Biological Control

1. Historical Background What is Biological Control Principles Examples “If you want milk with little blue dots, you’ll have it, as long as you’re willing to pay for it.” Richard Cotta, CEO of California Dairies Inc., Biological Control

2. The first possible use of biological control was somewhat ancient and most likely accidental

3. The Aztec people were a hunter-gatherer people, late comers to the region in Central Mexico that served host to other developed civilizations. According to legend, they would find their new home where and eagle holding a snake would be perched on a cactus on an island. Thus they settled in an marshy area now known as Mexico City, where ruins can be found.

4. Chinampas – “floating gardens” constructed of wattles or reeds tied together and layered with mud, lake sediment, and aquatic weeds.

5. The richness of the chinampas encouraged antagonistic organisms Eventually the chinampas became anchored by plant roots Grew plants in seed beds and transplanted to chinampas Soil contained many different biological control agents in equilibrium such as Trichoderma, Pseudomonas, and antagonistic Fusarium

6. Vile Concoctions Nectria galligena – a fungus, European Apple Canker Austen, 1657 - treat fresh pruning wounds with cow dung and urine to prevent apple canker Wounds are prime sites for infectious agents such as fungi and bacteria

7. Vile Concoctions for Tree Wounds Forsyth, 1791 - fresh cow dung, lime, wood ashes, and sand Le Barryais, 1785 - fresh mud Weidlich, 1979 – soil on Cryptonectria parasitica (Chestnut Blight) cankers, Trichoderma sp.? MacDonald et al., 1979 - soil applied to American chestnut caused Endothia parasitica cankers to heal - Trichoderma sp.?

8. What is Biological Control? Pest suppression with biological agents operating in a background of integrated control that does not depend on host resistance, sterilization of the target pathogen, or modification of pest behavior

9. Is Biological Control Biotechnology? Biotechnology is a set of tools that utilize living things (and more recently, derivatives of living things) to solve problems or to produce products. Of course it is!

10. Biological Control Involves Destruction of the propagative units or biomass of the pathogen. Prevention of inoculum formation. Weakening or displacement of the pathogen in infested residue. Reduction of vigor or virulence of the pathogen by agents such as mycoviruses or hypovirulence determinants.

11. Where Do You Find BC agents? Suppressive soils Old world New world Plant pathogens By accident On plant materials On “sick” pathogens and pests

12. It’s a Matter of Survival… Most of the antibiotics discovered since Fleming’s discovery of penicillin are from soil saprophytic microorganisms Meanwhile…….. Pythium debaryanum – pine seedling damping-off, Hartley, 1921 Streptomyces scabies – potato scab, grass clippings reduced disease, Millard and Taylor, 1927

13. Biological Control Sanford and Broadfoot, 1931 - first used “Biological Control” in plant pathology 40 bacteria, 24 fungi Organisms or culture filtrates in sterile soil Found organisms more effective against Gaeumannomyces graminis var. tritici Suppressive soils are locations or sites where a disease decreases gradually over time under continuous cropping with the same crop.

14. Suppressive Soils Reinking and Manns, 1933 Central America soils Fusarium oxysporum f. sp. cubense - Panama disease of banana Pathogen isolated from sandy soil but not from clay soils Sandy soil plantings last 10 years (conducive)‏ Clay soil planting last 20 years (suppressive)‏

15. How Do Suppressive Soils Work? Gerlagh, 1968 4 successive crops in soil increased suppression of Gaeumannomyces graminis var. tritici Steaming destroys antagonists R. James Cook, David Weller, Linda Thomashow USDA/ARS, WSU Pseudomonas fluorescens, P. aureofaciens 2-fluoroglucinol

16. What Kinds of Things Function as Biological Control Agents? Microorganisms Bacteria Fungi Nematodes Viruses • Macroorganisms • Insects • Man • Animals

17. Biological Control Mechanisms Competition – the BC agent more efficiently utilizes space and nutrients. Antibiosis – the BC agent produces one or more deleterious compounds. Parasitism – the BC agent utilizes the target for food or for reproduction. Induced resistance – the BC agent indirectly stimulates the plant to be resistant.

18. How are Biological Agents Applied? Importation Augmentation Conservation of Natural Enemies

19. Importation When the pathogen is exotic. Identify origin of pathogen or pest. Search for natural enemies Get USDA permission to import Adult Bathyplectes anurus , a parasitoid of alfalfa weevil larvae. Photo courtesy USDA APHIS

20. Augmentation • Augmentation is the direct manipulation of natural enemies to increase their effectiveness. • Mass production and periodic release (colonization) is the most common approach. • Genetic enhancement • Augmentation is not permanent, and requires reapplication of the agent.

21. Conservation Conservation is the identification and modification of any number of factors to increase the effectiveness of natural enemies.

22. Biological Control Targets Agents that cause plant disease Agents that cause plant damage Weeds

23. Plant Diseases vs Plant Damage: What’s the Difference? Plant disease is the abnormal physiological response of the plant to a chronic association with a primary causal agent. Plant damage is destruction of tissue due to an acute association with an agent.

