IFAS recommendations for ACP management

1. IFAS recommendations for ACP management

2. Today’s presentation • Overview of recent research on ACP management with soil-applied neonics • Followup confirmatory surveys for insecticide resistance • Current ACP management recommendations • Ongoing work by IFAS entomologists

3. Season-long ACP control (foliar applications to prevent pesticide resistance to neonics shown in orange)

4. Refining Use Rates of Soil-applied Neonicotinoids • Refine use rates based on tree size? • Dilution of product in larger tree canopies • How much product is needed in a leaf to control ACP? Dr. Kevin Langdon (Graduated Dec 2017)

5. Amount of imidacloprid needed in leaf to control ACP? • Setamou et al. 2010 correlated psyllid control with 200PPB imidacloprid in leaf tissue • Since been used as the standard target dose in plants for psyllid control studies

6. Correlating application rate with imidacloprid concentration in leaf • Based on tree size, how much soil-applied imidacloprid is needed to reach 200 ppb in leaf tissues? • Trees treated in grove • Leaves analyzed for imidacloprid concentration using LC-MS-MS • Correlate psyllid populations with known concentrations in plant tissues to validate 200 ppb target threshold

7. Correlating application rate with imidacloprid concentration in leaf • At CREC groves, psyllids found reproducing on trees with >10 PPM (10,000 ppb) in leaf tissues • Resistance assay performed using vial assay method • RR = 2.4 (negligible)

8. How much imidacloprid needed in leaf tissue to control psyllids? • Tim Ebert (Post-doc) • Used EPG to correlate neonic residues in plants with psyllid mortality/feeding • ~50PPM imidacloprid in leaf reduced phloem-related feeding behaviors by 85% (July 2015) • Uneven distribution in leaf?

9. How much imidacloprid needed in leaf tissue to control psyllids? • Kevin Langdon (PhD student) • Artificial diet bioassay to develop LC50 for psyllid exposure to imidacloprid via feeding • Compared feeding LC50 to contact (vial assay) LC50

10. Langdon & Rogers 2017, JEE 110(5): 2229-2234. Response of laboratory susceptible D. citri strain to imidacloprid by ingestion and contact. a. Number of adult D. citri tested. b. Parts per million (ppm) active ingredient. c. Ratio of ingestion LC50 divided by contact LC50. • Average concentration in leaves from commercial groves = 7 PPM; range <1PPM – 30PPM. • LC90 for feeding mortality = 62.0 PPM (62,000 PPB), much higher than the 200 PPB threshold suggested • Suggests feeding deterrence, not mortality, is the mechanism for soil-applied neonic protection of young citrus trees.

11. Response of laboratory and field collected D. citri to imidacloprid by ingestion and contact in 2016. a. Number of adult D. citri tested. b. Test of differences in mortality at the mean dose level where means differ significantly at α ≤ 0.05. (Contact: 19.5 ppm; Ingestion: 97.7 ppm). c. Parts per million (ppm) active ingredient. d. Ratio of ingestion LC50 divided by contact LC50 by location. e. Percent mortality in negative control containing no diet at 72h. Langdon & Rogers 2017, JEE 110(5): 2229-2234.

12. Response of laboratory and field collected D. citri to imidacloprid by ingestion and contact in 2016. a. Number of adult D. citri tested. b. Test of differences in mortality at the mean dose level where means differ significantly at α ≤ 0.05. (Contact: 19.5 ppm; Ingestion: 97.7 ppm). c. Parts per million (ppm) active ingredient. d. Ratio of ingestion LC50 divided by contact LC50 by location. e. Percent mortality in negative control containing no diet at 72h. Langdon & Rogers 2017, JEE 110(5): 2229-2234.

13. Response of laboratory and field collected D. citri to imidacloprid by ingestion and contact in 2016. a. Number of adult D. citri tested. b. Test of differences in mortality at the mean dose level where means differ significantly at α ≤ 0.05. (Contact: 19.5 ppm; Ingestion: 97.7 ppm). c. Parts per million (ppm) active ingredient. d. Ratio of ingestion LC50 divided by contact LC50 by location. e. Percent mortality in negative control containing no diet at 72h. Langdon & Rogers 2017, JEE 110(5): 2229-2234.

14. Findings from Langdon’s Dissertation Research • Greater sensitivity of ACP to neonics through contact vs ingestion exposure • Foliar sprays are more effective in killing • Should be considered for future stewardship of neonic products • Failure to achieve lethal concentrations of neonics in leaf tissue following soil applications • Activity primarily through feeding deterrence

15. Findings from Langdon’s Dissertation Research • Persistence of neonic concentrations in leaf tissues <1 PPM through 12 weeks post-application • Sublethal exposures that may promote resistance development • Data from this study suggest resistance development to neonics at all study sites • Need to look at more grove locations!!!

