Proactive biocontrol of “pre-invasive” fruit pests: an example from the tephritid flies

1. Proactive biocontrol of “pre-invasive” fruit pests: an example from the tephritid flies John Sivinski, USDA-ARS, CMAVE, Gainesville, FL

2. POTENTIALLY INVASIVE FRUIT PESTS BEAR WATCHING – INCLUDING: False codling moth, Mexican fruit fly, West Indian fruit fly, Natal fruit fly, orange blossom bug, spined citrus bug, strawberry tortrix, summer fruit tortrix moth, orange spiny whitefly, apple blossom weevil, plum fruit moth, yellow peach moth, sweet orange scab, light brown apple moth, fruit tree weevil, Australian citrus whitefly, apple caspid, citrus flower moth, ….etc.

3. Why proactive control outside of the USA? 1. Develop and perfect means of biocontrol: as in the case of the APHIS pink hibiscus mealybug project in the Caribbean 2. Lessen the threat of invasion through pest suppression outside the country: tephritid fruit flies

4. vesuviana Costa Frugivorous Tephritidae Pest Tephritidae are about the size of house flies and develop in ripening fruit and vegetables the types of natural enemies 1- predators 2- parasitoids 3- frugivores 4- pathogens The forms of Biological Control 1- conservation 2- introduction 3- augmentation

5. The life cycle of a “typical” opiine braconid parasitoid Female parasitoids locate larvae through chemical and sound cues, and lay a single egg. The parasitoid larva completes development in the host’s puparium

6. As fly populations climb, parasitism by D. longicaudata climbs as well. Naturally occurring mortality rates of ~ 90% are common, but these levels occur in dense infestations that are typical of the latter part of a particular fruiting season. If parasitoids could be augmented in the early stages of pest population growth the target’s density might be kept low.Sivinski et al, 1996

7. Area-wide Biological Control techniques: Augmentative Control of the Caribbean Fruit Fly Release rate of 60,000/ square km.- a rate much lower than the typical sterile release which can be as high as 400,000/ square km. The typical end of the export grapefruit harvest season (a critical period in caribfly control) Sivinski, Holler, Calkins, Brambilla

8. The Mediterranean fruit fly, Ceratitis capitata- foreign exploration and integration with SIT Medfly attacks over 300 species of fruits and vegetables and is responsible for export restrictions wherever it occurs There would be serious economic consequences if medfly became established in the USA. A University of California study estimated that California alone would loose $1.1 billion dollars annually. The 1997 Florida eradication program cost >$24 million.

9. The international organization MOSCAMED uses insecticides and SIT to prevent the movement of medfly from Central America into Mexico and ultimately into the United States. Its present efforts center on the Guatemala-Mexico border The barrier is increasingly porous and in order to improve and expand it- MOSCAMED is looking for new techniques, like biocontrol, for integrationinto the program Medfly is a dangerous neighbor

10. WHY EMPLOY BIOCONTROL? Lake Atitlan National Park, Guatemala Because of potential non-target effects this is a location unlikely to be subjected to repeated insecticide-bait spray treatments- Like Florida, there are places where repeated bait-sprays are unlikely to be tolerated. These might include cities, parks, and organic farms recent research site

11. Potential for synergy between SIT and parasitoids Opposite pest density effects in SIT and parasitoid augmentation Parasitoids are often more effective at high host densities (many species disperse from places where the hunting is poor) SIT works better as the population declines (more sterile flies / fertile)

12. Choice of parasitoid(s) • Given the costs of augmentative release, both efficacy and rearing expense need to be considered • Efficacy- 1) host vulnerability and 2) environmental compatibility • Rearing expense- 1) host use and 2) rate of increase

13. What makes an effective parasitoid for augmentative release?: host vulnerability Diversity in Mexican Anastrepha spp. braconid parasitoids –its possible to get 5 species from a single piece of fruit The common opiine parasitoids of Anastrepha attack similar ages of larvae often in the same fruits, but have curiously large differences in ovipositor length J. Sivinski et al., 2001

14. Those species with longer ovipositors are able to reach larvae in a greater variety of fruit, both large and small. All other things being equal, long- ovipositor species can exploit hosts in a greater range of fruit. However another option is to use parasitoids that attack A more vulnerable stage than the larva Sivinski et al., 2001

15. For one thing….there are egg-pupal parasitoids Parasitism of Bactroceradorsalis in Guava Fruits in Oahu by the egg-pupal parasitoid Fopius arisanus Fopius arisanus is credited with lowering some Oriental fruit fly populations by as much as 90% and certain medfly populations by 50%. The now narrower host range of medfly may be due to relaxed competition for prefered hosts

