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Plant Insect Interactions Phytophagous insects that eat plants...phyto-plant--phagous-eating Macerate Rip off, chew up, and make a pulpy mess from plant material A. Insects feed on plants where? 1) Insect inside plant 2) Insect outside of plant a. Borers go inside plant tissue b. Miners eat out the idle of the leaves c. cause plant deformations (e.g. Galls) d. Can suck plant juices e. Can chew plant tissues 3) Insects and their host plants a. Monophagus an insect that eats just one host species...mono-one--phagous-eating b. Oligophagous have a few host plants they will eat c. Polyphagus eat many plant species 4) How do they find host plants? a. Trial & error b. Mom c. Colony B. Types of insect feeding 1) Chewing heads are heavily muscular; consume leaf tissue (most chewers) a. Margin feeders feed on the edges b. Skeletonizers feed on the upper OR lower layers of the leaf c. Miners eat between the upper and lower layers of the leaf (?asdyrksasdfkj?) 2) All leaf diners are in 1 of 4 orders a. Lepidoptera b. Diptera c. Hymenoptera d. Coleoptera 3) Leaf rollers, tyers, folders 4) Boring insects very powerful mandibles a. Legless b. Mouthparts point forward (prognathus) c. Pale and white d. Very powerful mandibles e. Micro organisms in gut to break down cellulose from plant to make energy f. Some make characteristic galleries i. Patterns beneath bark adults eat wood ii. Feed on fungus in galleries immatures g. Some bore through fruits h. Some bore through seeds i. get H2O by making it 1) ?Metabolic? water 2) Use hydrogen + oxygen C. Challenges to feeding 1) Penetration a. see handout A 2) Leakage a. Occurs when it penetrates the cell and doesn't do anything b. Refer to drawing in notes c. Salivary Gland Contains enzyme (Runny saliva) i. Viscous saliva 1) Plugs hole (chewing gum) 2) Pushed through salivary channel first 3) When w/air almost immediately turns solid 3) Digestion a. Material goes through food channel b. Two reasons why they poop a lot i. Excess H2O ii. Low concentration of protein, high carbs iii. Don't need it, so ingest and let out 4) Ingestion a. Honeydew i. watery, sugary, poop (solution) b. Allows food to go to food channel D. Galls 1) Plant makes more tissue to wall at point of invasion 2) Emits chemicals that make plants create galls so it can feed on it 3) Abnormal growths: Buds, leaves, stems, roots 4) Formed by a. Fungi b. Bacteria c. Nematodes d. Mites e. Insects trick plant into forming galls i. Following orders 1) Diptera (midges) 2) Hymenoptera (some wasps) 3) Coleoptera, Homoptera, Hemiptera, Lepidoptera a. Only a few of these species 5) Types a. Indeterminate slightest swelling of plant tissue with no distortions or coloration i. hard to see use unless know plant species b. Determinate obvious distortions in plant tissue and different color/textures E. How does an insect find an acceptable host plant? (Host finding sequences) 1) Search for a suitable habitat vision 2) Settle on a plant and the most suitable plant parts a. Some vision but mostly by order 3) Food plant acceptance taste testing a. Critical step b. Odor, gustatory (taste), texture 4) Feeds to satiation a. Phagostimaulants = feeding stimulus i. Must be present to keep insect feed on plant F. How nutritious are plants 1) Cellulose a. Complex carbs b. Most insects cannot use for nutrition 2) Proteins a. Most must come from plant 3) Cholesterol a. Insects cannot live w/out it b. Must get these from plants 4) Vitamins D, K, B a. can synthesize several of these i. especially in `B' group 5) Vitamin C a. Must obtain from plant 6) Vitamin A a. Need to get from plant tissue 7) Age of plant tissue matters a. youngest i. best proteins ii. most moisture rich iii. concentrations of other special nutrients Insect plant interaction: Wrap up on phytophagus insects Polyphagy v. monophagy A. Polyphagy eat many plants 1) Advantages a. Lots of food b. Food is nearby minimizes searching c. Advance Distribution into different areas B. Monophagy eat one food 1) Advantages a. Reduced competition for food b. Much easier to find a mate c. Chemical smell repels nasty insects 2) Disadvantages IF your host goes extinct, so do you Insect Plant Interactions Plant Defense Against Insect Attack (Virulent) Phytophagus eat susceptible plant species (they eat almost all of em). Resistant plants are fine for awhile, most insects that fed of them die. Some live and they can eat the resistant plants and cycle starts again. Co-evolution 2 species significantly influence each others development through time. Categories of Plant Defenses Against Insect Attack I. Morphological Resistance 1) Disrupt the host finding 2) Stop/slow indigestion 3) Impedes digestion 4) Interfere w/mating 5) Interfere w/egg laying A. Remote Factors 1) These operate remotely (at a distance) 2) Changes in shape by host plant 3) Changes in color of host plant B. Close Range 