Volume 7, Issue 8                                                                                                       May 21, 1999


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

Cucurbits. Cucumber beetles can be found in fields throughout the state, especially if Furadan was not used at planting. Cucumbers and muskmelons are the most susceptible to bacterial wilt so be sure to check fields soon after emergence or transplanting for beetles. Sevin or a pyrethroid will provide control.

Melons.

Aphids, mites and thrips can all be found on watermelons planted in Sussex County. If 10 to 20 percent of the plants are infested with aphids, Lannate or Thiodan should be applied. The treatment threshold for mites is 10 – 15% infested plants/crowns. Agri-Mek or Kelthane will provide the best control. Although there are no thresholds for thrips, controls will be needed if: 1.) plants are drought stressed and mites or aphids are also present, and 2.) you are beginning to see leaf curling. If all three insects are present, the threshold for each should be reduced by 1/3.

Potatoes.

Adult Colorado potato beetle feeding and egg laying activity still remains light. In potato growing areas, European corn moth catches are averaging 5 per night in Kent and New Castle Counties and 10 per night in Sussex County. Pheromone trap catches range between 8 and 10 moths per night throughout the state. We continue to see moth egg laying in the earliest planted fields. A treatment should be applied if you find an average of one egg mass per plant or 25% infested terminals. If you are scouting for infested terminals, Furadan or Monitor will provide the best control. If you are basing sprays on local blacklight or pheromone trap catches, the first spray should be applied one week after finding 8–10 moths per night in local blacklight or pheromone traps. Generally, 4 applications of Ambush, Pounce or Penncap-M applied on a 7-day schedule will be needed. Potato leafhopper adults can now be found in fields that were not treated with Admire. As a general guideline, controls should be applied if you find to one adult per sweep and/or one nymph per every 10 leaves. A pyrethroid or Provado will provide control

Snap Beans.

Begin to check your earliest planted fields for thrips and leafhoppers. At this time, populations are very light; however, they could explode quickly if the weather remains hot and dry. The treatment thresholds are 5-6 thrips per leaflet or 5 leafhoppers per sweep. If both insects are present, the best control option would be Lannate in fresh market beans and Lannate or Orthene in processing beans.

Sweet Corn.

Flea beetle and cutworms remain active in fresh market sweet corn. The treatment threshold for flea beetles is 5% infested plants and the cutworm threshold is 10% leaf feeding or 3% cut plants. A pyrethroid will provide cost effective control of both insects. On the earliest planted corn, be sure to begin checking for the first signs of European corn borer activity. No controls should be needed in fresh market sweet corn until you find 15% of the whorls infested with live larvae. The best time for treatment will be at tassel emergence. v


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

Potatoes.

Potato growers are reminded that if tuber rots caused by pink rot or Pythium leak are a concern, treat with 2.5 lbs./A of Ridomil Gold MZ when tubers are nickel-sized and 14 days later. Apply a full rate of protectant fungicide between sprays of Ridomil Gold. No additional protectant fungicide needs to be added to the Ridomil Gold application for tuber rot control.

Tomatoes.

Continue to apply a copper fungicide plus mancozeb as a foliar spray shortly after transplanting and 7-days later to reduce problems from bacterial diseases. Apply Bravo or Quadris for early blight and late blight control once fruit reach the size of a quarter, or earlier if tomatoes have been grown in the same area often.

Pepper.

Planting on rounded, raised beds is important if Phytophthora root and crown rot has been a problem. Apply Ridomil Gold 4E soon after transplanting and repeat in 30 and 60 days for control. Apply a copper fungicide plus maneb as a foliar spray soon after transplanting and 7 days later for control of bacterial leaf spot.

 

LATE BLIGHT REPORT

DSV accumulations as of May 20, 1999 are as follows:

Location/

Emergence Date

DSV’s

May 20

DSV’s

May 17

Recommendation
Baldwin – 4/19

28

19

7-day, low rate
Jackewicz – 4/30

29

20

7 day, low rate
Art Wicks – 4/26

29

20

7-day, low rate
Ken/Chris Wicks – 5/3

26

19

7 day, low rate

For any potatoes that emerged after May 6 or 7 this last rain period pushed your severity values from 7 to 9, still below the threshold of 18 DSV’s. For all the other potatoes we have accumulated enough DSV’s to warrant a 7-day spray interval. Most areas received some much needed rainfall. v


Vegetable Diseases - Kate Everts, Extension Vegetable Pathologist, University of Delaware and University of Maryland; everts@udel.edu and Phil Shields University of Maryland; ps136@umail.umd.edu

MELCAST Program for Watermelon.

