WCU Subscription Options for 2013: Mail, Fax, Email or Text

Vegetables
Vegetable Crop Insects
Transplant Losses and Replant Options
Shadecloth for Hot Season Vegetable and Fruit Production
Fusarium Wilt of Watermelon in the Southern US in 2013
Heirloom Tomatoes and Fusarium Wilt

Fruit
Strawberry Notes: Crop Progress and Virus Situation Update

Agronomic Crops
Agronomic Crop Insects
Wheat Disease Update
Corn Herbicides and Soil Insecticide Interactions
Burndown for No-Till Soybeans at this Time
Field Crops Growers Can Conserve Nitrogen in Poultry Litter While Retaining Benefits of No-Till
Pokeweed is Poking Up in a Lot of Corn Fields

General
Brown Marmorated Stink Bug Resources
Funding Now Available for Water Quality Monitoring on Farms

Announcements
High Tunnel Mixed Vegetable Production Workshop – May 21
Retail Farm Market School – May 29
Blueberry Educational Meeting and Field Tour – June 8
UD Cooperative Extension Horticulture Short Course: Pest and Beneficial Insect Walks – June 26
University of Delaware Weed Science Field Day – June 26
Wye Weed Science Field Day – June 27

Weather

Delaware’s Clear Brook-Nanticoke River Watershed has been approved for potential edge-of-field monitoring projects. Delaware NRCS is encouraging producers within the selected watershed to sign up by June 14 to monitor the water quality benefits of various conservation practices, such as no-till, cover crops, nutrient management and more.

Selected producers will work with consultants, universities, and state and local agencies to develop a monitoring plan meeting NRCS approval and to conduct monitoring. Producers will be able to receive funding for monitoring through the Environmental Quality Incentives Program. Only the highest ranked applications will be funded as this is a competitive process throughout the Bay Watershed.

“We are committed to demonstrating that voluntary conservation efforts implemented at the farm level are invaluable,” said Russell Morgan, Delaware NRCS State Conservationist. “As monitoring progress is made, we will be better able to help farmers focus conservation practices on the areas of greatest need using the most effective conservation systems.”

The data collected from these projects will be used to validate NRCS water quality modeling efforts that will benefit agriculture across the nation. All data will be protected under the Farm Bill privacy rules, and details will be shared only as authorized by the producer.

Delaware’s selected watershed is also the focus on our National Water Quality Initiative (NWQI) program. Only producers within the Clear Brook-Nanticoke River Watershed, which is located in the western region of Sussex County between Bridgeville and Seaford, are eligible to participate.

All applications for funding consideration for the edge of field monitoring project must be received by June 14, 2013; however, NRCS accepts applications for funding assistance on a continuous basis throughout the year.

If you live in or near the Bridgeville and Seaford areas, contact the USDA Service Center in Georgetown to see if you are located in the selected watershed. To learn more, call 302-856-3990 x 3 or visit www.de.nrcs.usda.gov.

The Northeast IPM Center is producing a video series on BMSB highlighting the work of the SCRI Coordinated Agricultural Project on Biology, Ecology, and Management of Brown Marmorated Stink Bug in specialty crops (Joanne Whalen and Brian Kunkel are both members of this project in Delaware). The first two videos can be seen at http://www.stopbmsb.org/video with more to come in the next couple of months.

I have seen a number of corn fields with pokeweed emerging along field edges or in patches. These areas should be sprayed before the plants are 10 to 12 inches tall and as result may require some spot applications before the whole fields need to be treated for summer annual weeds. In addition to glyphosate, other effective postemergence treatments include Callisto, NorthStar, Yukon, dicamba (1 pint/A), or Status (5 oz/A). Also note that NorthStar, Yukon and Status all contain dicamba (Banvel) and take precautions so that sensitive plants will not be affected.

There are many benefits of long term no-till. However, using surface applications of poultry litter in no-till has several drawbacks. The following are some thoughts on how to manage poultry manure to reduce nutrient losses while maintaining some of the benefits associated with no-till.

