Welcome to the University of Connecticut Cooperative Extension System's
Vegetable Pest Message.
This message is being recorded on Friday afternoon August 1 by Jude Boucher.

This week's message will cover:

Corn earworm
The number of CEW moths per night in pheromone traps this week ranged from a low of 0.5 in Falls Village, where they are on a 6 day spray schedule on fresh silking corn, to a high of 40 moths per night in Shelton.  Actually, Shelton was capturing 40 moths/night earlier in the week, but as of today, they are down to just 1 to11.5 and are now on a 4 day schedule again.  Northford and the Glastonbury meadows captured 13.5 and 23  moths per night and are on a 3 day schedule. Wallingford, East Lyme, Berlin, East Hartford, South Windsor and Somers all captured between 1.1 and 11.5 moths per night and are on a 4 day schedule on fresh silking corn.  If you do not have traps up on your farm, you should be spraying silking corn on at least a 4 day schedule this week and possibly a 3 day schedule if you are in the Connecticut River Valley.   

Here are the CEW trap thresholds: 

moths per night   recommended spray interval
0-0.2   No spray
0.2-0.5   6 day schedule
0.5-1   5 day schedule
1-13   4 day schedule
>13 moths   3 day schedule

Fall armyworm
Seven FAW moths were captured this week in the Glastonbury meadows, while Shelton, East Hartford, and Somers only captured 1-2 moths each, and Northford, East Lyme, Berlin, and South Windsor failed to capture any new FAW moths.  Shelton and East Lyme had 14-16% of the plants in whorls stage plantings infested and needed to spray for FAW larvae this week.  In Berlin and East Hartford, which had lower levels of FAW in whorl and pre-tassel stage corn, we noticed that most of the damaged pre-tassel stage plants had no larvae in them.  That means that it has been warm enough to push the caterpillar development ahead to the pupal stage before the ear formed. Obviously these plantings did not need spraying.  However, it demonstrates how important it is to open a few damaged plants in the pre-tassel stage to see if worms are still present. Since most locations are capturing very few new FAW moths at this time and thus there are few new eggs to hatch, you may want to hold off on whorl sprays even if the field is over the 10-15% threshold. It is unlikely that the infestation will increase in older whorl and pre-tassel stage fields, because the moth prefers to lay eggs in young whorl stage corn, unless moths are at very high levels. I would recommend just scouting pre-tassel stage corn this week and base your spray decision on the percent of plants with live worms. 

European corn borer coming back 
We captured 10 ECB moths this week in East Lyme and 51 in Northford.  Shelton, Berlin and East Hartford all captured 3 to 4 moths, up from 0 moths last week, which means that the second generation of corn borer has arrived.  It will take a couple of weeks before we start seeing many borer larvae in whorl stage corn, however, sites with over 7 moths/week, such as East Lyme and Northford, need to begin spraying peppers for borer this coming week.  Most sites are probably going over threshold as I write this message and will need to apply their first pepper spray for borer by August 7.  The UConn Pepper IPM Program recommends alternating between two selective insecticides, such as Intrepid and SpinTor, on a 7-14 day basis during the second generation moth flight.  SpinTor lasts for 7 days and Intrepid last for 10-14 days, and both products can be sprayed the day before harvest.     

Here is a list of infestations found at different sites while scouting sweet corn this past week. *means that the planting is over threshold and should be sprayed. MW=mid-whorl, LW= late-whorl, PT=pre-tassel, S=silk. 

Town % infested plants Stage of planting ECB  & FAW moths / week CEW moths/N
Shelton 14%* MW 3ECB, 1 FAW 11.5 = 4-day schedule
Northford 0% MW 51ECB, 0 FAW 13.5 = 3-day schedule
Wallingford       5 = 4-day schedule
East Lyme I 16%* FAW PT-LW 10 ECB, 0 FAW 5.5 = 4-day schedule
East Lyme II 0%
2% FAW
6% FAW		 PT
LW
MW		    
Berlin 2% FAW
9% FAW
6% FAW		 PT
LW
MW		 4 ECB, 0 FAW 3.1 = 4-day schedule
Glastonbury      7 FAW 23 = 3-day schedule
East Hartford 0%    
0% FAW
6% FAW		 PT
LW
MW		 4 ECB, 1FAW 9 = 4-day schedule
South Windsor      0 FAW 9 = 4-day schedule
Somers      2 FAW 1.1 = 4-day schedule
Falls Village 0% PT-LW   0.5 = 6 day schedule

As promised, another Impact herbicide update
I told you a few weeks back how I planted Bt sweet corn 4 weeks in a row without any pre-emergence herbicide and then sprayed all 4 plantings with 3/4 oz. Impact, 1.5 gallons of methylated seed oil and 2 pounds of ammonium sulfate.  The first planting is now at the pre-tassel stage.  The weed control in that planting is still almost perfect, just a few purslane plants. In the second planting, which had 3 inch tall weeds when I sprayed, instead of 6 inch weeds like in the first planting, there is a fair amount of purslane and shepherds-purse, neither of which will compete with the corn.  There is also an occasional lambsquarter or pigweed plant that escaped in the second  planting. I'm not sure why I got better control of the purslane when it was larger, and remember, purslane is not listed on the label as a controlled weed.  The third planting  still looks perfect and shows no sigh of weed regrowth.   I'll update you on the weed control once more at harvest later in the season.   

