2018 UD Weed Science Field Day

Wednesday, June 20, 2018     8:30 a.m.
University of Delaware
Carvel Research and Education Center
16483 County Seat Hwy, Georgetown, DE

The UD Weed Science Field Day will begin with registration at 8:30 at the Grove near the farm buildings and new office building on the north side of the road. We will start to view the plots at 8:45 am.

The weather has been a challenge to get plots planted. All of our corn studies will be part of the tour, which includes most of the commercially available herbicides. Some of corn trials include different approaches and timings of herbicide application. Most of our soybean trials were recently planted, but we will view various burndown trials for full-season no-till production. We will also talk about the various cover crop trials. Our trials with Xtend soybeans, Liberty Link, and Enlist soybeans will not be at a stage to view until later this summer.

Coffee, juices, and donuts will be provided. We will also provide sandwiches for lunch.

Pesticide credits and Certified Crop Advisor continuation credits will also be available.

Dr. Michael Flessner, VA Tech, will hold a field day on Tuesday, June 19th at Blackstone, VA

Dwight Lingenfelter, Penn State, will hold a field day on Thursday, June 21st at Landisville, PA

2018 Delaware Cooperative Extension Horticulture Short Courses

Register for these courses online.

Pest and Beneficial Insect Walk
$15, 2 Pest., 1 CNP, 2 ISA credits
Wednesday, June 6, 4-6 pm
Sussex County Extension Office
16483 County Seat Highway, Georgetown
Wednesday, June 20, 4-6 pm
University of Delaware Botanic Gardens
531 S College Avenue, Newark,
Meet at the entrance to Fischer Greenhouse.
Learn to identify insect and disease pests, as well as beneficial insects in the landscape at either the Sussex County Extension Office or the University of Delaware Botanic Gardens. Instructors: Nancy Gregory, Brian Kunkel, Carrie Murphy, and Tracy Wootten

Guess the Pest! Week #3

Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu

Test your pest management knowledge by clicking on the GUESS THE PEST logo and submitting your best guess. For the 2018 season, we will have an “end of season” raffle for a $100.00 gift card. Each week, one lucky winner will also be selected for a prize and have their name entered not once but five times into the end of season raffle.

This week, one lucky participant will also win A Farmer’s Guide To Corn Diseases ($29.95 value).

You can’t win if you don’t play!

Guess the Pest! What is this insect?

Guess the Pest! Week #2 Answer: Lace Bug

Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu

Congratulations to Kathleen Heldreth for correctly identifying the insects as lace bugs and for being selected to be entered into the end of season raffle for $100 not once but five times. Everyone else who guessed correctly will also have their name entered into the raffle. Click on the Guess the Pest logo to participate in this week’s Guess the Pest challenge!

Lace bugs are sporadic pests of eggplant and occasional pests on other solanaceous crops including tomatoes and potatoes. As true bugs, they have piercing-sucking mouth parts, feeding on plant leaves causing a whitening/yellowing of the leaves. The holes in the leaves in the photos above are not a result of lace bug feeding but more likely damage from flea beetles, another pest of eggplant.

This is a great example of how the type of damage can give clues as to which insect caused the damage. In this case, even though the lace bugs are easily found on leaves with shotgun hole feeding, we know that the holes were not caused by the lace bugs because they have piercing-sucking mouthparts, not chewing mouthparts.

Lace Bug Feeding Injury

Controlling Perennial Weeds When They Emerge from Seed

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Perennials often produce seeds that are adapted to being moved by the wind (hemp dogbane, milkweed, or Canada thistle) or produce large seeds or berries that are eaten by birds and animals and spread around (pokeweed). We conducted a greenhouse study (funded by DE Soybean Board) to examine soil-applied herbicide control of some perennials when they originate from seeds. Perennial seedlings (emerged from seeds), can produce a perennial root system after only 3 to 4 weeks. Being able to select the correct herbicide when you know seeds are coming into your fields can help prevent headaches and frustration in years to come. If at all possible, keep the perennials mowed along ditches and field edges to reduce (or eliminate) seed production. Prevention is the best approach.