We have three field seasons of experience with the MELCAST program in trials at the University of Delaware REC near Georgetown and University of Maryland LESREC in Salisbury, and on two growers farms near Laurel, DE. This model was developed at Purdue University. It uses weather data to schedule protectant fungicide applications for anthracnose and gummy stem blight of watermelon, so that instead of spraying on a 7-day schedule, fungicides are applied according to the weather. This year we have set up a network of eight weather stations on Delmarva (located in Sussex, Dorchester and Wicomico counties) to collect data for MELCAST. We will publish EFI information in the Weekly Crop Update and on the University of Delaware IPM web page (http://www.udel.edu/IPM/). It will also be available by fax or e-mail, twice weekly. If you would like to receive the EFI information, please call UD REC at 856-7303 and give your name, address, phone and fax or e-mail number to Mrs. Edna Marvil. In Maryland, call UM LESREC at (410)742-8788 and give this information to Mrs. Vanessa Fitzmaurice.

When to Spray with MELCAST. Do not use MELCAST if there is a disease outbreak in your field, it is a preventative program. The first fungicide spray should be applied when the vines begin to run. Once you have applied the first spray, begin to accumulate EFI (Environmental Favorability Index) values. The EFI are based on temperature and moisture readings and reflect how favorable it is for disease development. Daily EFI will vary from one to ten. In addition to weather based EFI, add two EFI if you apply overhead irrigation to the crop. The accumulated EFI units are the "spray counter". When the spray counter reaches 30, apply a fungicide spray. Reset the spray counter to zero and begin accumulating the EFI values until you reach 30 again.

MELCAST for Fungicide Application on Watermelons.

Do not use MELCAST if there is a disease outbreak in your field, it is a preventative program. Below are the EFI values from weather stations located on the Eastern Shore May 12-19. Any questions please call Phil Shields at (410) 742-8788 or e-mail: ps136@umail.umd.edu

EFI Values for 1999

Location

5/12

5/13

5/14

5/15

5/16

5/17

5/18

5/19

U of M, LESREC
Salisbury,MD
 

0

0

0

0

0

0

2

Wootten Farms, Galestown,MD  

0

0

0

0

0

1

1

Mark Collins,
Laurel, DE
 

0

0

0

0

0

0

1

Vincent Farms Laurel, DE  

0

0

0

0

0

1

1

D C Farms,
Bridgeville, DE
 

0

0

0

0

0

1

1

Balvin Brinsfield,
Vienna, MD
 

0

0

0

0

0

1

1

Charles Wright,
Mardela Springs, MD
 

0

0

0

0

0

0

1

DE U of D, REC Georgetown, DE

0

0

0

0

0

0

0

0

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.v


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

Field Corn.

We have started to see an increase in damage from cutworms. In spike to 3-leaf stage corn, a treatment

will be needed if you find 10% leaf feeding or 3% cut plants. As plants reach the 4 to 5-leaf stage, no sprays will be needed unless you find 5% cut plants and larvae are present. Due to the dry soil conditions, larvae can be found feeding underground causing plants to appear wilted instead of cut-off at the soil surface. When plants are dug up, you can find a large hole in the side of the plant where the cutworm has fed on the growing point. If cutworms are feeding below the soil surface, rescue treatments are often ineffective. In these situations, control will be improved if: 1.) insecticides are applied in at least 20 gallons of water per acre and directed to the base of the plants, 2.) treatments are applied as late as possible in the evening, and 3.) insecticides are cultivated into the soil when practical. Bird damage, which can be confused with cutworm damage, can also be found in spike to 4 –leaf stage corn. 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. We have also had a number of reports of corn fields with wireworm damage. Remember that there is no rescue treatment for this soil insect pest. Since they spend multiple years in the larval stage and continue to feed all season, an in-furrow soil insecticide will be needed if a replant decision is made. Counter, Force or Regent will provide control. If populations are heavy, the highest labeled rate is needed.

Small Grains.