Powdery mildew on pumpkins
We found powdery mildew on pumpkins in East Lyme and Gales Ferry this week.  Scout the underside of 50 leaves on a weekly basis and spray if you find even a single small spot of powdery mildew.  The best place to check is along the eastern edge of the field if there are trees that will shade the plants along that border, and cause the dew to linger, so that the leaves stay wet in the morning. 

Along with powdery mildew we will be trying to control Plectosporium blight, black rot and scab, but keeping our eye out for downy mildew which can necessitate a change in your planned spray program.  The most effective materials for powdery mildew are the systemic products that help control the disease on the underside of the leaves where it gets started. The problem is that these products are very prone to resistance so should only be used a single time in a season and then put away until next year, and pathologists suggest that they are always used mixed with a protectant or non-systemic material. Some of these systemics and sulfur only control powdery mildew so must be mixed with a protectant to provide control of the other major diseases which can rot the fruit.  Here is a suggested program that will control all the major diseases, except downy mildew, and provides the best resistance management. 

1st spray - Pristine or Pristine and maneb

2nd spray - Procure or Nova and Bravo

3rd and 4th spray - Sulfur and Bravo

Try to spray every 10 days, but tighten the schedule by a couple of days during rainy periods and loosen it by a couple of days during dry periods.  Do not use sulfur on melons.  One form of sulfur that is inexpensive and dissolves nicely so that it will not clog your sprayer is a brand called Microthial Disperse sold by UAP.  

No downy mildew yet
While you are scouting for powdery mildew, you should be checking the vines for Plectosporium and downy mildew.  Plectosporium appears first on the large main vines running along the ground, so you have to separate the leaves and peer down through the canopy to check for the small, white slits or lesions on the vines.  If you find Plectosporium before you find powdery mildew, spray Bravo and continue to scout the plants weekly for powdery and downy mildew. Downy mildew first appears as yellow polka-dots on the leaves.  These yellow spots quickly turn into square or almost square brown lesions that are restricted by the small leaf veins.  Next the older leaves begin to curl upwards at the margins and finally all the foliage in the field dies.  If you see the yellow polka-dots or brown mosaic-like lesions you will need to respond quickly with an effective material because it only takes a week to 10 days for the foliage to die.  The problem is that every year we get a different strain of the disease that makes it to Connecticut, and any particular strain can be resistant to any of the fungicides. Last year some of the least expensive products, such as Ranman, ProPhyt, and maneb,  worked better than some of the more expensive products, but past performance does not guarantee future success.  Other products that are listed as very effective against downy mildew include Ridomil Gold Bravo, Previcur Flex, Tanos, Curzate and Pristine.  Curzate has a very short residual period so should be applied with another protectant such as maneb.  Strobiluron fungicides, such as Cabrio or Flint, are very effective on Plectosporium blight but there tends to be a high probability of resistance against either downy or powdery mildew. 

So far, downy mildew has been found in western NY and southern NJ and the forecast for New England on the downy mildew web site is for low to moderate risk of infection for the coming two days.  The UConn IPM program recommends that you scout for this disease, and save your downy mildew products until the disease is found in CT. 

That=s all for this week.  This message will next be updated in on Friday afternoon August 8.

Jude Boucher

 Previous Vegetable Pest Messages - 2008

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The information in this material is for educational purposes. The recommendations contained are based on the best available knowledge at the time of printing. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension system does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.All agrochemicals/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulations as of the date of printing. If the information does not agree with current labeling, follow the label instructions. The label is the law.Warning! Agrochemicals/pesticides are dangerous. Read and follow all instructions and safety precautions on labels. Carefully handle and store agrochemicals/pesticides in originally labeled containers immediately in a safe manner and place. Contact the Connecticut Department of Environmental Protection for current regulations.The user of this information assumes all risks for personal injury or property damage.Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Kirklyn M. Kerr, Director, Cooperative Extension System, The University of Connecticut, Storrs. The Connecticut Cooperative Extension System offers its programs to persons regardless of race, color, national origin, sex, age or disability and is an equal opportunity employer.

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