North American Fruit Explorers mailing list at ibiblio

[david.maxwell@dal.ca]

I'm not sure how successful you will be with spreading tarps.  The eggs hatch 
around petal 
fall, and the first instar larvae gnaw on the skin, leaving the 
characteristic winding trail. Then 
they chew into an adjacent fruit, penetrate to the core and dine there, 
shedding their skin and 
becoming a second instar.  This in turn chews its way out and penetrates 
another fruitlet, and 
so on for up to 5 instars.  At some point they manage to abort the fruit so 
it drops.  Your tarps 
would work well in catching these drops, but you need to maintain them for up 
to a month or 
more, as the EAS larvae are chomping on the fruit above over an extended 
period, and the 
fruit will drop over an equally extended period.  But you are correct in 
thinking that a physical 
barrier is a good idea - once the fruit is on the ground the larva crawls out 
and burrows into 
the ground (about 5 cm./2 inches deep), and forms a cocoon, emerging next 
year as an 
adult.  There is a wasp, Lathrolestes, which lays its eggs in the cocoon, but 
Vincent & Belair, 
(I think it was), reported that they don't kill enough EAS to provide 
adequate control. There 
are also a couple of beneficial nematodes which have been tried.  Again, 
while they kill a 
substantial proportion, more than enough remain to cause major damage. Trying 
to get them 
with an insecticide sprayed into the ground is I think not likely to work - 
you would have to kill 
all living things to get the EAS.  The only point at which commercial growers 
seem inclined to 
try to intervene is at the first instar, when the larva is chewing on the 
skin of the first apple.  
They aim to poison the skin, and kill off the larvae before they manage to 
migrate into the 
next fruit.  (Obviously, once they are into the second fruit, insecticides 
sprayed on the outside 
aren't likely to do anything.)