Phyllocnistis citrella Stainton
Taxonomic placing: Insecta, Holometabola, Lepidoptera, Gracillariidae
Common name: Citrus leafminer
Geographical distribution: The origin of this pest is in Southeast Asia. It now occurs wherever citrus is grown; in the Middle East since 1994.
Host plants: Mainly plants of the family Rutaceae, mostly on various Citrus species and cultivars.
Morphology: The adult is about 2-3 mm long, silvery-white with black spots, and four dark stripes on each forewing. The larvae are light-green in color, almost transparent, up to 3 mm in length.
Life cycle: Each female deposits about 50-130 eggs, placing them on the very young leaves and the youngest twigs. The emerging larvae enter the leaves and burrow therein, forming uneven mines (Figure 1), where pupation takes place. The larvae have 4 instars: the 1st to 3rd instar larvae feed, whereas the 4th instar is spinning larva that does not feed. The pest may raise a generation in a fortnight at 25°C and long day conditions, thus completing several generations in a year. It has no diapause.
Phenology: Due to its specificity for citrus and preference for young leaves as oviposition sites, the phenology of the pest is determined by the host’s growth or flashing cycles. The first and main flash, in the spring, is rarely affected in Israel. This is due to the low winter temperatures and/or because of natural enemy activity in the former year. The mid-summer and late summer flashes, which in any case are usually smaller, may be more damaged by the pest.
Economic importance: A major pest of citrus throughout its distribution. The main damage is to seedlings in nurseries, young trees (1-3 years old) and to the young growth after grafting. Fruit-bearing trees are seldom damaged. The mining of the larvae within young citrus leaves distorts them and destroys the epidermis. Mining within the fruit’s peel, although uncommon (except for pummeloes), causes direct damage.
Figure 1:Citrus leaves mined by the citrus
Management:
Crop resistance: No species or varieties of citrus are clearly resistant to the pest.
Chemical control: As soon as the pest is first noted on young trees (1-3 years old) in the spring, they should be treated. This may include a spray with abamectin and a concurrent soil treatment with the systemic imidacloprid). An alternative is to brush the systemic acetamiprid on the trunks; the precise method is dependent on tree age and trunk diameter. Confidor and Mospilan can also be applied to control infestations that occur during later growth flashes. Fruit-bearing trees do not need to be treated.
Biological control: In Jordan 9 eulophid parasitoids attack P. citrella. In Israel three of them, namely: Cirrospilus ingenuus Gahan, Citrostichus phyllocnistoides and Semielacher petiolatus (Girault) control the pest.
References
Argov, Y. and Rossler, Y. 1996. Introduction, release and recovery of several exotic natural enemies for biological control of the citrus leafminer, Phyllocnistis citrella, in Israel. Phytoparasitica 24: 33-38. .
Argov Y. and Rossler Y., 1998. Rearing methods for the citrus leafminer Phyllocnistis citrella Stainton and its parasitoids in Israel. Biological Control 11: 18-21.
Ateyyat, M.A. 2002. Parasitoid complex of citrus leafminer, Phyllocnistis citrella on lemon in the Central Jordan Valley. BioControl 47: 33-43.
Heppner, J. B. 1993. Citrus leafminer, Phyllocnistis citrella, in Florida (Lepidoptera: Gracillariidae: Phyllocnistinae). Tropical Lepidoptera 4: 49-64. .
Knapp, J.L. (and 9 co-authors)1995. Citrus leafminer, Phyllocnistis citrella Stainton: Current status in Florida - 1995. Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 35 pp.
Ujiye, T. 2000. Biology and control of the citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) in Japan. Japan Agricultural Research Quarterly 34: 167-173.
Yael Argov E-mail: yael@jaffa.co.il
The Israel Cohen Institute for Biological Control; Citrus Marketing Board of Israel, P.O. Box 80, 50250 Bet Dagan, Israel.