Effects of salicylic acid elicitor against aphids on wheat and detection of infestation using infrared thermal imaging technique in Ismailia, Egypt

Wheat (Triticum sativum L.) is one of the most important cereal crops in Egypt. Insect\udpests, such as aphids, are major threats in terms of yield reduction. Induced resistance in\udwheat using salicylic acid as a foliar application was tested on the farm of the Faculty of\udAgriculture, Suez Canal University during 2012/2013 and 2013/2014 seasons. Three wheat\udcultivars, Gemeza 9, Sakha 93 and Giza 168, were sprayed three times with two concentrations\udof salicylic acid (SA), 200 mg/l and 100 mg/l, after early detection of aphid infestation by\udinfrared thermal imaging.\udThe infrared thermal imaging technique is based on significant differences in surface\udtemperature between infested and healthy leaves. Imaging data are digital, and a computer\udprogram can be used to detect infestation rapidly. The results showed that aphid infestation\udraised the temperature of infested leaves, compared to healthy leaves. The range temperature\uddifference between maximum and minimum temperatures (At) was 1.1 ºC in healthy leaves\udand 3.9 ºC in infected leaves. The results of SA application showed significant differences in\udthe mean number of aphids and in reduction of infestation among treatments and cultivars.\udThe higher of the two SA rates (200 mg/l) gave higher efficacy in the three cultivars than\udthe lower rate (100 mg/l) over the five weeks of trial. The highest efficacy against aphids\udwas reached one week after application (86.28% for Giza, 85.89% for Gemesa and 70.54% for\udSakha). Moreover, SA treatment enhanced the wheat yield of all three cultivars, compared\udwith control plants. The three cultivars (Giza, Gemesa and Sakha) produced higher yields\udthan the control when sprayed with 200 mg/l SA. Their grain yield was 2,491.5, 2,455.0, and\ud2,327.25 kg/feddan (1 fed = 0.42 ha), respectively. In conclusion, infrared thermal imaging\udcan be employed in identification of infected leaves. Also, the application of SA on wheat\udinduced plant resistance to aphids