Effects of Two Adjuvants (Scorch and Torpedo п) on Efficacy of Imidacloprid and Flonicamid to Control the Aphis gossypii Aphid in Greenhouse Cucumber

Cucumber, Cucumis sativus L. is one the most important economic vegetables crop cultivated in Iran and many countries of the world. The cotton-melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is one of the most destructive polyphagous pests of Cucurbitaceae plants in greenhouses and open fields. A. gossypii can cause severe damage in commercial fields. The honeydew that aphid excretes decreases the photosynthetic activity of plants and contaminates fruit, resulting in severely reduced quality. Moreover, A. gossypii can transmit more than 80 type of viral diseases that can cause substantially greater losses than the damage from direct feeding of the insect. The focus of the control methods against this pest in our country is the use of insecticides. Additionally, A. gossypii has developed different levels of resistance to many insecticides. Agricultural adjuvants can improve the efficacy of pesticides and can be effective in reduction of pesticides use. In the current research, the effects of two adjuvants (Scorch and Torpedo п) on efficiency of imidacloprid (SC35%) and flonicamid (WG50%) to control this aphid were investigated on cucumber in greenhouse. These two insecticides have systemic property doing their job after leaf penetration. It is known that the leaf penetration step is very determinative for systemic pesticides. Besides, Scorch and Torpedo п are multi-functional adjuvant, showing penetration, wetting, adhesion and spreading properties.

The project was performed based on a completely randomized design with 15 treatments and 3 replicates. The efficacy in the sampling units was recorded at 1, 3, 7 and 14 days after treatment. The treatments were: 1) imidacloprid (recommended dose); 2) imidacloprid+Scorch; 3) imidacloprid+Torpedo п; 4) imidacloprid (10% reduction of dosage)+Scorch; 5) imidacloprid (20% reduction of dosage)+Scorch; 6) imidacloprid (10% reduction of dosage)+Torpedo п; 7) imidacloprid (20% reduction of dosage)+Torpedo п. Flonicamid was replaced by imidacloprid in the treatments 8 to 14. The control treatment (No. 15) was sprayed by water only. The efficacy was calculated using the Henderson and Tilton formula. Statistical analysis was performed using the SAS software (ver. 9.1). One row was considered as the distance between the experimental units. Two rows on either side of the greenhouse were also considered as margins.

The combine analysis of variance showed that interaction of treatment × place was not significant, meaning that the experimental treatments had the same respond in different locations. Therefore, the data were statistically analyzed based on this, without considering the locations (Urmia and Karaj). The results showed that both adjuvants were able to improve the efficacy of imidacloprid and flonicamid, as it was confirmed at all times after spraying. For example, three days after spraying, the efficacy of imidacloprid alone was estimated at 81.47%, while "imidacloprid + Torpedo" and "imidacloprid + Scorch" were estimated at 92.60% at 93.43%, respectively. Similarly, seven days after spraying flonicamid alone showed 87% efficiency, whereas the treatment of "flonicamid+Torpedo" and "flonicamid+Scorch" exhibited 94.34% and 95.31%, respectively. When Torpedo п was used in combination of reduced doses of imidacloprid, the efficacy was severely reduced. Thus, the addition of Torpedo п is not recommended with reduced doses of imidacloprid. Instead, adding the Scorch when reducing the imidacloprid dosage, the efficacy was remained as high. For example, three days after spraying, "Imidacloprid with 10% dose reduction + Scorch" and "Imidacloprid with 20% dose reduction + Scorch" treatments were 93.65% and 94.23% efficacy, respectively. Besides, by reducing the flonicamid dosage and adding both adjuvant, the efficiency was as high as to the treatment using the recommended dosage. For example, 14 days after spraying, flonicamid with 10% dose reduction + Scorch and flonicamid with 20% dose reduction+ Scorch showed 93.94% and 93.48% efficacy, respectively. Our results can be important from both economic and environmental point of view, as the obtained results indicated that imidacloprid and flonicamid dosage can be reduced by 20%. However, it should be keep in mind that other factors, such as the price of adjuvants, are involved in their practical and field use by farmers, which should be taken into account.