Volume 14, Issue 19                                                                               August 4, 2006


Soybean Rust Update

 

 

National Commentary, August 1

Soybean rust has been found in two sites in Jefferson County, SW Mississippi. Rust was confirmed on both kudzu and soybeans in that county. This is the first report of rust from Mississippi in 2006.

 

The weather forecast for the next several days is for more favorable conditions for rust in the panhandle of FL and in SW Georgia. Tropical Storm Chris is forecast to track west-northwest towards the Florida Straits and enter the warm waters of the Gulf of Mexico; rapid intensification is possible to major storm status. The tropical system is expected to reach the open Gulf of Mexico by the end of the period. Its circulation should cause widespread showers and thunderstorms in the Gulf States, especially along the coast and the Florida peninsula. As with all tropical systems the impact on soybean rust transport is dependant on the exact path and intensity of the system. We will continue to monitor the development of Chris.

 

Check the PIPE website www.sbrusa.net for further developments. They have added a 1-3 day and 3-5 day forecast to the site which will be valuable.

 

Bob Mulrooney

 

 

Vegetables

 

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

 

Cabbage

The first cabbage loopers and diamondback larvae have been detected in fall cabbage. Treatments should be applied before larvae move into the heart of the plants. If both species are present, Avaunt, a Bt, Proclaim or Spintor have provided control in the past. If cabbage looper is the predominant species, a pyrethroid, Intrepid, or Confirm will also provide control. We also received a label for Rimon 0.83EC this spring on head and stem brassica for cabbage looper and diamondback control.

 

Lima Beans

Continue to scout fields for lygus and stinkbugs. The higher labeled rates of insecticides will be needed if stinkbugs are the predominant insect present. As earworm trap catches start to increase, be sure to scout fields for earworms as soon as pin pods are present. A treatment will be needed if you find one corn earworm larvae per 6 ft-of-row. Capture (bifenthrin), Mustang MAX, Lannate, Proaxis and Warrior (lambda-cyhalothrin) are labeled for corn earworm control in lima beans. The higher rates may be needed if population levels are high and worms are large at the time of treatment. As you approach harvest, be sure to check all labels for days from last application to harvest as well as other restrictions.

 

Melons

Continue to scout all fields on a weekly basis for aphids, cucumber beetles and spider mites. All three insects can still be found in fields. As harvest continues, be sure to watch for cucumber beetles and beet armyworm larvae feeding on rinds. The only material labeled on melons that will provide beet armyworm control is Spintor. The highest labeled rate should be used if larvae are large at the time of treatment.

 

Peppers

In areas where corn borers are being caught in local traps and pepper fruit is ¼ inch or more in diameter, fields should be sprayed on a 7-day schedule for corn borer control. As soon as corn borer trap catches increase to above 10 per night, a 5 to 7-day schedule may be needed. Since trap catches can increase quickly at this time of year, be sure to check local moth catches in your area at http://ag.udel.edu/extension/IPM/traps/latestblt.html. We are starting see an increase in beet armyworms (BAW) so be sure to watch for feeding signs and apply treatments before significant webbing occurs. You will need to use a product like Spintor, Avaunt, or Intrepid for BAW control.

 

Snap Beans

As corn borer and corn earworm populations continue to increase, you will need to consider treatments for both insect pests. Sprays are needed at the bud and pin stages on processing beans for corn borer control. As earworm trap catches increase, an earworm spray will also be needed at the pin stage. Just as a reminder, Orthene has not provided effective corn earworm control on processing snap beans. Since corn borer and corn earworm trap catches have started to increase, you will need to check our website for the most recent trap catches to help decide on the spray interval between the pin stage and harvest for processing snap beans (http://ag.udel.edu/extension/IPM/traps/latestblt.html and http://ag.udel.edu/extension/IPM/thresh/snapbeanecbthresh.html). Once pins are present on fresh market snap beans, a 7-day schedule should be considered for corn borer and corn earworm control.

