Volume 12, Issue 14                                                                     June 25, 2004



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


We continue to see an increase in aphid populations. A treatment should be applied for aphids if 10 to 20 percent of the plants are infested with aphids with 5 or more aphids per leaf.  Fulfill, Thionex or Lannate will provide aphid control. Be sure to watch for bees foraging in the area and avoid insecticide applications on blooming crops.

Continue to scout all melons for aphids, cucumber beetles, and spider mites. We continue to see an increase in the number of fields with spider mite and aphid infestations. If spider mite populations are high at the time of treatment, 2 sprays spaced 5 days apart may be needed. The threshold for mites is 20-30% infested crowns with 1-2 mites per leaf. Acramite, Capture, Danitol, Agri-Mek or Kelthane will provide control, but should be rotated to avoid the development of resistance. We just received our 24C label allowing aerial application of Acramite on melons. Only one application is permitted per season and the rate is 1 lb/acre. This registration remains valid, unless disapproved by EPA within 90 days of issuance, for 5 years (Federal) and one year (Delaware). The treatment threshold for aphids is 20% infested plants with at least 5 aphids per leaf. Be sure to check runners carefully for aphids.  For a treatment to be effective, fields should be sprayed before you see significant leaf curling.  Be sure to watch for bees foraging in the area and avoid insecticide applications on blooming crops.

n areas where corn borer trap catches are above 2 per night and pepper fruit is ˝ inch in size or larger, fields should be sprayed on a 7-10 day schedule for corn borer control.  You will also need to consider a treatment for pepper maggot. If Orthene is used, it will also provide pepper maggot control. Otherwise, dimethoate should be added to the mix.


Continue to scout fields on a weekly basis for Colorado potato beetle (CPB) adults and larvae. The larval threshold is 4 small larvae per plant or 1.5 large larvae per plant. The threshold for each should be reduced by 1/3 to ˝ if all stages of larvae are present.   Avaunt + PBO, Actara, cryolite, Spintor,  Provado or newly labeled Rimon will provide control. We just received our state label for Rimon. Although labeled at 9-12 oz/acre, the 12 oz rate is recommended. Remember from the last newsletter, it will not control adults and has buffer zone and buffer strip restrictions for aerial application.  We are also starting to see the emergence of summer adults. Unfortunately, most of our labeled products are most effective on larvae. The higher labeled rates of Spintor and cryolite have provided some level of adult suppression; however, may not be adequate under high population pressure. Actara, Leverage and Provado provide adult control but should not be used where Admire, Platinum or Gaucho were used at planting to avoid development of resistance.  Economic levels of potato leafhopper adults and nymphs can still be found in many fields. As a general guideline, controls should be applied if you find ˝ to one adult per sweep and/or one nymph per every 10 leaves. Dimethoate, a  pyrethroid, Actara or Provado will provide control. We have just found our first green peach aphids in potatoes. No controls will be needed until you find  2 aphids per leaf during bloom and 4 aphids per leaf post bloom. If melon aphids are found, the threshold should be reduced by ˝.  If green peach aphid is the predominant species, Fulfill, Lannate, Monitor, Provado, or Vydate will provide control. If Fulfill is used, a penetrating surfactant should be used to achieve good coverage and achieve optimum control.

Snap Beans.

All seedling stage beans should be scouted for leafhopper and thrips activity. The thrips threshold is 5-6 per leaflet, and the leafhopper threshold is 5 per sweep. If both insects are present, the threshold for each should be reduced by 1/3.  Dimethoate, Lannate, Asana, Capture, or Warrior will provide control of both insect pests. Once corn borer catches reach 2 per night, fresh market and processing snap beans in the bud to pin stages should be sprayed for corn borer. Acephate should be used at the bud and pin stages on processing beans. Once pins are present on fresh market snap beans and trap catches are above 2 per night, a 7-10 day schedule should be maintained for corn borer control.  Lannate, Asana, Capture, Warrior or Mustang are labeled. Acephate has a 14-day wait until harvest. Since this can change quickly, be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decision in  processing snap beans 

(http://www.udel.edu/IPM/traps/latestblt.html and


Sweet Corn.
All silking sweet corn should be sprayed on a 5- 6 day schedule. Be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decision in silking sweet corn (http://www.udel.edu/IPM/traps/latestblt.html and http://www.udel.edu/IPM/thresh/silkspraythresh.html).