16. Annual Survey to Monitor For Insecticide Resistance Lukasz Stelinski Lab Four purposes: • Monitor for insecticide resistance in D. citri field populations • Study the changes that occur over time in the insecticidal response of D. citri • Determine the natural variation in D. citri insecticidal response • Refine spray schedules

17. Average LD50 Resistant Ratios • RR50 = Field Population LD50 / Laboratory Strain LD50 • 2009: ratios were on the rise for some major classes of insecticides • 2013 and 2014 fell back to susceptible levels • Hypothesis: Improved spray regimes through CHMA were working *Average of RR50 from all sites surveyed

18. 2017 Resistance monitoring in 6 locations in Florida (LD95s) (Lukasz Stelinski) LC95RR MOA 1A,1B MOA 3 MOA 4A MOA 28 LC95RR MOA 4D

19. Dr. Lukasz Stelinski lab, 2017 Group 4A (Admire Pro)

20. Dr. Lukasz Stelinski lab, 2017 Group 4A (Platinum)

21. Dr. Lukasz Stelinski lab, 2017 Group 1B (Dimethoate)

22. Dr. Lukasz Stelinski lab, 2017 Group 1B (Lorsban) ND ND

23. Dr. Lukasz Stelinski lab, 2017 Group 3 (Danitol) ND ND

24. Dr. Lukasz Stelinski lab, 2017 Group 4D (Sivanto) ND

25. Dr. Lukasz Stelinski lab, 2017 Group 28 (Exirel) ND ND

26. Dr. Lukasz Stelinski lab, 2017 Group 5 (Delegate)

27. Psyllid Populations (Florida)

28. HLB infection rates in new plantings Groves ~2 years of age (2014) 2017: Growers reporting HLB infection rates of 20-30% in plantings 1-2 years old

29. New MAC planting (CREC 2017)

30. Current status of insecticide resistance in Florida populations of Asian citrus psyllid and emerging management strategies Lukasz L. Stelinski1, Philip Stansly2, Jawwad Qureshi3, and Michael Rogers1 University of Florida, Entomology and Nematology Department, CREC1,SWREC2, IREC3

31. How should neonicotinoids be used for young tree protection in the face of resistance? • Soil applications do not deliver sufficient neonicotinoid toxicant into the plant to kill resistant or semi-resistant ACP—application failures are occurring now • Sub-lethal concentrations of neonicotinoids persist in non-bearing citrus trees during the period when ACP are not effectively controlled, further exacerbating resistance selection

32. How should neonicotinoids be used for young tree protection in the face of resistance? • Moving forward, growers choosing to continue use of soil-applied neonics should closely monitor their groves to ensure the soil applications are still providing effective “control” • Keeping plants “psyllid free”

33. How should neonicotinoids be used for young tree protection in the face of resistance? • If control failures are observed after applications of soil-applied neonicotinoids, we recommend using neonicotinoids only as foliar sprays in new plantings along with a rigorous rotation with other foliar-applied chemistries (recommendation from 1 registrant) • e.g., whitefly example from Europe

34. Current consequences of resistance • Preliminary investigations indicate that at least 6 months of completely ceasing selection pressure will be required for ACP populations to fall back to susceptible levels • After populations reverse to susceptibility, they may remain forever ‘primed’ to becoming resistant faster than was required initially, making rigorous resistance management a top priority into the future • A rotation of at least 5 modes of action in sequence has been shown to effectively prevent development of resistance

35. Future Monitoring and Managing Pesticide Resistance in ACP Populations • Funding has been provided by APHIS to greatly expand resistance monitoring effort throughout the state • Repeated monitoring will be conducted in selected CHMAs • Product rotations will be recommended by CHMA based on results of resistance monitoring

38. ACP Management Summary • Pay attention to level of control when spraying • Pull back on use of a particular MOA if control failures observed • May need to switch from soil to foliar applied neonics if control is not sufficient • ROTATION is key • 5 MOA’s in sequence preferred • Kaolin clay (dry season) • Reflective mulch

39. Questions?

40. Response of laboratory and field collected D. citri to imidacloprid by ingestion and contact in 2016. a. Number of adult D. citri tested. b. Test of differences in mortality at the mean dose level where means differ significantly at α ≤ 0.05. (Contact: 19.5 ppm; Ingestion: 97.7 ppm). c. Parts per million (ppm) active ingredient. d. Ratio of ingestion LC50 divided by contact LC50 by location. e. Percent mortality in negative control containing no diet at 72h. Langdon & Rogers 2017, JEE 110(5): 2229-2234.