16. Very large field cages used to examine the combined effects of parasitoids and sterile males

17. MEDFLY BIOLOGICAL CONTROL_ PARASITOIDS AND SIT IN COMBINATION- In very large field cages placed over coffee bushes in 4 Guatemalan locations, the addition of 2 species of braconid parasitoids always gave significant suppression of Mediterranean fruit flies. Steriles males suppressed medflies in one location and in that particular site there was also a significant interaction with parasitoids. Suppression was sometimes of the scale that it might be possible to eradicate the pest without prior use of chemical bait-sprays. This could be particularly useful in environmentally sensitive areas like national parks and cities. An extreme example of the consistently significant effect of parasitoids, alone or in combination with sterile males The single case of significant suppression by sterile males Rendon, Sivinski, Holler and Bloem

18. ENVIRONMENTAL COMPATABILTY Unfortunately, multiple attempts to establish F. arisanus in the New World have been largely unsuccessful- the best result was in Costa Rica, where at one time ~2% of medflies were parasitized….Its not clear if this parasitoid population still exists.

19. This and information on host preferences is helping to guide parasitoid introductions during the present APHIS Caribbean initiative Some parasitoid distributions are influenced by altitude- for example, Doryctobracon areolatus is more abundant at low altitudes…. While Dorytobracon crawfordii is more abundant at high altitudes Such relationships are due to more than just temperature and moisture. Host predictability and diapause are also involved Sivinski and Aluja

20. Most species have environments where they thrive- this can be on a large “geographical or n a “microenvironment scale In this particular fruit species, Dorytobracon areolatus (medium ovipositor)is more abundant in the outer portions of the canopy While Utetes anastrephae (short ovipositor) is concentrated in the inner Such information is guiding Caribbean introductions into St. Kitts and Nevis Sivinski et al., 1997

21. ? • Are there other egg-prepupal parasitoids that could be even better suited to the Central American environment and specialized on medfly

22. Oddly enough, until recently, none of the parasitoids used in medfly control actually originated from medfly and only a few were from the the medfly’s area of origin in east Africa. New collection sites are marked in red- explorations were funded by “interlocking” grants awarded to ARS and colleagues at the the University of Hawaii and Texas A&M University KENYA

23. The principal destination for African parasitoids is a new quarantine constructed on the outskirts of Guatemala City A collaborative venture with APHIS and MOSCAMED

24. Several of the people responsible for the construction, certification and running of the quarantine facility (conspicuous in his absence is Pedro Rendon)

25. One of the first and most interesting new parasitoids to be received in the Guatemala quarantine….After colonization it was distributed to several locations including Hawaii, Israel and African off-shore islands Among its potentially important traits is that, like F.arisanus, it is an egg-pupal parasitoid and capable of attacking vulnerable hosts near the fruit surface F. ceratitivorus

26. Another attractive quality is that it appears to be a medfly specialist. It is attracted to other fruit fly oviposition sites, but never attempts to oviposit …and subsequently never develops in Anastrepha….this makes it environmentally safer under certain circumstances. Production of adult parasitoids Absence of adult parasitoids Lopez, Sivinski , Holler, Bloem…et al., 2003

27. Rearing costs • Parasitoids are more expensive than their hosts • Economy of scale • Radiation and cohort purity • Use of female larvae • Sequential parasitism • All-female lines (Wolbachia)

28. Rearing efficacy- F. ceratitivorus is cheaper to rear than arisanus and costs/million are expected to go down as more are raised. (Parasitoid release rates are typically 0.1 -0.2 that of sterile male flies) Cost for 1million D. longicaudata Cost for 1 million sterile male flies Rendon et al., 2005

29. IN ADDITION-Large facilities can afford he very finest quality controls. Quality control tests included emergence and periodic comparisons with wild individuals of ability to attack larvae Taste testing of parasitized fruit fly larvae by APHIS detects infections

30. Practical problems with parasitoid mass-rearing and release include preventing the release of fertile flies at the same time The original experiment showing that larval irradiation allows the development of the parasitoid, but prevents that of the fly Sivinski and Smittle, 1990

31. Another practical problem is expense- hosts can be obtained from otherwise useless mass-reared females and this can represent considerable savings. One means of obtaining female larvae is to exploit sexual differences in maturation rates. Sivinski and Calkins, 1990

32. Pachycrepoideus vindemiae In Mexico, we have colonized 4 species of fruit fly pupal parasitoids. Three of these are ectoparasitic Coptera haywardi Eurytoma sivinskii Could these develop in flies that escaped parasitism by larval parasitoids and be an inexpensive second line of defense? Dirhinus sp. Sivinski, Aluja and Holler