 

Sweet Corn

With the increase in corn earworm trap catches, especially in a number of pheromone traps, silk sprays are needed on a 2 to 3-day schedule in many locations. In the Bridgeville, Harrington, Killens Pond, Milford, Greenwood and Seaford areas a 2-day silk spray schedule is needed. Be sure to check trap catches for the current spray schedule since trap catches quickly change. Trap catches are generally updated on Tuesday and Friday mornings. (http://ag.udel.edu/extension/IPM/traps/latestblt.html and http://ag.udel.edu/extension/IPM/thresh/silkspraythresh.html). You can also call the Crop Pest Hotline for current trap catches (in state: (800) 345-7544; out of state: (302) 831-8851). Continue to watch for fall armyworm feeding in whorl stage corn. We continue to see an increase in the number of fields with damage and in the percent infested plants. A treatment is needed if you find 12-15% of the plants infested. Multiple whorl applications are generally needed for fall armyworm control. In addition, you may need to combine a fall armyworm material with a pyrethroid for the first 2-3 silk sprays if fall armyworm pressure was heavy in whorls.

 


 

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

 

Downy Mildew on Pickling Cucumbers

Maintain fungicide sprays for downy mildew. The disease continues to be identified on unsprayed plants in home gardens and in research plots. The hot weather has certainly slowed it down but it continues to survive.

 

Look for more downy mildew on other cucurbits as we get into August and September. The article that Dr. Kate Everts wrote back in mid-July on downy mildew on other cucurbits is reprinted in this issue and is still applicable.

 

Downy Mildew on Lima Beans

When cooler nights and heavy dew begin, along with heavy rainfall associated with tropical storms and hurricanes, downy mildew can threaten the fall lima crop. Last season downy mildew was seen only once in the Plant Disease Clinic. Race F of Phythophthora phaseoli was the only race identified in 2004, which may predominate if downy mildew should appear again. Preventative applications of 2 lbs. fixed copper, 2 lbs. Ridomil Gold/Copper, or 4 pts. Phostrol have provided control of downy in the past. I got good results of lower rates of Phostrol at 2 or 3 pts/A when disease pressure was light to medium but am not willing to recommend it at reduced rates under severe conditions until I can test it under those conditions. The best controls continue to be Ridomil/Gold Copper or Phostrol, especially when disease pressure is high. Application at flowering or when pods are first forming is recommended if weather is favorable for disease. If disease is present, Ridomil/Gold Copper and Phostrol have shown to provide some curative activity if applied when downy mildew is first seen. Be sure to have a copy of the label on hand since Ridomil/Gold Copper and Phostrol have 24c labeling in DE. http://www.cdms.net/ldat/ld186002.pdf.

The following is a spray recommendation matrix for control of downy mildew on baby limas.

 

Fungicide

Preventative

Curative*             

 

High Disease

Low Disease

High Disease

Low Disease

Ridomil Gold/ Copper

2 lb 2x

7-day interval

2 lb 1x

2 lb 2x

7-day interval

2 lb 1-2x

7 to 10-day interval

Phostrol

4 pt 1-2x

7 to 14-day interval

2-4 pt 1-2x

7 to 14-day interval

4 pt 2x

7-day interval

4 pt 1x or 2-4 pt 2x

7 to 10-day interval

Copper**

2 lb 4x

7-day interval

2 lb 2x

7 to 10-day interval

Not Recommended

* When disease first seen, very low incidence- less than 1% of pods or racemes infected

** Copper fungicides include Champ DF, Kocide, Cuprofix Disperss and other labeled coppers

 

Lima Bean Pod Rot

Lima bean pod rot, which is our name for infection of lima bean pods by Phytophthora capsici, was diagnosed at the end of last week. When rainfall is abundant, or when water sits in low areas of the field, lima beans in contact with the soil can get infected by the soilborne fungus Phytophthora capsici. This is the same fungus that causes fruit rot in cucurbits and crown canker in peppers. Unfortunately we do not have any effective fungicide controls for this disease but copper applied for downy mildew may give some suppression.

 

Nova (myclobutanil) from Dow AgroSciences has received a section 18 registration from EPA for use on lima beans and other succulent podded legumes for the control of soybean rust. The Delaware Department of Ag has approved it and it is now available for use in Delaware if needed. It has still not been determined how susceptible lima beans and snap beans are to soybean rust under field conditions but it appears at this time that they are not very susceptible. This label was pursued to cover the legume vegetable crops in groups 6 and 7 which includes our lima beans and snap beans. Labels will be available on our Soybean Rust site as soon as we receive an electronic copy for posting.

