Posts Tagged ‘17:24’

WCU Volume 17, Issue 24 – August 28, 2009

Friday, August 28th, 2009

PDF Version of WCU 17:24 – August 28, 2009

In this issue:

Vegetables
Vegetable Crop Insects
Late Summer and Fall Cover Crops for Vegetable Ground
Tomato Buckeye Rot
More About Tomato Ripening Problems and the Role of Potassium

Agronomic Crops
Agronomic Crop Insects
Selecting Head Scab Resistant Wheat Varieties
Soybean Sudden Death Syndrome
Weed Control in Seedling Alfalfa
Weed Control for Grass or Mixed Pasture Plantings
Options for Harvest Aid Treatments

Announcements
Beekeeping Meeting @ Wye REC – September 12
Friends of Agriculture Breakfast – September 18
Pole Lima Breeding Line Evaluation @ Georgetown – September 24
Equine Pasture Walk – September 29
Grass Finished Livestock Conference – October 23 & 24

Weather

Pole Lima Breeding Line Evaluation

Friday, August 28th, 2009

Thursday, September 24, 2009     5:30-7:00 p.m.
Carvel Research and Education Center
16483 County Seat Hwy.
Georgetown, DE 19947

Attention Pole Lima Bean Enthusiasts!

Come help to evaluate the pole lima varieties and breeding lines being tested at the Georgetown research farm. Lines to look at include twelve varieties, thirteen hybrids and four diverse populations developed from crosses.

Please contact Emmalea Ernest by Tuesday, September 22 if you plan to attend: (302) 856-7303 or emmalea@udel.edu.

Options for Harvest Aid Treatments

Friday, August 28th, 2009

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

A harvest-aid may be a consideration to dry down vegetation prior to harvesting and to reduce foreign matter in the harvested grain. For corn Defol (sodium chlorate) is labeled for applications 14 days prior to harvest and it can be applied by air. Defol will dry down plants but it does not have herbicide activity. Dry down is slow; expect at least 14 days for dry down. Glyphosate is labeled but must be used with care do to potential injury to desirable vegetation. Apply glyphosate at 35% moisture or less and black layer has formed. Allow 7 days between application and harvest. Refer to the glyphosate label for rates. Gramoxone Inteon is labeled for broadcast treatments. Application rates are 1.2 to 2 pts/A plus a non-ionic surfactant, and must be applied at least 7 days prior to harvest. Be sure to read the label for all precautions.

2,4-D amine is labeled but due to volatility and off-target movement, use of 2,4-D is not recommended. Applications with air temperatures above 85°F increase the likelihood of off-target movement. Application timing is after the hard dough or dent stage.

Weed Control for Grass or Mixed Pasture Plantings

Friday, August 28th, 2009

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

Weed control options are very limited for establishing a grass or mixed stand pasture. There are no products to use pre-plant incorporated or preemergence that will provide residual control and not injure the crop. Early postemergence options are also very limited. Ally, Banvel, Overdrive, Crossbow, or 2,4-D can be used for pure grass seedlings (they will kill clovers and alfalfa) but grasses need to be well established at time of application. Ally can injure fescue and ryegrass. Fescue injury can be reduced if Ally is tankmixed with 2,4-D.

