Posts Tagged ‘20:6’

WCU Volume 20, Issue 6 – April 27, 2012

Thursday, April 26th, 2012

PDF Version of WCU 20:6 – April 27, 2012

In this issue:

Vegetable Crops
Vegetable Crop Insects
Lettuce and Spinach Disease Control
Third Party GAP/GHP Audits and Produce Food Safety Plans
Understanding Seed Waivers and Seed Born Diseases
Seedcorn Maggot and Cabbage Maggot Damage Possible in the Next Few Weeks
Watermelon Pollenizer Variety Selection Matters
NEW Bacterial Fruit Blotch Factsheet

Agronomic Crops
Agronomic Crop Insects
Wheat Disease Update
Another Risk of Frost on the Small Grain Crop
Pasture and Hay Crop Nitrogen Fertilization
Grain Marketing Highlights

2012 Wye REC Strawberry Twilight – May 9
University of Delaware Small Fruit Twilight – May 22



Grain Marketing Highlights – April 27, 2012

Thursday, April 26th, 2012

Carl German, Extension Crops Marketing Specialist;

Market News Brief
Some analysts believe that corn and soybean acres could turn out to be much larger than indicated in the March 30 planting intentions report. Most would agree that we can go either way from current levels with the caveat being strength in the soybean market and a possibility that old crop corn supply may need to be rationed.

Corn Analysis
The corn market is due for a seasonal rally, particularly for the old crop. However, competing factors have thus far prevented that from happening. Chinese buying this past week provided for a short lived ‘buy the rumor, sell the fact’ rally, only to back off again with the market aiming sights on potentially huge planted acreage for the 2013 crop. On May 10 USDA will issue the next monthly supply and demand report. Feed, export, and corn for ethanol demand will be of interest in determining whether corn needs to bid up in order to ration old crop supply with carryover stocks estimated at 801 million bushels for the current ‘11/‘12 marketing year. The weekly export sales report was viewed as neutral.

Soybean Analysis
The soybean market continues to rally with old crop futures making new highs and new crop futures testing resistance. Reports from the Southern Hemisphere are calling for reductions in previous soybean production estimates. This make the U.S. a major supplier of export needs for the remainder of the marketing year into 2013. USDA will need to confirm South American production estimates in the May report. The weekly export sales report was viewed as bullish.

Wheat Analysis
Chicago SRW wheat futures continue to follow corn even though U.S. and World wheat supplies are bearish with a stocks-to-use ratio of 36.2% and 30% respectively. The Ukraine has nearly cut their production estimate in half from last year leaving their share of the export market to other providers including the U.S. The weekly export sales report was viewed as neutral to slightly bearish.

Market Strategy
Overnight commodity prices are not unlike the levels of a week ago with the exception of soybeans. Dec ‘12 corn futures are currently trading at $5.40; Nov ‘12 soybeans at $13.64 (9 cents higher than last week); and July ‘12 SRW wheat at $6.30 per bushel. Outside market forces and the weather will continue to influence these markets.

For technical assistance on making grain marketing decisions contact Carl L. German, Extension Crops Marketing Specialist.

Pasture and Hay Crop Nitrogen Fertilization

Thursday, April 26th, 2012

Richard Taylor, Extension Agronomist;

The very dry spring that we’ve experienced in 2012 has made it questionable as to whether a second or late spring application of nitrogen (N) might be advisable or economical. Thanks to the rainfall last weekend and the possibility of additional rainfall this week and over the coming weekend, another application of N to pastures and hay fields following the first cutting of hay should have a much reduced chance of injuring your grass crop and should also produce additional grazing or second cutting of hay. However to be on the safe side before you apply that additional N fertilizer, take a soil probe, hand trowel or shovel and check the soil moisture level in your soil. What you would like to find is that the subsoil moisture level has recovered and that the crop will be able to not only draw on soil water from the normal 0-8 inches of soil where most of the roots can be found but also can pull water from the deeper soil layers to support growth when temperatures begin to warm up in May and early June.

