Antibiosis of Salicylic acid pre-hardening treatments of Cowpea on development of Pod sucking bug, Clavigralla tomentosicollis Stal. (Hemiptera: Coreidae)

Abstract

Induced plant response using Exogenous Salicylic acid has a significant potential to control physiological interactions of Phytophagous insects The experiment was conducted at the University Research farm, Faculty of Agriculture Bayero University, Kano (11°58 ‘N, 8° 25’ E and 457m above sea level) to evaluate the effect of SA-treatment on Development of Pod sucking bug of cowpea. Four different cowpea varieties (IT97K-1069-6, IT98K-205-8, IT89KD-288 and Dan’ila) pre-hardened with Salicylic acid were established in various replicated field cages in completely randomized design. Five-pairs each of fresh bugs were introduced into the various cages. These were allowed for 2-weeks to mate and oviposit after which all adult insects are removed. Introduced insects showed variable developmental response to the different Pre-hardened cowpea varieties in SA hormones (P<0.001). Interactions of treatments and varieties was also found significant (P<0.001).Cowpea seeds treated with lower (5ppm) concentrations of SA show greater deleterious effects on the development of the pod bugs than the higher (10 & 20ppm) concentrations and the controls (Distilled water & Untreated seeds). Of the four Cowpea varieties screened, IT97K-1069-6 and IT89KD-288 of 5ppm SA-treatments show higher antibiosis on development
of C. tommentosicollis, resulting to low oviposition (41.33 and 45.67), higher percentage nymphal mortalities (71.59% and 77.24%) and mean unhatched eggs of 27.33 and 32.00 respectively, with smaller adults bugs (3.55mg and 3.27mg) at emergence. Phytochemical screening of the treatments using GC-MS analysis showed high concentrations of cumene, eugenol and sesquiterpenes in the tolerant varieties. These relations should be explored extensively toward sustainable plant protection.