Laboratory Report About Infection Of An Insect With Fungi (Lab Report Sample)

Exercise VIII: Infection of an Insect with Fungi
Telan, Jose Angel Jude B 5/28/18 ENT 275
-2286021844000Abstract
-17145228473000Entomogenous fungi infect insects by direct penetration to the insect cuticle unlike other entomopathogens which require ingestion in order to cause infection. Some of these entomogenous fungi are being used for biological control projects, such as Meterhizium anisopliae and Beauveria bassiana. In this experiment, Metarhizium anisopliae and Beauveria bassiana infection process will be observed which should be enough in order to get the students familiarized to infection of entomogenous fungi to insects. Both culture suspensions and spore suspensions were previously prepared prior to this experiment. Castor leaf discs fit in petri dishes were disinfected and prepared to be submerged in these suspensions. Ten Spodoptera litura larvae were subjected to each treatment, with the spore suspension setups having two replicates while the culture suspension setups have only one replicate. Mortality was achieved on all replicates after 72hrs. but the setups exposed to culture suspensions achieved complete mortality quicker than spore suspensions. This signifies that the students were able to get familiarized with the entomogenous fungal infection process against insects.
Introduction
Fungi are eukaryotic organisms that reproduce through spores. They are heterotrophs, and some have sexual and asexual phase. Entomogenous fungi are fungi that infect insects. Unlike most entomopathogens, they do not require to be ingested and first develop and germinate in the cuticle surface upon exposure before cuticle penetration in order to develop internally. They usually require high moisture and humidity in the atmosphere to proliferate. (Mora et al. 2017) Popular fungi used for insect pest management strategies include Metarhizium anisopliae and Beauveria bassiana. They are commonly known as green muscardine fungus and the white muscardine fungus respectively. (Butt et al. 2008) In this experiment, students will be familiarized with the infection process of the mentioned fungi species.
Materials and Methods
The working area and the materials to be used including leaves were disinfected prior to this experiment. Castor tree leaves were utilized in this experiment and cut into leaf discs in sizes fit to be stored in a petri dish. The cut leaves were then sterilized further in chlorox solution for 5 mins then washed in flowing water for 10 mins. The washed leaves were then blot dried in a paper towel before usage. Larvae to be used were then submerged in a specific solution for 2 minutes. 10 larvae were prepared prior to each treatment, with one treatment using the sterilizing solution and the other treatment using conidial suspension. Daily observation was conducted and any particular change in symptoms were recorded. Once mycelium growth is observed in larvae, they were individually kept in microcentrifuge tubes and stored in the refrigerator for further observations. Treatment involving cultures were also prepared. Previously grown cultures of M. anisopliae and B. bassiana were mixed with distilled water and the resulting suspension was applied on castor leaf setups. Surface sterilization of the larvae were conducted then rinsed in sterile distilled water. The treated larvae were then stored in a prepared petri plate with potato dextrose agar (PDA) and observed for mycelial growth after a week.
Results and Discussion
Table 1. Tabulized data representing the mortality of the exposed Spodoptera litura larvae on certain hours post infection.
Mortality after:

24hrs

48hrs

72hrs

Replicate

1

2

1

2

1

2

Control

5

3

7

6

8

7

M. anisopliae suspension

7

0

7

0

8

0

B. bassiana suspension

8

7

9

9

10

10

M. anisopliae culture

8


10


10


B. bassiana culture

4


10


10


43338751390015Figure 1a - 1c. Left: Notice the greenish irregular colony on the upper right side of the PDA plate, this colony was preliminarily described as M. anisopliae. Top right and Bottom right: Setups with the S. litura exposed to M. anisopliae and B. bassiana respectively. Notice the bloated specimens and seemingly frozen appearance of the cadavers.00Figure 1a - 1c. Left: Notice the greenish irregular colony on the upper right side of the PDA plate, this colony was preliminarily described as M. anisopliae. Top right and Bottom right: Setups with the S. litura exposed to M. anisopliae and B. bassiana respectively. Notice the bloated specimens and seemingly frozen appearance of the cadavers.25012652962275002501900137414000132715137414000Fungal growth on the surface cuticle was not observed on both setups with Metarhizium anisopliae and Beauveria bassiana. However, they were able to achieve mortality as compared to the control setup ...