Preliminary results on developing a reliable monitoring system forPhyllocnistissp. (Lepidoptera:Gracillariidae) inProteaceaein Portugal

Abstract

Protea leafminer, Phyllocnistis sp., has been reported in South Africa since at least the 1990's. In Portugal, infestations were first reported on Southwest coastal farms in 2008. In this region, this pest can damage up to about 80% of flower production in several Protea cultivars, if control measures are not applied. Depending on whether the damaged leaves can be removed from cut flower stems and on the severity of the infestation, leafminer damage may make a significant impact or have little economic importance. Control of this pest has been achieved through the spraying of insecticides in combination with a mineral summer oil. At the farm level, decision-making for the need of control measures is based on observed incidence of attacks on plants, except in the case of very susceptible cultivars. In the last case, plants are sprayed as a precaution whenever they are in the susceptible phenological phase. In order to develop a friendly to use system to monitor Protea leafminer, sexual pheromone white delta traps baited with Phyllocnistis citrella pheromone were evaluated. Some of the trapped insects were sampled to conduct genitalia observations to check if they were P. citrella. In addition, 50 flowering stems of each studied cultivar (ʹBrendaʹ, ʹCandidaʹ, ʹGrandicolorʹ, ʹLiebencherryʹ, ʹPink Iceʹ, ʹRupy Whiteʹ, ʹSheilaʹ and ʹWhite Nightʹ) were inspected weekly for mines, containing either live or dead larvae. Very few adults of the genus Phyllocnistis (but no P. citrella) were caught in traps, so this pheromone is not considered suitable for monitoring purposes. The phenological stage “new growth” was moderately, but significantly correlated with the proportion of plants with larvae inside mines. Presence of new growth on branches explained more than 60% of the attack Protea leafminer.