Hay producers are at the biggest risk for the current moisture to dissipate before the first hay harvest is taken. If you produce hay, you should be certain to check the soil moisture levels before applying N after the first harvest. Even if inadequate soil moisture is present, N fertilizer will promote more top growth and this growth response under unfavorable conditions can lead to plant death or injury reducing stand longevity. Timothy producers should be especially careful since the first harvest often occurs very late in the spring and unless they are using one of the more heat tolerant varieties such as ‘Derby’ stands can be significantly impacted.

Finally, consider using at least some potash (K) fertilizer when fertilizing in the mid-May to mid-June period. I understand that K has become very expensive but it is the best nutrient to add to help forage grasses and legumes to tolerate the heat and drought stresses of summer. In addition if you are growing orchardgrass, there is a growing concern that we are not adequately fertilizing this crop with enough K to balance the N used to promote yields. There is some evidence that the orchardgrass decline problem that we’ve been experiencing in the Mid-Atlantic may, in part, be caused or at least aggravated by too little K fertilizer in relation to the N rate used.

Another Risk of Frost on the Small Grain Crop

Thursday, April 26th, 2012

Richard Taylor, Extension Agronomist;

Although the various forecasting sites differ in what morning will be the coldest over the weekend and into early next week, several suggest the possibility that frost pockets will develop in the Mid-Atlantic region with the greatest risk for the northern areas of the region. The winter wheat crop is beginning to reach heading and will be at one of its most susceptible stages for frost injury. It’s hoped we won’t have freezing temperatures which can completely destroy the seedhead turning it into a watersoaked mass that will not recover (See Photos 1 and 2).

Photo 1. Freeze damage to winter wheat in northern Delaware causing tiller injury, seedhead death, and leading to infection with many secondary pathogens. (Photo taken two weeks after a severe frost.)

Photo 2. Emerging flag leaf following severe frost injury.

Although there’s nothing producers can do to effectively prevent frost damage on their small grains, they should scout their fields to assess the amount of damage a few days to a week or so after the injury occurs. This should help with their marketing plans.

When the frost injures the pollen containing anthers, the seedhead will emerge normally but you may be able to detect white awns or white florets or heads that may remind you of wheat scab (Photo 3). In his “Wheat Disease Update” in this issue of WCU, our Plant Pathologist, Bob Mulrooney, comments on the possibility of scab in wheat this year and indicates that even in irrigated fields the chance is rather low due to the extremely dry spring weather. Therefore if you see heads that remind you of scab, the more likely explanation will be frost or freeze injury. Unfortunately, the impact of this type of injury on yield is severe. A number of good publications are available on the internet showing photos of injury symptoms and discussing yield implications. In particular, the University of Kentucky and Dr. Lloyd Murdock has had a lot of experience with this problem.

Photo 3. White, water soaked florets from frost/freeze damaged wheat in 2012

Wheat Disease Update – April 27, 2012

Thursday, April 26th, 2012

Bob Mulrooney, Extension Plant Pathologist;

We have had several more reports and a sample of Barley yellow dwarf mosaic virus in wheat. Irregular patches of varying height reductions, yellowing and purple flag leaves indicate BYDMV infection. Since this virus is aphid transmitted there are no controls at this time.

Fusarium Head Blight
With the much needed rain that came and the forecast for more Thursday and possibly Saturday as well some have been asking about the possibility of head blight or scab appearing. The forecast at the present time is the probability is low. The corn residue on the surface needs to be wet for a long time before spores are produced that can infect the wheat at flowering and the temperatures need to be in the mid-70s for significant infection to occur. The temperatures have been and are too low now for infection. As long as the wheat flowers between now and next Wednesday when the forecast is for warmer temperatures the wheat will no longer be in a susceptible stage of development for scab to infect. I think the risk of scab it very low and specific sprays for scab control are unwarranted at this time.

