Efficacy of foliar spraying of squash (<i>Cucurbita pepo</i>) with some elicitors for certain biochemical traits for <i>Bemisia tabaci</i> (Hemiptera: Aleyrodidae) protection

Secondary metabolites in plants are bioactive scaffolds that are crucial for plant growth and survival in the environment. Also, to maintain a defence mechanism from pests. Four basic elicitors, (Benzoic acid, salicylic acid and acetyl salicylic (Aspirin) acid) at the rate of approximately 0.01 mol/l of each (i.e. 1.25, 1.4 and 1.8 g/l, respectively) and sulfonic acid was used at the rate of 1 % of product (Potassium hydroxide 0.6 g/l was added as a dissolver to sulfonic acid) were applied on squash plants Cucurbita pepo L. as a foliar treatments during vegetative growth stage at 15 days after planting in the open field to reduce the whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) infestation. The foliar application treatments of elicitors or inducers (Were applied at 15th after cultivation as one spray weekly for 3 weeks) over two successive growing seasons; 2022 and 2023 in autumn plantation. The effects of the four elicitors were close to each other in reducing B. tabaci numbers over the tested seasons compared to control treatments. The change in certain biochemical traits of the sprayed leaves particularly in different plant stages was successfully investigated. In the seedling or early stage (Represented by the period from seedling to 30 days after cultivation but leaves were taken for analysis after spraying at 21 days after cultivation), it was found in sprayed leaves that sulfonic, salicylic and benzoic acids treatments increased phosphorous versus control. Moreover, benzoic acid and sulfonic acid increased levels of total carbohydrates compared to those found in the control. However, salicylic, acetylsalicylic and sulfonic acids increased total phenols versus control. Sulfonic, acetylsalicylic, benzoic and salicylic acids increased titratable acidity. Sulfonic acid and benzoic acid increased the activity of alpha esterases. Also, sulfonic acid increased beta esterases activity versus control. Salicylic, acetylsalicylic and sulfonic acids increased peroxidase activity. In the late stage of plant (44 days after cultivation), data revealed that acetylsalicylic acid increased phosphorous content compared to control. Moreover, sulfonic, acetylsalicylic, salicylic and benzoic acids increased titratable acidity. While salicylic acid and sulfonic acid increased the activity of the peroxidase enzymes compared to control. This approach shed light on the efficiency of benzoic acid, salicylic acid, acetylsalicylic acid and sulfonic acid in reducing B. tabaci infestation via enhancement secondary metabolites and increasing defensive mechanisms of squash plants. In conclusion, these elicitors could be recommended to be used in combating the whitefly, B. tabaci in integrated pest management (IPM).