Weed Control in Seedling Alfalfa

Friday, August 28th, 2009

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

Getting seedling alfalfa off to a good start is critical for a long-term quality stand. The following herbicide suggestions are for pure alfalfa stands. Gramoxone or Roundup can be used prior to planting to kill emerged weeds. Balan or Eptam can be used pre-plant incorporated for control of small-seeded broadleaves such as pigweed or lambsquarters and most annual grasses. Residual control of either Balan or Eptam is only a few weeks. Butyrac, Buctril, Pursuit, Raptor, and others can only be used after the alfalfa has emerged and developed trifoliate leaves. Fall postemergence treatments include Butyrac 200 (2 to 4 alfalfa trifoliates), Buctril (at least 4 trifoliates), Kerb, Poast Plus, Select, or Pursuit or Raptor (at least 2 trifoliates). Pursuit or Raptor provides the broadest spectrum of control, and can be tank-mixed with Buctril or Butyrac to improve control. The addition of Buctril to Pursuit will improve German moss, lambsquarters, and henbit control. Kerb will provide the best common chickweed control, but it must be applied when soil temperatures are 50°F or less and requires rainfall for activation. Applications to small weeds are critical for effective control. Poast Plus and Select are effective only on grasses, and cannot be used on alfalfa plus grass stands. Most of the labeled herbicides can cause some crop injury to the alfalfa.

Soybean Sudden Death Syndrome

Friday, August 28th, 2009

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Sudden death syndrome (SDS) has been tentatively identified from a soybean field in Sussex County and several fields in New Castle County this week. We have not seen this disease in Delaware since 2000 when it was first identified. The reason we are seeing it again is that we have had weather conditions that were very favorable for SDS just like in 2000. It has to be cooler and wetter than normal in the early part of the season for SDS to appear. What does SDS look like in the field? Yellow blotches form between the veins, usually developing first on the uppermost leaves. In a few days the yellow blotches will coalesce and begin to turn brown. The end stage is complete tissue death between the veins, with the only green tissue remaining being that associated with the primary leaf veins. The edges of severely diseased leaves will roll inward. Over time the diseased leaflets may fall off the leaf stalks (petioles) or they may remain attached to the plant. When you dig up the infected plants primary, secondary and tertiary roots are severely rotted. Nitrogen-fixing nodules are mushy. The exterior of the stem appears healthy but the interior of the stem is a milky-brown color, compared to the yellow-white color of a healthy stem. Serious yield loss usually only occurs when plants are exhibiting serious foliar symptoms BEFORE mid-pod fill. After that time, plants can look pretty rough, but yields may not be affected much. Individual and groups of plants, 10-50 feet in radius, usually show a range of symptoms ranging from some leaf spotting to complete defoliation. Wet or otherwise stressed areas of fields from compaction or other causes, such as along field edges, will usually be the first to develop symptoms. In extreme cases, entire fields may show symptoms. When SDS is severe, symptoms will first develop in “hot spots” and later progress into other areas. This gives the effect that the disease is spreading, but in reality it is not. Rather the time of infection, crop health, and field conditions vary, so disease symptoms are expressed at varying times and rates. The only control is reducing plant stress by reducing compaction, and planting resistant or tolerant varieties. Rotation is of little to no value in controlling SDS. Be careful to check plants carefully for these symptoms because stem canker can also produce similar symptoms.

foliar SDS symptomsFoliar symptoms of SDS

SDS root symptomsInfected root on the left with diseased leaf compared to healthy stem and leaf

Selecting Head Scab Resistant Wheat

Friday, August 28th, 2009

Dave Van Sanford, Wheat Breeder, University of Kentucky and Bill Bruening, Variety Testing Specialist, University of Kentucky

Bob Mulrooney Notes: This is an excellent article from Kentucky Pest News (#1210 Aug 25, 2009) that is very timely for Delaware growers.

Selection of wheat varieties is one of the most critical management decisions Kentucky wheat producers will make. The decision is complicated this fall by the fact that 2009 was a year in which Fusarium head blight (FHB) or head scab, was a problem for KY wheat growers. The real question is “how important is head scab resistance?” Clearly, in a bad head scab year, growers recognize that FHB resistance is very important. After a year or two with little or no head scab, however, farmers tend to underestimate the value of scab resistance. In any given year, how likely is it that head scab will be a serious disease in Kentucky? We know that with our corn‐wheat‐soybean rotation we will always have plenty of inoculum. Although we don’t know if the moisture requirements of the disease will be met when the crop is flowering, it is reasonable to assume that we will always have a chance of seeing FHB in our Kentucky wheat crop. How serious is the disease? In addition to reducing yield and test weight, the thing that sets FHB apart is the toxin (DON or vomitoxin) that is produced by the fungus. Elevated DON levels can result in serious discounts or even rejection of loads at the elevator or mill. For this reason alone,we need to take head scab very seriously.