Keep up to date with scab by visiting the website and using the 2012 Predictor. This will be important if we should get more rain later in the week.  Make sure the predictor says 2012 across the banner. For some reason my browser is going back to the 2011 site. If you run into the same problem here is the 2012 link

Leaf Rust & Stripe Rust
More of a possibility is the occurrence of some late season leaf rust and stripe rust. There has been stripe rust reported in NC earlier in the week and now a report of leaf rust and stripe rust from Mt. Holly, VA in university test plots. These reports are fairly close and after a big rain event like we had with some more possibly on the way we may see some develop within the next two weeks. If growers have a variety that is susceptible to leaf rust or stripe rust, there is a chance that we could see more rust two weeks from now depending on the temperatures. Again that might justify application of a fungicide at flowering if you have rust present now or are growing a susceptible variety. With the lack of water there may be undetected leaf rust in the lower canopy and with the recent rain there could be spread to the upper canopy. Be sure to get out and check the wheat before making a spray decision. Prosaro plus a non-ionic surfactant can be applied to wheat until 30 days before harvest; for scab control it needs to be applied at early flowering in 5 gal/A if applied by air. Tilt can only be applied until full head emergence. With the low risk of scab, strobilurin fungicides such as Headline and Quadris could also be considered for protection against leaf and stripe rust as well as tan spot, and the Septoria complex if those diseases are present, which have not been seen because of the dry weather. Be sure to check labels for application restrictions. Our past experience has shown that diseases that appear late (after flowering) usually do not have time to infect the upper leaves that are important for grain fill and reduce yield. If diseases are present in the canopy at flowering there is more of a risk of diseases reducing yield and/or quality of the grain.

Some information from Dr. Christina Cowger from USDA at NC State Unversity indicates that the following varieties are susceptible to stripe rust and might warrant spraying especially if any rust is present now. There are some gaps in our knowledge about susceptibility to stripe rust, so this is a very limited list of known susceptibility for varieties that are grown in the Mid-Atlantic:

Coker 9436, DG Shirley, NC Cape Fear, NC Neuse, NC Yadkin, P26R12, SS520, SS560, USG3209, USG3592, USG3665, SS8404

Freeze Injury
We just received a wheat sample from Kent County, DE with random bleached awns as well as tips of some heads. If you see some irregular bleaching of heads don’t panic about scab. We suspect at this point since no fungus appears to be present on this sample that the damage is from freezing. From spike emergence through flowering, freezing can cause symptoms that range from minimal bleaching of the awns to severe grain yield loss, depending on the duration and degree of freezing.(See Photo 3 in the article by Richard Taylor, “Another Risk of Frost on the Small Grain Crop”, which is in this issue of WCU) If normal kernel development does not occur, then freeze injury can be suspected.

Agronomic Crop Insects – April 27, 2012

Thursday, April 26th, 2012

Joanne Whalen, Extension IPM Specialist;

Field Corn
As the first plants emerge, we often can see both cutworm and bird damage in the same field. In general, small cutworms feed on leaves before cutting plants. You can distinguish bird damage from cutworm damage by the pattern in the field. Generally longer strips of damaged plants, plants pulled out of the ground, and/or plants cut high that are compressed at the base of the stems, all indicate bird damage. Although birds can cut plants off at the soil surface, they tend to pull plants out of the ground. In addition, if you look closely you will see “bird prints” near the missing plants or holes where birds have pulled plants out of the ground. As a reminder, we did receive a 24(c) Special Local Needs Registration for Avipel Hopper Box (dry) Corn Seed Treatment for bird management on field corn in Delaware a number of weeks ago as reported in WCU 20:3. The 24 (c) label should be on the pesticide canisters. If you need a copy of the label, please contact Dave Pyne at the Delaware Department of Agriculture.

We are starting to get questions about stink bugs in wheat. We can find low levels of native brown stink bug populations (not brown marmorated stink bugs) on heading wheat. At this time, little is known about the impact of stink bugs on wheat in our area. Information from southern states indicates that wheat may be susceptible to native stink bug feeding at the milk and soft dough stages. They also state that it takes extremely high numbers to cause damage to heading wheat. Thresholds in the South for native stink bugs range from one per head to one per 5 to 10 heads. In addition, they find the highest populations of stink bugs along field edges. We plan to gather more information in the Mid-Atlantic region this year on both native and brown marmorated stink bugs in small grains.

