• Downy mildew alert for cucurbits

• Corn earworm

• Huge fall armyworm flight

• Dinky European corn borer flight

• New corn insecticide: Belt

• Scout basil for downy mildew

• Phytophthora now on beans

Downy Mildew alert for cucurbits
On Monday the 10^th, we found the first downy mildew of the year in CT on cucumbers and musk melons.  It also showed up in MA on the same day. Two weeks ago it showed up on Long Island but only on the cucumbers, then by last week it had spread to the melons, and this week they are finding it on all cucurbits.  Remember, this is another water mold like late blight and can defoliate your entire crop in as little as 5-10 days.  So, I am recommending that you add a downy mildew material to your spray mix that should already include something for powdery mildew, Plectosporium, Black rot and scab.  For example, if you are making your second pumpkin spray, you may want to use a mix of Procure for powdery mildew, Presidio for downy mildew and Bravo for black rot, Plectosporium and scab.  If you are using Pristine for most of the diseases you could just add Ranman for downy mildew control.

The good news is that you already have the fungicides that should control downy mildew because you are already spraying your tomatoes with them for late blight.  According to university efficacy tests, some of the most effective materials include Ranman, Presidio and Previcur Flex, which ranked higher than Tanos and Curzate, which were better than Forum, Gavel and phosphorus acid type materials such as Prophyt.  Other fungicides that work in some years include Ridomil Gold Bravo, maneb, copper, and Cabrio, but the last three do not rate high in efficacy trials. 

The bad news is that each year the strain of DM that arrives in CT is resistant to some fungicides, and we never know which ones until we try them.  So, it will be important for you to scout your cucurbit crops, especially your cucumbers and melons, every 5 -7 days.  If you have downy mildew already, be sure to go out and check how well the fungicide you apply is controlling the disease about 3-4 days after you spray.  If the symptoms are getting noticeably worse, then apply a different DM material immediately.  Remember that pathologists want you to apply a protectant, such as Ranman, Bravo, Maneb or copper, for resistance management purposes with all systemics except for Gavel, which already contains a systemic plus mancozeb, but which can not be used on pumpkins or winter squash and may cause phytotoxicity to some melon varieties.          

When scouting first look for yellow polka-dots on the leaves.  The spots then expand and kill the tissue between small leaf veins producing widely spaced, brown, squared-off spots that give the leaves a mosaic painting type look.  Finally, the oldest leaves toward the base of the plants start to cup and then die, and this symptom rapidly spreads down the vine to younger leaves.  If you want to see pictures of these symptoms see >Scouting for DM= on the UConn IPM Web Site.

Corn earworm
The number of CEW moths in pheromone traps dropped off at all locations this week except in E. Hartford where they captured 21 moths per night and are still on a three day spray schedule on fresh silking sweet corn.  Traps in Shelton, Northford, E. Lyme and Ellington dropped to between 2.5 and 12 moths per night putting those locations on a 4 day spray schedule.  Berlin dropped to 1 moth per night and is on a 5 day spray schedule.  Growers who do not have traps should probably be on a 4 day spray schedule on fresh silking corn at this time. 

Here are the CEW thresholds: 

Huge fall armyworm flight

A trap in Ellington captured 82 FAW moths this week, while traps in Shelton, E. Hartford, E. Lyme and Berlin captured between 18-24 moths.  The are high numbers, and 82 is a  huge number of moths for FAW.  The last time we saw a flight this large was in 1994 when the corn pests went through the roof.  With populations of 90 moths per week in a trap, even peppers start to be attacked. We=ll see if the moths continue to increase next week.  In sweet corn plantings we found infestations as high as 70% of the plants with caterpillars in young whorl stage blocks and 42% in some pretassel stage plantings.  If you normally don=t scout for this insect in your pre-tassel stage corn, it may be a good idea to check this week, because there may be a high infestation and the caterpillars will migrate to the ear when the tassel pops open and before silk sprays are applied.   SpinTor, Avaunt, and Intrepid all work well on this pest.  Warrior and other synthetic pyrethroids works well some of the time, but not all the time.

 

Dinky European corn borer flight   

The two farms in Shelton and Northford that last week exceeded the 7 moth per week pepper spray threshold, fell off to just 3 moths each in traps this week.  That means that they may have just applied there first and only pepper borer spray of the season.  Wouldn=t that be nice.  One farm in E. Lyme captured 16 moths this week and will make a pepper spray next week (or one week after exceeding threshold).  Other traps in Berlin and E. Hartford remained below threshold and are not spraying peppers at this time.  Intrepid will kill only caterpillars and lasts up to 14 days, and can be alternated with SpinTor, which lasts for 7 days, if a second application is even  needed this year.

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.

New corn insecticide: Belt
In the past, I have told you how they are having trouble with CEW insecticide resistance for products such as Warrior and other synthetic pyrethroids out in the upper Mid-West.  I also mentioned last year that Bayer has a new product called Belt which contains the active ingredient flubendiamide, which represents a new and separate chemical family. Belt controls these caterpillars by causing them to stop feeding when ingested.  It is registered to kill CEW, ECB, FAW, and even black cutworm on sweet corn and pop corn.  It has a 12 hour reentry interval, a 1 day-to-harvest restriction and is applied at 2 to 3 ounces per acre, with a limit of 12 ounces per acre.  Last year it wasn=t registered in CT but this year it is. So if you are looking for a different mode-of-action to rotate into your sweet corn caterpillar control, it has arrived and is called Belt.

Scout basil for downy mildew
Downy mildew on basil is a new disease that just entered the country in 2007 and is caused by a different species of water mold than the species that infects cucurbit crops. For instance, one important difference is that the basil species can infect seeds while the cucurbit species can not.  Basil DM was distributed by big box stores just like late blight was this spring and was found on  a commercial farm on Long Island last week.  It was also found in a commercial greenhouse here in CT.  The basil DM can easily be confused with nutrient deficience because the first symptoms involve yellow discoloration of the upper side of the leaves, which is often confined to the leaf tissue between two or more leaf veins.  So, if your basil is looking like it needs a little nitrogen, the true is it may be DM. Registered fungicides are limited to the phosphorous acid type products Prophyt and k-Phite and the OMRI approved Actinovate AG, all of which list basil or herbs and downy mildew on the label.  Tests have shown that phosphoric acid controls the disease well if applied before infection occurs.
 

Phytophthora now on beans
With the heat last week, Phytophthora really hit farms hard, with whole squash or pepper fields collapsing and dying.  We also found Phytophthora on beans for the first time in CT.  This essentially eliminates beans as an effective rotation crop for this disease.  The best rotation crops are still sweet corn and Brassicas.  Water management is the best way to stop this disease since it require three components to start the disease cycle: the Phytophthora spores in the soil, a susceptible host crop and 24-48 hours of saturated soil, usually standing water.  If you would like more detail on water management techniques you should read the article on Phytophthora in the pepper section on the UConn IPM Web Site.