Insecticidal Activity, Growth Inhibitory and Biochemical Effects of Plant Lectins and Bacillus thuringiensis var. kurstaki against the Pink Bollworm, Pectinophora gossypiella

Abstract

Insecticidal activity and sublethal effects of white kidney bean and soybean lectins compared to Bacillus thuringiensis var. kurstaki were evaluated against pink bollworm (PBW), Pectinophora gossypiella (Saunders). The in vivo effects of these lectins on the total proteases and αamylase activities of PBW were also carried out. Results revealed that, B. thuringiensis (LC50 = 61.7 and 36.1 µg / g diet) was approximately 4.7 and 4.8 times more toxic than kidney bean lectins (LC50 = 289.2 and 175.0 µg / g diet) and 2.2 times more toxic than soybean lectins (LC50 = 134.3 and 81.2 µg / g diet) after 5 and 6 days of treatment on the 2 nd instar larvae. The LC25 equivalent concentration of B. thuringiensis and soybean lectins achieved the highest reduction of larval weight (11.9 and 13.0 mg / larva compared to 27.1 mg / larva in control) after 9 days of treatment. While kidney bean and soybean lectins at LC10 and LC25 increased the average time to pupation of PBW, B. thuringiensis at LC25 decreased the average time to pupation compared to control. All treatments significantly decreased the pupal mean weight and adult emergence rates compared to control. Kidney bean lectins, soybean lectins and B. thuringiensis at LC25 reduced the average number of eggs laid / female (fecundity) to 35.2, 31.5 and 34.5, respectively, compared to 89.0 in control. In addition, %egg hatch (fertility) significantly decreased to 53.8, 51.7 and 49.1% in kidney bean lectins, soybean lectins and B. thuringiensis LC25 treatments compared to 93.0% in control. Kidney bean and soybean lectins inhibited the activity of total proteases and α-amylase. Results of the present study suggest that kidney bean and soybean lectins can be used as suitable alternatives for B. thuringiensis in integrated management programs of pink bollworm.

Entomotoxic Properties of White Kidney Bean and Soybean Lectins and their Effects against Two Digestive Enzymes of the Spiny Bollworm, Earias insulana (Boisd.)

“…GML and PhVL proved to have toxic and negative effects on the growth and development of SBW. In addition, in previous studies GML and PhVL had the same effects against S. littoralis (Mohsen et al, 2020) and pink bollworm larvae (El-Deeb, 2021). These insects are the main cotton pests causing great reduction of production.…”

“…GML and PhVL significantly reduced the SBW fecundity and fertility when the 2 nd instar larvae fed diet contains concentrations equivalent to LC10 and LC25. Reduction of reproductive parameters (fecundity and fertility) of SBW caused by PhVL and GML has been recorded in other insect pests such as S. littoralis (Mohsen et al, 2020) and pink bollworm (El-Deeb, 2021). The investigation reveals that GML and PhVL have detrimental impacts on growth and reproductive parameters, which are partially explained by the evident inhibitory effects of total proteases and α-amylase activity in SBW.…”

“…Sclerotium rolfsii lectins were shown to have a notable mortality rate for Spodoptera litura larvae (Vishwanathreddy et al, 2014). Moreover, high mortality of S. littoralis and pink bollworm larvae treated with GML and PhVL were reported (Mohsen et al, 2020 andEl-Deeb, 2021).…”

“…Most lectins did not display strong acute toxicities against insect pests instead they are known to have distinct negative effects on insect development and reproductive (Caccia et al, 2012;Mohsen et al, 2020 andEl-Deeb, 2021). From a practical point of view these negative effects on insect development are suitable for IPM programs as the insect population is negatively affected.…”

“…So, they attracted many plant protection researchers and were known to be one of the best studied groups of lectins (Mohsen et al, 2020;Cavada et al, 2020 andCavada et al, 2021). White kidney bean, Phaseoulus vulgaries lectins (PhVL), and soybean, Glycine max lectins (GML) were known to have fungicidal (Mohsen et al, 2018) and insecticidal activities (Mohsen et al, 2020 andEl-Deeb, 2021). The present study investigated the entomotoxic and insect developmental effects of PhVL and GML and their effects on two digestive enzymes of SBW.…”