Pickling Cucumber Harvest Begins – Harvest Timing Means $$$ Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu


Pickling Cucumber Harvest began last Saturday, one of the earliest starts in memory.  This reflects the warm growing conditions we experienced through most of the spring, and probably more sunshine than usual.


Growers are reminded that choosing the proper day for harvest can make a significant positive economic impact.  With the once-over destructive harvest and the contract structured for different values for different size pickles, the gross return on any given harvest is directly affected by maturity.  A good “rule of thumb” is to harvest when 5% (by weight) of the pickles reach the 4A category, or between 2 and 2/18 inches.  Probably 70 to 80% of the load is in the 3A (1.5 to 1.75 inches) and 3B (1.75 to 2.00 inches) categories.  This seems to reflect the proper compromise between weight and declining value for the largest sizes.


Many growers sample 2-3 days prior to harvest to track the rate of maturity.  Growers are also encouraged to “do the math” when they get their grade sheets on particular loads.  Run the calculations based on the contract prices of each size and the percent of the load in each size.  Change the percentages and do the calculations to see how the value of the load can be affected by harvest timing.



Emerged Lima Beans Can Be Injured With Dual - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu


Dual is labeled and quite safe for preemergence use on lima beans.  However, I have seen fields and situations when Dual was applied as the beans were just emerging, or lima beans followed a small grain that was only disked in.  Only disking it in resulted in poor soil coverage of the lima bean seed.  In these situations, lima bean injury can occur.  To avoid these problems, be sure the seed slit is filled in with soil and do not delay application more than one to two days after planting.


Bee Hive Strength Related to Fruit Set – Derby Walker, Sussex County Extension Ag Agent, derby@udel.edu; Tracy Wootten, Extension Horticulture Agent, wootten@udel.edu



We have received questions on pollination of watermelon fields this week.  Lack of good pollination can be a result of weak bee hives.  A good hive should have 6 frames of brood with enough bees for 8 frames. Information on evaluating honey bee colonies for pollination can be found at the following Pacific Northwest Extension Publication:  http://wwwagcomm.ads.orst.edu/AgComWebFile/EdMat/PNW245.pdf.  Information on what is a colony, worker bees, colony size and efficiency, colony strength, disease, amount of comb, number of bees, food requirement, a normal queen and colony flight is discussed.  As mentioned in Derby’s column last week, environmental conditions will affect bee flight.  A stronger hive will begin foraging at a lower temperature than a weak hive, but only rarely will honey bees fly at temperatures below 55° F.  As temperatures reach 70°F, the number of bees foraging increases. 


Manganese Toxicity on Muskmelon – Derby Walker, Sussex County Extension Ag Agent, derby@udel.edu; Tracy Wootten, Extension Horticulture Ag, wootten@udel.edu


Manganese toxicity on muskmelon was observed this week.  Characteristic signs in the field are yellowing, lighter green spotting on the upper surface of the leaf and watersoaked “pin holes” on the lower surface of the leaf.  Holding the leaf up to the light will help with diagnosis.  These areas will become necrotic, and eventually the whole leaf will die.  Manganese toxicity is the result of low pH – below 6.0.  Unfortunately, this usually does not reveal itself until approximately 2 weeks before harvest.  We experienced this at the Research & Education Center in one of our trials.  There is no “in season” remedy for this problem.  The manganese toxicity is corrected with an increase in pH with lime application.  The best you can do is try to maintain the foliage that you have through harvest.  We were able to maintain the foliage of our melon plants with FOLCAL at 1.5 pts./A.    See the label for application rates and timing.  Pictures of manganese toxicity can be found at the following link: 




Vegetable Crop Diseases - Bob Mulrooney,

Extension Plant Pathologist, bobmul@udel.edu


Late Blight Advisory.