Resistant Varieties
The best known and most widely studied genetic resistance comes from Sumai 3, a Chinese spring wheat variety. Pioneer Brand 25R18 is an example of an older soft red winter wheat variety that has Sumai 3 resistance. This is Type II resistance, or resistance to spread of the fungus in the head which means that under heavy FHB pressure, there might be many heads that are infected, but the severity of infection on each head will be low. In addition to the Sumai 3 resistance source, there are numerous adapted SRW varieties with varying levels of scab resistance. Truman and Bess are two varieties released by the University of Missouri which have good scab resistance that is not derived from Sumai 3. Due to the heavy scab pressure throughout Kentucky in 2009, we had a good opportunity to rate scab symptoms on all 88 entries in the state variety trial (Table 1). Keep in mind that these ratings are based on chaff symptoms observed between flowering and physiological maturity. These symptoms often provide a good indication of kernel damage that is likely to occur, but the relationship is not perfect.

Combining Resistance with Fungicides
When we define FHB resistance, our targets include a low level of infection, plump kernels with no yield or test weight reduction and low DON levels in the grain. In a year like 2009 under heavy scab pressure, it takes a combination of good genetic resistance and a well‐timed fungicide application to hit these targets. In Table 2 we present two years of data from our inoculated scab nursery at Princeton, KY where varieties and breeding lines were evaluated with and without a fungicide application. Scab is a difficult disease for farmers, millers and researchers. It takes several years of testing and retesting to really get to know the scab profile of a variety. For this reason, the data in Tables 1 and 2 should be studied very carefully before deciding which wheat varieties to plant this fall. It is also important to apply the other risk management strategies that we have discussed in previous variety selection articles. In particular it is important to remember that wheat growers can minimize their risks by planting several varieties with good yield and test weight potential that complement one another for disease resistance and maturity. Choosing varieties of differing maturities makes sense for a number of reasons, but it is especially important when considering head scab. In those years when head scab is problematic, if the early flowering varieties are hit hard, then the later flowering types often face less scab pressure, and vice versa. A final suggestion is to avoid planting varieties that appear to be very susceptible to head scab. If a variety completely lacks genetic resistance, a fungicide application will not be sufficient to prevent yield loss and elevated toxin levels during an epidemic scab year.

 

Table 1. Scab Ratings (1=excellent; 9=poor) Based on Chaff Symptoms; Each Value Represents the Average of Ratings at 6 Variety Trial Locations in Kentucky, 2009