No-till has been shown to reduce erosion losses from fields and, therefore, reduce the transport of nutrients attached to soil particles that would subject to erosion. Phosphorus losses are reduced considerably upon initial adoption of no-till. Nitrogen losses from surface flow are also reduced, but a significant portion of nitrogen in runoff exists in a soluble form rather than a particulate form. Over time, surface additions of poultry litter in continuous no-till leads to a buildup of soil P at the surface, which can increase soluble P losses in surface runoff. In addition, surface applications of poultry litter do not conserve the ammonium fraction. If litter is not incorporated shortly after application, much if not all of the ammonium can be volatilized and lost to the atmosphere as ammonia gas; only the organic fraction remains, thus reducing the fertilizer (and economic) value of the manure. Long term no-till provides significant soil quality and productivity benefits by increasing organic matter in soils. Tillage will greatly reduce organic matter accumulation by increasing oxidation rates. Balancing the benefits of long term no-till with the disadvantages of P surface buildup and ammonia losses when poultry manure is surface applied is difficult.

However, there are some management options that provide many of the benefits of no-till (such as reduced erosion and organic matter accumulation) while conserving ammonium N in applied poultry litter and reducing stratification of P. A number of farmers in Delaware have adopted the use of special minimum tillage tools, including aerators, vertical tillage devices (Turbotill), and “no-till harrows”. These devices allow for partial incorporation of poultry litter, which helps to conserve some of the ammonium N and reduce P stratification. The action of these devices is such that much of the benefits of no-till remain. Surface cover is reduced minimally, ensuring that erosion rates will not increase significantly; in some cases infiltration rates are improved further reducing erosion potential. Organic matter oxidation is increased under minimum tillage, but organic matter accumulations will be higher than what is expected when using standard tillage practices.

Another innovation that is on the horizon is a poultry litter injector. A narrow furrow is opened; the dry poultry litter falls into the slot and then the slot is closed again with closing wheels. The process of litter injection is expected to better maintain no-till benefits, conserve most of the ammonium N, and reduce surface P stratification than minimal tillage options.

Our current recommendation is to apply poultry litter and use an aerator, vertical tillage device, or no-till harrow to do a partial incorporation, while leaving as much crop residue as possible. Once poultry litter injectors become available, farmers may want to adopt that technology, if economically viable (cost of purchase and operation is less than the benefits received).

If no-till soybean fields have not been sprayed yet, we are facing an uphill battle. Most of the horseweed (or maretail) is now well over 6” tall, and so are a lot of the other winter annual weeds.

It’s too late to rely on 2,4-D to control marestail because you need the 1 qt rate to provide effective control. The 1 qt rate of most 2,4-D products require 4 weeks before planting and in too many places sensitive plants have emerged. If you are on appropriate soil type, Sharpen with all the required adjuvants is an option (see the label). Sharpen is not an option for coarse-textured soils because it requires 4 weeks between application and soybean planting due to concerns with safety to soybeans. A chlorimuron-based herbicide is another option, but you need to use rates that will provide good suppression/control. Chlorimuron rates equivalent to 1.7 oz of Classic are what we have found for more consistent activity (see table). This is probably a higher rate than is typically used, but you will need these higher chlorimuron rates to provide the best level of suppression.

We have found populations of horseweed that are resistant to ALS-inhibiting herbicides, so this approach is not a recommendation for use every year.

Two other considerations are Liberty 280 and Gramoxone. Liberty 280 is in tight supply and maybe hard to get. Gramxone SL will require two applications. One of the Gramoxone applications should be applied with a metribuzin containing-product (Canopy, Boundary etc) because it will improve the performance of the Gramoxone. Both Liberty 280 and Gramoxone should be applied with at least 20 gallons per acre of water and flat fan nozzles to provide the best coverage of the weeds.

All of these products mentioned above perform best on small plants. Given the size of the weeds, I would not expect complete control. Following up with an early postemergence application of Liberty (for Liberty Link soybeans), FirstRate, or glyphosate will further suppress the marestail and allow the soybean canopy to get over the top of the marestail.

A number of corn herbicides have label precautions about use of an organo-phosphate insecticide at planting due to potential crop injury. This includes the insecticides Counter (terbufos), Lorsban (chlorpyrifos), and Fortress (chlorethoxyfos). The herbicides include both soil-applied and postemergence herbicides. Some of the common products include Callisto (Halex GT); Resolve (Steadfast, Basis); Accent; or Capreno. Many of the Group 2 (or ALS-inhibiting herbicides) have these precautions. The list of herbicides can be found at http://extension.udel.edu/ag/files/2012/08/CornWeedguide.pdf and go to Table 19.

