Volume 9, Issue 11                                                                           June 8, 2001

Vegetables

 

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

 

Cucumbers.

Continue to watch pickles and fresh market cucumbers for economic levels of aphids and cucumber beetles populations. Beetles can easily be found in seedling stage cucumbers. Actara, Thiodan, a pyrethroid or Lannate will provide control. Aphid populations are starting to build so scout fields carefully for aphids. As temperatures increase, populations will quickly explode since predators were lagging behind with the recent cooler weather. A treatment should be applied for aphids if 10 to 20 percent of the plants are infested with aphids. Actara, Thiodan or Lannate will provide control.

 

Melons.

Economic levels of cucumber beetles, aphids and spider mites continue to be found. If Agri-mek is used for spider mite control, it should not be combined with fungicides with sticker formulations similar to the sticker in Bravo Weatherstik. Since Agri-mek is translaminar, these stickers prevent the material from moving into the leaves. Recent applications of Agri-Mek applied when numerous eggs and nymphs were found have provided good spider mite control. Capture has provided good control of exploded mite populations. Be sure to rotate miticide chemistries to avoid the development of resistance.

 

Peas.

Continue to sample fields for pea aphids starting at the bud stage and continuing through harvest. Populations continue to increase in fields throughout the state.  A treatment is needed if you can find 50 or more aphids per sweep.

 

Peppers.

The first corn borer sprays will be needed when fruit is ½-inch in size or larger.  Sprays should then be applied on a 7–10 day schedule depending on material selection and corn borer pressure.  Orthene or Address (both acephate) should be used on a 10-day schedule and will also provide pepper maggot control.  Remember - only 2 applications of acephate at the 1 1/3 lb. per acre rate can now be used.   If a pyrethroid or Lannate is used, sprays should be applied on a 7-day schedule and dimethoate should be added to the mix for pepper maggot control. If no fruit is present, be sure to watch for larvae tunneling into the main stems of peppers. Sprays must be applied before larvae move into the stems to achieve effective control.

 

Potatoes.

Economic levels of CPB adults, small and large larvae can be found in many fields. Actara, Leverage, Spintor, or Provado will provide control. Agri-Mek will also provide control of larvae and should be considered as a rotational material. ECB egg masses and stem entrances can be found in potatoes. If trap catches are being used to time sprays, a treatment will be needed this week. Ambush, Baythroid, Furadan, Leverage, Penncap, or Pounce will provide control. If you are scouting for infested terminals, the first treatment should be applied when 20-25% of the terminals are infested. Furadan or Monitor will provide the best control if you are waiting until you see infested terminals. Potato leafhopper populations have started to increase and nymphs can be found.  As a general guideline, controls should be applied if you find ½ to one adult per sweep and/or one nymph per every 10 leaves. A pyrethroid, Actara, Leverage or Provado will provide control. Cutworm activity has also been detected by a consultant in later planted potatoes. Although no thresholds are available, a treatment should be considered if 3-5% of the stems are cut and larvae are less than 2 inches long. A pyrethroid will provide control. Aphid populations are still low in most fields. From bloom until 2 weeks from harvest, the treatment threshold is 4 per leaf. If melon aphids are found, the threshold should be reduced by one-half. Actara, Provado or Fulfill will provide control.

 

Snap Beans.

Fresh market and processing snap beans in the bud to pin stage should be sprayed for corn borer in areas when corn borer trap catches range from 2 to 5 per night.  Orthene or Address should be used at the bud and pin stages on processing beans. Once pins are present on fresh market snap beans, a 7-10 day schedule should be maintained for corn borer control. Lannate, Asana or Capture are labeled. Capture has a 9-day REI (restricted re-entry interval) in fresh market snap beans. Continue to watch for thrips and leafhoppers in seedling beans. We are starting to see an increase in the levels of both insects. A treatment is needed if you find 5-6 thrips per leaflet or 5 leafhoppers per sweep. If both insects are present, the threshold of each should be reduced by ½ the level for each insect. If plants are small and no buds are present, dimethoate will provide cost-effective control of both insects. Asana, Capture or Orthene will also provide thrips and leafhopper control.

 

Sweet Corn.