Variety

Head Scab

AgriPro Branson

6.6

AgriPro COKER9511

3.9

AgriPro COKER Oakes

5.5

AgriPro W1104

4.5

AgriPro W1377

5.4

AgriPro W1566

6.1

ARMOR 3602

6.4

ARMOR ARX 6202

6.3

ARMOR ARX 840

6.8

ARMOR GOLD

7.0

ARMOR RENEGADE

5.0

Beck113

5.3

Beck122

5.7

Bess

4.0

Clark

5.7

Cumberland

6.0

Delta Grow1600

5.8

Delta Grow4500

6.2

Delta Grow5200

5.8

Delta King 9108

5.9

Delta King 9577

7.1

Dixie 907

5.9

Dixie 940

5.9

Dixie 989

6.4

Dyna-Gro 9911

5.3

Dyna-Gro 9922

5.3

Dyna-Gro Shirley

6.0

Dyna-Gro V9710

6.5

Dyna-Gro V9723

5.6

Dyna-Gro V9812

6.6

EXCEL 163

6.9

EXCEL 234

4.2

EXCEL 341

5.6

Exsegen Anna

6.4

Exsegen Candace

6.2

Exsegen Dinah

4.8

Exsegen Lois

5.6

Exsegen Lydia

6.5

Jamestown

6.3

KAS 5003

6.0

KAS 5058

4.9

KAS 7700

5.9

KY 00C-2059-24

5.7

KY 00C-2109-01

7.3

KY 00C-2175-10

6.0

KY 00C-2567-01

6.5

KY 00C-2697-04

5.9

KY 97C-0321-02-01

6.9

KY 97C-0508-01-01 A-1

5.6

KY 97C-0519-04-07

6.1

KY 97C-0540-01-03

5.7

KY 97C-0574-01-04

5.4

Merl

7.1

Milton

5.7

Pembroke

5.1

Pioneer variety 25R63

5.0

Pioneer variety 25R78

7.1

Pioneer variety 26R15

5.5

Pioneer variety 26R22

6.4

Pioneer variety XW07B

7.1

Pioneer variety XW07X

3.5

PROG ENY 117

5.5

PROG ENY 119

5.5

PROG ENY 130

5.3

PROG ENY 136

6.8

PROG ENY 166

6.3

PROG ENY 185

5.9

Red Ruby

6.2

SC 1298

5.8

SC 1318

6.7

SC 1325

5.6

SC 1328B

5.4

SC 1339

7.0

SC 1348

6.0

SS 520

8.0

SS 5205

6.4

SS 548

7.0

SS 8302

4.9

SS 8309

4.4

SS 8404

5.9

SS 8641

7.6

SS MPV-57

6.0

Steyer Geary

6.5

Steyer Jordan

5.4

Steyer Nofziger

6.2

Truman

2.6

USG 3350

6.0

VA 04W-90

5.7

Average

5.9

Table 2. Two Year Comparison of Wheat Varieties and Breeding Lines Treated vs. Untreated with Prosario Fungicide in Princeton Inoculated Scab Nursery, 2008-09 (DON data not available at press time)

Entry

Fungicide Treated

Untreated

Yield
(bu/A)

Test Wt
(lb/bu)

Scabby Seed (%)

Yield
(bu/A)

Test Wt
(lb/bu)

Scabby Seed (%)

