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Managing Pesticide Resistance on Avocados

Managing Pesticide Resistance on Avocados. Eduardo Humeres, Joseph Morse, Alan Urena, Lindsay Robinson, Pam Watkins, Paul Flores, Darren Anderson University of California Department of Entomology Riverside, CA. Presentation. What is pest resistance? Key avocado pests

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Managing Pesticide Resistance on Avocados

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  1. Managing Pesticide Resistance on Avocados

  2. Eduardo Humeres, Joseph Morse, Alan Urena, Lindsay Robinson, Pam Watkins, Paul Flores, Darren Anderson University of California Department of Entomology Riverside, CA

  3. Presentation • What is pest resistance? • Key avocado pests • Management of key avocado pests • Avocado pest resistance • Summary

  4. Pest Resistance

  5. The development of resistance to a pesticide is perceived in a number of ways (McKenzie, 1996): • Farmers, horticulturists or agricultural advisers • Recognize resistance as a decrease in the effectiveness of control of a pest provided by a chemical • Geneticist • Attempts to define the heritable basis of the resistance phenotype

  6. Toxicologist • Observes the change from susceptible to resistance as a shift in dosage-mortality lines

  7. A B Early in resistance evolution Proportion of population Resistant individuals at low numbers Fitness Concentration

  8. A B Selection (= pesticides sprays) Seleção Proportion of population Concentration

  9. A B Distribution after resistance has evolved Proportion of population Concentration

  10. Key Avocado Pests

  11. Avocado Thrips Scirtothrips perseae (Thysanoptera: Thripidae)

  12. Biology (Hoddle & Morse 2004)

  13. Avocado Thrips: food source

  14. Avocado Thrips Damage

  15. Avocado Fruit Set

  16. Persea Mite Male Oligonychus perseae (Acari: Tetranychidae) Female

  17. Biology (Hoddle, 1999)

  18. Avocado Persea Mite Damage • Hass cultivar most damaged • Mites occur mainly on the underside of the leaves along the midrib, main veins and leaf depressions • Lower epidermal, spongy parenchyma and palisade cells of the leaf tissue are destroyed and large necrotic areas on the leaf result from feeding (Aponte & McMurty, 1997)

  19. Avocado Pests Fluctuations Avocado Thrips Persea Mite

  20. Management of Key Avocado Pests

  21. Context of Chemical Control Research with Avocado Pests AvocadoThrips • Worldwide, few examples of complete biological control of pestiferous thrips species (chemical intervention often required) • Scirtothrips citri (Citrus thrips) • Scirtothrips aurantii (South African citrus thrips) • Scirtothrips dorsalis (Chili or yellow tea thrips)

  22. AvocadoPersea Mite • Considerable research has focused on control using augmentative releases of various predaceous mite species • Released mites do not appear to persist from year to year • Generally, cost of effective annual augmentative releases is considered prohibitive

  23. General observation – avocado thrips and persea mite can build to economically injurious levels quickly under ideal conditions • Optimal weather conditions (cool coastal weather) • Presence of leaf, leaf flushes or young fruit (avocado monoculture = a banquet) • Low endemic levels of biological control agents Thus, an integrated approach is needed with key avocado pests

  24. An Integrated Approach to Avocado Pests Management • Classical biological control - search in native range of avocado thrips and persea mite for effective natural enemies, import and release them • Monitor field populations / natural enemies and apply selective treatments only as needed, based on economic thresholds (potential for fruit damage) • Monitor field populations for pesticide resistance development • Continue to search for new selective chemical control materials

  25. Should I Spray for Avocado Pest Control? • Suggest growers might employ a knowledgeable pest control advisor to assist in monitoring / spray decisions • Monitor immature avocado thrips on young leaves, then move to fruit when the thrips do • Monitor for adult persea mite on mature leaves

  26. Good treatment decisions are tricky - several factors are involved: • Tree size and health (vigor), grove topography • Timing (leaf flushes), weather • Natural enemy levels • Grower tolerance for fruit scarring (short-term economics versus natural enemy and thrips susceptibility maintenance) • Leaf drop tolerance for persea mite feeding (increases when > 7.5-10 % of the leaf surface is damaged) • Spray equipment availability • Many groves do not require an avocado thrips or persea mite treatment in a particular year

  27. Monitoring for Avocado Thrips in Spring • Use a 10-14X hand or head lens to count the number of immature avocado thrips on the undersides of leaves prior to fruit set

  28. Monitoring for Avocado Thrips in Spring • Study by Phillips and Faber on Hass avocados in Ventura Co. When 3-5 thrips are Resulting % found per leaffruit scarring 97 days before fruit set 26-38% 75-36 days before fruit set 18-28% During fruit set 6-15%

  29. Monitoring for Avocado Thrips in Spring • Avocado thrips do best under moderately cool temperatures (68-76 °F) • Under hot conditions (> 90 °F), populations crash • Smaller fruit are more susceptible to damage by avocado thrips • As fruit become larger (1.5 inches or more in diameter) - large numbers of thrips are needed to cause significant levels of fruit scarring