1) Operate when they are on the plant attacking 2) Thickened cell walls a. Cellulose and lignim no nutritional value b. Takes longer to chew c. Takes longer to and interferes w/digestion 3) Stem characteristics a. Solid stems b. Wound response i. Sap ii. Fast growing cells c. Trichomes (little hairs) greatest morphological defense against insect attack i. Mechanical Impale insects OR hooks tear open insect cuticle ii. Most effective when they are denser 1) Angled at 90 degrees 2) Pointed in shape 3) Longer is better iii. Glandular sticky trichomes most effective against piercing/sucking parts d. Silica some plant cells have this i. rice/ horsetails e. Surfaces waxed i. gums up mouth parts, impedes digestion II. Chemical Defenses most important deterrent to insects a plant can have 1) Are allomones 2) Deters feeding 3) Act as repellents 4) Can be and often are toxic to insect, can also regulate insect growth A. Nitrogen Compounds 1) Prevent insects from using ingested plant tissues, protein blockers B. Alkaloids 1) Complex nitrogenous compounds C. Terpenoids 1) One of the largest and most biologically important classes of plant defense chem. i. Widely distributed, chemically diverse ii. No nitrogen iii. Primarily feeding deterrents iv. Can be toxic v. Pyrethrins come from chrysanthemum D. Phenolics i. Functions as protein absorbers ii. Functions as feeding inhibitors iii. Functions to reduce digestibility iv. Tannins Oak Leaves v. Rotenone Kills insects or makes sterile E. Proteinase Inhibitors clings to enzymes to prevent them getting cut up F. Insect Growth Regulators 1) Juvenile Hormones i. Release hormones to keep in youth state ii. Plant does well in long run 2) Molting Hormones i. Lethal premature molt ii. Or becomes sterile from molt III. Nutrition 1) Plant to plant variation 2) Plant part to plant part varaiation 3) Weather Drought stressed is more nutritious to insects 4) Fertilizer nitrogen rich insects do better 5) Escape in time in place IV. Attracting Natural Enemies 1) Extra floral nectarines a. Produce a sugar that draws predators enemies V. Insect eating plants Insectivorous or Entomophogous 1) Must have a way to attract insects 2) Must have a way to entrap insects 3) Must have a way to digest insects 4) To trap they use one of three things: a. Sticky surfaces b. Modified structures don't move c. Modified leaves that move VI. Types of eating plants 1) Fly catcher plant a. Dry regions of Protugal and Morocco b. Sticky attractant Gland c. containing enzymes 2) Pitcher Plant a. Modified structure that doesn't move b. Trichomes that only open one way 3) Sundew Plant a. Modified leaves that move Entomophagous Predators and Parasitoids A. Entomophagous insects insects that eat other insects (Insectivorous) 1) Two kinds of Entomophagous insects a. Predators insects that capture and consume prey b. Parasitoids Insects that live in or on an insect host feeding and eventually killing B. Predators catch prey in three ways 1) Search in air, on ground, or on plant surfaces 2) Stalk Relatively still, start creeping up on prey 3) Trap Make special structure/device C. Have adaptations to some body parts D. Most are oligophagous not polyphagous (Lady Bird Beetles) 1) Some are monophagous (few) E. Parasitoids characteristics 1) Adults do not feed on host, feed on nectar sources 2) Lay eggs on or in host 3) Smaller in size than host 4) Sometimes, numerous parasitoids develop within a single host a. Superparasitoidism also called (superparasitism) 5) In some cases, parasitoids are hosts to other parasitoids a. hyperparasitoids, a parasitoid that emerges from another parasitoid F. Diversity among parasitoids 1) Oviposition (egg laying) a. Lay one egg in host b. Lay many eggs in one host c. Lay eggs in host egg d. Lay eggs in host immatures larvae pupae e. Lay eggs in adults 2) Metamorphosis a. Hypermetamorphosis extra metamorphosis 3) Embryology a. One Egg Many progeny All same gender/genetically 4) Reproduction a. Parthenogenitally w/out fertilization asexual b. Mate occasionally males exist, but are rare c. Some mate always -Life histories 1) Phoresy wasp that waits on mantid for it to lay eggs All Parasitoids Are In One Of Two Orders A. Diptera : Tachina Flies 1) Characteristics of Tachina Flies a. Hairy b. Almost all tachina flies complete development inside host c. Most lay eggs on immatures d. None are hyperparasitoids e. Most lay eggs on outside of host B. Hymenoptera 1) Characteristics a. Many, many, species b. Highly adaptable to being parasitoids c. Detect host w/odors d. Lays eggs w/ovipositor e. Ovipositor can be short or long Blood Feeders, Parasites, and Scavengers I. Why study some of these insects? 