Asian citrus psyllid, Diaphorina citri
Table of Contents
- Abstract
- Introduction
- Materials
- Procedure
- Results
- Discussion
- Conclusion
- Acknowledgements
- Bibliography
Abstract
The Asian citrus psyllid is the vector for huanglongbing (citrus greening), a devastating disease caused by Candidatus Liberibacter. An infected psyllid feeds on a healthy citrus plant and injects the bacterium into the phloem of the plant. Once a tree is infected with the bacterium, there is no cure for the disease. [2]
The objective of the present investigative study is to find a plant-based compound with citrus psyllid repellent activity. The essential oils – clove, peppermint, and tea-tree oil were evaluated for repelling activity against psyllid with water as a control variable.
The current study suggests that 10% concentration for each oil is the perfect amount.
Amongst all the oils tested, clove oil has significant psyllid repellent activity (92%). The positive results of the clove oil repellency may be a viable solution to control the asian citrus psyllid and in turn reduce the spread of citrus greening disease.[1]
Introduction
Citrus greening disease has caused the demise of millions of acres of citrus crops all across the United States and abroad. The citrus industry makes roughly 45,000 full time and part time jobs in Florida. In addition to jobs, the industry makes a valuable contribution to the economic growth of Florida each year. Citrus greening is spread by a disease-infected insect, the Asian citrus psyllid, and has threatened the future of America’s citrus. Infected trees produce fruits that are small, deformed, green, bitter, and unsuitable for sale as whole fruit or juice. Most infected trees die within a few years and there is no known cure. [1]
The psyllid, responsible for the spread of citrus greening, is almost as big as the head of a pin. The infected insect injects the bacteria and spreads the disease as it feeds on the tender leaves and stems of citrus trees. The infected psyllid remains a carrier of the greening bacteria throughout its life span. All commonly grown citrus varieties are susceptible to the disease. It seems logical that controlling and preventing the spread of bacteria in the first place can protect the citrus crop. This can be achieved by limiting the psyllid population and eradicating any infected trees.
The objective of the present investigation study is to study 3 different types of essential oils (clove, peppermint, and tea tree) and calibrating the concentration that repels the psyllid with minimum phytotoxicity to the plants. [3]
The olfactory system of citrus psyllid is highly sensitive to many odorants released by citrus plants and presents a perfect opportunity to create new attractants and repellents. Studies have shown that essential oils could be effective against most insects. Essential oils may be effective against the psyllid because their stringent smell masks the smell of orange leaves. The hypothesis is that if the essential oils are used on tender orange leaves then the psyllid might be repelled from citrus trees because of the stringent smell and bitter taste of essential oil and the spread of citrus greening disease will be controlled and prevented. [2]
Materials
- Psyllid
- Miniature Sprayer
- 10 Insect collection tubes
- Tender Orange leaves
- Water
- 2 Flasks 250 mL
- Essential Oils (tea tree, peppermint,
- clove.)
- 3 clear PVC pipes
- Y olfactometer
- Pipette
- Aspirator
- Protective goggles
Aspirator
Y-Olfactometer
Procedure
A Y olfactometer – a simple Y shaped device to present the essential oils’ odor to the psyllid – was constructed from 3 clear PVC pipes, 1 Y plastic connector and two clear 250 mL flasks. Two clear PVC pipes were inserted on either side of the PVC Y connector. The free end of the pipes was connected to 250 mL glass flasks on each side. A third PVC pipe was inserted into the free end of the Y connector.