Disease Severity Value (DSV) Accumulation as of June 24, 2004 is as follows:

Location: Joe Jackewicz Farm, Magnolia, DE. Greenrow: April 25, 2004




Daily DSV

Total DSV

Spray Recommendation

4/25- 5/18










































































Application rates for protectant fungicides (Dithane, Bravo, etc.) should be at the high end of the rate with the amount of foliage present and likelihood of favorable weather for infection.


Early blight and black dot. Many fields are flowering or approaching flowering and this is a good time to consider switching to an application or two of Gem, Headline or Quadris (Amistar) for early blight susceptible varieties. This can also be helpful for late season varieties including russets if stress makes plants susceptible to black dot. Make one or two applications at the end of flowering and repeat 14 days later. Apply mancozeb or chlorothalonil 7-days later between the two applications.

If pink rot control is important and you did not treat at planting, foliar applications of either Ridomil Gold MZ or Ridomil Gold/Bravo, or Flouronil when tubers are nickel-sized is suggested.  A second application should be made 14 days later.


For specific fungicide recommendations, see pages F132-33, 2004 Delaware Commercial Vegetable Production Recommendations.





Field Crops


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



Continue to sample all fields on a weekly basis for leafhopper adults and nymphs. If economic levels are present, early cutting may be the best option for control. However, be sure to check fields within a week of cutting for leafhoppers that can quickly damage small plants. The treatment thresholds are 20 per 100 sweeps on alfalfa 3 inches or less in height, 50 per 100 sweeps in 4-6 inch tall alfalfa and 100 per 100 sweeps in 7-11 inch tall alfalfa.

Grasshoppers, thrips and potato leafhopper can be found in economic levels in many fields throughout the state.  The treatment threshold for grasshoppers is 1 per sweep and 30% defoliation. Asana, dimethoate, Furadan, Lorsban, or Warrior will provide grasshopper control. The treatment threshold for thrips is 8 per leaflet with plant growth is being held back. Be sure to sample carefully for thrips since populations are higher compared to past years. The treatment threshold for leafhoppers is 4 per sweep in drought stressed fields and 8 per sweep in non-stressed fields. Dimethoate or a pyrethroid will provide control of thrips and leafhoppers.  Caution: OP insecticides (like dimethoate or Lorsdan) should not be combined with SU/ALS herbicides (like Harmony GT).

Continue to watch for spider mites, especially in no-till fields where a heavy weed cover was present before planting as well as early planted fields that are starting to bloom. Treatment will be needed when you find 20-30 mites per leaflet or 10% of plants with 1/3 or more leaf area damaged. At this point, the only materials available for mite control in soybeans are dimethoate and Lorsban.




Yellowing Soybeans Can Be Symptoms of Several Different ProblemsDerby Walker, Sussex County Extension Ag Agent, derby@udel.edu


Yellow soybeans can be a symptom of several different problems including pH, insect, diseases, nutrient deficiencies or nematodes. This week, I have found spider mites and thrips in one field.  Leafhoppers are another insect that can cause soybeans to yellow.  One field had several spots showing manganese deficiency, most likely caused by high ph.  The beans were blooming and needed to be sprayed with a foliar manganese product to correct the problem. A couple of fields were dropping their older leaves because of a minor leaf spotting disease. It looks like Septoria Brown Spot.


Three fields appeared to be nitrogen deficient. They were nitrogen deficient, but the problem was soybean cyst nematodes that prevent nitrogen fixing nodules from developing. They were soybean cyst resistant but they were not resistant to the Race in these fields. Planting same race resistant beans year after year will shift the race of cysts to another race most likely to Race 1 or Race 5. How can you tell which it shifted to? Hoe out a section of beans where there is cyst problem and plant varieties that have different Race resistances (non-resistant, Race 3, Race 1, and any other race you can find).  Then 30 to 35 days later dig up of plants and count the number of cyst on each variety. The one with fewest is type of resistant beans you need. The odds are good that Race 3 shifted to Race 1. We do have some Race 1 resistant varieties, however most are very late group 4 or group 5 beans. Also you will probably have to return to standard soybean varieties and herbicide programs instead of Roundup Soybeans.


