What is Biological Control and Why is it Needed? --Get student views and background --What do you know now about biological control? --What do you hope to learn? Read chs 1 and 2 of text Goals of Biological Control • Global invader suppression: Lower density of invasive pest in the whole landscape, permanently • Help farmers: Keep pest density in crops below injury levels, for one or more seasons Target Groups Usual targets • Insects (whiteflies, aphids, mealybugs, weevils) • Mites (2-spotted spider mite-via augmentation) • Plants (waterhyacinth, Salvinia, thistles, spurge) Rarely targets, but has been done • Other invertebrates (snails, millipedes) • Vertebrates (rabbits, cats) Types of Natural Enemies • Parasitoids • Predators • Pathogens (of both in insects, weeds, vertebrates) • Specialized herbivores Techniques of Biological Control Area wide, Field level permanent control control Against insects or weeds XX XX I, W Habitat manipulation XX I Pathogens as pesticides XX I (W) Insectary releases XX I Classical biocontrol Reasons BC is Needed 1. Invasions of new exotic pests 2. Problems with pesticides Invasions of new exotic pests INSPECTIONS TO SLOW RATE OF PEST INVASION Invasions of new exotic pests INCREASING LOAD OF INVASIVE PEST INSECTS Invasions of new exotic pests OVER HALF OF INVASIVE INSECTS BECOME PESTS Problems with pesticides MANY PESTS ARE RESISTANT TO PESTICIDES A history of the development of resistance to pesticides by Colorado potato beetle on Long Island, New York lead arsenate cryolite flood cryolite pyrethrum pyrethrum sabadilla flood sabadilla lead arsenate nicotine sulphate/fish oil Before 1945, pesticides were based on minerals (e.g., lead, cryolite, arsenic) and plant extracts (e.g., pyrethrum, sabadilla, nicotine, etc) DDT dichloro-diphenyl-trichloroethane Paul Hermann Müller (1899 1965) In 1939, the insecticidal properties of a synthetic chemical, DDT, were discovered. The large scale use of DDT to delouse soldiers and civilians in WWII spurred the creation of an industry for chemical (rather than botanical) pesticides. flood DDT DDT DDT flood DDT flood flood DDT DDT Lead arsenate DDT DDT flood Lead arsenate DDT became widely used for most pests The 1950s and 1960s were the era of chemical pest control This control system 1. Was based on rapid development of many new pesticides 2. Employed pesticides as the sole method of control 3. Used preventative and calendar based applications 4. Treated at the first sign of pests in crop, regardless of number 5. Did not monitor to learn current pest density 6. Was inexpensive and effective but polluting and not sustainable Problems with pesticides USE OF PESTICIDES IN MAJOR CROPS Reasons for the End of the Chemical Pest Control Era 1. Pest control failures due to pesticide resistance 2. Pest outbreaks due to resurgence 3. Pest outbreaks due to secondary pests 4. Environmental contamination with residues Pest Resurgence Natural Enemy (3) www.uky.edu/Classes/ENT/530/Lecture_Notes/ mar29/mar29.ppt Pesticide is applied Pest = 2 Natural Enemy = 0 Pest = 7 Natural Enemy = 3 Pest = 14 Problems with pesticides: Pest control failures due to the destruction of natural enemies (pest resurgence or secondary pest outbreaks) DeBach demonstrated resurgence by using DDT to eliminate Aphytis melinus from citrus groves. Red scale populations exploded Pesticide applied to kill target pest Secondary Pest Outbreak Target pest natural enemy of secondary pest secondary pest In the absence of its natural enemies, the “secondary pest” rapidly increases in density Outbreaks of two spotted spider mites are routinely caused when pesticides applied for other pests kill most of the phytoseiid predator mites that normally control spider mites Pesticides also damaged the environment Influential book sounding alarm over pesticide abuse Pesticides in food chains Bioaccumulation refers to the concentration in a food chain of a fat soluble material such as DDT or PCB. This lead to loss of eagle and falcon populations in wide areas Thin-egg-shell syndrome in raptors, pelicans and other wading birds Illness in farmworkers exposed to fresh pesticide residues use new pesticide Pesticide Treadmill resistance use more pesticide START: Pest Problem chronic outbreaks use more pesticide resurgence & replacement use pesticide www.agls.uidaho.edu/hort_disease/ Lectures/Lecture02_IPM.ppt Shift to IPM In the 1960s, pesticide use dominated pest management. IPM was invented as process to reinsert natural enemies into the control system Critical paper: Stern, Smith, Hagen and van den Bosch,1959 “The Integrated Control Concept” Critical Project: control of the spotted alfalfa aphid Robert van den Bosch was an outspoken critic of pesticide misuse To monitor mites in apples, for example, one has to count the mites on samples of leaves, frequently (1 or 2 times per week) Counting mites Traps can be used to track relative abundance of pests in crops White traps for apple sawflies Yellow traps for whiteflies Red ball traps for apple maggot flies SPRAY DO NOT SPRAY Infestation Level Pest injury levels indicate what density of pests really cause losses spray Economic Injury Level Economic Threshold with control May June July August Deformed frogs: An unsolved problem Caused by herbicides? Looking back: how did use of biological control get started? Before use came knowledge, beginning with understanding of the existence and biology of natural enemies. Predators were obvious, but parasitoids and pathogens were first understood in the 18th and 19th centuries, in Europe parasitioids 1662 WOODCUT IN EUROPE #1. Precedent for classical biological insect control: Vedalia beetle, in CA, controlled cottony cushion scale and saved an young but important industry To import predators into CA from the native range of cottony cushion scale (Australia) required long ship journeys, which required rearing the insects through several generations on board OVER HALF OF INVASIVE INSECTS BECOME PESTS Cryptochetum iceryae also was an important but less visible natural enemy of cottony cushion scale Data showing control of CCS in Australia on caged and uncaged plants- caging raises scale survival from 5 to 50% (Prasad 1989) Data showing that source of control of CCS in Australia varies by season, with Rodolia being the key agent in warm periods and the fly during cooler months (Prasad 1989) Making a Science out of It 1. 