1) They bite 2) They're parasitic nature 3) Some transmit serious disease causing organisms II. Blood Feeding Insects Hematophagous 1) Most blood feeding insects feed on warm blooded animals a. Exception: A single midge (diptera) i. Lands on wings of Gpidoptera 2) Most Hematophagous Insects a. Hemiptera b. Diptera c. Exception: Eye Moth only one group sucks blood 3) Problems faced by blood eaters a. Must efficiently find host b. Must be able to pierce skin and pump blood c. Must be able to engorge to satiation without being detected/destroyed d. Must be able to live on blood, which is protein rich but deficient in vitamins 4) Mycetomes pockets of symbiotic microorganisms 5) Biting flies characteristics a. Very mobile b. Breed in locations far removed from where they feed c. Diverse ways of finding hosts i. Horseflies attracted to moving objects ii. Mosquitoes thermotaxis and chemotaxis d. Steps for Mosquito feeding = vessal feeders i. Land on host ii. Taps stylets on skin iii. Stylets pierce skin iv. Stylets search for and pierce capillary vessel 1) Then insert into capillary 2) Retracts a little and laps up bleeding v. Injects anticoagulant in or around capillary vi. Sucks blood and saliva into midget vii. Feeds until saturation 6) Horse flies, deer flies pool feeders a. Slice a hole in skin b. Produces lots of saliva c. Laps blood pooling in the hole III. Parasites A. Ectoparasites 1) Live in close association with hosts 2) Draw sustenance from host 3) Typically do not kill the host 4) Two insect orders a. Siphonaptera--Fleas b. Phthiraptera--Lice B. Common Characteristics of Ectoparasites 1) Claws/spines helps them to cling to host 2) Flattened bodies 3) Poor eye sight if at all 4) Most wingless 5) Most are blood feeders 6) Most are small in size C. Lice Extoparasites 1) Chewing lice a. Do not take blood meals b. Feed on mammals/birds c. Host specific d. Feed on skin/hair/feathers 2) Sucking lice a. Feed on blood b. Attack mammals only c. Vector disease d. Host specific, can't hang on D. Endoparasites 1. Most parasitic on warm blooded animals (ex. Stylops, Strepsiptera) a. Influence development of reproductive organs b. Intersexes have male and female parts c. Reproductively sterile Parasite constraint 2. Most in diptera a. Endoparasitic only as larva b. Fly larvae infesting wounds of animals = Myiasis i. Facultative Myiasis Doesn't have to be endoparasitic ii. Obligatory Myiasis Have to be endoparasitic iii. Gadding cattle running away from adult fly (Gadfly) iv. Warble bump on back of cattle containing larva of cattle grub IV. Scavengers A. Saphrophagous insects that eat dead stuff i. Necrophagous insects eat dead animal tissue ii. Coprophagous insects that eat fecal matter Insect Bioeconomics, Samplings, and Management Suppression time honored way to deal Synthetic Insecticides work well used exclusively Eradication Emphasis after insecticides became available Insecticide Resistence is a naturally occurring phenomenon **Economic Injury Level Amount of damage caused by insect pest (# of insects) which is equal to the cost of control Indirect damage Damage done to a plant by insects but parts damaged don't go for sale Direct damage Damage done to marketable part of plant, overcompensation can occur Yield curve 3 areas tolerance, linear decrease, disaster Yield curve goes up a bit then drops is the overcompensation jump Economic threshold Level of insect infestation at which were fairly certain will increase to the Economic injury level or beyond ET<EIL Sampling 1) Select small part of field 2) Examine those selected parts 3) Take results from examinations and infer them to whole field 4) Representative sample Relative Methods expressed as number of insects caught per unit of sampling effort 1) Apirator number caught in a 5 min period 2) Sweep nets number caught per sweep 3) Black light trap number caught per night 4) Yellow green sticky paper number caught in a day Absolute methods expressed as number of insects caught per unit area yd2 Insect Pest Management 1) Must know how many are there and then you can use curves to determine yield lost then you compare with economic injury level A. Prevent insect populations from attaining the Economic injury level or greater levels of infestation while at the same time, avoiding unfavorable ecological (eat all food), economic, and sociological (injure peoples perception) consequences The 7 steps of Insect Pest Management (How it is used) 1) Identify the problem 2) Asses the damage by sampling 3) Cost/Benefit analysis...Use ET/EIL 4) Select management tactics 5) Implement the tactic 6) Efficiency assessment 7) Periodic follow-up assessments Management Tactics Regulations Regulatory control works best when geographic barriers are present Host Resistance breed it into the plant Biological Control naturally occurring things that hunt down certain pests predators and parasitoids Biological Control using microorganisms viruses, bacteria, fungi, nematodes Genetics and sterility due to radiation...screw worm fly Behavioral techniques produce sex pheromones place in slow release capsules Insecticides

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