Baute Bug Blog

Some scouts are starting to notice tiny WBC  larvae that have hatched that crawling in the whorl or making their way down to the ear of the plants.  To help you know whether they are WBC larvae, here are some photos.  You can click on them to enlarge them.

They start out with spots along their bodies (spots have tiny short hairs coming out of them).  You will need a handlens to really see the spots.

Newly hatched WBC Larvae (T. Baute, OMAFRA)

Closeup of newly hatched WBC larvae (Photo Credit: Chris DiFonzo, MSU)

Within a few days they start to develop stripes.

2nd or 3rd instar WBC larva (Photo Credit: T. Baute, OMAFRA)

To know for sure that they are WBC, watch how the way.  The itch their way along a leaf like an inchworm.  Click on video to see how they crawl.

Trap counts sent in to the network this week from last week’s moth catches indicate that moth flight increased dramatically.  And from tweets on Twitter and emails coming in from participants, even higher numbers are being caught this week in some traps.  So we haven’t quite reached peak moth flight yet here in Ontario.  The top counties that caught the most moths last week were Lambton (93/trap), Haldimand/Norfolk (88/trap) and Chatham-Kent (63/trap).  I’ve summarized the results for the top 9 counties so far this year in a graph below:

Top 9 County Trap Catches So Far

What does this mean?  We still have more scouting to do.  With moth counts still increasing, egg laying is also still on the rise.  Hot spot areas like Bothwell will start to be less ideal for the moths to lay eggs, as the corn starts to advance into full tassel/pollen shed.  Other counties with high trap counts and younger corn are at risk.  Though I suggest everyone scout their corn fields at least once or twice these next few weeks, even if trap counts are not that high.  Some of the original sites we found the most eggs in this year had very low trap counts initially.  Focus scouting efforts to corn fields that have plants with at least a tassel developing in the whorl of the plant to those fields with the tassel fully emerged but not fully shedding yet.  These are the fields that seem to be the most attractive for the moths.  And if fields have variable plant heights, we also noticed that there tends to be a higher concentration of eggs on what some tease about as “Baute” height corn.  No offense to my family members who are taller than me but those who have seen me know that I am a little vertically challenged.  So scout shorter corn in a field first before moving deep in.

Since peak flight has not happened yet, dry bean scouting is not quite necessary yet.  Most of the crop is still just starting to flower and develop pods.  Ideal management timing is when pod feeding can be easily found, which typically takes place 10 to 20 days after peak flight.

The official announcement came through today.  Coragen Insecticide is now also approved for use in dry beans and other legumes (except soybeans) for WBC control in Canada through the URMULE system.   Rate is 250 to 375 mL/ha.  Use a minimum of 100L/ha of water for ground app.  1 day PHI.  Click link to see revised label: Coragen CG6 except soybeans E Label 2011.’

WBC management recommendations for dry beans will come later this week once we can determine if we have hit or are close to peak moth flight.

Despite the heat, western bean cutworm activity is increasing.  Trap catches over the past week have climbed significantly, indicating that peak flight is here or soon to be here.  The counties that have accumulated the most moth catches so far include Chatham-Kent (544), Lambton (256), Middlesex (244), Huron (206), Haldimand-Norfolk (138), Essex (155) and Elgin (105).  Click here to see the accumulated map catches for Southwestern Ontario. The Chatham-Kent trap sites with the highest catches are actually still in and around Bothwell which border the three counties of CK, Lambton and Middlesex.  Chatham-Kent and Lambton are both currently averaging 9 moths per trap, though some traps have caught 100s in just a few days.  To see trap catches for all of our trap sites, click here and view Week 6 maps.

Newly hatched WBC Larvae (T. Baute, OMAFRA)

More reps and scouts are finding corn fields with eggmasses at above threshold levels.   Though so far above threshold infestations have been mainly found in the greater Bothwell area and south of Tillsonburg, many more fields are going to be ideal now for moths to lay eggs in.  Those fields that were not planted with a Bt that protects against WBC need to be scouted.  Target fields that are in the early pre-tassel to early tassel emerged stages.  In this heat a freshly laid eggmasses can hatch in 4 to 5 days.  Remember you want to target a spray application just after egg hatch, if the 5% threshold is reached.  Young larvae will hang out in the whorl/tassel of the plant for a few days before heading down to the developing ear.

Don’t spray in the heat of the day during this heat wave.  Wait until the evening when temps are in the lower 20s to high teens.

I have been negligent in not mentioning the newest insecticide to be registered for WBC control in corn.  I have no excuse except that I been conveying product information through links to Publication 812, Field Crop Protection Guide and the product didn’t get registered for WBC control in time to make the printing deadline.  So it is going to get a special blog entry to make up for it.

Coragen Insecticide is now registered for WBC control in corn.  The active ingredient is chlorantraniliprole.  Rate would be 101-151 mL/acre or 250-375 mL/ha.  Use a minimum of 100 L/ha of water. 12 hr re-entry period.   Follow all label precautions which can be found the Coragen_en_2011.

Great to have more products to tackle this new pest.