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The Effect of Various Treatments on the Mold Growth of Red D'Anjou Pears

Researched by Colin A.


The purpose of this experiment was to determine the best way to reduce blue mold (Penicillium), and gray mold (Botrytis cinerea) on red D’Anjou pears, in open air.

I became interested in this idea when I talked to Doug Anyan, and he told me of a similar experiment that he had done at his work.

The information gained from this experiment would benefit most fruit growers, especially pear growers, by reducing their reliance on fungicides.



My first hypothesis was that vegetable oil would be the most effective treatment to stop mold on post harvest, red D’Anjou, pears.

I based my hypothesis on the many experiments done with oil wraps that I have read about, and the fact that they have all been very effective.

My second hypothesis was that the chlorine solution would be the worst treatment to stop mold on red D’Anjou pears.

I based my hypothesis on the thought that the chlorine solution would run off the pear, and provide little protection after that. I also read that when chlorine is used it may not be effective enough. 



The constants in this study were: 
* The type of pear being used (red D’Anjou)
* The temperature at which the pears will be set out (21 degrees Celsius)
* The place were the products where tested
* The procedures for measuring the mold growth
* The amount of trials per Treatment
* The way of inoculating the pears

The manipulated variable was the type of product used to stop blue and gray mold.

The responding variable was how much blue or gray mold developed on the pear.

To measure the responding variable I made a visual scale (1-10. One being little or no mold, and 10 being mold encrusted), and rated each pear.  I then averaged the ratings.




40 Red D’Anjou pears
4 Pear Trays
1 roll of paper towels
1 bottle of vegetable oil
1 Pair of rubber gloves
1 Set of safety goggles
1 facemask
1 Screw driver
1 50-ounce container
1 Pitcher
1 sink
128 ounces of water
8.8 milliliters of Clorox chlorine (500 parts per million)
4 ounces of powdered zinc oxide
1 notebook
1 syringe
12 disposable, glass, pipettes
4 ounces of zinc oxide powder
1 extremely moldy pear


1. Put on gloves, goggles, and mask.
2. Pour 32 ounces of water into the mixing container (the 50oz container).
3. Add 8.8 ounces of chlorine (500 parts per million).
4. Take one pear and (using your dominant hand) dip the pear in the solution for 7 seconds.
5. Repeat step 4 (make sure to pick up the next pear with the hand that has not been in the solution, so all the pears do not have that solution), for 9 more pears.
6. Pour out the container, and wash it out with tap water.
7. Wash gloves.
8. Pour 32oz of water into the mixing container.
9. Repeat steps 4-5.
10. Repeat step 6
11. Repeat step 7
12. Repeat step 2
13. Take 4oz of zinc oxide powder, and pour it into the container.
14. Stir the solution.
15. Repeat steps 4-5
16. Repeat step 6-7
17. Take a paper towel, and saturate it with the vegetable oil.
18. Take one pear and wipe the towel over it (making sure to get the stem and bowl).
19. Repeat step 18 for the remaining pears.
20. Take a disposable pipette and put the tip of it into the mold, and puncture the fruit.
21. Take a screwdriver and enlarge the wound, made by the pipette.
22. Repeat steps 19, and 20 for three pears in each of the groups. 
23. Clean gloves, and throw them away (so no bad stuff is in the garbage) 
24. Clean the screwdriver, and dispose of the pipettes.
25. Let the pears sit for 14 days.
26. After the 14 days take all the pears and, using the visual guide and safety procedures (in step 1), grade each pear.
27. Repeat steps 2 and 3 and soak one pear group, and dispose of them.
28. Repeat step 27 for the remaining pear groups. 



The original purpose of this experiment was to determine what treatment would prevent mold from growing on a red D’Anjou pear.

The results of the experiment were that oil was the best treatment to prevent mold growth on red D’Anjou pears. The results of this experiment also indicate that zinc oxide was the worst treatment to prevent mold growth on red D’Anjou pears 

See the table and graph below



My first hypothesis was that the oil treatment would be the best at preventing mold. My second hypothesis was that the chlorine would be the worst at preventing mold.

The results indicate that my first hypothesis should be accepted because the oil treatment had an average of .15. The results of this experiment also indicate that my second hypothesis should be rejected, because zinc oxide was the worst treatment to prevent mold. 

Because of the results of this experiment, I wonder what would happen if I where to use a different pear, instead of the Red D’Anjou.

If I were to conduct this project again I would test a different type of pear, and see if the same results occurred. I would also use a fungicide, and see how well it compares to the other treatments.



Pears are an important part of our economy. Pears are also a great tasting food. Without a tasty treat life wouldn’t be fun.  Although there are many ways that pears can go bad, the two most common are Blue and gray Mold. There are many ways to treat pears to resist mold.


