reported to be ongoing in the barley and wheat fields on the Eastern Shore. These caterpillars can do two types of damage—leaf feeding and head cutting. Leaf feeding is rarely extensive enough to warrant control, especially if fields are within a couple of weeks of harvest. Head cutting is less tolerable. For some reason no one has been able to explain, caterpillars will sometimes eat through the stem below the heads casing them to drop to the ground. Finding otherwise healthy looking heads-short stems on the ground is a good indicator that true armyworms are present and still active. It is often hard to find them on plants during the day as they typically feed more at night and seek cover under plant residue during the day. When we have worked with this pest, we found that fields with the most plant residue on the soil surface tended to have the heaviest infestations.
We do have thresholds for true armyworm for those motivated to scout for them. As a general rule, barley should be treated if the number of armyworms exceeds one per linear foot between rows and most of the worms are greater than 0.75-inch long. In wheat, armyworms tend to nibble on the tips of kernels rather than clip heads; thus, populations of two to three worms per linear foot between rows are required to justify control. In high management wheat fields with 4-inch rows, treatment is recommended when armyworm levels exceed 3 to 5 per square foot of surface area, or per linear foot of row.
If a treatment is warranted, there are a few good choices but the PHI (Pre Harvest Interval) may be a challenge. Some work we did many years ago showed that pyrethroids were generally effective but have a PHI of 14 days (example, Mustang Max) to 30 days (example, Baythroid), which could be a problem for barley, wheat not so much. Lannate has a PHI of 7 days but did only an OK job in our trial and not as good as the pyrethroids. We chalked that up to the fact that although Lannate has great efficacy against most caterpillar species, it has almost zero residual activity. So a day-time spray may not have had as much horsepower by the evening when caterpillars become active. Since our work was done, several new products have been introduced to the market that we have not tested, like Prevathon (PHI 14 days), and Besiege (PHI 30 days). These should work well. See the Pest Management Guide Field Crops 2016, 4-49, p. 53 for more product listings (http://www.pubs.ext.vt.edu/456/456-016/Section04-Insects-1.pdf).
With any treatment, coverage will be essential so deliver the highest volume you can live with and direct it to go as deep into the canopy as possible.
EPA just granted a Section 18 for use of Transform™ WG in Virginia against sugarcane aphid in sorghum. Transform (50% a.i. sulfoxaflor), manufactured by Dow AgroSciences, may be applied through April 8, 2017 on a maximum of 16,591 acres of sorghum fields (grain and forage) in the following counties: Accomack, Albemarle, Alleghany, Amelia, Appomattox, Augusta, Bedford , Botetourt, Brunswick , Campbell, Caroline, Carroll, Charlotte, Charles City, Culpeper, Cumberland, Dinwiddie , Essex, Fauquier, Floyd, Fluvanna , Franklin, Frederick, Gloucester, Goochland, Greensville, Halifax, Hanover , Henrico, Isle of Wright, George , King William, King and queen , Loudon, Louisa, Luneburg, Madison , Mathews, Mecklenburg, New Kent, George , Prince William, Rockbridge , Rockingham , Russell, Southampton, Spotsylvania, Suffolk, Surry, Sussex, Virginia Beach, Washington, Westmoreland, and Wythe.
The following directions, restrictions, and precautions must be observed. Foliar applications may be made by ground or air at a rate of 0.75-1.5 oz of product (0.023-0.047 lb a.i.) per acre. A maximum of 2 applications may be made per year, at least 14 days apart, resulting in a seasonal maximum application rate of 3.0 oz of product (0.09 lb a.i.) per acre per year. Do not apply product 3 days pre-bloom or until after seed set.
To minimize spray drift and potential exposure of bees when foraging on plants adjacent to treated fields: applications are prohibited above wind speeds of 10 miles per hour (mph) and must be made with medium to course spray nozzles (i.e., with median droplet size of 341 µm or greater). A restricted entry interval (REI) of 24 hours applies to all applications. Do not apply within 14 days of grain or straw harvest or within 7 days of grazing, or forage, fodder, or hay harvest.
Environmental Hazards Statement: “This product is highly toxic to bees exposed through contact during spraying and while spray droplets are still wet. This product may be toxic to bees exposed to treated foliage for up to 3 hours following application. Toxicity is reduced when spray droplets are dry. Risks to pollinators from contact with pesticide spray or residues can be minimized when applications are made before 7:00 am or after 7:00 pm local time or when the temperature is below 55 degrees Fahrenheit (°F) at the site of application.”
We will provide updates on the presence and spread of sugarcane aphid as the season progresses.
Gowan has a new supplemental label for Sandea on cucumber, allowing for a 14 day pre-harvest interval. This label will be on the bottle next production run, but for the time being growers wanting to use the supplemental label will need to have a copy of the supplemental label on file. This new label will replace the 24c (Special Local Needs label) label that covers the same use. If you have any questions do not hesitate to contact me. Below is the supplemental label.
