Some pests in dooryard citrus
By Dr. Mongi Zekri, University of Florida, IFAS, 863 674 4092
Aphids. Are closely associated with new growth flushes and new emergent succulent leaves.
Aphids can be light green-yellow, grey-green, brown, and black. The brown citrus aphid is the
most effective vector for the Tristeza virus. Aphids are quite small (less than 2 mm). Colonies
can be composed of wingless and winged forms. Rapid population growth is initiated with the
spring flush. Heavy populations of aphids can also be noticeable on early summer flushes.
Infestations and sustained feeding result in distorted growth and stunting following by leaf
cupping and curling or twisting. Aphids are more damaging to young trees. Honeydew caused
by aphids can be observed on infested flush, and sooty mold fungi may build up around the
infestation. Among the natural enemies of aphids is the ladybird beetle or ladybug.
Citrus Leafminer. The hatching citrus leafminer larvae enter the leaf tissue and begin feeding
on the epidermal (surface layer) cells. The larvae create mines in the leaf. The mines enlarge
as the leafminer develops and molts. Symptoms of infestation include curling of leaves and
serpentine mines, usually on the lower side of leaves. The epidermis appears as a silvery film
over leaf mines. Citrus leafminer can occur on new flush throughout the growing season, but
usually does not affect the first spring flush. Citrus leafminer generally does not noticeably
affect growth and yield of mature trees. Biological control through natural enemies already
present in Florida and the introduced parasitoid wasp makes a significant contribution in
suppressing the problem. However, young trees are very vulnerable to severe leafminer
damage because of their frequent flushes. Scouting is necessary to determine larval activity
during flushing periods to increase the efficacy of oil sprays.
The citrus psyllid. High populations of the citrus psyllid can cause severe damage because
they attack young tender growth (flush), causing leaf distortion and curling. They also produce
honeydew, which leads to sooty mold infestations, and badly-damaged leaves will die and fall
off. Feeding by the citrus psyllid on the young flush of citrus trees causes damage to leaves
and shoots because the psyllid has a toxic saliva. Each female may lay up to 800 eggs during
her two-month lifespan. The life cycle takes about 20 days and there may be up to 30
overlapping generations per year. Oil should provide adequate control.
Citrus Rust Mite. When rust mite injury occurs on young fruit before fruit maturity, epidermal
cells are destroyed resulting in smaller fruit. Later, epidermal cells become brownish-black
and rusty looking. Citrus rust mites may be found on all citrus cultivars throughout Florida.
On some cultivars such as Sunburst, Fallglo, and Ambersweet, rust mite damage can be severe
on stems and foliage and may cause leaf drop. Mite populations usually begin to increase in
April on new foliage and reach a peak in June-July. Depending on weather conditions and the
occurrence of natural enemies, citrus rust mite populations usually decline in August and
September, but increase again in October and November. Oil should be effective in
suppressing rust mites.
Rouse, R.E. and M. Zekri. Citrus culture in the home landscape. HS-867, 6 pages.
http://edis.ifas.ufl.edu/pdffiles/HS/HS13200.pdf
Zekri, M. and R.E. Rouse. Citrus problems in the home landscape. HS-876, 10 pages.
http://edis.ifas.ufl.edu/pdffiles/HS/HS14100.pdf