Continue to check wheat for armyworms and sawflies. Head clipping by the grass sawfly has been detected in wheat in Sussex County. The treatment threshold is 2 per 5 foot of row innerspace. We should be at the peak in sawfly activity and head-clipping damage should be over in the next 2-week period. Armyworms continue to be found sporadically in barley and wheat fields. Armyworm larvae still vary in size from to one-inch long. Since armyworms prefer to feed on the vegetation in the lower part of the canopy, no sprays should be needed in wheat until you begin to see head clipping or if larvae begin to move up the plants feeding extensively on the foliage. Remember that armyworms will clip heads faster in barley so fields approaching threshold levels of one per foot of row should be watched closely for damage.

Soybeans.

Seed corn maggot flies are still actively laying eggs; therefore, all full season no-till soybeans should still be treated with a seed treatment containing diazinon. Due to the dry weather, grasshopper nymphs can also be found in no-till fields and along field edges. Early control of nymphs will provide the best control. Once grasshoppers are found in a field, a treatment is needed if you find one grasshopper per sweep and 30% defoliation. Asana, Sevin or Warrior have provided the most consistent control. v


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

Wheat.

The only virus disease that I have been able to verify to date has been barley yellow dwarf, which was confirmed by serology tests. It apparently is widespread within the state causing leaf streaking and yellowing of the foliage. Barley yellow dwarf usually occurs in small patches and sometimes individual plants can be infected. Since most of the plants that we have seen are not stunted we believe that the infections are mostly from aphid feeding this spring.

At the present time besides powdery mildew there are few diseases present. Most of the wheat is flowering and beyond and will not respond to late season fungicide applications. Once flowering has occurred, there are no labeled fungicides for use on wheat.

As mentioned last week, be on the lookout for stunted plants and white heads caused by take-all.

Barley.

Leaf rust is beginning to appear. The best control is the use of resistant varieties. There has been some leaf scald, but it has been minor compared to last season. Choosing resistant cultivars is the best control for all the barley diseases. v


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

Commodity Markets Trending Sideways to Lower

Generally speaking the corn, wheat, and soybean markets are, momentarily, said to be trending sideways, with some exceptions. Soybeans and wheat appear to be the exceptions. Technicians are still indicating that further price weakness is within the realm of possibility, particularly for 1999 new crop production (Nov. '99 beans, and July '99 wheat). This comes at a time when the wheat market is reportedly bottomed, with some major upside price swing potential expected. The major question is how much can the wheat price recover, and when will the recovery take place? The wheat price is expected to make a recovery, bearing in mind that current resistance is $ 2.73 for July '99 and $3.00 for December wheat futures. A significant price recovery is not expected until after the 1999 wheat harvest is in the bin. Analysts are divided, some say the recovery is just beginning, while others argue that July '99 wheat futures are headed lower.

USDA's recent price forecasts for soybeans for the 1999/2000 marketing year were placed at $ 3.95 to $4.75 per bushel. This forecast is based upon the possibility of predictions of rather burdensome soybean supplies, both in the U.S. and world. The price forecast stems in part from a 1999 U.S. soybean production estimate of 2.88 billion bushels and a 1999/2000 projected record carryout of 595 million bushels, despite a sharp increase in export demand. The stocks to use ratio is projected
to be 21.9%, compared to the 1986/87 stocks/use ratio of 21.3%, when the national average soybean price was $4.78 per bushel. One major difference between now and then is that there are much higher world stocks now, due mainly to the booming South American production. This will place added pressure on soybean prices. By the end of the 1998/99 marketing year world soybean stocks will likely be record high by a large margin. v


 
Two Corn Herbicides That Did Not Get Mentioned Last WeekMark VanGessel, Extension Weed Specialist; mjv@udel.edu

Last week I wrote about herbicides for use in corn to control emerged grassy weeds. I forgot to mention Basis and atrazine. Basis will control emerged foxtails and fall panicum and atrazine will control emerged foxtails (but not fall panicum). Basis will provide some control of small crabgrass (less than 2 leaves). Basis must be applied to young corn plants (2 visible collars or less 5 visible leaves). Do not apply Basis to corn previously treated with Counter 15G. Applications to corn previously treated with Counter 20CR or Thimet may cause unacceptable crop injury, especially on soils of less than 4% organic matter; applications to corn previously treated with Dyfonate, Lorsban, or other organophosphate insecticides may result in temporary crop injury.

The key to effective postemergence grass control in corn at lowest possible cost is to spray early and be sure of the weed species you are trying to control.