The psyllids were collected using an aspirator from infected citrus trees and were put in bottles. An essential oil mixture was created by pipetting out 90 mL of water and 10 mL of essential oil. The solution was mixed and poured into the mini sprayer. The 6 uninfected orange leaves were sprayed with the essential oil at 10% calibration. The 6 uninfected leaves were placed into the other flask without any essential oils. Goggles and gloves were used to handle the essential oils and the psyllid in the bio safety cabinet. The psyllids were released and the container was closed. The psyllids were observed for 10 minutes and then counted on each side. This process was repeated for each essential oil after cleaning the flasks with soap and hot water[3]
Results
Percentage Repellency of Essential Oils Against Psyllids
|
Tea Tree Oil |
|||||||
|
set 1 |
set 2 |
set 3 |
set 4 |
set 5 |
Average Repellency |
||
|
No of psyllids released |
25 |
25 |
25 |
25 |
25 |
||
|
No. of psyllids that entered into the tube |
16 |
14 |
13 |
13 |
12 |
||
|
No. of psyllids that stayed in the bottle |
9 |
11 |
12 |
12 |
13 |
||
|
% of repellency |
36% |
44% |
48% |
48% |
52% |
45.60% |
|
Graph of % repellency of Tea tree oil
|
Clove oil |
||||||
|
set 1 |
set 2 |
set 3 |
set 4 |
set 5 |
Average repellency |
|
|
No of psyllids released |
25 |
25 |
25 |
25 |
25 |
|
|
No. of psyllids that entered into the tube |
2 |
3 |
1 |
0 |
4 |
|
|
No. of psyllids that stayed in the bottle |
23 |
22 |
24 |
25 |
21 |
|
|
% of repellency |
92% |
88% |
96% |
100% |
84% |
92% |
Graph of % repellency of Clove oil
|
Peppermint oil |
||||||
|
set 1 |
set 2 |
set 3 |
set 4 |
set 5 |
Average repellency |
|
|
No of psyllids released |
25 |
25 |
25 |
25 |
25 |
|
|
No. of psyllids that entered into the tube |
19 |
16 |
20 |
19 |
18 |
|
|
No. of psyllids that stayed in the bottle |
6 |
9 |
5 |
6 |
7 |
|
|
% of repellency |
24% |
36% |
20% |
24% |
28% |
26.40% |
Graph of % repellency of Peppermint oil
No of Trials
|
Percentage of repellency of Essential oils |
|
|
Type of Oil |
Percentage |
|
Clove Oil |
92% |
|
Peppermint Oil |
26.40% |
|
Tea tree Oil |
45.60% |
|
Water (controlled variable) |
||||||
|
set 1 |
set 2 |
set 3 |
set 4 |
set 5 |
Average repellency |
|
|
No of psyllids released |
25 |
25 |
25 |
25 |
25 |
|
|
No. of psyllids that entered into the tube |
23 |
23 |
21 |
20 |
23 |
|
|
No of psyllids that stayed in the bottle |
2 |
2 |
9 |
5 |
2 |
|
|
% of repellency |
8% |
8% |
36% |
20% |
8.00% |
16% |
|
Calibration of Phytotoxicity Rating Scale 0-10 |
||||||||||
|
Concentration |
leaf 1 |
leaf 2 |
leaf 3 |
leaf 4 |
leaf 5 |
leaf 6 |
leaf 7 |
leaf 8 |
leaf 9 |
leaf 10 |
|
70% |
9 |
10 |
9 |
9 |
10 |
9 |
9 |
9 |
10 |
10 |
|
60% |
9 |
9 |
9 |
8 |
9 |
9 |
8 |
8 |
9 |
10 |
|
50% |
8 |
8 |
9 |
9 |
9 |
9 |
9 |
9 |
8 |
9 |
|
40% |
8 |
7 |
7 |
9 |
8 |
8 |
7 |
7 |
7 |
9 |
|
30% |
4 |
3 |
3 |
4 |
5 |
3 |
3 |
9 |
9 |
8 |
|
20% |
2 |
1 |
1 |
0 |
1 |
0 |
0 |
0 |
1 |
0 |
|
10% |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
The percent area of leaf affected by the oil was used to calibrate the phytotoxicity of oil concentration. This was because the oil was very stringent and showed signs of burning the leaves during the dry run.
70% concentration oil burnt the entire leaf. 10% concentration oil did not affect the leaf at all. This was used on a scale from 1-10; 1 being very minimal side effects and 10 being very extreme: almost burning the entire leaf.
Table of concentration of oils and average phytotoxicity.
|
Concentration |
Average Phytotoxicity |
|
70% |
9.9 |
|
60% |
8.8 |
|
50% |
8.7 |
|
40% |
7.7 |
|
30% |
5.1 |
|
20% |
6 |
|
10% |
0 |
Discussion
Consistent data was gathered from all 5 trials (the psyllid counting). From the data collected in this experiment, the results on an average, showed a trend that more stringent the essential oil, the higher the repellency of the psyllid. The Y-Olfactometer clearly represented the repellency of the psyllid and created a realistic environment for them. This is shown because the sensory receptors of the psyllids are masked by the stringent smell of oil, suggesting that the essential oil smell masks the tender orange leaves’ smell. Previous research studies have shown that botanical oils have repelling activity on the asian citrus psyllid. [5]
The purpose of this study was to analyze the effects of essential oils on the psyllid. Some essential oils have a repellent property but, it is evident that the stringent oils have more repellency. From the data it shows a huge gap between clove oil and peppermint oil, due to the stringent smell. The calibration of concentration of the essential oils to 10% demonstrated lack of phytotoxicity on the leaves. This step was essential because high concentration of essential oils burnt the leaves, and even if there is a slight hint of phytotoxicity in laboratory then in the field application, the phytotoxic symptoms can be multiplied in presence of heat and sunlight.
