The presentation described the walnut caterpillar and possible treatments at the Beauregard Parish Garden Forum, February 23, 2018

1. Protecting your Pecan
Trees from the Walnut
Caterpillar
2018 Spring Garden Forum
February, 23
Brought to you by the
Beauregard Master Gardeners

2. Basics
• Walnut Caterpillar
– Native insect of eastern US & parts of
Canada
– Feeds on pecan, black walnut & hickory
trees
– Last major outbreak in the 1980’s
– Outbreaks last 2-3 growing seasons
– 2-3 generations per growing season
– REPEATED DEFOLIATIONS CAN
KILL TREES

3. WC in the News
• 2014
– Fort Bend, TX
• 2016
– DeRidder, LA
– Martha’s Vineyard, MA
– San Angelo, TX

4. Stages of WC
Walnut caterpillar egg mass. These egg masses are reflective
and can be detected at night with strong flashlight

5. Stages of WC
Mature walnut caterpillar
caterpillars feeding

6. Stages of WC
Immature walnut caterpillar
larvae preparing to molt.

7. Stages of WC
Mature walnut caterpillar causes most of the defoliation,
then it pupates in the soil.

8. Stages of WC
Adult walnut caterpillar
emerges after pupation
in the soil. Adult lays
eggs under leaves of
susceptible trees.

9. I have good news (maybe)
• The sustained freezing
temperatures in January may have
suppressed the walnut caterpillar.
• This outcomes depends on how
deep the pupa was in the soil during
the freeze.

10. & I have bad news.
• The cold temperatures may NOT
have any effect on WC, and we may
have another season of defoliation.

11. Getting Ready
• Detection:
– Get your flashlight & check under
leaves at night
– The egg masses reflect back
• If you find egg masses, pull off the
leaves that you can reach & destroy
those leaves.

12. Treatments
• Small trees
– Chemical spray
• Sevin (carbaryl)
• Malathion
• Acelepryn
– Biological (organic) spray
• Dipel, Thuricide, Javelin, Biobit,
Condor, Foray 48B, etc.(Bt)
• Spintor 2 (Spinosad)

13. Treatments
• Large trees
– Arena 0.25G
– “G” is dry granular
– Can be applied with lawn
spreader; similar to applying
fertilizer
– Rate: 0.5 to 1.0# per diameter inch
of tree
– Labeled for non-bearing trees

14. Added Benefits
• Shrubs
• Bedding Plants
• Flowering Plants
• Foliage Plants
• Ground Covers
• Evergreens
• Ornamental Trees
• Non-bearing Fruit & Nut Trees &
Vines

15. Added Benefits
• Turf
– White Grubs
– Armyworms
– Chinch Bugs
– Crane Fly Cutworms
– Nuisance Ants
– Sod Webworms
– Mole crickets

16. Frequently Asked
Questions
• “I’ve lived here all my life and have
not seen these caterpillars before.
Where did they come from?”
– ANSWER: The walnut caterpillar
is a native insect. A range map of
the United States indicates that 27
states, mostly eastern, have WC.

17. Frequently Asked
Questions
• “Why did they appear now?”
• ANSWER: That is a tough question
to answer. One part of the answer
may be the recent mild winters.
Another answer is that insects have
population cycles, and the WC was
due for an outbreak.

18. Frequently Asked
Questions
• “Will they come back?”
– ANSWER: Possibly Yes, the cold
weather might suppress WC
– Also, these outbreaks last 2 to 3
years, and 2018 may be the 3rd
year of WC

19. Frequently Asked
Questions
• “Will the pecans be any good?”
– ANSWER: Arena is labeled for
non-bearing nut trees. However,
homeowners will probably apply
anyway to prevent tree mortality.
It is better to be safe than sorry so
avoid eating pecans for a season.

20. Frequently Asked
Questions
• “After treating the trees with Arena,
will the pecans kill squirrels?”
– ANSWER: This class of
insecticide has very low toxicity
for people and mammals.
However, it is very toxic to
aquatic invertebrates like
crawfish.

21. Frequently Asked
Questions
• “Will Arena kill pollinators after it is
in the pecan tree?”
– ANSWER: Probably not, because
pecan trees are WIND pollinated
and does need insect pollinators.

22. Frequently Asked
Questions
• “Is Arena safe for pets?”
– The label for Arena says: “Do not
enter or allow entry into treated
areas during the restricted entry
interval (REI) of 12 hours.” This
statement means no people or
pets on the treatment site,
probably your yard, for 12 hours.
After 12 hours, access to the yard
would be OK.

23. More Questions?
• Colin Powell says: “There is no
such thing as a stupid question,
only stupid answers".
• Albert Einstein, “The only stupid
question is one not asked.”
The 2018 Spring Garden Forum is
pleased to have O’Neal’s Feeder
Supply and Highland Growers as
sponsors.