2. 3. 4. 5. 6. 1913-hired to give direction to BC efforts of Hort. Comm., which were drifting Began to place use of BC on scientific basis Healed rift with USDA allowing CA to continue to import natural enemies Served as head of BC efforts from 1913 to 1951 Oversaw movement of BC programs from state to University in 1923 Trained first graduate students in biological control Paul DeBach career: 1945-1983 1. Wrote 1964 basic text for science 2. Solved the red scale problem 3. Developed methods to evaluation natural enemy impacts Paul DeBach Control of a GWSS, Plant Disease Vector Mark Hoddle Glassy wing sharpshooter Mark Hoddle and other worked to control glassy wing sharp shooter, a threat to the wine industry. Control has been achieved in CA, Tahiti, and other islands More precedent projects #2. Precedent for classical biological weed control: Introduced moth controlled Opuntia cactus in Australia Infestation in Australia in the 1920s before natural enemy release Of 50 species considered, one (Cactoblastis cactorum) was dramatically successful in reducing cactus density After natural enemy release----collapsing, dying stands of cactus OVER HALF OF INVASIVE INSECTS After death of cacti, land BECOME PESTS became economically valuable for crops again #3. First classical weed biological success in the US : St. Johnswort infestation in CA in 1940s, dominating grasslands Yellow is dense infestation of weed Two species of Chrysolina beetles (Chrysomelidae) controlled the weed in the western US in the 1950s and 1960s Same release site after insects suppressed the weed: a return to native and economically valuable vegetation #4. Precedent for CBC of an insect using a pathogen : Control of the palm pest, rhinoceros beetle, in the South Pacific with an introduced baculovirus On Pacific islands, coconut palms are a basic crop. Rhinoceros beetle larvae feed in and destroy palms An Oryctes virus was found in the pest in Malaysia and introduced to Western Samoa, using artificially infected females as vectors Oryctes virus of rhinoceros beetle on coconut is one of few examples of successful use of an insect pathogen as a classical biological control agent Key biological feature was survival of infected females long enough to vector virus to larval group feeding sites #5. Precedent for augmentative BC of greenhouse insects: Whiteflies are a long standing pest in greenhouse vegetable crops Whitefly nymphs Encarisa formosa showed up spontaneously and was later commercially produced Commercial production methods for E. formosa were developed and a release card that allowed a repeatable number to be applied As hung in the greenhouse As received in the mail #6. Precedent for biopesticides based on insect pathogens: Healthy caterpillar vs one killed by Bacillus thuringiensis healthy Killed by Bt #7 Precedent for CBC of Weeds with Plant Pathogen: Skeleton weed infestations in Australian wheat fields Close up of skeleton weed plant Release of skeleton weed rust as a classical biological control agent MY formative experience with biological control: suppression of alfalfa weevil by introduced parasitoids in the 1970s Hypera postica, the alfalfa weevil, an invasive insect from Europe In the 1970s most alfalfa (millions of acres) in the northeastern US had to be sprayed once or twice per year to control this insect Defoliation of alfalfa by alfalfa weevil larvae Hypera postica, the alfalfa weevil, an invasive insect from Europe Defoliation of alfalfa by alfalfa weevil larvae Bathyplectes curculionis, an ichneumonid from Europe that attacks H. postica larvae Microctonus aethiopoides, a braconid that attacks H. postica adults, reducing oviposition before death Control was complete in the eastern US, eliminating the need for annual pesticide applications on millions of acres alfalfa Kinds of natural enemies • Parasitoids (against insect pests) • Predators (against insects and mites) • Herbivorous insects and mites (against plants) • Pathogens (against insects, mites, plants and vertebrates) Parasitoids Diptera Hymenoptera • Tachinidae • and 11 other minor families • Aphelinidae • Encyrtidae • and 34 other families of some importance TACHINIDAE Compsilura concinnata an important tachinid parasitoid of browntail moth APHELINIDAE (Aphytis melinus) on California red scale PREDATORS Predatory Insects Other Predators • Many orders, especially species in • Coleoptera • Hemiptera • Hymenoptera • Diptera • • • • • spiders mites snails small mammals birds Coccinellidae- ladybirds-mostly generalist predators Twicestabbed ladybird Phytoseiidaepredaceous mites ARTHROPOD PATHOGENS • • • • • Bacteria (e.g., Bacillus thuringiensis) Viruses (e.g., NPV of gypsy moth) Fungi (e.g., Beauveria bassiana) Nematodes (e.g., Steinernema feltiae) Protozoa (e.g., Nosema sp.) Bacillus thuringiensis healthy caterpillar (top) and Bt-killed one (bottom) Insect cells infected with NPV Fungus-killed caterpillar Entomophagous nematode-see stylet Nematode-killed termite HERBIVOROUS ARTHROPODS • • • • • • MANY FAMILIES Dactylopidae Curculionidae Chyrsomelidae Tephritidae Many moth families Dactylopids are important for control of cacti Curculionidae-the weevil Crytobagous salviniae controlled Salvinia molesta