AgriPro Branson

77.2

51.3

5.4

60.3

48.1

9.6

AgriPro COKER 9511

75.2

57.9

1.9

67.9

57.0

2.8

AgriPro W1377

69.7

55.8

4.5

56.1

52.2

7.5

Bess

78.8

56.9

2.4

61.9

54.6

5.9

Clark

62.5

54.2

2.7

53.5

51.0

6.7

Cumberland

74.2

52.0

5.6

56.9

47.8

14.9

Delta Grow 1600

70.3

51.5

7.5

50.4

48.5

9.9

Delta King 9577

61.8

49.6

7.2

45.7

45.7

16.6

KY97C-0508-01-01A-1

76.6

53.5

4.2

53.3

49.7

10.7

KY97C-0540-01-03

59.9

51.9

4.8

53.9

50.4

13.8

KY97C-0574-01-04

67.0

53.2

5.2

41.1

47.8

14.9

MO 011126

63.8

54.5

3.8

51.1

50.8

7.7

Pembroke

77.2

54.3

4.1

53.6

50.9

5.6

Pioneer variety 26R15

80.2

51.6

7.0

69.0

49.9

8.3

Pioneer variety 26R22

62.2

50.0

4.8

45.1

44.8

17.0

SS 520

63.0

52.1

5.2

50.4

47.3

12.7

SS 8302

70.1

54.3

2.9

63.8

51.9

8.0

SS 8309

77.2

53.4

3.5

58.5

49.6

8.5

SS 8404

67.0

54.0

3.8

54.0

49.6

11.5

SS MPV-57

65.2

51.6

5.7

57.0

47.2

14.5

Truman

82.5

56.0

3.0

72.9

54.5

3.8

Agronomic Crop Insects – August 28, 2009

Friday, August 28th, 2009

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Alfalfa
Be sure to watch for fall armyworm, beet armyworm, webworms and corn earworm which can quickly defoliate alfalfa. Mixed populations of larvae can be found in fields and controls should be applied before significant defoliation occurs. Defoliators can be destructive in last cuttings, especially during drought conditions. When defoliators are present, early harvest may eliminate the problem. Although there are no specific thresholds, as a general guideline if the crop is more than 2 weeks from cutting and 25 to 30% of the terminals are damaged, treatment is suggested.

Soybeans
As the potential for late season insect control increases, be sure to check all labels for the rates, days from last application to harvest as well as other restrictions.

Corn Earworm Alert
The potential for corn earworm pressure in soybeans is high statewide. Trap catches remain high throughout the state, moths can be found laying eggs in double crop fields statewide and larvae are being found. With the continued high trap catches throughout the state, be sure to check all fields for earworms. Although open canopy blooming fields will be the most attractive to egg laying moths you should check all fields to be sure you do not miss an infestation. As a general guideline, a treatment should be considered if you find 3 podworms per 25 sweeps in narrow row fields and 5 podworms per 25 sweeps in wide row fields (20 inches or greater). However, these static thresholds were calculated for a 10-year average soybean bushel value of $6.28. The best approach is to access the Corn Earworm Calculator (http://www.ipm.vt.edu/cew/) which estimates a threshold based on the actual treatment cost and bushel value you enter. As reported in previous newsletters, states to our south, including Virginia, have reported control failures with pyrethroids in soybeans in 2007 and 2008. As of the 2008 season, poor control with pyrethroids in our area has been the result of treating too late, treating large worms or using too low of a rate. If a pyrethroid is used for earworm control, you need to be using the highest labeled rate. In addition to the pyrethoids, Steward, Lorsban or Larvin should also be considered, especially if armyworms are in the mix. In some fields, fall armyworm and beet armyworm can also be found.

You will also need to continue to scout for soybean aphids. With the recent cooler night temperatures, we are seeing an increase in populations in all three counties, especially in later planted fields and economic levels have been found in fields in Kent County. As a general guideline, treatment is needed through the R5 stage (seed is 1/8 inch long in the pod of one of the four uppermost nodes on the main stem) of soybean development if economic levels are present. It may also be beneficial to spray through R6 stage (pods containing a green seed that fills the pod cavity at one of the four uppermost nodes on the main stem) — reports vary as to the benefit of spraying once plants reach the R6 but in some years and some situations there has been an economic return. Spraying after R6 stage has not been documented to increase yield in the Midwest. The suggested treatment threshold from the Midwest is still 250 aphids per plant with 80% of the plants infested with aphids. This number should provide a 5 to 7-day lead time for treatment to avoid economic loss.

Although populations have been generally lower this season, we are also starting to see an increase in populations of stinkbugs. You will need to continue to scout for stinkbugs in fields that are in the pod development and pod fill stages. Economic damage is most likely to occur during these stages. You will need to sample for both adults and nymphs when making a treatment decision. Available thresholds are based on beans that are in the pod development and fill stages. We are currently following the same guidelines that are being used in Virginia. Thresholds are based on numbers of large nymphs and adults, as those are the stages most capable of damaging pods. As a general guideline, current thresholds are set at 1 large nymph/adult (either brown or green stink bug) per row foot if using a beat sheet, or 2.5 per 15 sweeps in narrow-row beans, or 3.5 per 15 sweeps in wide-row beans.

