Diaprepes root weevil (Diaprepes abbreviates) also called as citrus weevil is one of the economically important insect pests of citrus and many ornamental plants in California and Florida. Adults cause leaf notching by feeding on the margins/ edges of leaves whereas their larvae mainly feed on the roots of their hosts. In the severe cases larvae can girdle main roots that can result into death of citrus trees.
Overwintering adults of Colorado potato beetle generally emerge from soil early in the spring. After mating in the spring, females lay yellow eggs on the underside of the leaves in a cluster of over 50 eggs and over 200 eggs during their lifespan. Eggs hatch into small larvae (grubs) within one week. After hatching from eggs, tiny larvae immediately start feeding on the leaves of host plants and become mature within 3 weeks by passing through four developmental stages. Matured larvae then move into soil for pupation. After 1- 2 weeks, adults emerge from pupae and life cycle continues. Colorado potato beetles can complete its lifecycle within one month and a total of 2-3 generations in a year.
Generally, both adults and larvae feed voraciously on leaves of potatoes and other host plants. In case of sever infestation; this insect can completely defoliate potato plants within a short period of time and defoliation can affect the bulking of potato tubers. Both adults and larvae can also feed on small tomato and egg plant fruits.
Beneficial entomopathogenic nematodes are currently used as the safe biopesticides alternatives to chemical pesticides in managing Diaprepes root weevil. Both naturally occurring and applied beneficial entomopathogenic nematodes in the soil can find, infect and kill soil dwelling stages like larave and pupae of diaprepes root weevil. For example, mature larva of Colorado potato beetle that moves in the soil for pupation can be a very good target for beneficial entomopathogenic nematodes. Beneficial entomopathogenic nematode species including Steinernema carpocapsae, Steinernema feltiae, Heterorhabditis megidis, Heterorhabditis marelata and Heterorhabditis bacteriophora have shown a very high efficacy against adult, larval and pre-pupal stages of Colorado potato beetles. Of these 5 nematode species, Steinernema carpocapsae, Steinernema feltiae, and Heterorhabditis bacteriophora are commercially available and can be applied at the rate of 1 billion nematodes per acre for the effective control of Colorado potato beetles.
Armer, C.A., Berry, R.E., Reed, G.L. and Jepsen, S.J. 2004. Colorado potato beetle control by application of the entomopathogenic nematode Heterorhabditis marelata and potato plant alkaloid manipulation. Entomologia Experimentalis et Applicata. 111: 47-58.
Berry, R.E., Liu, J. and Reed, G. 1997. Comparison of endemic and exotic entomopathogenic nematode species for control of Colorado potato beetle (Coleoptera: Chrysomelidae). Journal of Economic Entomology. 90: 1528-1533.
Cantelo, W.W. and Nickle, W.R. 1992. Susceptibility of prepupae of the Colorado potato beetle (Coleoptera, chrysomelidae) to entomopathogenic nematodes (Rhabditida, Steinernematidae, Heterorhabditidae). Journal of Entomological Science. 27: 37-43.
Ebrahimi, L., Niknam, G. and Lewis, E. E. 2011. Lethal and sublethal effects of Iranian isolates of Steinernema feltiae and Heterorhabditis bacteriophora on the Colorado potato beetle, Leptinotarsa decemlineata. Biocontrol 56: 781-788.
Ebrahimi, L.,Niknam, G.and Dunphy, G.B. 2011. Hemocyte responses of the Colorado potato beetle, Leptinotarsa decemlineata, and the greater wax moth, Galleria mellonella, to the entomopathogenic nematodes, Steinernema feltiae and Heterorhabditis bacteriophora. Journal of Insect Science 11, Article Number: 75.
Nickle, W.R., Connick, W.J. and Cantelo, W.W. 1994. Effects of pesta-pelletized Steinernema-carpocapsae (all) on western corn rootworms and Colorado potato beetles. Journal of Nematology. 26: 249-250.
Trdan, S., Vidrih, M., Andjus, L. and Laznik, Z. 2009. Activity of four entomopathogenic nematode species against different developmental stages of Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera, Chrysomelidae. Helminthologia. 46: 14-20.
The following beneficial organisms can control the Colorado potato beetles