Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design



Committee Chair

Yong-Lak Park.


The use of natural enemies is an effective strategy to control and suppress pest populations in a given agroecosystem; however farmers are not motivated to adopt this method because of the high cost and temporal unavailability of natural enemies. This thesis reports findings of a series of laboratory experiments carried out to investigate ecological behavioral of two major natural enemies; Harmonia axyridis and Cryptolaemus montrouzieri (Coleoptera: Coccinellidae) Laboratory studies was conducted to determine if H. axyridis could be attracted to companion plants with different olfactory and visual cues, to investigate the within-plant distribution of long-tailed mealybug, Pseudococcus longispinus (Hempitera: Pseudoccoccidae), to quantify the searching and handling time of C. montrouzieri on three different plants heights and to determine preference of C. montrouzieri to the size of P. longispinus. Ten potential plants that can attract and provide H. axyridis with nectar and pollen were selected for a preference test. The result of the olfactory preference test showed that there was significant difference in the plant preference by H. axyridis; sunflower was the most preferred attractant plants. In a visual preference test, H. axyridis preferred yellow to other colors. P. longispinus was found more on the upper parts of the plants regardless of the height. The time C. montrouzieri spent to find the first P. longispinus was significantly (P < 0.05) different among the three different plant heights at two different releasing points. However, there were no significant differences in handling time and cleaning time. Cryptolaemus montrouzieri preferred smaller size of P. longispinus to medium and larger size. The results presented in this thesis suggested that H. axyridis and C. montrouzieri could potentially be used as economical and sustainable biological control agents.