24. What is a Plant Disease? Plants can become “sick” due to infection by a variety of organisms. Insects Fungi Bacteria Viruses Nematodes Definition of a plant disease: The abnormal physiological response of a plant due to a chronic association with a primary causal agent.

25. Sick Plants Display Symptoms Blemishes or lesions (dead tissue)‏ Leaves, stems, flowers, fruit Reduction in growth Loss of color Abnormal growth Browning or yellowing Wilt Death

26. Sick Plants May Show Signs A sign is a direct evidence of the presence of the pathogen Insect poop Bacterial ooze Cottony fungal growth Nematode cysts

27. How Do We Control Plant Disease? Crop Rotation - lower inoculum density Adding Amendments - antagonist stimulation Alter pH Tillage - modify soil structure or aeration Planting date selection Apply organic amendments Irrigation practices Trap plants Adding antagonists Kenneth Baker and R. James Cook. The Nature and Practice of Biological Control of Plant Pathogens

28. Biological Control Targets Agents that cause plant disease Agents that cause plant damage Weeds: Any plant that is growing where it is not wanted

29. Insects are the primary biological agents that have been used to combat noxious weed pests

30. Why Insects are Good Biological Control Agents Can be raised in mass quantities Fairly specific Mobile Reproduces in the field Can be combined with other insect agents

31. Weeds Cause Problems Prevent establishment of a good crop Compete with the crop for: Water and nutrients Sunlight In some instances, harbor pathogens

32. What is a Weed? A weed is a plant that is growing where you do not want it. A Noxious Weed is a weed that is Not native – i.e. alien Aggressive Highly competitive Highly invasive

33. Traditional Weed Control Herbicides Effective Low labor demands Cost effective Chemicals such as 2,4-Dichlorophenoxyacetic acid (2,4-D) made significant impacts on weed control. RoundUp (Monsanto) – binds phosphoenolpyruvate, stopping amino acid synthesis

34. Why Bioherbicides? High yield losses still occur $619 million in vegetable, $441 million in fruit and nut crops in the US Herbicide resistant weed population Detrimental effects on non target organisms Native plants FQPA 1996 World War II

35. Why Bioherbicides? Demand for decreased use of pesticides Large areas where herbicide application not possible or not cost effective Damage to the environment Contamination of our water supply

36. Noxious Weeds Leafy spurge has infested three million acres of rangeland. It is an aggressive weed that displaces native vegetation and degrades grazing lands.

37. Leafy Spurge A deep rooted perennial that reproduces by seeds and roots

38. Leafy Spurge First introduced into the United States in 1827. Blazed across the US to the west. Reduces rangeland productivity by 50 to 75 percent

39. Leafy Spurge Cattle usually avoid eating leafy spurge However, when cattle eat leafy spurge they become sick and even die Economic losses in Montana, South Dakota, North Dakota, and Wyoming are estimated to exceed $120 million However leafy spurge is still sold as an ornamental plant

40. Leafy Spurge Control Difficult Deep rooted Can expel seeds up to 15 feet Dispersed by birds Biological agents Six species of flea beetles One specie of slender beetle

41. Leafy Spurge Control Biological Agents One specie of moths One specie of flies Reduces bud gall fly Beetles and moths reduce plant growth Adult feeding Larval feeding on roots Sheep and goats

42. Other Weed Killers Insects Bacteria Fungi Man Animals

43. Attributes of Bioherbicides Produce abundant and durable inoculum in culture Be target specific Be genetically stable Be capable of killing a significant portion of the weed population under a variety of environmental conditions (weed densities)‏

44. Fungal Weed Killers First pathogen isolated for weed control, Colletotrichum gloeosporioides, 1971. Strangler vine on a Cyprus tree. The weed became a major pest of citrus groves in Florida.

45. Fungal Weed Killers – De Vine Phytophthora palmivora - DeVine, Abbot Laboratories, 1981. First commercial microbial product for weed control. Chlamydospores Strangler vine in citrus orchards Isolated from dying plants found in a grove 96% weed kill and lasts 2 years post application Pathogenic on onion, cantaloupe, okra, tomato, endive, cucumber, squash, etc.

46. Non-commercial Success Chondrilla rust - skeleton weed - Australia Skeleton weed Mediterranean and Middle East origins Invaded southeast Australia Three morphological forms Puccinia chondrillina - rust fungus Narrow leaved strain Intermediate and broad leaved strain

48. Bacterial Biological Control Agents Xanthomonas campestris pv. poannua - postemergence activity on annual bluegrass in bermudagrass lawns (Johnson, 1994: Johnson, Wyse, Jones, 1996). Pseudomonas syringae pv. tagetis - Canada thistle in soybean (Johnson, Wyse, Jones, 1996).

49. Nematodes - Roundworms Small (0.60 – 2 mm long), microscopic eukaryotic worms. Lifestyles – Good and Bad Animal pathogens Plant pathogens Nematode feeders Insect pathogens Saprophytic

50. As Plant Parasites Stunting Chlorosis Mid-day wilting Leaf drop Small fruit Yellowing Curling and twisting of leaves and stems Galls Stubby roots Reduced growth