 


 

Downy Mildew on Watermelon, Pumpkin, Squash and MuskmelonKate Everts; Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

 

Although downy mildew has been confirmed on cucumber in Delaware, it has not been seen on watermelon, squash, pumpkin or muskmelon. We know that different pathotypes of the downy mildew organism may affect one cucurbit but not another. However, we don’t know what pathotype we are currently dealing with. In 2004 and 2005, downy mildew became established in July on cucumber but many other crops were not affected until much later in the growing season. However the potential for severe epidemics remains. A good strategy on watermelon and summer squash is to apply a protectant such as mancozeb, and to apply maneb on pumpkin and winter squash. Continue to scout the crops intensively. When downy mildew is observed within the crop or reported on watermelon, squash or pumpkin in the region, fungicides targeted specifically for downy mildew should be applied. These products include Ranman, Previcur Flex, Curzate and Tanos. Gavel also has good activity and is a good choice for watermelon or summer squash, but cannot be applied to pumpkin or winter squash because it contains mancozeb.

 

This approach (protectant applications of mancozeb until downy mildew is seen on the crop) also can be used for muskmelon (cantaloupe). However, be aware that some preliminary reports indicate that muskmelons are more susceptible than pumpkins or squash to the cucumber strain. While this is quite preliminary information, muskmelon growers may opt to apply the more targeted fungicides to manage downy mildew.

 


 

Heat, Irrigation, and Lima BeansEd Kee; Extension Vegetable Specialist; kee@umd.edu

 

The tremendous heat we’re experiencing makes irrigation of lima beans more critical. Blossom drop occurs when the plant is stressed, and even with adequate irrigation blossoms will abort with high temperatures. However, maintaining soil moisture is important to keep the plant cool, which alleviates stress and reduces blossom and pod drop. Lima beans will use 0.25 inches of water per day through evapotranspiration when temperatures are in the nineties. Reducing plant stress as much as possible will help in the retention of “pins” (small pods) and larger pods.

 


 

Potato Disease Advisory #24 – August 2, 2006, Bob Mulrooney, Extension Plant Pathologist

 

Final Edition of the Late blight Advisory

 

Disease Severity Value (DSV) Accumulation as of August 1, 2006 is as follows:

Location: Byfield Farms field east of Magnolia, DE.

 

 

LATE  BLIGHT

EARLY BLIGHT

Date

Daily DSV

Total DSV

Spray Recs

Accumulated

P days*

6/27-6/29

3

37

7-day

524

6/29- 7/4

0

37

7-day

557

7/4- 7/5

2

39

10-day

565

7/5- 7/6

3

42

7-day

575

7/6- 7/9

0

42

7-day

603

7/9-7/12

0

42

10-day

622

7/12- 7/13

2

44

10-day

629

7/13-7/14

2

46

10-day

637

7/14- 7/15

2

48

7-day

645

7/15-7/16

0

48

7-day

650

7/16- 7/19

0

48

7-day

665

7/19-7/20

1

49

7-day

671

7/20-7/21

1

50

10-day

676

7/21-7/23

2

52

10-day

693

7/23-7/24

1

53

7-day

701

7/24- 7/25

0

53

7-day

710

7/25-7/26

2

55

7-day

717

7/26-8/1

0

55

10-day

742

 

·         Continue to make fungicide applications for early blight control.

·          Fungicide rates should be at the high end of the rate range at this time of the season.

 

Early blight is the disease of concern now; if you have potatoes with foliage keep up your fungicide sprays at this time. There have been no new reports of late blight on potato in the region. Unfortunately our colleagues up north in Maine and New Brunswick are not as fortunate as we were this season. 

 

This newsletter concludes the regular Potato Disease Advisory for the 2006 season. If you have any suggestions for improving this newsletter, please email or call at bobmul@udel.edu or 302-831-4865.

 

 

Agronomic Crops

 

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

 

Alfalfa

Continue to sample fields on a weekly basis for leafhopper adults and nymphs. Remember, once plants are yellow damage has already occurred. A treatment is needed if you find 20 per 100 sweeps in alfalfa 3 inches or less in height; 50 per 100 sweeps in 4-6 inch tall alfalfa; 100 per 100 sweeps in 7-11 inch tall alfalfa and 150 per 100 sweeps in alfalfa 12 inches or taller in height.

 

Soybeans

Continue to scout double crop soybeans for defoliators including grasshoppers and green cloverworm. The prebloom threshold is 30% defoliation and once fields reach the bloom to pod-fill stage the threshold drops to 15% defoliation.

