Insecticidal action of phytohemagglutinin (PHA) against the grain aphid, Sitobion avenae

The effects of phytohemagglutinin (PHA) on development, fecundity, and mortality of the grain aphid, Sitobion avenae (Fabricius), were determined. Also determined were the effects of PHA on the activity of gut enzymes involved in sugar and phosphorus metabolism (α- and β-glucosidase and alkaline and acid phosphatase) and on the feeding behavior of adult apterae.When added to a liquid diet, PHA increased the pre-reproductive period, decreased fecundity, and increased mortality of S. avenae. PHA also increased the developmental time and reduced the intrinsic rate of natural increase. The aphids fed on sucrose-agarose gels with higher concentrations of PHA lectin exhibited no phloem-feeding behavior. The number of the gel penetrations was reduced and duration of the pathways was increased by higher concentrations of PHA. In addition, activities of α-glucosidase and alkaline phosphatase in homogenates of adult aphids were reduced. The results indicate that PHA has potential in a biotechnological approach to insect management.

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► The PHA lectin decreased fecundity and increased mortality of adult apterae.
► The aphids fed on sucrose-agarose gels with higher concentrations of PHA lectin did not show any typical phloem activity.
► The adult apterae exposed to PHA reacted by reduction in activity of α-glucosidase and alkaline phosphatase.