The Botanical Pesticides Free Essay Example

The botanical pesticides are the potential natural source and possible alternatives to synthetic pesticides for the control of agricultural and household pest (Afshar et al., 2017; Benelli et al., 2019). Sophora alopecuroides is effective against various agricultural pests including Diaphorina citri (Rizvi et al., 2018a), Myzus persicae and Macrosiphum avenae (Ma et al., 2018a), Brontispa longissimi (Chen et al., 2011) and Helicoverpa armigera (Cai et al. 2009). The phytochemical studies revealed that quinolizidine alkaloids are main bioactive constitutes in S. alopecuroides (Ma et al., 2018a). Similarly, S. alopecuroides grew under the climatic condition of Skardu Baltistan, Pakistan also enriched in alkaloids with sophocarpine (33.90%) and sophoridine (6.23%) (Rizvi et al., 2018a).

Plant volatile plays an integral role in phytophagous insects host finding and selection processes (Birkett et al., 2004; Bruce and Pickett, 2011). The citrus psyllid largely depend on its visual and olfaction to locate its potential host plants (Sanchez, 2008; Silva et al., 2016; Wenninger et al., 2009). The VOCs released by the non-host plants have ability to mask the odor of potential host plant that is perceived by the phytophagous insects, which results in avoidance of potential host plant (Isman, 2006; Pavela et al.

, 2016; Zhang and Schlyter, 2004). Regarding the deterrence activity of SAE-EC against citrus psyllids, results indicated there was a concentration-dependent effect. The adults showed a strong preference for settling on the control sweet orange seedlings as compared to the treated seedlings. ACP settling was not significantly reduced after 24 h after release as compared to the control.

However, after 48 and 96 h of release, only a few numbers of adults were observed on the treated plant as compared to the control. From the results of previouse studies it is indicated that host finding and selection ability of psyllids were reduced when the host plant was treated or exposed to the non-host plant secondary metabolites (Afshar et al., 2017; Mann et al., 2011; Mann et al., 2013; Zaka et al., 2010). Several non-host plants secondary metabolites mixture and blends have showed behavioral effects against psyllids including guava, lavender, rosemary, Allium spp and S. alopecuroides (Hall et al., 2008; Rizvi et al., 2018a; Silva et al., 2016; Zaka et al., 2010). The HLB bacteria can only grow and multiply within the body of the eukaryotic host (Al-Chalabi and Hardiman, 2013).The spread of HLB from infected to uninfected plants mainly attribute by the nymph and adults of psyllid (Lopes et al., 2007; Silva et al., 2016). Furthermore, we found that SAE-EC greatly reduces the feeding activity of ACP, measured as a number of purple spot on treated leaf disc. SAE-EC at 20 and 30 mg/mL reduced 72.86 and 85.5% honeydew secretion as compared to control. Further examination should be ensued by using EPG (Electrical penetration graph) technology to obtain more precise information concerning the antifeedant activity of SAE-EC.

Management of citrus psyllids in orchards mainly relies on use of braod spectrum synthetic insecticides of variouse classes (Kanga et al., 2016; Srinivasan et al., 2008; Tiwari et al., 2011). Mostly insecticides are used against psyllids at the adult stage (Tiwari et al., 2011). Very limited literature is available regarding the use of chemicals target the eggs and nymph of psyllids. The result of the current investigation showed that potted M. paniculata potted seedlings treated with SAE-EC give a concentration-dependent ovicidal activities, only 11.75% and 30.44 eggs were able to hatch into adults when confined with dry residue of SAE-EC at 20 and 30 mg/mL, while in control and 10 mg/mL concentration the hatching percentages were 93.45 and 93.78% respectively. Our current investigation revealed that SAE-EC has ovicidal activity against ACP. Alkaloids have multitarget mechanisms of action including the cytoplasmic membrane disruption, respiratory inhibition and inhibition of cell division (Cushnie et al., 2014; Marutescu et al., 2017) and also by binding of muscarinic acetylcholine receptors (Andersson et al., 2008; Wink et al., 1998).Which results in modulation of respiration, heart rate and central nervous system functions (Chowa?ski et al., 2016). There possible mode of entry in living cells is due to hydrophobic mechanisms in which the alkaloids diffuse with varying efficiencies into living cells or into the vicinity of target molecules (Larson et al., 1988).