 

You should also continue sampling fields for soybean aphids. With the recent hot weather, population levels still remain low. However, remember that this aphid is favored by cooler temperatures so we could still see population increases, especially if we experience moderate temperatures later in August.

 

Be sure to sample all fields that are in the pod development and pod fill stages for stinkbugs. Populations of stinkbugs are higher in some fields and economic damage is most likely to occur during this stage. You will need to sample for both adults and nymphs when making a treatment decision. As indicated in last week’s newsletter, 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. Information from Ames Herbert in VA indicates that “thresholds are old but consistent with most other states in the eastern US. Our thresholds are also based on numbers of large nymphs and adults, as those are the stages most capable of damaging pods. 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.” In Ames Herbert’s 2005 stinkbug control trial, the only labeled materials he tested were Orthene 97 and Baythroid and they both provided stinkbug control. Ames also stated in his report that “the only pyrethroid we tested was Baythroid. Others would most likely perform well.” Other pyrethroids labeled on soybeans for stinkbug control in addition to Baythroid include Warrior (lambda-cyhalothrin), Proaxis, Mustang Max and Asana (green stinkbug only on label). The highest labeled rate of a pyrethroid should be used for stinkbug control. In addition, if earworms are also of concern, a pyrethroid would be the best choice if both insects are present.

 

You should also begin sampling for corn earworm. Preliminary results of Virginia’s corn earworm survey indicate a higher potential for corn earworm compared to last season. We are also starting to see a significant increase in trap catches. In most cases, full season fields should escape damage; however, it will be important to check those fields at least 1-2 times to be sure that you do not miss an infestation. With the recent increase in corn earworm trap catches, open canopy blooming fields will be attractive to egg laying moths. A treatment should be considered if you find 3 per 25 sweeps in narrow fields and 5 per 25 sweeps in wide row fields (20 inches or greater).

 

As we enter August and the potential for insect control increases, be sure to check all labels for the days from last application to harvest as well as other restrictions.

 


 

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

 

Soybeans

Soybean cyst nematode was seen this past week. Look for stunted plants in irregular areas. Soil testing or checking the roots for the white and yellow cysts if present will verify the presence of SCN.

 


 

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

 

Market News Brief

The next supply and demand estimate due out from USDA will be released on August 11th. The corn market needs the August report to establish a practical base line production number or there needs to be a dramatic change in the weather in order to change the dynamics of the market. The August production estimates are based upon actual field surveys. Heat stress is causing some damage to crop yields throughout the country, however, the area most affected by severe drought is estimated at 20% of the Western Corn Belt. Current trading is see-sawing back and forth with traders split on expectations for the size of the '06 U.S. corn and soybean crops. Commodity market prices coupled with weak basis offerings are currently at levels that discourage crop sales in the Mid-West. Gulf Port basis levels for corn are said to be currently running as much as much as 10 under Dec, as compared to a normal of 20 over for this time of year. Spot cash bids for new crop corn in the Corn Belt are currently having the net effect of placing a freeze on new crop selling. The net price achievable in the Corn Belt at the present time is not that much better than the loan rate. 

 

Marketing Strategy

Basis levels for new crop corn and soybeans are currently being bid at 5 over Dec for new crop corn and 15 under Nov for new crop soybeans. With the Eastern Corn Belt crop considered to be made it is likely that basis levels for new crop corn and soybeans will weaken from their current levels. Current basis levels being bid on the Eastern Shore are already on the low side of historical offerings. The big question or dilemma this harvest season is likely to be storage availability? Therefore, grain marketers must now take measures to shore up pre-harvest sales and storage space for corn and soybeans.

 

 

Weather Summary

http://www.rec.udel.edu/TopLevel/Weather.htm

Week of July 27 to August 2, 2006

Readings Taken from Midnight to Midnight

 

Rainfall:

0.16 inch on July 28

0.20 inch on July 31

 

Air Temperature:

Highs ranged from 95°F on August 2 to 90°F on July 27 and July 29.

Lows ranged from 78°F on August 2 to 71°F on July 27.

 

Soil Temperature:

85°F average.

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

 

The Weekly Crop Update is available online at

http://www.rec.udel.edu/TopLevel/Publicat.htm

 

Weekly Crop Update is compiled and edited by Emmalea Ernest, 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. Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Delaware Cooperative Extension, University of Delaware. It is the policy of the Delaware Cooperative Extension System that no person shall be subjected to discrimination on the grounds of race, color, sex, disability, age or national origin.