More About Tomato Ripening Problems and the Role of Potassium

Friday, August 28th, 2009

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu 

In last week’s issue of WCU Gordon Johnson did a nice job of explaining some of the problems with tomato ripening that we are seeing in the area in the article titled Ripening Disorders in Tomatoes. The ripening problems are called various names such as blotchy ripening, yellow shoulder, graywall, internal whitening, etc. (Fig. 1). They all have the same root cause; lower levels of potassium (K+) than what is needed by the fruit to ripen properly. But, just as with blossom end rot, the factors that can lead to the ripening problems are more complex than just reduced levels of K+ and that is what I would like to discuss. The first problem I was aware of, mostly because it was happening in my research high tunnel was internal whitening (Fig. 2). This is different from graywall because there are blotches of hard, white, corky tissue instead of collapsed dark tissue (common in graywall) in the outer wall of the fruit. In addition the corky white tissue is not confined to the outer wall of the fruit but is found throughout the interior walls of the fruit. Tomatoes look good on the outside but bad on the inside. Other high tunnel growers in the southern part of Maryland and on the Eastern Shore were also having these same problems at the same time. There were many peculiar factors with this problem; first that it happened over a large geographical area, second that it happened across many varieties and third that the ripening problem occurred much more frequently in high tunnels than outside. A couple of high tunnel growers took soil and foliar samples and consistently found that the soil was at adequate or even high levels for K+, but the tissue samples were low to very low in K+. What could cause a reduction in K+ in the plant when there was plenty in the soil? The best explanation for this is the weather we had in May and June. As you recall we either set records or came close for those two months for rain. This also meant we had very cloudy skies. Whether it was the excess moisture, the cloudy skies or both, the plant’s ability to take up enough K+ was seriously reduced. This may seem odd, but anything that interferes with the ability of the plant to take up K+ will result in ripening problems, especially when there is a heavy fruit load on the plant (which there was in high tunnels, but not in the field in May and June). What makes me think the fruit load is important? In a small study I removed 50% of the fruit (various sizes of all green fruit) from tomato plants scattered throughout a high tunnel. A month later the incidence of ripening problems was about 20% on the plants with all their fruit and almost 0% for plants that I had removed the fruit.

Now we are seeing problems in the field and high tunnels with yellow shoulder and uneven ripening (Fig. 3). It comes around in mid to late summer when plants are putting on fruit and temperatures and humidity are high. The cause is the same, K+ levels too low in the plant, but for different reasons. Some of the reasons could be inadequate moisture and a poor tomato root system, which results in a plant that cannot take up the proper amount of K+. If the roots are concentrated in the top 6 inches of soil and the plant canopy is poor this can expose the black plastic to the sun and raise soil temperatures to the point where water as well as K+ and other nutrient uptake is reduced enough to cause ripening problems.

You will notice that I have not mentioned any real solutions to the various factors that cause ripening problems. Saying “be sure you have enough K+ in your soil” as I have over the years does not seem to be the best solution any more. I know that some growers use a foliar spray of potassium sulfate or potassium phosphate after flowering to move more K+ into the plant. I have no idea whether this will work or not. Some growers use white plastic mulch to reduce soil temperatures and many have fewer problems with yellow shoulder in late summer. What I hope to do is conduct several studies looking at many of the above factors next year.

tomato ripening problems

tomato ripening problems

tomato ripening problems

yellow shouldersFigure1. Various forms of ripening problems for tomatoes in the Mid-Atlantic

internaltomatowhitening2internaltomatowhitening1Figure 2. Internal whitening of tomato fruit, mostly found in high tunnel tomatoes early this summer

more yellow shoulderFigure 3. Various forms of yellow shoulders showing up now in the field and high tunnels

Tomato Buckeye Rot

Friday, August 28th, 2009

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Be on the lookout for buckeye rot caused by Phytophthora nicotianae. This is primarily a disease of processing tomatoes that are ground grown, not trellised. Large brown water soaked spots with concentric rings that resemble a buckeye are seen on the fruit. Once seen it’s too late for control. Ridomil or MetaStar needs to be applied to the soil surface under the vines 4-8 weeks before harvest.

tomato buckeye rot