Sandea 81880-18 cucumbers (aprvd 5-11-16)
Due to the frequent rains in May, only and estimated 50% or so of our cotton is planted and maybe even less of the peanut crop. A later planted crop may require some changes in how we manage pests and thrips are a good example. Thrips are a major challenge for both crops and for this pest at least, later planting has advantages. Although the crops are delayed, the thrips population seems to be on a pretty normal schedule, that is, we are seeing a lot of adults active on volunteer peanut plants and feeding injury symptoms. We typically see one major peak of thrips activity when adults move from spring weeds into crops, so later planted fields may escape this peak—which means less thrips pressure compared to years when we plant on time. Also with the moisture we have in our fields, once the weather warms up (expecting that next week) we will see quick emergence and rapid seedling growth. This combination of rapid growth and reduced thrips pressure means less need for protective insecticide treatments.
My recommendations are that any cotton planted from today (May 17) forward should only need a standard insecticide seed treatment. And importantly, I would NOT automatically follow with a foliar application to the seedlings. Plant the seed-treated cotton and wait to see if anything more is needed. This could be year when the seed treatment will provide enough protection—a standalone.
For any peanuts planted from today forward, I would not put any insecticide into the seed furrow, or at least only a low rate. Scout fields after plants emerge and clean up any visible thrips injury with a broadcast application of either acephate or spinetoram.
We were hoping to be about half way finished with our soybean plantings by now, but we haven’t put a planter in the field in two weeks. The rain continues to delay us, but I hope that we will get back into the field next week.
The rain and cooler weather has lowered soil temperatures somewhat and this means that we need to take a few extra precautions, especially pertaining to seedling disease. I wrote a detailed blog a few years ago on seedling disease; little has changed and, for more details, you can view that blog here:
Fungal Seedling Disease in Soybean
Planting soybean in cool soil will lead to delayed emergence and increased chance of seedling disease that can reduce stands, weaken emerged plants, and inhibit early-season growth. I stress that the greater time required for emergence, the greater probability that the seed will become infected with soil-borne disease. If you are planting into cool soils, I strongly suggest using fungicide-treated seed as an insurance against seedling disease. These treatments will protect the seed and seedling if emergence is delayed.
But, seed treatments should not be a substitute for other practices that encourage rapid seedling emergence. Here is my checklist for insuring a good stand free of seedling disease:
I was recently made aware of a long list of fungicides involving the European Union and their restriction on some chemical residues on peanuts. Over the last couple of weeks there were rumors that these restrictions have been relaxed but apparently these rumors are unfounded, I was told. Well, for the industry that exports peanut this is quite serious because any trace of any of the chemical on that list may result in failure to their business. The list includes many fungicides for bacterial diseases, which are not a common problem in the VC region; others, however, like Tilt Bravo SE are. For the sake of staying informed and alerted at what it is and what may come, here I provide that list, with the recommendation that growers do not use any product on that list. Notice to Growers – Products Not To Be Used
Slug damage on no-till corn.
With all of the rain during the first week of May, and with seedling corn having emerged, we are hearing about slug pest problems, particularly in no-till corn. Eastern Shore of Virginia is one area reporting issues. Slug problems are a common concern in no-till systems when conditions are wet in the spring (see VCE Factsheet No. 444-109 https://pubs.ext.vt.edu/444/444-109/444-109.html) . Another useful VCE factsheet on slug management in no-till corn from Bobby clark and Rod Youngman is: http://offices.ext.vt.edu/shenandoah/programs/anr/CropandSoilEnvironmentalSciences/Slug_Fact_Sheet.pdf
Growers must keep four things in mind right off the bat: 1) corn plants are often not killed outright by the slugs and quite often have the ability to outgrow the leaf feeding injury by these slimy little beasts unless populations are very high and weather conditions are bad. Soybean cotyledons, however, are more susceptible to being killed because their growing point can be damaged; 2) if it stops raining for a few days, then the slugs will go away and hide as they require high moisture levels; 3) replanting is an option, but a grower needs to factor in the economics see VCE Fact Sheet https://pubs.ext.vt.edu/2905/2905-1293/2905-1293_pdf; and 4) if you are considering a chemical control measure, keep in mind that there are only a select few effective options such as slug bait products containing metaldehyde or iron phosphate. These are not easy to apply (need to be broadcasted) and are fairly expensive. However, these products are efficacious and will most often alleviate the slug problem long enough for your seedling plants to reach a sufficient size to no longer be economically damaged by slugs. See VCE Fact sheet No. ENTO-178 for a recent efficacy evaluation that we did with slug baits. http://pubs.ext.vt.edu/ENTO/ENTO-178/ENTO-178-PDF.pdf
Italian ryegrass is one of the most troublesome weeds infesting small grain fields throughout Virginia. Currently, only Hoelon-resistant ryegrass has been confirmed in Virginia. However, many growers have complained the ALS-inhibitors (Osprey and PowerFlex) and Axial XL (ACCase-inhibitor) have failed to control ryegrass. To get a better handle on herbicide-resistant Italian ryegrass in Virginia, the VT weed team plans to screen ryegrass from across the state for herbicide resistance. Year 1 of the project will focus on the I95 corridor east. We will be traveling this area and collecting ryegrass seed for herbicide screening this fall. However, if you have had complaints of resistant ryegrass in your neck of the woods and are interested in screening it this year, we welcome your samples and will add them to our screen this fall.
If you are interested, see the sample information sheet below for sample, handling, and shipping information. For the sample, GPS coordinates are critical. If you have any questions, feel free to contact me.
“One year to seed; seven to weed”