Johnsongrass, bermudagrass, Canada thistle, hemp dogbane, common milkweed, common pokeweed, and horsenettle were planted in the greenhouse and sprayed with common soil-applied herbicides (Dual, Prowl, Command, Lorox, metribuzin, atrazine, and Canopy). Next to each weed are the herbicides that provided the best level of control (over 90% control). This study was conducted a few years ago and neither Lumax, Valor, nor Authority were available at that time for testing.

Bermudagrass: Dual, Prowl, Command, and metribuzin

Johnsongrass: Command.

Canada thistle: Command, metribuzin, atrazine, and Canopy.

Hemp dogbane: Command, Canopy, metribuzin, and atrazine.

Common milkweed: metribuzin and Canopy.

Common pokeweed: Canopy, and metribuzin.

Horsenettle: metribuzin, atrazine, and Canopy.

Postemergence Spraying in Wheat and Barley

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

The cool spring has meant winter grains have not progressed as quickly as normal and some fields may not have been sprayed yet. With the forecasted weather, grains will begin growing quickly and there might be a short window before the weeds are too tall or the crop canopy closes and prevents good spray coverage. If you are considering a postemergence spray, 1) be sure weeds are small, 2) the crop has not reached the maximum stage for application, and 3) the replant interval allows a late spray.

Herbicide Maximum Stage Rotation to Soybeans Rotation to Vegetables
Axial XL Pre-boot No restrictions 30 days
Harmony Extra Before flag leaf emergence 7 days 45 days
Huskie Flag Leaf emergence 120 days 9 months
Quelex Flag leaf emergence 90 days 15 months
Starane Ultra Early boot stage 120 days in MD
90 days in DE, VA
4 months
Sentrallas Before flag leaf emergence 120 days
90 days in DE, MD, VA
4 months

Have You Purchased this Year’s Mid-Atlantic Field Crop Weed Management Guide?

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

The guide covers weed control in corn, sorghum, soybean, small grains, and hay and pastures. The guide includes information on commonly used herbicides for these crops, including relative effectiveness for burndown, preemergence, and postemergence control of most of the common weeds in the region. There are tables on premixes and what is included in the premixes, and a section on management of problem weeds. To find out more about the guide watch this short you-tube video at https://www.youtube.com/watch?v=wH5AyULjKL0

The guide can be ordered on-line at https://extension.psu.edu/mid-atlantic-field-crop-weed-management-guide. Available on-line are the printed copies for $25; an enhanced pdf copy for use on computers and tablets for $15 or both a hard copy and pdf for $35 + shipping. A free low resolution pdf is available at http://extension.udel.edu/ag/weed-science/weed-management-guides/. Note the low-resolution version is not “searchable”.

Controlling Grape Hyacinth and Star of Bethlehem

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

I have gotten a few phone calls about both Grape hyacinth and Star of Bethlehem. For those not familiar with these species, they are both perennial weeds that have long, narrow, fleshy leaves. They both form numerous underground bulbs. Star of Bethlehem is in the lily plant family while grape hyacinth is in the asparagus family. While both are present in fields this time of year, Star of Bethlehem emerges in the spring and then produces white flowers. Star of Bethlehem leaves have a faint white stripe that runs the length of the leaf. Grape hyacinth emerges in the fall, over winters and then produces purple flowers in the spring. Both species flower in the spring and then die back quickly but they can impact planting of summer crops if they have high infestation levels. They can also interfere with the growth of small grains and forages. Grape hyacinth will also interfere with soybean harvest in the fall because the leaves can get up to 8 to 10 inches tall and if the infestation is severe, the waxy succulent leaves will interfere with the cutter bar.

Management of these two species is very different.

Star of Bethlehem leaf with faint white stripe

Star of Bethlehem flowers

Flowering grape hyacinth

Star of Bethlehem Control. In a field study, Star of Bethlehem was sprayed in the early spring and both Aim at 1.5 fl oz and Gramoxone at 2 qts were excellent for “burning down” emerged Star of Bethlehem. Glyphosate teatments at rates of 1.5 or 1.9 lbs ae/A [48 or 57 fl oz of Touchdown Total] were not effective. When rated the following spring (one year after treatment), Gramoxone treated plots had 93% Star of Bethlehem control, whereas two applications of glyphosate at 1.9 lbs ae each application provided 77% control and Aim did not reduce spring emergence the following year.

