Bollworm Biology in North Carolina
 Script 6. Bacheler. April 17, 2003

Although stink bugs and thrips can sometimes contend for the title of 
“North Carolina’s Most Serious Cotton Insect Pest”, corn earworms, 
or bollworms, are potentially our most damaging cotton pest and account 
for the most control costs.  In today’s message, we’ll take a look at how 
the bollworm develops and later invades other crops in such high numbers.

Bollworms spend the winter in our area about an inch or so under the soil 
surface in the pupal stage, and emerge from the soil as moths in early to 
mid May, dry their wings, mate, and fly to spring hosts such as weeds 
and whorl stage corn.  In this first generation of caterpillars, the developing 
corn earworms remain at low levels and typically do little economic damage.  

The next generation of moths (often called the first field generation) is 
highly attracted to silking corn, and often builds up to high levels on 
untreated field corn ears.  This strong association with field corn is both 
good and bad.  The good news is that at this stage, often through much 
of July, the worms leave other major NC field crop alone.  The bad news
is that the next which generation of bollworm moths that leaves this field 
corn often does so in large numbers, and the subsequent caterpillars 
commonly infest others crops, such as cotton, in large numbers.

Fortunately, these major bollworm moth flights can be tracked and 
anticipated by light and pheromone traps.  Alert scouts can also often 
tell when a moth flight has begun.    Also, pyrethroid sprays, if well timed 
and applied at adequate rates, still do a good job in controlling these 
potentially damaging pests.  For the 2003 growing season, even on 
conventional cotton, bollworms remain a pest that should cause minimal 
damage to conscientious growers.