The mealybug destroyer (Cryptolaemus montrouzieri) is a beneficial lady beetle (Coleoptera: Coccinellidae) that preys on mealybugs and other sap-feeding hemipterans. Both the larval and adult stages are predatory and may contribute to the suppression of pasture mealybug populations in sugarcane. However, the presence of mealybug destroyers is not necessarily an indicator of pasture mealybug infestations, as they also feed on other mealybug species, aphids and soft scales.

Native to Australia, the mealybug destroyer was introduced into California in 1891 as a biological control agent for citrus mealybug. While populations established successfully in some coastal areas, the species has generally been limited by cold winter temperatures. The climate in south Louisiana is suitable for sustaining populations of mealybug destroyers that contribute to the natural suppression of pasture mealybug.

Adult mealybug destroyers (Figure 1) are small lady beetles, approximately 3-4 mm long, with a dark brown body and a tan to orange head and posterior. Unlike many coccinellids, they lack bright coloration and can easily go unnoticed during field scouting. Adults are also highly mobile and quickly move away when disturbed.

The larval stage is even more likely to be overlooked because it closely resembles the mealybugs it attacks (Figures 2 and 3). Mealybug destroyer larvae are covered with dense, white filaments that give them a “floured” appearance. Although they superficially resemble pasture mealybugs, several characteristics can be used to distinguish them. The waxy covering of mealybug destroyer larvae forms dense tufts along each body segment rather than the long filamentous projections characteristic of pasture mealybugs (Figure 4). Size can also be a useful distinguishing trait, as mature mealybug destroyer larvae may reach approximately 13 mm in length, making them more than twice as large as the largest pasture mealybugs, which typically measure 2-5 mm. However, early instar mealybug destroyer larvae may overlap in size with pasture mealybugs and can be more difficult to distinguish. Additionally, shed cuticle of mealybug destroyer larvae may be mistaken for pasture mealybug nymphs, potentially leading to misidentification during scouting efforts.

Mealybug destroyers attack their prey throughout development. Adults and young larvae preferentially consume mealybug eggs, while older larvae readily feed on mealybugs of all developmental stages. However, because pasture mealybug females give birth to live nymphs rather than laying eggs, the predator-prey relationship may differ somewhat from that described for other mealybug species. Nevertheless, a single mealybug destroyer larva may consume as many as 250 mealybugs before pupating, highlighting the potential impact of this predator when populations are abundant.

Observations of mealybug destroyers in Louisiana sugarcane raise the possibility that this predator may provide some level of biological control of pasture mealybug. However, the extent to which its seasonal activity overlaps with pasture mealybug populations remains unclear. Additional field observations and research are needed to determine whether mealybug destroyer populations develop in sufficient numbers and at the appropriate time to significantly impact pasture mealybug infestations.

As scouting efforts for pasture mealybug continue, growers and crop consultants should become familiar with the appearance of both larval and adult mealybug destroyers. Correct identification will help avoid confusing this beneficial insect with the pest it attacks and provide a better understanding of natural enemy activity within sugarcane fields.

If you suspect pasture mealybug infestation in sugarcane, please email the LSU AgCenter at bwilson@agcenter.lsu.edu or the Louisiana Department of Agriculture and Forestry at PastureMealybug@ldaf.state.la.us.

Figure 1. Adult mealybug destroyer. Adobe stock photo by Peter Oetelshofen

Figure 2. Mealybug destroyer larvae. Photo by Schyler Thibodeaux

Figure 3. Mealybug destroyer larva among aphids. Photo by Schyler Thibodeaux

Figure 4. Pasture mealybug nymphs and adults. Photo by Schyler Thibodeaux