By Jawwad A. Qureshi
Citrus under protective screen (CUPS) is a novel system for large-scale citrus production in screen houses covered with a tightly woven mesh screen on all four sides and the roof. The primary goal of this shift from a traditional open orchard to a CUPS system is to protect citrus crops from huanglongbing (HLB) disease, which is transmitted by the Asian citrus psyllid (ACP). Once an infected citrus psyllid carrying the HLB pathogen feeds on a citrus tree, it transmits the pathogen, initiating the disease process, which is further exacerbated by additional psyllid feeding. In traditional open orchards, it is difficult to curb the ACP infestations and severity of HLB.
Long-term protection afforded by CUPS against HLB to produce disease-free citrus has been demonstrated at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Indian River Research and Education Center and the Citrus Research and Education Center. Research showed only a few psyllids were detected in the CUPS studies, and there was no spread or impact of HLB for years.
CUPS is now implemented by several growers covering large acreage. However, pest incursions are a concern. The most common route for pest entry is through the CUPS doors, mainly due to personnel and equipment movement. Any materials, including plants to be used in CUPS, can carry ACP or other pests and can cause an infestation in the structures.
To avoid pest entry, it is important to follow standard decontamination procedures and remove any debris, such as leaves, which may harbor pests. Additionally, monitoring CUPS screens for holes, tears or any other damage is important to reduce pest incursions and management needs.
To detect pests in the CUPS, trees should be regularly inspected for pest presence by direct observation and examination of feeding damage.
Yellow sticky traps can be installed and checked regularly to detect ACP adults and other pests, such as thrips.
Other methods, such as tap and suction sampling, can be performed in the tree canopy. Tapping shoots will dislodge ACP, citrus leafminer (CLM), thrips and spider mites onto a laminated sheet of white paper held on a clipboard underneath the branches.
Pheromone traps for CLM provide good information on male activity.
A magnifying lens is a useful tool for detecting ACP eggs and nymphs as well as CLM larvae in young shoots, thrips in flowers, and rust mites and spider mites on leaves and fruit.
The notching around leaf margins from ACP feeding activity is easy to detect by visual inspection. Distorted, curled and twisted leaves may result from the activity of ACP, CLM or aphids and may contain these pests upon examination. CLM larvae damage leaves, shoots and sometimes fruit by making serpentine mines in the cuticle, which are easy to recognize.
To check for scale insects, examine limbs, twigs and trunks where they are more common, as well as leaves and fruit.
Implementing routine inspections and monitoring procedures helps to avoid infestations or treat them promptly.
Jawwad A. Qureshi is an associate professor at the UF/IFAS Southwest Florida Research and Education Center in Immokalee.
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