Life history of Dactylopius opuntiae (Hemiptera: Dactylopiidae) on Moroccan resistant cactus germplasm

The important damages caused by Dactylopius opuntiae (Hemiptera: Dactylopiidae) to cactus crops around the world require an integrated pest management (IPM) approach, based on the combination of several techniques (varietal resistance, biological, chemical methods, etc). In this sense, this study evaluated the resistance of 10 Moroccan cactus genotypes to D. opuntiae in order to characterize the expression of antixenosis and/or antibiosis. Antixenosis was accessed in the greenhouse and in the laboratory (26{+/-} 2{degrees}C) using choice and non-choice tests with 1st instar nymphs. Aakria and Cherratia showed a strong antixenosis effect towards D. opuntiae (0-0.3 D. opuntiae alive 30 after infestation). For antibiosis assessment, 30 1st instar nymphs were confined on cladodes of the 10 selected genotypes under the same laboratory conditions to allow their development, as well as the life cycle performance and behavior of D. opuntiae on the 10 selected cactus genotypes, were evaluated under greenhouse conditions. No influence of genotypes on insect oviposition was observed, indicating that the mealybug does not prefer any genotypes over the others for oviposition. The mealybug failed to develop on genotypes Aakria and Cherratia and did not grow beyond the young female stage on all other resistant genotypes tested. Similarly, first instar nymphs fed on genotypes Marjana, Melk Zhar, and A200 died without reaching the second instar nymph stage. In addition, all genotypes tested had a negative effect on nymph viability (<24%), indicating resistance (antibiosis and/or antixenosis) to the cactus scale. These cactus genotypes may all be useful in breeding programs focused on cactus resistance to mealybugs.