Asian citrus psyllid & the citrus disease huanglongbing: Training for retail nurseries and garden centers Psyllid Huanglongbing Matt Daugherty, UC Riverside mattd@ucr.edu Photography: M. Rogers, M. Keremane, S. Halbert, M. Hoddle, and E. Grafton-Cardwell

The psyllid (pronounced: síl - lid) is a small insect, about the size of an aphid Adult It has an egg stage, 5 wingless juvenile stages called nymphs, and winged adults Egg 5 Nymphal instars

Adult psyllids feed on young or mature leaves Adult psyllids feed on young or mature leaves. This allows adults to persist year-round When feeding, the adult leans forward and tips its rear end at a characteristic 45o angle.

Yellow-orange eggs are tiny and tucked into the tips of new shoots, making them difficult to see Female ACP strongly prefer to lay eggs on new leaves and shoots (“flush”)

Nymphs can only survive on young, tender leaves and stems. Nymphs produce sugar-filled waxy tubules as they feed. The tubules are unique and easily seen Nymphs can only survive on young, tender leaves and stems. Thus, nymphs are found only when the plant is producing new leaves.

Twisted, notched leaves are an indicator the psyllid has been there. As the psyllid feeds, it injects a salivary toxin that damages flush. If leaves survive, they twists as they grow Twisted, notched leaves are an indicator the psyllid has been there.

What plants does the psyllid attack What plants does the psyllid attack? All types of citrus and related plants in the family Rutaceae Citrus (limes, lemons, oranges, grapefruit, mandarins…) Fortunella (kumquats) Citropsis (cherry orange) Murraya paniculata (orange jessamine) Bergera koenigii (Indian curry leaf) Severinia buxifolia (Chinese box orange) Triphasia trifolia (limeberry) Clausena indica (wampei) Microcitrus papuana (desert-lime) Others….. Calamondin

The psyllid feeds and reproduces on plants that we don’t think of as citrus, such as ornamentals Plants that continuously produce new foliage, such as orange jessamine (Murraya paniculata) are preferred by the psyllid. Nursery shipments of this plant contributed to psyllid spread in Florida

Why are we so worried about this psyllid? ACP can transmit the bacterium that causes huanglongbing (HLB) Bacterium blocks nutrient transport, affecting tree growth, survival, and fruit production Candidatus Liberibacter asiaticus

Yellowing, poor quality fruit, tree decline, and death Earliest symptoms include blotchy, irregular yellowing of leaves Fruit don’t develop properly: small, deformed, poor flavor Lack of tree vigor, stunting; excessive fruit drop Tree mortality in as little as 5 years No cure! HLB Zinc

Human-assisted spread of the psyllid and disease in Florida The psyllid was first detected in 1998, after which it spread rapidly throughout the state assisted by shipment of infested ornamentals Within 3 years the disease spread to all citrus growing regions citrus production is ~1/2 of what it was production costs 50% higher ACP & HLB in Florida

Where are ACP and HLB in California? ACP was found in San Diego in 2008 now present throughout Southern California (residential and commercial citrus) parts of the Central Valley parts of the Bay Area More than 20 cases of HLB have been found in Los Angeles County

What is being done to manage ACP and limit HLB in California? 1. Statewide monitoring for ACP and HLB residential and commercial trapping inspections of nurseries 2. Quarantine zones established around infested areas regulations on nursery shipments 3. Treatments of residential citrus 4. Biological control 5. Area-wide treatments of commercial citrus

How can nurseries help prevent spread of the pest and disease? Quarantines exist for the psyllid (blue lines) and the disease (red line) to limit spread 1. Help maintain the psyllid quarantine educate customers 2. Minimize infestations on nursery plants adopt a set of best management practices

The psyllid quarantine and plant tagging system Quarantines: 1. Prohibit plant movement to areas outside the quarantine 2. Requires insecticide treatment of plants prior to shipping to retail. Retreatment after 90 days The color of a plant’s tag reflects its origin: Blue: plant came from production nursery outside of quarantine Yellow: came from within the quarantine zone