  30. Monitoring for Persea Mite (Machlitt, 1998) Number of persea mites per leaf = Total no. of mites counted is divided by 10 (average no. mites per leaf) x 12 (correlation factor)

  31. 2004 Section 18 Allowing Agri-Mek Use • Agri-Mek available 1999-2004 under a Section 18 Emergency Exemption for avocado thrips • 1999-2003: two applications per season allowed by air or ground

  32. 2004 Section 18 Allowing Agri-Mek Use • Initial decision by EPA (Feb. 17) was to deny the 2004 (Year 6) Section 18 request due to the availability of a registered alternative (Success registered in 2000) • Request submitted by CAC 9/03 • Economic analysis 11/5/03 • Additional data 2/6/04 • Analysis of data from 23 UC field trials prepared 2/16/04

  33. 2004 Section 18 Allowing Agri-Mek Use • Only last-minute CAC intervention and CA-DPR supporting a “Crisis Exemption” resulted in a compromise with EPA (Feb. 18, 2004) • A single Agri-Mek application was allowed in 2004 and only by air • Monthly conference calls (Guy Witney, Steve Peirce, Joseph Morse) with Syngenta to make sure full registration will be obtained for 2005 • Appear on track for registration Feb., 2005 • We have not yet seen the draft Section 3 label • Suspect will allow 2 applications per year • Unclear what filter strip requirements will be

  34. Pesticides available for avocado thrips • ABAMECTIN - Agri-Mek 0.15 EC • SPINOSAD- Success 2 SC - Entrust 80% • SABADILLA  - Veratran D 0.2%

  35. 2004 Section 18 Language ABAMECTIN - Agri-Mek 0.15 EC 10 - 20 fl oz / acre Add 0.25 - 4 % NR-415 oil in 50 or more gpa Single application per season; 12 h REI, 14 d PHI Application allowed only by air See Section 3 label for 2005 restrictions and reporting requirements

  36. ABAMECTIN - Agri-Mek 0.15 EC Agri-Mek relatively slow in killing avocado thrips Quite persistent in leaves, with control persisting 6-10 weeks or more Also effective in suppressing persea mite populations pH of water should be 5-9, better above 6

  37. SPINOSAD– Success 2 SC • 4 - 10 fl oz / acre • Add 0.25% or more NR-415 oil by air or ground • In order to delay thrips resistance development, do not apply Success more than 2 times per year; 4 h REI, 1 d PHI • Do not apply more than 29 oz Success (0.45 lb spinosad) per acre per crop 10 oz + 10 oz + 8.8 oz = 0.45 lb ai • 1.25-3 oz Entrust 80% + an organically approved oil (http://www.omri.org/OMRI_brand_name_list.html )

  38. SPINOSAD– Success 2 SC • Similar chemistry as Agri-Mek (both are termed macrocyclic lactones and are produced from Actinomycetes in fermentation vats) • Efficacy against Lepidoptera but almost no mite activity • More rapid kill of avocado thrips than Agri-Mek but less persistent in leaves • Do not acidify the spray tank as with Veratran D (ph 7-9 is optimal)

  39. Success Residual Activity with NR-415 Oil on Avocado Thrips, Field/Laboratory Bioassay; Bonsall, CA 1999 Corrected mortality (%) Age of residues (days)

  40. SABADILLA– Veratran D • 10-15 lb Veratran D 0.2% in 10-40 gpa by air or 20-100 gpa by ground; If 200 gpa is used, increase to 20 lb per acre; 24 h REI • Botanical pesticide made from the ground seeds of a lily-like plant from Venezuela • Screen size should be 20 mesh or larger (to avoid plugging) • Acidify water to pH 4.5 (citric acid or other) prior to adding Veratran D

  41. SABADILLA– Veratran D • Do not use additives (is a stomach poison and may reduce thrips feeding activity) • More effective in warm weather (when thrips are actively feeding) • Not persistent (50% gone after 4 days, control may last 1-3 weeks)

  42. Avocado Pest Resistance

  43. Pesticide Resistance – A Major Concern with Avocado Pests • Loss of persea mite susceptibility to Agri-Mek seen in a Ventura Co. avocado grove (Humeres & Morse 2005a, in press) • Avocado thrips resistance to Veratran D seen in two Ventura Co. avocado groves (Humeres & Morse 2005b, submitted)

  44. Pesticide Resistance – A Major Concern with Avocado Pests • History of citrus thrips resistance on citrus • Loss of citrus thrips susceptibility to Agri-Mek seen in a Ventura Co. citrus grove with concurrent loss in susceptibility to Success • Avocado thrips resistance monitoring recently initiated

  45. History of Citrus Thrips Pesticide Resistance Development Year First Used Year Pesticide Pesticide CommerciallyResistance Appeared Tartar emetic 1939 1941 DDT 1946 1949 Veratran D 1948 ?? Dieldrin 1953 1954 Malathion 1954 1961 Dimethoate 1969 a 1980 Carzol 1972 b1986 Baythroid 1991 1996 Agri-Mek 1994 ?? (2004) Success 1998 ?? (reports investigated) a Registered for use on non-bearing citrus in 1962. bNot used extensively until dimethoate resistance appeared in the early 1980’s.

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