Biological Pest Control: Conditioning the Parasitoid Wasp Microplitis croceipes to

Associate Plant Chemical Compounds with the Host Helicoverpa zea

Bailee Slack Camdenton High School

Background Information:Helicoverpa zea

-most costly agricultural pest in country

-can damage up to 50 % of sweet corn crop in southern states

-leaves the crop susceptible to diseases

- Insecticides are inefficient in many cases http://extension.missouri.edu/explore/images/

g07110art02.jpg

Background Information: Microplitis croceipes

-identify hosts through a scent found in host frass

-deposit eggs inside a host using kairomones

-have associative learning capabilities

-can prevent up to 1,800,000 corn ear worms from ever developing

http://images.usatoday.com/news/_photos/2005/12/26/wasp-inside-3.jpg

Purposes

Whether or not the parasitoid wasp Microplitis croceipes could be conditioned to associate the natural scent of corn with their host Helicoverpa zea in order to act as a more effective form of biological pest control.

To create a device to capture the ovipositor probing exhibited during wasp testing so that farmers or distributors of the M. croceipes can ensure that wasps have been correctly trained to associate hosts with the corn scent before releasing them into the field.

To create a device to capture the ovipositor probing exhibited during wasp testing so that farmers can use it to quickly and easily detect early corn ear worm infestation.

Hypotheses

After the Microplitis croceipes has been exposed to the natural corn scent in association with stinging a host during training sessions, they will later exhibit foraging behaviors when exposed to the corn scent without a host.

Microplitis croceipes that have been exposed to only the corn scent or only the host during the training sessions with no host will not demonstrate foraging behaviors when later exposed to the corn scent.

A modified version of the “Wasp Hound” can be developed to view ovipositor probing during training.

A modified version of the “Wasp Hound” can be developed for farmers use to easily detect early corn ear worm infestations.

Variables

The independent variable in this study was the wasps that had been exposed to the corn scent in association with depositing eggs in a host.

The dependent variables in this study were the reactions of each group of wasps to the corn scent after each training session.

The constant variables were: the wasps’ diet (amount of food, what they were fed, and how often they were fed), the wasps’ cages (all identical), how old the wasps were when tested, location of testing, gender of specimens (female), amount of time exposed to stimulus, the software used to observe the testing

Control Group

The control groups were the wasps exposed only to the corn scent and the wasps exposed only to the hosts.

Method

Setup Phase-aim: to condition wasps to actively search for hosts

-cocoons are received

-wasps are placed into rearing cages

-females are placed into labeled jars for experimentation

-Wasp Hound

http://www.nrc.govt.nz/upload/5352/Tomato%20fruit%20worm%20wasps%20(200).jpg

Initial Training Phase-trained inside “Wasp Hound”

-given acclimation period then video recorded using webcam

Initial Testing-all wasps were exposed to corn scent inside wasp hound one at a time

-video was recorded from webcam

Revised Training-spoke with Dr. Rains

-tinfoil was used to cover corn sample and holes were made

-conditioned and control host groups are re-trained on tinfoil so that egg depositing is visible

Final Training/ Testing-after no results were visible in “Wasp Hound” were visible, it was decided to train the wasps to associate corn scent with food

-while the first experimental wasp was trained, ovipositor probing was observed

-it was decided to record the number of ovipositor probes per minute

Modified “Wasp Hound”: Laboratory Testing

-“Wasp Hound” could not be used to observe all behavioral cues

-The Olfactinator was created to observe training

Modified “Wasp Hound”: Field Testing-problems with outdoors

-hallway used for testing

-Olfactinator was connected to laptop and rolled down hallway

Results

Results

Wasp Group Mean # of Ovipositor Thrusts

Control Hosts 0

Control Corn 0

Conditioned 39.44

p<.001

significant

Wasp 1Wasp 2Wasp 3

Conclusions

  The initial hypothesis that Microplitis croceipes could be trained to correctly

associate the host Helicoverpa zea with the scent of corn was supported (p < 0.001)  The initial hypotheses that Microplitis croceipes that have only been exposed to the

corn scent or those only exposed to Helicoverpa zea (hosts) during training sessions would not demonstrate foraging behaviors when later exposed to the corn scent was supported. (Mean number of “control corn” and “control corn” wasp ovipositor probes=0)

The initial hypothesis that a modified version of the “Wasp Hound” could be created to view ovipositor probing and other foraging behaviors during training was supported.

The initial hypothesis that a modified version of the “Wasp Hound” could be created to allow farmers to easily test their fields for early corn ear worm infestations is currently still being developed with results pending more field trials; however, early results indicate that this is possible.

Future Studies

Collect enough data to adequately determine whether or not the Olfactinator could be used to detect early corn ear worm infestations

Condition Microplitis Croceipes to other crops affected by the Helicoverpa Zea.

Develop a device to train Microplitis Croceipes in mass

Determine how long Microplitis croceipes retain their conditioned behavior

The Olfactinator could be used for corn ear worm detection, which could help farmers know if they have an infestation that needs controlled (pending more results)

The Olfactinator can be used for laboratory training and testing of the wasps

Data suggests that wasps can make a significant connection between parasitizing a host and the scent of corn, implying that they could be conditioned to search the corn for hosts, and act as biological pest control Could potentially prevent 1,800,000 corn ear

worms from ever being born

Applications