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The Heat Is On!

March 29, 2016
by Rick Brandenburg

March 18, 2016cu

The Heat Is On

Rick Brandenburg
Turfgrass Entomologist

 

There has been a lot of discussion about the winter weather of 2015-2016 and not just in North Carolina.  I want to add some data to the discussion to help illustrate where we are and what it might mean.  I will update this each week as we move forward. 

First, December was an epic month for warmth. We typically measure warmth, for biological purposes, with degree day accumulations. This is simply a quantitative method to say just how hot or cold it has been. For insects we use a base temperature of 50 F, somewhat of a universal threshold for insect activity. So the hotter the day and the more the average temperature of the day is above 50, the more degree days we would accumulate.

In Raleigh, NC the average degree days accumulated in December, based on the 30 year average is about 61.  Charlotte is very close to that, Asheville about half that, and Wilmington twice that number.  During December of 2015 Raleigh accumulated 243 degree days in December, four times the normal level.  December was actually warmer than it normally is in November or even April, so it was indeed a very warm month.  However, that by itself didn’t mean too much because if January and February were really cold, we could be somewhat near normal.  However, as cold as those months seemed in contrast to December, the first two months of 2016 actually had twice as many degree days as normal (granted these numbers are small and don’t contribute much, but it does say they were not below normal). 

And then March came along.  By mid-March we already had twice as many degree days as we would normally accumulate for the WHOLE month!  In fact we have accumulated more degree days in March than we normally see in April.  Through March 27, we have accumulated more than 260 degree days in Raleigh. Compare this to the normal degree day accumulation for the whole month of March of 71, based on the 30 year average and you can see that March 2016 has been just as special as December 2015 for those who like it warm.  The average April degree day accumulations is just 177, so you can also see March blew even the April degree day counts out of the water.  We typically have just 123 degree days accumulated in Raleigh through the end of March and 300 through the end of April, so we are way ahead of schedule. The total for March does not include Monday, March 28 which was a warm day as well.

The result? Trees and plants blooming early, mole crickets and fire ants very active earlier than normal, and warm season turf a lot greener than we have seen for this time of year.  Despite the cold weather of March 19-20 with light frost in some areas, we have moved ahead of schedule.

What does it mean? It means stay on your toes, stay alert, be prepared for things to happen earlier.  But, if April turns out to be cooler than normal we may not be as far ahead as degree days indicate. Also remember that other factors such as day length affect some pests, so temperatures can only push pests ahead but so fast. The take home message: Be ready for pest occurrences to be earlier this spring than normal. I will try to provide updates each week. throughout April to provide more information on where we are with degree day counts for 2016 as compared to “normal?”