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

2. 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

3. 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.

4. 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”)

5. 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.

6. 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.

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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
UC IPM “Quick Tips”

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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)

25. 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

26. 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

27. 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

28. 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

29.
Downloadable brochure
General information on psyllid and disease biology, identification, and control
Share with customers

30. Online ACP & HLB training course for retail nurseries

31. ACP Distribution and Management