We continue to find economic levels of true armyworms in sweet corn planted into a burned down small grain cover. The treatment threshold is 15% infested plants.  Continue to watch the earliest planted fields for European Corn Borer larvae. We continue to find larvae in whorl stage sweet corn.  A treatment should be applied if 15% of the plants are infested. The best timing for a treatment is just as the tassels are emerging from the whorls. In recent years, the best corn control has been achieved with Ambush, Pounce, Penncap or Warrior. Since corn earworms are starting to fly, a silk application will be needed as soon as corn planted under plastic begins to silk. Be sure to check local trap catches which are updated on the IPM website three times per week at http://www.udel.edu/IPM/traps/latestblt.html .

 

 


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

 

Potatoes. 

 

Late Blight Update

Disease Severity Value (DSV) Accumulations as of June 5, 2001 are as follows:

Location: Joe Jackewicz Farm, Magnolia, DE

Remember that 18 DSV’s is the threshold to begin a spray program

 

Date

Total DSV

Spray 

Recommendation

5/16

0

 

5/17

11

 

5/20

29

 

5/30

51

5-day, low rate

6/3

57

5-day, low rate

6/5

57

5-day, low rate

 

Potatoes that have reached greenrow (50% emergence) since May 18 have all reached more than 18 DSV’s.

 

Growers should be applying a fungicide for late blight control at this time. Early blight susceptible varieties will also benefit from a fungicide application beginning now. The early blight prediction model, which is part of the WISDOM software I use for late blight predictions, recommends beginning a spray now for early blight. We will exceed the 300 P-days in a few days, which is the target for beginning a spray program for early blight caused by Alternaria solani.

 

To control pink rot caused by Phytophthora erythroseptica and P. nicotianae, and leak caused by Pythium apply Ridomil Gold MZ, Ridomil Gold /Bravo, or Flouronil between the time the potatoes are nickel-sized until flowering, and repeat 14 days later.

 

 


Vegetable Diseases -  Kate Everts, Extension Vegetable Pathologist, University of Delaware and University of Maryland;  everts@udel.edu

 

 

MELCAST for Watermelons

EFI Values (Environmental Favorability Index)

Do not use MELCAST if there is a disease outbreak in your field, it is a preventative program.  Any questions, please call David Armentrout at (410) 742-8788 or e-mail: da88@umail.umd.edu

 

Location

5/30

5/31

6/1

6/2

6/3

6/4

6/5

6/6

Bridgeville, DE

 

0

0

5

4

0

1

1

Laurel, DE

(Collins Farms)

 

0

0

3

1

0

1

2

Galestown, MD

 

0

0

5

3

0

1

2

Georgetown, DE

1

0

0

4

3

0

0

1

Hebron, MD

 

0

0

5

2

0

1

4

Salisbury, MD

0

0

0

4

2

0

1

4

Laurel, DE

(Vincent Farms)

 

0

0

4

3

0

1

2

Watermelon Fields should be sprayed with a fungicide when 30 EFI values have been accumulated by the weather station nearest your fields.  Add 2 points for every overhead irrigation.  After a fungicide spray, reset your counter to 0 and start over.  If a spray has NOT been applied in 14 days, apply a fungicide and reset the counter to zero.  The first and last day above can be partial days so use the larger EFI value of this report and other reports for any specific day

 

More detailed information concerning MELCAST and sample data sheets are available on the web at http://www.agnr.umd.edu/users/vegdisease/vegdisease.htm. .     v

 

 


Field Crops

 

Field Crop Insects - Joanne Whalen, Extension  IPM Specialist;   jwhalen@udel.edu

 

 Field Corn.

Continue to watch for true armyworm larvae moving from small grains to corn. We continue to find corn fields infested with armyworms including no-till fields and fields next to small grains. The treatment threshold is 25% infested plants with larvae one inch in size or less. The first ECB larvae can be found in the earliest planted non-Bt fields. Fields should be sampled for larvae by looking for infested plants and pulling out the whorl to determine if live larvae are present. A treatment may be needed at the pretassel stage when 50% of the plants are infested in irrigated corn and 80% infested in dry land corn.

 

Small Grains.

