Beneficial Insects and Plant
Diversity
in Community Gardens of NYC
-Description of Field
Methods-
Animals
to be collected: Small wasps that lay their eggs in pest insects (generally
called parasitoids) and the leaf feeding pest insects that are their prey
Insect
collecting methods: We will place a few small pans out that will have about 1.5
inches of water. These will also have a dab of dishwashing detergent and a few
tablespoons of salt for preserving the insects. The pans will be left out for 5 days.
Insect
processing methods: After the 5 days, we will harvest the traps and will skim out
all the insects from the traps. The insects
will be placed in a small vial with 70% ethanol. We will then take the insects
back to our laboratory and sort and identify them there.
Plant
information to be collected: We will also need to
detail the abundance of each species of plant that is present in the
garden. This information will be
collected in the intervening days that the traps are in place.
1.
Should be primarily a vegetable garden.
2.
Preferably close to 2500 square feet in area, no more than a few
hundred meters on either side of that number.
3.
Call the garden manager to describe the project and get
permission.
4.
Visit the garden to ascertain that it is the size given to us as
well as that it meets the above criteria.
Gardens are in constant flux and we need to ground check the
information.
Setting the
Traps
1.
Receive permission ahead of time from the garden manager.
2.
Ideally all traps will be set out in the same day and retrieved
in the same day. If this is not possible, do them in consecutive days.
3.
Gather deli salad trays, cut them in half along the hinge
between the two clamshells – trays don’t have to be clear, but we need to use
all the same type.
4.
Entomologists have found that yellow helps to attract flying
insects. Spray the outside bottom of the trays with some yellow spray paint
before you get to the site.
5.
Place a predetermined number of traps around the garden. Use a
number that you’ve found to capture sufficient insects in preliminary tests.
6.
Do not place the traps closer than 2 m from a fence or anywhere
else people would be able to see or reach the traps from outside the garden. Do
not place them in walkways within the garden.
7.
As you place the traps, fill them to about 1 cm below surface of
the lip. A bit less than a liter of water per trap should be sufficient. Tap
water is fine.
8.
Be certain that the traps are level. If necessary, put some
sticks or dirt under the low corners.
9.
Add a squirt of liquid dishwashing soap and two tablespoons of
salt to each trap.
10. Stir
the liquid around to mix the soap and salt.
11. Leave
the traps out for five days. If you
place them on a Monday, then harvest them on the following Friday – as close to
the same time of the day as you set them out as possible.
12. Record
weather conditions in Manhattan for the interim – high and low temperature, quantity
and type of rainfall, approximate average wind speed per day.
Characterizing the Site
1.
This should be done during one of the days between when the traps
are installed and when they are harvested.
2.
Bring the following: notebook, pen, digital camera, cheap Ziploc baggies
3.
Before you go to the field, measure your normal pace using a tape
measure.
4.
On a single notebook sized piece of paper, draw a rough aerial view
of the garden and brief descriptions of surroundings – include approximate sizes
and locations of immediately adjacent buildings, roads, road size or traffic
intensity, vacant lots, rubbish, standing water, etc.
5.
Pace out the garden’s dimensions and multiply by the length of your
pace.
6.
Write in the dimensions of the gardens.
7.
Record all immediately adjacent vegetation, including species,
approximate size, and location on aerial view illustration.
8.
Record the location of all traps in garden.
9.
Record the location, approximate abundance, growth stage, and
species of the plants in the garden.
10.
Record date and time that you collected this information.
Collecting the Traps
1.
After five days have passed from when you set them in a given
garden, we need to strain out the insects from each trap.
2.
We will collect and analyze the insects from each trap separately
from the others. Each trap will serve
as repeated measures (or subsamples) within the replicate that is the garden.
3.
You will need the following: a fine meshed aquarium
net, the same number of small plastic vials with sealable tops as there are
traps, a squirt bottle with 70% ethanol, another bottle with tap water (small
soda bottle works fine), small preprinted labels with the following: garden
number code, trap number, date collected, and person collecting.
4.
In an area outside the garden, where you can pour out the soapy
water, prop up the net so that you can gently and slowly pour the water through
the net.
5.
Ideally, you can pour the water towards an area at the front of the
net, rather than directly on the bottom of the net where all the insects will
accumulate. This helps to minimize specimen destruction.
6.
Wash out the trap with some tap water to make certain that you get
all the insects that were trapped.
7.
Transfer the insects from the net into a vial, using the 70%
ethanol squirt bottle.
8.
Insert the preprinted label for that trap.
9.
Fill the vial with ethanol, but leave some air space.
10.
Cap and store the vial.
11.
Repeat for all of the traps in the garden.
Sorting the Insects
1.
Things you will need: dissecting microscope, soft forceps,
eyedropper, small paintbrush, squirt bottle with 70% ethanol, 5 multiple-well
sorting trays, 5 sorting dishes, specimen vials, computer or printouts of data
sheets, interesting music.
2.
Separate out the parasitoid wasps from each trap into one sorting
dish, and the pest insects into another. Discard all plant matter and other
non-insect material.
3.
All other insects can be put into the original sample vial with the
label.
4.
Starting with the parasitoid wasps, separate and record the number
of morphospecies and the abundance of each.
5.
Repeat the procedure for the pest insects.
6.
For each new morphospecies collected of either the parasitoid wasps
or the pest insects, put them in a new well in the small well tray. These will serve as the reference
collection.
7.
When you record the species, use the tray letter (W for wasps and P
for pests) and well number of each.
8.
Enter the data into an Excel spreadsheet – use the garden code, the
sample number as separate identifiers in the first two columns of each
row.
9.
Use separate sheets within a single file for the wasps and the
pests. Enter each well number in the first row (your column title row) and then
put the number of that species collected for that sample in the appropriate
cell.
For More Information, Contact
Us!
Email: Lauren
Sacks (ljs44@columbia.edu) or Kevel Lindsay (kcl10@columbia.edu)
Phone: Dr.
James Danoff-Burg, 212-854-0149
Mail: James
Danoff-Burg, Center for Environmental Research & Conservation, Columbia
University, MC 5557, NY, NY 10027
Web: James Danoff-Burg Lab Page