Height Restrictions On Corn Herbicides - Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Below is the maximum corn size for over the top application of the respective herbicide.

HERBICIDE CORN HEIGHT
Accent up to 20" or less than 6 collars
Aim up to 8 collars
Atrazine up to 12"
Banvel/Clarity up to 36" at pts/A
Basis 6" or 4 leaves
Basis Gold up to 12"
Beacon up to 20" or 6 collars max
Bladex up to 4 leaves
Celebrity up to 20" or less than 6 collars
Distinct 4 to 10" at 6 oz rate and up to 24" at 4 oz/A
Exceed 4 to 20" or 6 collars max
Hornet up to 20"
Liberty up to 24" or 7 collars max
Marksman up to 8" or 5 leaf stage
Permit up to 48"
Resource 2 to 10 leaf stage
Roundup Ultra up to 30" or 8 collars max
2,4-D less than 8"

Recent Registration of Distinct Herbicide - Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

BASF recently received registration of Distinct for postemergence control of broadleaf weeds in corn. Distinct is a combination of dicamba (sodium salt) and another plant growth regulator herbicide (diflufenzopyr). Dicamba is the active ingredient in Banvel and Clarity. While the sodium salt results in different environmental characteristics of the dicamba molecule (i.e. volatility, temperature), there needs to be caution in how it is used. The dicamba amount at the 6 oz rate of Distinct is the same as 6 fluid ounces of Banvel. The 4 oz rate of Distinct is comparable to 4 fluid ounces of Banvel. So read the label concerning cautions with Distinct use. v


Hay Heating and Combustion - Gordon Johnson, Extension Agent; gcjohn@udel.edu


Although drying conditions have been better than usual this May, we are running into cases where hay was baled at too high of moisture and is undergoing heating.

For safe storage, hay should be 20% moisture or less at baling. In general, use the following guidelines when making hay:
1) Mow forage early in the day and spread into wide swath.
2) Rake or ted hay at 40-50% moisture to speed drying. If the ground is still moist, turning the windrows an additional time using a windrow turner or rake can also aid in speeding the drying process.
3) Bale hay at 18-20% moisture.

Drying times can vary from as little as one day in the middle of the summer and as much as 4-5 days in the spring and fall.

Use of a forage moisture and temperature sensor can help greatly in taking the guesswork out of hay making and storage decisions. These sensors are readily available from many sources and give an instant digital readout.

If hay is baled at greater than 25% moisture the potential for heating is greatly increased. At these higher moistures, microbial activity increases and heat is generated from the microbial action.

If hay heats in storage above a temperature of 100 F, browning of hay starts. This browning causes the feed value of the hay to decrease. At 140 F severe browning damage has occured. At 150 F hay will blacken and spontaneous combustion is possible. Hay at this temperature should be moved out of barns and spaced out to try to cool it. At 160 F combustion (fire) is likely and if the temperature has reached 180 F the fire company should be called.




Birds = Armyworms?
- Gordon Johnson, Extension Agent; gcjohn@udel.edu


Many farmers over the years have noticed birds flying and diving in small grain fields and upon inspection have found armyworms feeding in these fields. This has led to the common notion that when the birds are flying in small grains they need to be sprayed for armyworm.

Although this may be the case in some fields, you should not make this a rule since bird activity does not always mean armyworms. Many times the birds may be feeding on other insects or may be in the fields for other reasons. Often, there are high numbers of beneficial insects such as Syrphid larvae feeding on aphids on the grain and the birds are feeding on them.


PSNTGordon Johnson, Extension Agent; gcjohn@udel.edu

Now is the time to plan for taking pre-sidedress soil nitrate tests (PSNT) in corn. Any fields that corn is grown on that have received recent applications of manures, organic wastes, or have had leguminous cover crops and that have received less than 50 lbs. of starter fertilizer nitrogen are candidates for the test.

The PSNT measures the amount of nitrate nitrogen in the soil just prior to sidedressing. Field trials in many states have taken these PSNT results and correlated them to corn response to different levels of sidedress nitrogen addition. By doing this an accurate recommendation can be given
for any additional nitrogen needed at sidedressing.

Take soil samples for the PSNT from the middles in-between rows at a depth of 12" in corn that is 10-12" tall. Multiple cores should be taken for each field and then mixed and quickly air dried by spreading them on paper in a warm area. Once dry they should be immediately tested. If they must be stored place them in refrigerated conditions. Samples should be representative of each field and if different manure rates have been used in a field, they should be sampled separately. Also avoid taking samples immediately after a heavy rain or irrigation, wait a day or two instead.