Continue to sample barley and wheat for armyworm populations. Head clipping and economic levels continue to be found. In general, sawfly larvae have almost completed their cycle. In general, if head clipping is 2 to 3 times the worm count then it is generally too late to treat for sawfly. The treatment threshold for armyworms on wheat is 2 per foot of row and on barley the threshold is one per foot. On wheat, Warrior, Lannate or Parathion can be used. On barley, Lannate or Parathion can be used. Warrior has a 30-day wait until harvest, Parathion a 14 day wait and Lannate a 7-day wait.

 

Soybeans.

Unfortunately, as predicted, slugs are causing stand losses in no-till soybeans. In some cases, slugs are eating the seed before germination. Damage is being found in fields planted into corn stalk and soybean residue. If slugs are feeding below the ground, then baits will probably not be effective. Once plants emerge from the ground, the mini-pellet formulations of the metaldehye baits (Deadline MPs or Trails End LG) will provide the best control. They should be applied at a rate of 10 lbs per acre. Bean leaf beetles can also be found in newly emerged fields. Damage will appear as small holes in the first true leaves. Although they are always present in soybeans, a treatment will not be needed from plant emergence to the second trifoliate until you find 2 beetles per ft. row and a 25% stand reduction. A pyrethroid or dimethoate will provide effective control.

 

 

 

Bean Leaf Beetle Adults - Vary in Color with and without spots.

 

- Note backwards pointing black triangle behind the head present on all adult beetles regardless of color variation.

 

 

Grasshoppers in Field Crops.

As barley is harvested and soybeans are planted, be sure to watch fields carefully at emergence for grasshopper activity.  We are also seeing an increase in activity in full season no-till soybeans. As a general guideline, non-crop areas should be treated if you find 20 or more grasshoppers per square yard. In corn and sorghum, a treatment is justified if you find 5-8 grasshoppers per square yard. In soybeans, the threshold is one per sweep and 30 percent defoliation. In all 3 crops, dimethoate, Lorsban, Asana and Warrior will provide control but multiple applications may be needed. Furadan is also labeled on corn and soybeans and has also provided good grasshopper control.

 

 


Field Crop Diseases - - Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

 

Wheat. 

Powdery mildew is the most prevalent disease present, but it should not impact yield much depending on how much infection is present. Rust is beginning to appear but wheat is beyond being damaged at this time. Septoria leafspot (Septoria nodorum) is present and if the rain continues we may see some glume blotch developing on unsprayed fields. Scab levels are low in wheat, I have seen. Few heads are partially infected. Infected heads are straw-colored and often have the pink discoloration on the glumes during wet weather. Infected seed is white and moldy appearing. Check when you see whole heads that are white to straw-colored. Some white heads are due to insect clipping at the base of the plant.

 

Soybeans. 

Early planted soybeans are being infected by Septoria glycines, which causes brown spot. Early symptoms include irregular dark brown spots that vary in size from very small specks to ¼ inch. Unifoliate leaves are infected heavily and drop; trifoliate leaves become infected and develop irregular light brown spots (lesions). This disease is very common when weather is wet and warm. It often disappears when summer arrives, but can continue if the weather remains wet. Rotation is the best control. Varieties vary in susceptibility, but there is no known source of resistance.

 

Alfalfa.

Leptosphaerulina leafspot (Lepto leafspot) is present in alfalfa now. This common disease is favored by cool, wet weather. Lesions or spots can start as small black ‘pepper spots’ or enlarge to small spots with dark brown borders and tan to light brown centers. They can be very numerous and cause leaf loss. Harvest as early as possible to avoid additional leaf loss. There are no resistant varieties, but some cultivars loose fewer leaves than others.

 

 


Grain Marketing Highlights - Carl German, Extension Crops Marketing Specialist; clgerman@udel.edu

 

Commodity Price Direction Dependent Upon Weather
Currently, weather remains the critical factor in determining price direction for commodities this summer. Simply stated, the corn and soybean market is braced to go either way depending upon how growing conditions develop. This phenomena makes for any call on making cash grain sales decisions to be a 50/50 proposition at this point in time.  In the case of wheat, as the 2001 harvest nears full swing we are likely to see some retracement to recent lows. Farmers needing to discuss wheat marketing decisions are invited to contact Carl German at 302-831-1317 or <clgerman@udel.edu>.