Watermelon Pollenizer Variety Selection Matters

Thursday, April 26th, 2012

Emmalea Ernest, Extension Associate-Vegetable Crops;

For several years now seed companies have been offering special pollenizer varieties for use in the in-row planting scheme for seedless watermelon production. Ideal pollenizers for the in-row system will produce many male flowers throughout the season, be non-competitive with the seedless watermelon plants and possess a high level of disease resistance. Many special pollenizers do not produce marketable fruit.

In 2011 we set up an experiment to evaluate some of the special pollenizer varieties that are available, as well as some seeded Allsweet-type hybrids (large, elongated fruit shape) in an in-row pollenizer planting scheme. The plots in this trial were isolated from one another by at least three rows of seedless watermelons without pollenizers, so we were able to collect meaningful yield data from the seedless melons in the experimental plots and draw conclusions about pollenizer variety performance.

My interpretation of the results from this trial is summarized in the table below. Many of special pollenizers supported a good total yield of seedless melons, however some produced significantly lower yields. In terms of total yield, only one of the Allsweet-type hybrids, ‘Stargazer’, performed as well as the best special pollenizer varieties. The other Allsweet-types were too competitive with the seedless plants, however would still work for dedicated bed systems where they are not growing with the seedless plants. We saw big differences between the special pollenizers in terms of early and late yields. For plantings where you are targeting an early market it will be especially important to choose a pollenizer that isn’t working against your goals. Similarly, pollenizer choice will also affect how long you can keep a field in production, as some pollenizers did not have the longevity of others.

The full report on this trial is available online at: or by contacting me at (302) 856-7303.

* Allsweet-type hybrid, all others are special pollenizer varieties.

Seedcorn Maggot and Cabbage Maggot Damage Possible in the Next Few Weeks

Thursday, April 26th, 2012

Jerry Brust, IPM Vegetable Specialist, University of Maryland;

The unusually warm and dry spring we have had up to now has led many growers to transplant some of their melon and other vegetable crops early. The cool wet weather we have had in the last few days will make some of these fields vulnerable to seed corn maggots Delia platura (SCM) or less commonly found in cucurbit fields, cabbage maggots, Delia radicum (CM). Both species overwinter in the soil as a maggot inside a brown case. In March and April small, grayish-brown flies emerge. Adult flies are most active from 10 a.m. to 2 p.m. and are inactive at night, in strong winds and when temperatures are below 50o F or above 80o F. Female cabbage maggot flies seek out and lay eggs on the lower portions of stems of young host seedlings or in nearby cracks in the soil. Within a few days the eggs hatch and the tiny maggots burrow down to the roots and begin feeding. SCM eggs are oviposited in soils with decaying plant material or manure. The adults are also attracted to the organic media around the roots of transplants and germinating seeds. That is why fields that have been fumigated can still have problems with SCM. Maggots will move into small stems and move up the plant causing a swelling of the stem just above ground level, while also causing root collapse and decay. If these stems are split you will usually find the white cylindrical larvae (Photos 1, 2 and 3).


Photos 1, 2 and 3. Swollen stem of cucurbit plant with collapsed rotting roots. When stem is cut open the white maggots often can be found.

The adult flies are often found dead, stuck to vegetation during periods of warm wet weather (like we had in early April). These flies have been infected by a fungus, Entomophthora sp. These infected flies usually will be found at the top of a tall object in the field such as a grass seed head or a wire field-flag (Photo 4). Just before the fungus kills them they cement their body via their mouthparts to the tall object and die. If you look closely you’ll see the body is filled with the white fungus that has ruptured between the segments (Photo 5). Being on a tall object allows the spores of the fungus to move longer distances and infect more flies than if the fly had died on the ground. Even though we have had a dry spring, I still have seen many fungus infected dead flies this year. Unfortunately, the infection rate is not enough to reduce the SCM population and stop infestations.

