Nonpreference Among Gerbera Cultivars by the Leafminer Liriomyza trifolii (Agromyzidae: Diptera)

The leafminer, Liriomyza trifolii (Burgess) is a key pest of gerbera daisies (Gerbera jamesonii Bolus), which are among the most preferred cut flowers in the world. While insecticides often fail to control this pest, parasitoids have proven to be effective. To maintain the parasitoids in the system, pesticide applications should be avoided. However, the influx of secondary pests like mites, thrips, whiteflies, and aphids during the growing season necessitates chemical sprays, which are effective in controlling the secondary pests, but are often toxic to the natural enemy and hence disrupt biological control. Since chemicals are not easily avoided in this system, an alternative method to avoid leafminers was sought, using host plant resistance, which can be an important component of integrated pest management (IPM) programs. Sixty gerbera cultivars were evaluated for potential resistance to L. trifolii. A range in susceptibility measured as leaf punctures and developing mines was evident for the first five weeks of a six-week exposure period. Gerberas ‘Jaguar Pink’, ‘Jaguar Rose Deep’, ‘Jaguar Salmon Pastel’, and ‘Revolution Spring Pastel’ were the least damaged, exhibiting less than 20% of the highest damage on at least two observation dates. However, consistent exposure to high numbers of leafminers resulted in similar expression of damage among all cultivars after five weeks. Differences among cultivars in force required to puncture leaves could not be consistently associated with damage due to leafminers