The emulsifiable concentrate formulation have low persistence and are relatively safe for the environment and mammals (Knowles, 2008; Oka et al., 2006; Wiwattanapatapee et al., 2009). The emulsifiable concentrate containing S. alopecuroides extracts in both laboratory and semi-field condition significantly deter citrus psyllid. Moreover, the formulation did not cause phytotoxic symptoms on sweet orange mature leaves while minor phytotoxic symptoms (1-25 %) appeared on immature leaves treated with 50 mg/mL SAE-EC. Furthermore, the aqueous methanolic solution of SAE lost its persistence after 48 h after application while emulsifiable concentrate containing S. alopecuroides extract it presentence remains up to 168 h after application under semi-field conditions. The results of the current study revealed that the emulsifiable concentrate at 30 mg/mL has not shown any phytotoxic symptoms on the sweet orange potted plant. The formulations were significantly success in deterring the psyllid populations by over 80% compared to control in high population. Our results indicated that the persistence of SAE is enhanced when the extract was formulated as emulsifiable concentrate. Further research should be focus on more appropriate formulation i.e., nano-emulsions, encapsulation, cyclodextrins (CDs), and nanoparticle synthesis (AgNPs) and chitosan-based formulations for more better results.

The bioactivities of botanicals are largely a result of the synergism among their multiple constituents (Anaya-Eugenio et al., 2016), but in some cases, their dominant constituents are responsible for their biological action (Bakkali et al., 2008; Benelli et al., 2017). However, in our previous study, S. alopecuroides extracts dominant alkaloids sophocarpine and sophoridine showed behavioral effects against psyllids, albeit only at higher concentrations of 50 and 70 mg/mL as compared to the S. alopecuroides extract showed significant behavioral effect at 15 and 30 mg/mL concentration respectively (Rizvi et al., 2018a). Similarly, in some cases, minor constituents may also be responsible for high bioactivity. Furthermore, emulsifiable concentrate formulation concentrate did not cause the death of the males and females of parasitoid Eriborus argenteopilosus and did not cause phytotoxic symptoms on the broccoli leaves under field conditions (Eka et al., 2017) .

Regarding the stability of S. alopecuroides alkaloids in the emulsifiable concentrate the FTIR findings proved the presence of alkanes, an alkyl halide, amine, aldehyde, and alkane which shows major peaks at 820.66, 858.56, 8966.27, 962.21, 1072.48, 1249.77, 1737.06, 2852.42, 2923.77 and 3368.67 cm-1 in the emulsifiable concentrate after three months of placing the emulsifiable concentrate under room temperature. Similarly, a very strong absorption band appearing in this region suggested the presence of alkaloids (Pavia et al., 2008; Raja et al., 2013; Singh et al., 2017). Similarly, SAE-EC has excellent deterrence ability against citrus psyllids with minimal phytotoxicity to M. paniculata seedlings. Our current investigation revealed that our emulsifiable concentrate showed stable aqueous emulsion after 1:20 dilution. The SAE-EC increase the deterrence against psyllid in semi filed conditions, suggesting that the formulations would have the best efficacy up to 96 h after spraying, with minimal phytotoxicity to the M. paniculata seedlings. This may be the due composition of soybean oil, which contains emulsifiers, for example, long-chain polyunsaturated fatty acids and surfactant (Wang et al., 2006) that enhance the adhesion ability of the emulsifiable concentrate on the leaves surface. Mostly botanical pesticides due to their rapid degradation and volatility loss its persistence in a short period of time (Ahmadi et al., 2018). Similarly, the particle size in emulsions is one of the most key factors affecting its stability, reduction of the particle size usually precedes more stable emulsion formations and uniform spreading of active ingredient on the plant leaves surface (Charman et al., 1992). Therefore, the SAE-EC with 263.9 nm particle size with 0.35 PDI was selected for current bioassay with considerable deterrence, ovicidal and antifeedant effect against citrus psyllid. Furthermore, the efficacy of SAE-EC can be enhanced by repeated application or with the addition of some synergists to increase the effectiveness of SAE.

Due to the widespread natural abundance of S. alopecuroides in Skardu Baltistan region, this plant has the potential to be develop as a natural pesticide. Our current investigation concluded that SAE-EC showed behavioral effect against adult citrus psyllids under laboratory and semi filed conditions. It has been concluded that the emulsifiable concentrate containing S. alopecuroides extracts has the potential to be developed into natural prophylactic against Asian citrus psyllid. Further research should focus on their open field evaluation and their impact on natural enemies.