The soybean market continues to show signs of price momentum building. This is happening, at a time when production estimates for the 2001 Southern Hemisphere crop keep getting revised upward. Export sales for the week just ended were better than trade expectations for soybeans and the Chinese appear to be interested in booking more large shipments of U.S. soybeans, both for August and Oct/Nov shipment.

The Chicago market isn't likely to change much over this next week as traders await USDA's June Supply and Demand report. Dec. corn closed at $2.17, Nov. beans at $4.43, and July wheat at $2.61 per bushel in overnight trade on June 7th.  

Delaware FSA Announces 2001 Loan Rates
 

 

 

National

New Castle

 

Kent

 

Sussex

Corn

1.89

2.10

2.10

2.10

Sorghum (cwt)

3.05

3.00

3.00

3.00

Soybeans

5.26

5.38

5.38

5.38

Wheat

2.58

2.67

2.59

2.54

Barley

1.65

1.49

1.49

1.48

 

 


New Herbicide for Sweet Corn - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu

 

Callisto is a new field corn herbicide from Syngenta that provides broad-spectrum broadleaf weed control.  The one grass weed it has good activity on is crabgrass.  The active ingredient in Callisto is a new product, mesitrione.  This product can be used both preemergence and postemergence.  Postemergence rate is 3 fluid oz and the label says it needs to be mixed with crop oil concentrate and a nitrogen source (UAN or AMS).  Most broadleaf weeds are listed for 5 inches or less.  Label states not to use on corn treated with Counter or Lorsban.  Rotational restriction for small grain is 4 months and the following year for all other crops.  Callisto can be sprayed over 30 inch corn and is rainfast in one hour.  Supplies may be limited for this use season.

 

 

Postemergence Herbicide Activity - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu

 

The weather pattern the last week or so has been ideal for maximizing postemergence herbicide activity.  In our test plots, we are getting excellent control of many weed species that normally only get suppression.  The reason is that there has been excellent soil moisture and the day and night temperatures are cool.  The plants are growing rapidly and the leaf cuticles are thin.  The down side is that we are also getting more corn injury than we expect.  Be cautious of the additives you use with the spray solution.  When you have an option between crop oil and non-ionic surfactant, use non-ionic surfactant to minimize crop injury.  Likewise, do not add nitrogen if you have the option to leave it out.  

 

 

Poor Horseweed Control with Glyphosate - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu

 

This past winter we confirmed the presence of horseweed (or marestail) to glyphosate (Roundup and Touchdown) in Delaware.  I have gotten a few calls already this year about poor control of this weed with glyphosate.  If Roundup or Touchdown did not control the horseweed prior to soybean emergence, consider an additional application of paraquat.  Paraquat may not kill the plants, but will severely injury them and reduce their competitiveness.  Also, the paraquat will be more effective than the postemergence options.  If the soybeans have emerged, FirstRate is the first choice and Classic second choice.  Neither of these herbicides will kill large horseweed plants, but they will stunt them and reduce their competitiveness.

 

 


                    Weather Summary

Week of June 1 to June 6, 2001

Rainfall:

June 1: 0.10 inches

June 2: 0.34 inches

June 5: 0.32 inches

June 6: 0.42 inches

Readings taken for the previous 24 hours at 8 a.m.

Air Temperature:

Highs Ranged from 79°F on June 6 to 70°F on June 1.

Lows Ranged from 65°F on June 6 to 46°F on June 1.

Soil Temperature:

72°F average for the week.

(Soil temperature taken at a 2 inch depth, under sod)

 

Web Address for the U of D Research & Education Center:

http://www.rec.udel.edu

 


Compiled and Edited By:

Tracy Wootten

Extension Associate - Vegetable Crops


Cooperative Extension Education in Agriculture and Home Economics, University of Delaware, Delaware State University and the United States Department of Agriculture cooperating, John C. Nye, Dean and Director.  Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914.  It is the policy of the Delaware Cooperative Extension System that no person shall be subjected to discrimination on the grounds of race, sex, disability, age or national origin.