Figure 2: Lilac Borer Pheno Forecast
for April 3, 2018.
Photo: Adult Lilac Borer, Photo by
Mark Dreiling, Bugwood.org
Example: Planning for spring-
season lilac borer treatment
in Charlotte, North Carolina
Adult lilac borers overwinter in the heartwood of trees, then
emerge in early summer. According to the Center for Agriculture,
Food, and the Environment at UMass Amherst, trunk sprays
should take place preceding or coinciding with adult emer-
gence and subsequent egg hatch to kill larvae before they enter
trunks. Adult emergence begins around 500 GDD (50°F/10°C
base temperature) and continues until approximately 1,400
GDD; sprays should be implemented for this entire duration.
On April 2, 2018, the region for active treatment (shown in
green on Figure 2) encompassed southern Georgia, Alabama,
and Mississippi, and a wide swath to the north was approaching
the time when treatment should be taken (shown in yellow).
Regions farther north were considered not yet approaching
the treatment window, since, as of this date, more than 150
GDD were still needed to reach the 500 GDD threshold. The
current-day and six-day forecast maps displaying treatment sta-
tus for lilac borers can be viewed on the USA-NPN website.
Accessing the Pheno Forecasts through the USA-NPN visualiza-
tion tool offers the added benefit of allowing you to explore
the pattern of heat accumulation at your site. You can use this
information to evaluate whether you might expect to treat earlier
or later than usual. For example, as of April 2, 2018, Charlotte,
North Carolina fell within the "not approaching treatment win-
dow" category. By clicking on Charlotte on the map, we can see
that 263 GDD had accumulated by April 2 at this location. >>
For many pest insects, the
specific amount of heat
required to trigger a life
cycle event such as adult
emergence has been docu-
mented, making it possible
to anticipate the timing
of the event at a loca-
tion based on local tem-
perature measurements.
Accumulated heat is often
measured in cumulative
growing degree days (GDD),
defined as the number of
degrees the mean daily
temperature exceeds a
base temperature, below
which an organism will
remain developmentally
inactive. For more informa-
tion on GDD maps avail-
able through USA-NPN, see
the article in the January/
February 2018 issue.
www.urban-forestry.com 15
