Cochineal identification: how molecular techniques can distinguish between biological control agents and agricultural pests.
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Invasive Cactaceae cause considerable damage to ecosystem function and agricultural practices around the world but some cacti are also important and valued crop species. The most successful biological control agents used to combat cactus weeds belong to the genus Dactylopius (Hemiptera: Dactylopiidae), commonly known as ‘cochineal’, but the worst pests of cactus crops are also members of this genus. Cochineal lineages used for biocontrol of cactus weeds are host specific and only certain species and lineages will feed on cactus crops, so cactus biocontrol can be safely implemented without harm to cactus agriculture. Many of the Dactylopius species are so morphologically similar, and in the case of intraspecific lineages, identical, that numerous misidentifications have been made in the past. These errors may result in cactus farmers incorrectly assuming that the biocontrol agent is damaging their crop. This study aimed to generate a multi-locus genetic database to enable the accurate identification of dactylopiids. This was achieved through the nucleotide sequencing of three gene regions (12S rRNA, 18S rRNA, and COI) and two inter-simple sequence repeats (ISSR). Nucleotide sequences were very effective for species-level and D. tomentosus lineage-level identification, but could not distinguish between the two lineages within D. opuntiae commonly used for biological control of various Opuntia spp. Fragment analysis through the use of ISSRs successfully addressed this issue. This is the first time that a method has been developed that can distinguish between these two D. opuntiae lineages. Using the methods developed here, one can distinguish between what is a potential pest, and what is a beneficial biological control agent.
Citation: van Steenderen, C.J.M., Paterson, I.D., Edwards, S., and Day, M.D. 2021. Cochineal identification: how molecular techniques can distinguish between biological control agents and agricultural pests. 2nd International Congress of Biological Control (26 - 30 April 2021), Davos, Switzerland virtual conference.