Grape Hyacinth Control. We conducted a trial a few years ago with funding from the Delaware Soybean Board. Glyphosate was applied at two rates (1.0 and 1.5 lb ae/A or sequential applications of 1.5 lb ae of glyphosate. Treatments were made either April 10 or May 2, 2014. When evaluated shortly after soybean planting, treatments applied April 10 showed better control than treatments applied May 2. However, with later ratings these differences were not observed. When rated in the fall and one year after treatments, no treatment was highly effective. The best treatment was two applications of glyphosate at a rate of 1.5 lb ae/A.

In a separate trial conducted by Dr. Flessner at Virginia Tech, they examined a single application of glyphosate, paraquat, and glyphosate plus dicamba. However, they did not include sequential treatments of glyphosate. The found similar levels of control with all three treatments, when rated at soybean planting and in the fall.

Management of this weed is going to require diligent efforts to achieve long-term control. While a single application of glyphosate or paraquat can burn down grape hyacinth prior to soybean planting, it had limited impact in the fall or one year after application.

There is on-going research on management of this species.

Now that Spring has Sprung, is it Time to Plant Corn?

Amy Shober, Extension Nutrient Management and Environmental Quality Specialist, ashober@udel.edu; Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu; Phillip Sylvester, Kent County Extension Agent, phillip@udel.edu; Cory Whaley, Sussex County Extension Agent, whaley@udel.edu; and Richard Taylor, Retired Extension Agronomist

After what seems to have been a never-ending winter, temperatures this weekend are projected to reach the high 70s. Thankfully, the extended forecast suggests that those frigid temperatures may be behind us. With the warmer temperatures comes the itch to get your corn planted. Here are some considerations for deciding when to plant corn.

Corn germination begins once the soil temperature at a 2 to 3 inch depth reaches 50°F. Currently, maximum daily soil temperatures in Georgetown are nearing that 50°F mark, but soil temperatures are dipping into the mid-40s at night. Waiting for soil temperatures to warm just a bit more will be important to achieving the uniform stands needed to maximize yield. While we should be starting to see soil temperatures increase with the warmer air temperatures, it is important to note that other factors may affect soil temperature. Fields that receive tillage, conventional or conservation, will tend to warm faster than no-till fields. Residue can act as a mulching layer, limiting temperature variability later in the season, but also delaying the effects of warmer air temperatures. Checking soil moisture content is also a good predictor of soil temperature, as moister soils will take longer to warm up.

Waiting for soils temperatures to warm a bit will decrease the likelihood of delayed germination. If it takes more than two weeks for corn to emerge after planting, there is an increased risk of variability in the growth stage of seedlings. When seedlings differ by two or more leaf stages (a two fully emerged leaf plant versus a four fully emerged leaf plant), the smaller plants can act more like a weed to the corn crop than a contributor to the field’s yield potential. Plus, with poor or uneven stands, there will be a more open canopy which may allow for weed emergence and increased weed competition.

We suggest you hold off on planting until the soil temperature reaches 50°F to ensure rapid and even germination. Soil temperature should be taken with a soil thermometer in several areas of the field, especially those with variable soil types. Fields with better drainage, sandier soil texture, or high organic matter, as well as fields that were tilled or that will be tilled are better choices for earlier planting, as these fields are likely to warm the fastest. You can also encourage soil warming by using row cleaners or strip tillage to allow direct sunlight on the soil surface that can help warm the seed row. Deeper planting will expose seed to cooler temperatures compared to those planted at shallower depths; however, we do not recommend a planting depth of less than 1.5 inches.

The use of starter fertilizers (at a rate that will sustain the crop until sidedress) can also promote more rapid and even germination. We recommend using fertilizers with a lower salt index on sandy soils and avoiding placement of fertilizers in-furrow (pop-ups) to limit the potential for salt damage to the seed or young seeding. High salt concentrations can damage and/or dry out emerging roots, leading to uneven emergence, which can potentially reduce yields.