Biological control of the prickly pear cochineal Dactylopius opuntiae Cockerell (Hemiptera: Dactylopiidae)

The prickly pear cochineal Dactylopius opuntiae Cockerell (Hemiptera: Dactylopiidae) is a
serious pest that causes severe damage to prickly pear cactus species of the genus Opuntia.
Before its introduction to Morocco no control methods were available for use against this
pest. The current paper presents the results of the use for the first time of the mealybug
destroyer Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) and the biopesticide
D-limonene to control D. opuntiae. The efficacy of the biopesticide was evaluated
under field conditions. Corrected female mortality rates were >82% 6 days after application
of D-limonene at 60 ppm. The greatest mortality rates 6 days after treatment were 98% and
99% at 120 and 150 ppm, respectively. The data analysis showed that there was no significant
difference between the different doses 6 or 13 days after treatment. The LD50 recorded
was 33 ppm. In terms of biological control, the use of Cryptolaemus montrouzieri significantly
reduced the cochineal scale population by 92% 77 days after release. This effect was
maintained until 99 days after release of C. montrouzieri, and then the rate of population
reduction declined to the level observed 64 days after release (66%). These results suggest
that C. montrouzieri has the potential to suppress D. opuntiae populations to an acceptable
level and reduce the damage caused by this cochineal.