Effects of plant growth regulators on survival and fitness of the oleander aphid, Aphis nerii (Homoptera: Aphididae), and the citrus mealybug, Planococcus citri (Homoptera: Pseudococcidae)
Nerium oleander (oleander) and Viburnum odoratissimum (sweet viburnum) are garden and landscape plants with remarkable ornamental value, which can be infested by the oleander aphid (Aphis nerii) and the citrus mealybug (Planococcus citri), respectively. These insects affect young leaves, shoots, fruits and flowers, resulting in the reduction of the ornamental value because of leaf discoloration and distortion, as well as the honeydew excretions produced which favors smut fungi. Plant growth regulators (PGRs) are widely used on ornamental crops to affect various morphological and physiological characteristics. Beside this, it has been found that PGRs affect the biology of insects-pests of plants concerning their fecundity, development and evolution. In order to investigate the possible effect of PGRs on oleander aphid and citrus mealybug, N. oleander and V. odoratissimum plants, about 40 cm in height, were treated with chlormequat-chloride, daminozide or prohexadione-calcium. Unsprayed plants served as controls. To evaluate the effect of PGRs on the development and survivorship of the two insects, 1st instar nymphs were placed individually in Petri dishes containing oleander (A. nerii) and viburnum (P. citri) leaves, in growth chamber conditions. Development and mortality of immatures were recorded daily, until the emergence of the adult. Also, in order to evaluate the effect of PGRs on adult longevity and oviposition, newly emerged females were caged in petri dishes with leaves treated as mentioned above. The nymph (A. nerii) and the egg laying (P. citri) were recorded daily until the death of the females. PGRs negatively affected longevity and replicative capacity of the insects with significant differences at the reproductive capacity of P. citri between treatments and the control. It is also noted that prohexadione-calcium, prevented completion of development of immature A. nerii since all nymphs died before adulthood.
Tsagkarakis, A.E., Papathanasis, A.CH., Karamatzoglou, E.N., Papadoulis, G.T. and Papafotiou, M. 2015. Effects of plant growth regulators on survival and fitness of the oleander aphid, Aphis nerii (Homoptera: Aphididae), and the citrus mealybug, Planococcus citri (Homoptera: Pseudococcidae). Acta Hort. (ISHS) 1105:197-204
Nerium oleander, Viburnum odoratissimum, mealybug, plant growth retardants, prohexadione-calcium