Research studies show that often many farmers use chemical pesticides or insecticide to address pest issues. Although this may be an imminent solution for a few years, eventually the bug will gain resistance towards the pesticide and the pesticide runoff may deteriorate the soil and water quality. The goal of this experiment was to find an organic, viable, environmentally friendly solution that could repel the psyllid. [5][4]
In this experiment there was one possible source of limitation. The experiment was conducted in the laboratory and its efficacy needs to be tested in the field and on a molecular level. [4]
The results of clove oil were promising but this study needs to be further examined because the disease takes more than a year to actually have an effect on the trees. Further examination would be continuing the research for another 6 months or a year. The side effects of the treatment on the plants that might occur are yellowing fruit, yellowing of the leaves and low growth rates. Also variables such as doing the experiment in a greenhouse or in a field should be considered. This is due to the fact that there are many variables to be considered in the field such as exposure to sunlight, interaction with other bugs and proper nutrition of the plant. The factors are important to notice because the results may vary for the field experiment. With the exponential increase of the psyllid population, the citrus industry is being impacted negatively and finding a nontoxic viable solution for citrus greening disease is crucial . [5]
Conclusion
The relationship between variables in this experiment is that the psyllid repelling activity depends on the type of essential oil. Another relationship is that the acidity of the essential oil depends on how concentrated the oil is. On the basis of the data collected from all five trials, clove oil showed 92% efficacy. The calibration of the essential oils was a huge factor in the experiment. We found that 10% calibration is a great spot for conserving the oil, not burning the leaves, and keeping the repellency.
This project helped prove that there is an organic solution to repel the psyllid without harming the environment and humans. Clove oil could potentially develop into a commercial product used for personal and residential purposes. This organic product will reduce the harmful impact that a chemical commercial product has on the environment, aquatic animals and maybe humans in the long run.
Acknowledgements
My sincere gratitude to my mentor Dr. Balaji Aglave for guiding me through this project and offering his insight and expertise on this topic.
I could not have completed this experiment without the help of Florida Agricultural Research, I sincerely thank them for permitting to conduct my experiment on their premises. I also thank my science teacher Mrs. Carrie Prieto for taking her time out of her day to help me with my project by giving me tips on my research plan. I thank my mom and dad for taking me to the research center.
Bibliography
1 \”What Is Citrus Greening? – Florida Citrus Newsroom\”. 2018. Floridacitrus.Org. https://www.floridacitrus.org/newsroom/citrus-411/citrus-greening/what-is-citrus-greening/.
2 “Resources for Citrus Pest and Disease Information.” California Citrus Threat. The Citrus Pest & Disease Prevention Program. http://californiacitrusthreat.org/resources/.
3 Singerman, Ariel, and Pilar Useche. “Impact of Citrus Greening on Citrus Operations in Florida.” EDIS New Publications RSS. Food and Resource Economics, May 26, 2016. https://edis.ifas.ufl.edu/fe983.
4 “Asian Citrus Psyllid.” Asian Citrus Psyllid | National Invasive Species Information Center | USDA. http://www.invasivespeciesinfo.gov/animals/acp.shtml.
5 Kuhns, Emily, Xavier Martini, Angel Hoyte, and Lukasz Stelinski. \”Repellent Activity Of Botanical Oils Against Asian Citrus Psyllid, Diaphorina Citri (Hemiptera: Liviidae).\”
6 Mann, R. S., S. Tiwari, J. M. Smoot, R. L. Rouseff, and L. L. Stelinski. 2010. \”Repellency And Toxicity Of Plant-Based Essential Oils And Their Constituents Against Diaphorina Citri Kuwayama (Hemiptera: Psyllidae)\”. Journal Of Applied Entomology 136 (1-2): 87-96. doi:10.1111/j.1439-0418.2010.01592.x.
7 \”Asian Citrus Psyllid – Diaphorina Citri Kuwayama\”. 2019. Entnemdept.Ufl.Edu. http://entnemdept.ufl.edu/creatures/citrus/acpsyllid.htm.
8 Green, Amy. “Researchers Appear Close To A Remedy For Citrus Greening Disease.” NPR. NPR, May 12, 2016. http://www.npr.org/2016/05/12/477758594/researchers-appear-close-to-a-remedy-for-citrus-greening-disease.
9 Boina, Dhana Raj, and Jeffrey R Bloomquist. 2014. \”Chemical Control Of The Asian Citrus Psyllid And Of Huanglongbing Disease In Citrus.\”
10 \”CDFA – Plant Health – Asian Citrus Psyllid / Huanglongbing\”. 2016. Cdfa.Ca.Gov. https://www.cdfa.ca.gov/plant/acp/.
11 Mann, R. S., S. Tiwari, J. M. Smoot, R. L. Rouseff, and L. L. Stelinski. 2010. \”Repellency And Toxicity Of Plant-Based Essential Oils And Their Constituents Against Diaphorina Citri Kuwayama (Hemiptera: Psyllidae)\”. Journal Of Applied Entomology 136 (1-2): 87-96. doi:10.1111/j.1439-0418.2010.01592.x. ↑
About the Author
Shloke Patel, is from Tampa, Florida and a 7th grader at Carrollwood Day School. His favorite subject in school so far is science. During his free time he likes to bird watch, swim, cook, and play minecraft on the gaming computer he has built with 25pc. He is a first class boy scout working towards life rank. He has traveled to many countries and has a huge coin and souvenir bell collection. Motto : Game on !