Even combining glyphosate with certain herbicides and other products can give you a temporary yellowing and sometimes a stunting.




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


General Comments.

The old crop soybean supply situation has gotten the attention of traders in the soybean pits again this week, with old crop July futures currently at

$9.27 and new crop Nov. futures at $7.02 per bushel. To paraphrase the comments of one veteran trader this morning: "If old crop soybeans go to $9.50 today then they will most likely move to $10.00. Further, if we don't see $9.50 today then it will be awhile before old crop beans go higher, if at all."  The trader went on to say that "If USDA raises their ending stocks estimate in the June 30th report for soybeans, then we are not likely to move much higher on old crop soybeans". 


It is likely to be August before we get a realistic handle on the actual size of this year's
U.S. soybean crop. Barring any significant weather problems in the U.S. this summer, the current production forecast estimates the U.S. '04 soybean crop at 2.965 billion bushels, resulting in a build up in U.S. carry over stocks to 220 million bushels, 105 million bushels larger than the '03/'04 soybean stocks estimate. Factor in the production forecast for the '05 Southern Hemisphere soybean crop of 113 million metric tons (mmt), 25% larger than their '04 crop. USDA's average price projection for new crop soybeans at $5.70 to $6.70 makes sense.


World soybean carryover supplies are estimated to be 46.69 mmt versus 33.01 last year, a 41% increase. World soybean consumption, estimated at 210 mmt versus 195 mmt for the '03/'04 crop, continues to climb. However, production

forecasts are currently projected to outpace consumption.   



Corn export sales were disappointing this week, reported at a combined old-crop/new-crop total of 13.7 million bushels. The low end of the estimate was 15.7 million bushels. Pressure on the corn market could come from rains moving through parts of the Midwest again this morning. Technically, corn contracts posted bullish ranges on Wednesday. Follow-through technical buying could offset the bearish fundamentals with additional support possibly coming from spillover buying from the bean complex. USDA's average price projection for new crop corn is currently placed at $2.55 to $2.95 per bushel.



Wheat futures are being influenced by harvest pressure and disappointment over Egypt buying French wheat this week. Yields have been lowered and disease damage has increased, which should be supportive once the totals are know. USDA's average price range for new crop wheat is currently at $3.25 to

$3.85 per bushel.


Market Strategy.

The corn and soybean markets have trended lower over the past month. Each passing rain through the corn belt has resulted in the 'highs' and 'lows' getting a little lower. Technically speaking, these markets are bearish, and barring any significant weather development, we are not likely to see the month ago highs reached any time soon. For those who are sitting unpriced on new crop corn and soybeans it is time to bring forward cash sales to the 40% to 50% level of intended production. Current new crop price levels for corn and soybeans represent profitable sales opportunities. It is better to get sales done on the first 1/2 of intended production at profitable levels than to take a chance on holding out for higher prices that may or may not materialize.





2004 Delaware Weed Day- Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu


The 2004 Delaware Weed Day will be held Wednesday, June 30, at the University of Delaware Research and Education Center, Route 9 (County Seat Highway), Georgetown, DE.  The day will begin with registration at 8:00 a.m. and opening remarks at 8:30 a.m. at the Pine Grove near the farm buildings on the north side of the road.  Coffee, juices, and donuts will be served.  A variety of herbicide programs for conventional tillage and no-till are being evaluated.  Almost all registered corn herbicides are included, a number of studies examining surfactants are on-going, and evaluation of reduced rates of soil-applied herbicides are included. 






                       Weather Summary


Week of June 17 to June 24, 2004


0.15 inches: June 17

0.06 inches: June 18

0.05 inches: June 22

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


Air Temperature:

Highs Ranged from 89°F on June 17 & 18 to 76°F on June 20.

Lows Ranged from 71°F on June 17 & 18 to 52°F on June 21.


Soil Temperature:

80°F average.

(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

Sussex County Extension Agent – Horticulture

University of Delaware


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.


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