Inform customers about the pest and disease 1. Where they are relative to the quarantine zone signage near citrus trees explain tagging system 2. Psyllid & disease identification signage near trees provide brochures (quick tips) 3. Control options for psyllid (insecticides, soaps, oil) shelf talkers http://www.cdfa.ca.gov/plant/pe/interiorexclusion/acp_quarantine.html UC IPM “Quick Tips”

Monitor nursery plants regularly for pest and disease Check plants for evidence of the psyllid (especially flush) Check leaves for blotchy yellow disease symptoms Isolate any infested or suspected diseased plants Report any psyllid finds or suspected symptoms

Ensure turnover of host plant stock Prior systemic insecticide treatments are effective for upwards of three months Trees can reside at retail sites much longer 35% > 1 yr Long residencies increase risk of ACP infestation

Ensure turnover of host plant stock Prior systemic insecticide treatments are effective for upwards of three months Encourage sale of ACP host plants before they become unprotected 1. Initiate a labeling program to keep track of when plants arrived date or different colors 2. Distribute trees in a way that encourages the sale of “older” plants first

Use appropriate watering practices Adequate water is important for uptake of systemic insecticides. But, overwatering is problematic contributes to pesticide runoff limits retention of systemic insecticides in plants Use water volumes that limit excess runoff increase watering frequency and reduce amount

Minimize psyllid access to host plants 1. Screening barrier to ACP establishment the most effective, sustainable control measure 2. Place in shaded area ACP appears to prefer warm, sunny areas 3. Move plants inside temporarily house flushing plants in interior of store

Limit temporal overlap in nursery stock If possible, encourage brief absence of citrus and other ACP host stock Absence of suitable host plants, even briefly, may limit ACP populations no “reservoir” for insects limits spillover infestation onto new plants Encourage absence during season when citrus stock is normally low anyway

Conventional insecticides Mandatory treatments for nursery stock in quarantine protect plants for upwards of 90 days with appropriate watering may extend the effectiveness of systemic insecticides Retreatment may be necessary to protect plants for longer durations treatments can be made using labeled foliar and systemic insecticides if possible, consider retreatment by licensed applicator, which are likely to provide a longer duration of effectiveness

Insecticidal soaps Soaps can effectively kill ACP nymphs and adults by contact little to no residual period not effective against eggs Apply every 10 to 14 days when plants are flushing helpful for other common pests (mites, whiteflies)

Horticultural oils Horticultural oils decrease attractiveness of trees for psyllids ACP avoid trees, reduce oviposition for up to a few weeks after application With adequate coverage, can cause mortality of nymphs and eggs 0.5% - 1% adequate to see beneficial effects Don’t apply more than every 6-8 weeks, depending on climate

Avoid removing new flush Although pruning or hand removal of new shoots may temporarily decrease attractiveness to ACP, citrus responds by producing more flush labor-intensive pruning “treadmill” May have a longer-term negative effect on plant

Spray wash psyllids off plants Moderately high-pressure hosing to remove psyllid adults and nymphs (“bug blaster”) may not effectively dislodge psyllid eggs more effective if used in conjunction with soaps or oils Can contribute to overwatering or plant damage if done too often or too vigorously

Summary of Action Steps Inform customers about pest, disease, quarantine, control options Inspect plants, isolate infested plants, and report Ensure prior insecticide treatments are effective -encourage turnover of stock, don’t overwater Adopt supplementary control measures -screening, insecticidal soaps, pray washing Collectively these steps will minimize the potential for human-assisted spread of the psyllid and disease in California

http://www.ipm.ucdavis.edu/QT/asiancitruscard.html Downloadable brochure General information on psyllid and disease biology, identification, and control Share with customers

Online ACP & HLB training course for retail nurseries http://class.ucanr.edu/

ACP Distribution and Management http://ucanr.edu/sites/ACP/