Unfortunately, most corn seed companies no longer designate hybrids as either IT or IR. So if you are not sure, take the cautious approach and assume the hybrid is a “standard” hybrid (no enhanced tolerance for imidazolinone herbicides); and follow the most restrictive guidelines.

Stripe Rust on Wheat
Rusts are fungal pathogens that derive their name from their yellow to orange, rust-colored spores. Rusts typically are not of major concern unless disease levels are severe enough to limit photosynthesis and grain fill. We typically see leaf rust and stripe rust in Delaware, with the former more common than the latter. Stripe rust most commonly affects leaf blades and occasionally can be found on heads when disease is severe. Signs of the disease include small, round yellow/orange lesions that merge to form stripes on the leaf (Figure 1). When a symptomatic leaf is rubbed between the forefingers it will leave a characteristic yellow/orange, rust-colored powder on your fingertips. Stripe rust, unlike leaf rust, does best at cooler temperatures (60-70°F) and does not do well when temperatures increase (70-80°F). However, the disease can still develop under high temperatures with cool nights and rain. Disease development in this case will be much slower than under persistent cool, humid conditions.

We recently observed a small, localized outbreak of stripe rust on a field in Kent County and there have been reports of the disease in Virginia. Disease incidence and severity in all cases was low. At this time I would suggest fields be scouted for rust. If you observe signs of the disease on the flag leaf and your wheat has not yet flowered, you still have time to make a decision regarding treatment. If you made a fungicide treatment at boot or early heading with products such as Quilt™, Prosaro™, or Caramba™ you will have 14-21 days of rust control from the time of the application.

Figure 1. A wheat leaf with characteristic stripe rust lesions. Note how the rust runs with the leaf venation.

How can you determine if you have a rust issue that requires attention? Ask yourself these questions: 1) Is the rust on the flag leaf? 2) Has any fungicide been previously applied to the field? 3) What is the growth stage of the wheat? If you have a fair amount of rust on the flag leaves of wheat in your field, did not make a fungicide application at boot stage or early heading and plants are not past flower, then the field might benefit from a fungicide treatment. Check product labels to determine fungicide timings and preharvest intervals. Fungicides in the group 3 class (triazoles) have good activity against rust. These include Prosaro™ and Caramba™, which were mentioned last week for suppression of Fusarium head blight. If Fusarium head blight is not a concern, generic tebuconazole products may also be considered for stripe rust control.

Fusarium Head Blight Update
A long period of wet, humid weather followed by severe thunderstorms this past weekend resulted in increased risk levels of Fusarium head blight (FHB) throughout Delaware, particularly in Sussex and Kent Counties. This increased risk level only would have impacted growers who had wheat go into flowering over the weekend up until Mother’s Day (May 11-12). Those of you who just had wheat go into flower this week or are still waiting for your wheat to flower are not currently at a high risk for head scab development. The risk of FHB development in wheat that has not flowered will depend on when it flowers and if it rains. As of May 16, the scab risk has returned to low for Delaware, with the exception of a very small, southeast section of Sussex County (Figure 2). Growers are encouraged to continue to monitor the Fusasium Head Blight Risk Assessment Tool (http://www.wheatscab.psu.edu/) for changes in FHB risk levels. This tool, in combination with local weather forecasts, can help determine if fungicide applications to wheat are recommended.

Figure 2. Risk level for Delaware as of May 15, 2013. Photo obtained from http://www.wheatscab.psu.edu/.

In addition, if your wheat was in flower during the period of frost you may notice damage to heads that may resemble FHB. Suspect heads can be sent to the University of Delaware Plant Diagnostic lab for further analysis.