The PSNT helps the grower by taking the guesswork out of how much additional nitrogen is needed to grow a crop of corn. v


The Whys of Uneven Corn Emergence - Richard W. Taylor, Extension Agronomist ; rtaylor@udel.edu

Not surprising, the most common reason for uneven corn emergence is dry soil conditions either at planting or during the period between planting and emergence (especially when emergence is delayed by cold soil and air temperatures). In many cases, the problem is caused by either an uneven distribution of moist and dry soil at various locations along each row, seed size differences (larger seed need more moisture to begin the process of germination), or small changes in seeding depth that place the seed either in moist soil or just above moist soil. This latter case is often the problem on our very sandy soils where pockets of loose sand sink planter units too deep and hard packed sand prevents units from penetrating the soil to the desired depth.

When soils are worked too wet, cloddy seedbeds can result. These can lead to poor soil seed contact. Seed not in firm contact with the soil can not absorb enough water to germinate. These seeds will not germinate until after rainfall. Again, the stand will appear as a mixture of larger and smaller plants. If rainfall is delayed too long, the newly germinated plants can act as weeds and contribute little to the final yield. Plants more than two leaf stages apart seldom contribute much to yield.

How do we count leaf number? In the case above, an emerged leaf is defined as one in which the leaf collar (that whitish band between the leaf blade and the leaf sheath) has emerged out of the leaf sheath of the leaf immediately below it on the main stem. This definition differs from that often used to count leaf number for herbicide application. Usually for herbicide purposes, all visible leaves are counted or leaves where the leaf blade is at least horizontal or below the horizontal are counted. Since the definition used can vary from company to company, carefully read the herbicide label to see how to count the number of leaves. If the label is not clear, contact your company representative and ask how you should count leaf number.

Other causes of uneven emergence include soil temperature, soil crusting, herbicide injury, insect and disease injury, and replanting poor areas without killing the existing crop.

Uneven soil temperatures can be caused by poor distribution of crop residues or cover crop density. This is true especially in reduced tillage and no-till systems and when row sweeps or row cleaners are not used. It also is more likely to occur in early planted corn when soil temperatures are marginal for emergence. The variability in corn emergence will be noticeable until the crop begins rapid growth (shortly after sidedress time) afterwhich differences should be less visible. Other factors that can complicate soil temperature are uneven seeding depths, changes in soil type in a field, and changes in topography.

Is there a cost to uneven stands? For corn planted early or on-time and that has attained the target population, little to no yield potential is lost. For late planted corn even with a full stand, yields can be reduced by 5 to 15 percent by uneven stands. If the delay in emergence is less than 2 weeks, yield loss will generally be around 5 percent or less.v


Pesticide BriefsSusan Whitney, Extension Pesticide Educator; swhitney@udel.edu

Disposal of Pesticides and Containers

New Castle County

First Saturday of each month

Delaware Recycling Center

1101 Lambsons Lane, New Castle

Second Saturday of each month

Pine Tree Corners Transfer Station

Rd. 25 Townsend

Kent County

Third Saturday of each month

Cheswold Collection Station

Rd. 153, Cheswold

Sussex County

Fourth Saturday of each month

Southern Solid Waste Management Center

Route 20, Jones Crossroadsv


Upcoming Meetings…

Reminder…

Quarterly Pesticide Training

Delaware Department of Agriculture

June 2-3, 1999

For more informtion contact DDA at

(302-739-4811 or 1-800-282-8685)

 

Processing Pea Variety Trial Field Day Meeting

Tuesday, June 8, 1999

5:00 p.m. to Dusk

Research & Education Center, Route 9,

Georgetown, Delaware

More information to follow next week…

Annual Crops Field Day

July 27, 1999

For more information contact Carl Davis at the New Castle County Extension Office


Weather Summary

Week of May 13 to May 19

Rainfall:
0.79 inches: May 19, 1999
Readings taken for the previous 24 hours at 8 a.m.
Air Temperature:
Highs Ranged from 71F on May 17 & 18 to 60 F on May 14.
Lows Ranged from 60F on May 19 to 44F on May 15.
Soil Temperature:
71 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 College 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. 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.


Hit Counter