Pears are a very interesting fruit. They are a very fleshy fruit. Pears come in many different shapes, and sizes, they can have the most common shape, where the stem is pointed, and the bottom is much more rounded.  They also can look just like an apple, and can be as small as a cherry.  There are hundreds of different types of pears. Many of them have a core like an apple, containing, on average, about 10 seeds. A pear tree can be as tall as 45 feet, and 25 feet wide, at the base. Pear trees can live a very long time, sometimes up to 75 years. The most common pears are Bartlett, Comice, Anjou, Bosk, Hardy, Seckel, and Winter Nelis. It is not known when pears were first found, but there are hints. One poet wrote about the fruit in the 700’s B.C. Washington State is the number one producer of pears per year (14,830,000 bushels) in North America. 

Blue Mold
Blue mold is also known as Pennicilium. It is not a nesting mold (does not spread from fruit to fruit), unless the pears are in a water system, and one has a wound. Blue mold is first formed through the stem. Blue mold can grow on pears much longer after harvest than, on apples. This is because the pears stem remains moist, while the apples, dries up. Blue mold accounts for 24% of damaged harvest.

Gray Mold
Grey mold is also known as Botrytis Cinerea. Unlike blue mold, gray mold is a nesting fungus. As with blue mold, Botrytis Cinerea can be transferred by a water system. Gray mold is likely to occur in low temperatures. Grey mold accounts for 55% of damaged harvest. 

Mucor Rot
Mucor Rot is also known as Mucor Piriformis. Mucor rot usually begins in the soil of the areas where the fruit grows. If the soil is extremely moist, and there are many decaying things on the ground mucor rot is very possible. Mucor rot can also develop in winter.  It can also be spread to bins that have been laid on the ground.  The rot can be absorbed by the bin, and contaminate all pears in the bin.  Mucor rot is accountable for 8% of damaged crop every year. 

Bulls-Eye Rot
Bulls-eye rot is also known as Pezicula Malicorticis. This is a slow growing fungus. Bulls-eye rot is not usually discovered until storage. Although it usually starts when the pears are tiny.  Bulls-eye rot is indicated by the concentric rings, found inside the contaminated fruit.

Coprinus Rot
Coprinus rot is also known as Coprinus Psychromorbidus. It is commonly mistaken for bulls-eye rot. Even though coprinus rot is similar to gray mold, in the fact that it is a nesting mold. This rot comes from mushroom spores, found from a mushroom in the orchard.  It usually infects the fruit one month before harvest. Although it is commonly mistaken for bulls-eye rot the main difference is that coprinus rot looks like a cobweb like fungal growth on the surface of the fruit. 


Chlorine can be a very effective way to treat for mold and rot. It is a contact killer. It is commonly used in fruit dump tanks.  Although the concentration of the chlorine must be correct for it to be effective (if the spores are away from the main concentration then many fruit will still be infected). Chlorine minimizes the amount of dirt in the tank, which reduces the chance of infection. Chlorine does not, however cover the pears in the long run, such as from storage to the market.

Oil is a commonly used method of treating fruit for mold prevention.  Although usually oil itself is not the only thing on the fruit. Usually it is a special wrap that is impregnated with oil that remains on the fruit.  Oil is a contact killer, so if there is any mold on the pear then it should eliminate it. Making it complicated for other molds to grow on it.

Zinc Oxide
Zinc oxide is not a commonly used treatment for the prevention of postharvest mold, and decay. A common type of zinc oxide is Nutraphos-24.

In conclusion, mold and rot are very damaging things to the Washington economy, and agricultural economics around the world. With all the various types of mold and rot it is very complicated, if not impossible, to solve them all. Although thanks to many studies there are ways to stop the leading damages of harvest, and many other types of damages. 


“Acetic acid shows promise for control of fruit decay”. Dec,26,2004. 

Kupferman Eugene Dr., Robert Spotts: and David Sugar. “Practices to reduce post harvest pear Diseases”. Jan,25,2004.

Kupferman, Eugene Dr. “how to prevent diseases of fruit in storage”.  Dec,26,2003.

Lennox, Cheryl and Spotts, Robert. “Botrytis Gray Mold as a Post harvest Pathogen in D’Anjou Pear”. Dec,26,2003.

 Sanderson, Perter G Dr. and Bennett, Diane L. “Effect of paper wraps on post harvest decay and disorders of Anjou pear fruit.”  Dec,26,2003. 


I would like to thank the following people for helping make my project possible:
* My parents for driving me to the various places were I needed to be
* Mr. Newkirk for helping me with many aspect of my project
* Doug Anyan for allowing me to use his research lab to conduct my experiment
* Tom Eisley, John Baranowski, Dr. Gamlem, and Joel Hollingsworth for granting my SRC approval 


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