Past WCU articles on freezing injury to wheat may be found at:

http://extension.udel.edu/weeklycropupdate/files/2012/04/Voume15Issue3.pdf

http://extension.udel.edu/weeklycropupdate/?p=4070

Field Corn
Depending on the location in the state, we can find both cutworm and slug damage, mainly in no-till corn fields. Although we do not have pheromone traps out to monitor black cutworm moth populations, higher than normal populations are being reported in some areas of the Midwest as well as Pennsylvania. In past years, when populations were higher in the Midwest we have also seen a spike in damage. It is important to check all fields for cutworms, even where at planting treatments were used. The treatment threshold is 3% cut plants in spike to 3-leaf stage corn. In some cases you will need to check fields twice a week to be sure you do not miss an economic population. In addition to cut plants, be sure to watch for leaf feeding which can be an indication of the potential for significant cutting damage and yield loss.
http://www.ent.iastate.edu/imagegal/plantpath/corn/bcutworm/1287bwcholes.html

Small Grains
We continue to find armyworms and cereal leaf beetles in barley and wheat fields that were not treated. Population levels remain variable throughout the state, so scouting fields will be the only way to determine if an economic level is present. In addition, with the cooler spring we are seeing extended egg laying and hatch for both insects. Although armyworm can attack both wheat and barley, they can quickly cause significant losses in barley. Heavy defoliation of the flag leaf can result in significant economic loss. Armyworms generally begin head clipping when all vegetation is consumed and the last succulent part of the plant is the stem just below the grain head. Larvae can feed on the kernel tips of the wheat, resulting in premature ripening and lower test weight.

Soybeans
Seed corn maggot will be a potential problem in no-till soybeans, especially if the weather remains cool and wet. It could also be a problem in conventional soybeans where a cover crop is plowed under immediately before planting or where manure was applied. All of these situations are attractive to egg laying flies. Control options are limited to commercial applied seed treatments containing an insecticide and one hopper box material containing permethrin (Kernel Guard Supreme). Labels state early season protection against injury by seed corn maggot. No rescue treatments are available for this insect pest.

As the earliest beans emerge, be sure to watch carefully for slug damage. Remember, if you had a problem in past years, the slugs will still be present in fields and can quickly damage soybeans if they are feeding as plants emerge. You should also watch fields carefully for bean leaf beetles and grasshoppers.

We have a very late crop of strawberries this year. Plasticulture strawberries are finally in full production but reports are that the crop is lower yielding this year. We had some heavy wind storms that shredded row covers earlier this year leaving plants unprotected until recovered. Wild honey bee activity is down due to winter bee kills so only pollination from rented hives has been effective. Cold windy and rainy weather has also kept bees from flying during some of the bloom period, also reducing berry size in some cases.

Another factor has been virus infected plants that growers received this past year. These plants originated from tips grown by a nursery in Nova Scotia. Several growers on Delmarva received virus infected plants from this source. Strawberry Mild Yellow Edge Virus (SMYEV) and Strawberry Mottle Virus (SMoV) were identified in these plants. Symptoms included poor growth in some plants with older leaves turning red in color, leaf edges on new leaves showing a distinct yellowing, and some leaf margins becoming necrotic.

According to Chuck Johnson, Extension Plant Pathologist for Virginia Tech, “There is no cure for plant virus infection. Once infected, plants are infected for life, and every cell in an infected plant will eventually contain virus. There are no “silver bullets” or miracle cures, despite what some may claim. Infected plants can’t be cured, although growers could see some improvement in their appearance and growth during the spring. Those involved in strawberry plant production in Nova Scotia are aggressively working to correct their virus situation. Although many growers consider carrying strawberry plants over from one season to another, 2013 looks to be a very poor year for this. If possible, all strawberry plants should be destroyed after this season’s harvest is completed, to avoid potential carry-over of SMYEV and SMoV. Leaving potentially infected plants in the field this summer risks virus spread into next years’ crop. Fields in matted-row production should be monitored for potential virus incidence as well. Southern Region strawberry research and extension personnel met with national experts and Canadian representatives in late March to plan methods to avoid a repeat of this coming fall.”

We had frost in some areas on Monday and Tuesday and temperatures in the 80s expected later in the week. Because our strawberry crop is so late, strawberries are still blooming. These blooms have the potential to produce ripe berries in 4 weeks. To keep plants blooming and fruit setting during hotter periods where temperatures are in the mid-80s or above, cooling is advised. Run the drip irrigation very early in the morning and again in the afternoon to keep plants well watered and bed temperatures down. Evaporative cooling using mist or sprinklers can work but increases the risk of Botrytis, which may outweigh its usefulness. Shadecloth may be an option in smaller plantings and straw much over exposed black plastic can help keep beds cooler.