Soil temperatures two inches deep in the planting hole that are at or above 70o F reduce SCM egg laying and larval survival. If soil temperatures are above 70o F at planting but fall below this level for several days in a row (which they have just done), SCM adults will begin to oviposit eggs at the base of transplants. When wilted transplants are inspected in the field, maggots are often not found (they have already pupated), but their tell-tale damage can be seen as a hollowed out stem or root held together by a few strands of plant material. The use of treated seed or in-row banding of an insecticide gives some control of SCM, however, replacing dead transplants is the only solution after SCMs kill a plant. Once seed corn maggot damage is noticed, it is too late to apply control procedures. Thus, economic thresholds are not useful and all management options are preventative.

Photo 4. Two SCM flies killed by a fungus stuck to a wire field-flag via their mouthparts

Photo 5. Adult SCM killed by a fungus – white strands coming out of abdomen

Understanding Seed Waivers and Seed Born Diseases

Thursday, April 26th, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist;

A number of vegetable diseases can be transmitted through infected seed. For this reason, seed companies have developed quality assurance programs based on testing a certain amount of seeds in each seed lot for specific diseases. This most often involves the seed company growing out plants from these test lots and having trained individuals inspect the plants for signs of the disease. If there are suspicious plants, they are then further tested in the laboratory to confirm the disease. Sometimes seeds are tested directly for the specific disease organism (bacteria, virus, fungus). Only seed lots that have no disease detected are sold. For watermelon and cantaloupes, seed lots are tested for bacterial fruit blotch and often for gummy stem blight.

Because of past liability issues, growers are required to sign waiver forms to purchase watermelon and cantaloupe seeds from most companies. While this is often thought by growers to be a routine annoyance to purchase seeds, it is important to read the waiver forms and understand their implications.

These waivers commonly spell out what diseases the company tests for. The waiver will often have information on the testing process for these diseases. There will also be information about the diseases that the grower should know and often there will be detailed descriptions of how the disease develops and how to identify the disease.

In all waivers, there will be an important statement emphasizing that that the grower accepts the risks associated with those diseases.

The waiver may also include information on risk of nonperformance, assumption of risk, disclaimers or limitation of warranties, limits of liability, limits on damages, how to file a claim, statute of limitations on claims, arbitration of seed disputes (required by some states), expected remedies, limit on sales or transfers of seed, and attorney’s fees.

Once a seed waiver is signed then the seed company is protected from liability and this will reduce the ability of a grower to receive compensation if a seed borne disease does appear.

All growers are encouraged to understand what seed borne diseases are common with the vegetable crops that they grow, whether or not seed is treated or tested to reduce the chance of disease occurring, how to identify specific seed borne diseases, and how to manage seed borne diseases if they do occur (in greenhouse transplants or field plantings).

Growers should also maintain close relationships with seed suppliers and contact them immediately if a seed borne disease is suspected.

Third Party GAP/GHP Audits and Produce Food Safety Plans

Thursday, April 26th, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist;

Produce growers in Delaware selling directly to supermarkets, food service companies, and some wholesale distributors are being required to have a third party Good Agricultural Practices and Good Handling Practices (GAP/GHP) audit by these buyers. This is to insure that good food safety practices are being used in growing, harvesting, packing, and shipping produce.

Most of these buyers are accepting the Harmonized GAP/GHP standards that the industry and the USDA have worked on together to standardize the audit process (a few buyers have other requirements).

Harmonized GAP and GHP standards can be found at:

The audit process requires that a farm create a food safety plan and then implement that plan on the farm. The grower will then choose a private food safety auditing company, the USDA, or the state department of agriculture to perform the audit during the harvesting season. They will review the records documenting that the food safety plan is being carried out and then will inspect the growing areas and packing facilities. If the farm passes the audit, this will then satisfy the buyer’s requirements.

In Delaware, the Delaware Department of Agriculture can conduct a USDA audit using the harmonized standards.

For assistance with developing a produce food safety plan for your farm, contact Gordon Johnson, Extension Fruit and Vegetable Specialist with the University of Delaware