Feeding behaviour of the greenbug Schizaphis graminum on wheat plants treated with imidacloprid and/or silicon

Abstract

The greenbug Schizaphis graminum (Rond.) (Hemiptera: Aphididae) is one of the principal pests of Triticum aestivum L. and may be responsible for the injection of toxins, the transmission of viral infections and, ultimately, plant death. The aphid can be controlled by the use of selective insecticides or with the application of silicon. The objective of the present study was to investigate the influence of imidacloprid and silicon on the feeding behaviour of S. graminum on wheat plants. Aphids collected from and reared on sorghum plants were maintained in a growth room at 25 ± 2°C; 12 h photoperiod. Seeds of the wheat cultivar EMBRAPA 22 were planted in plastic pots containing a commercially available soil substrate and thinned out 8 days after sowing to leave two vigorously growing seedlings in each pot. Four treatments (each replicated 25 times) were applied: (i) seeds were treated with imidacloprid (36 g/100 kg) 1 day prior to sowing; (ii) silicon (50 ml of 1% silicic acid; equivalent to a dose of 1000 kg of silicon/ha) was applied directly to the substrate 10 days after plant emergence; (iii) the described treatments with imidacloprid and silicon were applied jointly; and (iv) neither seeds nor substrate were treated (untreated controls). Electrical penetration graph assays were performed 15, 30 and 45 days after plant emergence. The results showed that wheat seed treatment with imidacloprid and/or the application of silicon to the substrate reduced both the feeding time of S. graminum and the percentage of insects that fed on phloem sap. Moreover, this study provides further support that the action of silicon may not be restricted to physical resistance (constitutive or induced) but may also involve induced plant chemical defence.

Effects of Thiamethoxam Seed Treatments on Soybean Aphid (Hemiptera: Aphididae) Feeding Behavior

“…For the aphids that did not achieve xylem ingestion, it is possible that a small amount of insecticide may be present in the phloem sap, resulting in reduced feeding (Nauen and Elbert 1994). Our Þndings are supported by the work of Costa et al (2011), who observed similar feeding behavior in greenbugs, Schizaphis graminum Rondani, exposed to imidacloprid-treated wheat seed. Greenbugs exposed to treated plants exhibited signiÞcantly less phloem ingestion.…”

“…Greenbugs exposed to treated plants exhibited signiÞcantly less phloem ingestion. Unlike our study, feeding was affected within 8 h of imidacloprid exposure (Costa et al 2011). …”

Aleurocanthus woglumi (Hemiptera: Aleyrodidae) in Citrus: Opportunities and Challenges to Implement a Sustainable Management

“…Silicon promoted cuticle thickening and accumulation of crystals on the leaf stomata in sugarcane [54]. The action of silicon may not be only restricted to resistance constitutive or induced but may also involve induced plant chemical defense [51].…”

“…Mortality on egg (90-100%) Gamma irradiation (200 Gy) [45] essential nutritional element to the plants [49], but as potassium silicate, calcium silicate, and sodium silicate from other sources has determined the tolerance of many plant species to insects [50][51][52][53]. Silicon promoted cuticle thickening and accumulation of crystals on the leaf stomata in sugarcane [54].…”

Study of Potassium Silicate Spraying in Coffee Plants to Control <i>Oligonychus ilicis</i> (McGregor) (Acari: Tetranychidae)

“…Positive effects on the use of Si are evident in the reduction of feeding time of the aphid Schizaphis graminum (Rondani) (Hemiptera: Aphididae) in wheat (Triticum aestivum L., Poaceae) [12], protection of cucumber plant (Cucumis sativa L., Cucurbitaceae), eggplant (Solanum melongena L., Solanaceae), common bean (Phaseolus vulgaris L., Fabaceae) and corn (Zea mays L., Poaceae) against the two-spotted spider mite, Tetranychus urticae Koch (Tetranychidae) [13] and reduced the palatability of sunflower leaves (Helianthus annuus L., Asteraceae) to the attack of caterpillar Chlosyne lacinia saundersii Doubleday (Lepidoptera: Nymphalidae) [14].…”