33. Coptera haywardi (Diapriidae) The projections and concavities on the face of C. haywardi may serve as a shovel. In experiments with artificially buried pupae the parasitoid was able to destroy over half of the medfly pupae in the top 5mm of the soil and smaller proportions to depths of up to 5cm. Sivinski etal., 1998; Baeza, Sivinski, Holler, Bloem , 2000

34. Most pupal parasitoids of Diptera are ectoparasitoids and generalists- they shelter beneath the puparium and feed on the pupa as if it were a large piece of meat. C. haywardii is an endoparasitoid and a relative specialist. Specialism “focuses” the natural enemy on declining host populations and also results in environmentally safer biological control.

35. Unlike most pupal parasitoids, C. haywardi is not a hyperparasitoid. Thus hosts that are first exposed to a larval parasitoid can later be exposed to the pupal without loosing production. In the end its possible to double the number of natural enemies and increase the diversity of the release. One disadvantage of C. haywardii is that it does not develop in irradiated hosts Menezes and Sivinski, 1998

36. PARASITOID SEX RATIOS We have both parthenogenic and bisexual strains of one fruit fly parasitoid in quarantine and surveys in Mexico have yielded other candidates. it would be advantageous to horizontally transfer sex-ratio distorting endosymbionts, such as Wolbachia spp., into other species and create “custom” all-female lines for mass-rearing and inundative release. Such lines would automatically cut rearing costs in half. Aganaspis pelleranoi ? Odontosema anastrephae Copeland, Sivinski, Hoy and Holler

37. A word on conservation biological control- taking advantage of biodiversity …..very cheap or even profitable

38. “Augmentation” through conservation of natural enemies A case for the conservation of natural enemies- deforestation and the loss of parasitoids in Mexico The Llano Grande study site in the early 1990s Aluja and Sivinski, unpub.

39. Native forests are being lost to timbering and hasty agricultural practices. Many of the trees harbor economically unimportant fruit flies that share natural enemies with pests. As the tree are lost so are important parasitoid reservoirs. Notice the river beds are visible because the tree covers have been removed The Llano Grande site in 2000

40. A very ”long term” experiment- a small nursery is providing noneconomic- fruit fly host plants free to local growers to plant in the vicinity of their groves….. some species also produce valuable timber.

41. M. Aluja, T. Holler, P. Rendon, K. Bloem, G. Baeza, M. Lopez, Ma. Lopez, R. Montoya, T. Wong, R. Baranowski, E. Burns, J. Brambilla, B. Wharton, R. Messing, E. Harris, M. Purcell, E. Knipling, H. Glen, G. Posey, C. Calkins, S. Lux, B. Copeland, M. Trostle, J. Pinero, F. Jeronimo, G. Tween, D. Harris, J. Diaz, J. Cancino, B. Heath, P.Teal, C. Jenkins, V. Sugyama, V. Yokoyama, E. Menezes, A. Eitam, R. Vargas, S. Frazier, P. Graham, N. Lowman, H. Burnside, B. Dueben, R. Pereira by

42. A. BASIC SEXUAL BIOLOGY: Sterile Insect Technique (SIT) requires rearing sexually competitive and attractive males for release. The standards of effective quality control arise from a thorough understanding of the target species’ sexual behaviors. Tephritids produce chemical, acoustic and visual sexual signals. Past research has centered on the first two of these channels, but the last is are poorly understood. Recent work examines color patterns, including UV, on the wings. Sivinski, Pereira and Aluja

43. a a b b b b c c B. MANIPULATION OF DIET TO PRODUCE MORE FIT INSECTS: Sterile Insect Technique (SIT) is a biologically based technique that is widely used in fruit fly control and can be integrated with natural enemies. Applications of juvenile hormone and improved diets can improve released male sexual performance. Pereira, Sivinski and Teal

44. C. Ecology in support of novel genetic-based controls Conditional Genetic Expression techniques may eventually replace radiation as a means of obtaining males for autocidal controls. One possibility is to release males, unharmed by radiation, whose offspring will die when a certain temperature is reached. Such schemes relay on an understanding of the thermal environment of the target pest, including the temperatures encountered by eggs, larvae and pupae in fruit and in the soil. Sivinski, Holler and Handler

45. A. The “domestic” search for new natural enemies For example- new pupal parasitoids: pupal parasitoids might attack hosts that had escaped larval parasitoids and provide another “line of defense”. • Coptera haywardii • Eurytoma sivinskii • Dirhinnus n. sp (?) • Pachycrepoideus vindemiae (intr.)

46. Rendon, Sivinski, Holler, Bloem et al., submited