Use Beneficial nematodes to control leaf beetles / by Ganpati Jagdale

  • The leaf beetles, Altica quercetorum and Agelastica alni are serious pests of urban trees including Quercus sp and Alnus sp, respectively.  The elm leaf beetle Xanthogaleruka luteola is a serious pest that causes defoliation of eml trees (Ulmus spp.) in North America. Adults of these beetles generally feed on leaves by chewing holes through the leaf tissue.  Larvae skelotonize leaves by feeding on leaf tissues leaving veins and upper epidermis intact.
  • Entomopathogenice nematodes including Heterorhabditis megidis, Steinernema carpocapsae and S. feltiae can be used as potential biocontrol agents against different species leaf beetles (read Grewal et al., 2005 for more information).  It has been shown that both the pre-pupal and pupal stages of A. quercetorum and A. alni are very susceptible to H. megidis when applied in the soil. The last instar larvae of X. luteola are highle susceptible to S. carpocapsae when applied to the mulch.

How Entomopathogenic Nematodes kill leaf beetles

When the infective juveniles are applied to the soil surface or mulch, they start searching for their hosts, in this case leaf beetles grubs. Once a beetle grub has been located, the nematode infective juveniles penetrate into the grub body cavity via natural openings such as mouth, anus and spiracles. Infective juveniles of Heterorhabditis also enter through the intersegmental members of the grub cuticle. Once in the body cavity, infective juveniles release symbiotic bacteria (Xenorhabdus spp. for Steinernematidae and Photorhabdus spp. for Heterorhabditidae) from their gut in grub blood. In the blood, multiplying nematode-bacterium complex causes septicemia and kills grubs usually within 48 h after infection.  Nematodes feed on multiplying bacteria, mature into adults, reproduce and then emerge as infective juveniles from the cadaver to seek new larvae in the soil.

References: Refer following book to read more about efficacy of entomopathogenic nematodes against leaf beetles

1. Grewal, P.S. Ehlers, R.-U., Shapiro-Ilan, D. (eds.). Nematodes As Biocontrol Agents. CAB publishing, CAB International, Oxon