Chapter 1 Study Questions
List the Illinois noxious weeds & their life cycles
Annuals: common ragweed, giant ragweed, & marijuana/hemp Biennials: musk thistle Perennials: Canada thistle, Johnsongrass, perennial sowthistle, & sorghum-almum
What are the 4 important rules a scout should follow when monitoring pests?
1. All pest counts must be taken from representative areas of the field 2. A scout must keep a good record of each visit 3. Fields should be monitored @ least once a week 4. Scouts must efficiently use their time wisely
What are the 4 methods of disease control considered in an IPM program?
1. Avoidance 2. Exclusion 3. Eradication 4. Protection
List the 5 groups of plant pathogens that can cause infectious diseases
1. Bacteria 2. Fungi 3. Nematodes 4. Viruses 5. Parasitic Seed Plants
What are the 6 IPM methods of pest control?
1. Cultural Control 2. Mechanical Controls 3. Variety Selection 4. Biological Control 5. Regulatory Control 6. Chemical Control
Give an example of rodent/bird control for the 5 IPM methods
1. Habitat manipulation or sanitation: removing or modifying 1 or more of the ingredients (food, water, cover, etc.) necessary to support life 2. Exclusion: keeping animals out of an area through mechanical means 3. Repellents: using chemical or mechanical agents such as carbide cannons, to ward off or frighten pest animals 4. Relocation: trapping & relocating offending animals 5. Population reduction: killing animals that are causing damage by shooting, trapping, or poisoning
List 6 problems that you might encounter when scouting for diseases
1. Leaf blights 2. Leaf spots 3. Stem Cankers 4. Galls 5. Root Rot 6. Wilting, yellowing, stunted growth, & dead plants
Give an example of insect control using each IPM method
1. Pesticides: insecticides 2. Cultural Controls: crop rotation 3. Mechanical Controls: screens to keep out insects & traps to catch them 4. Resistant plant varieties: that limit insect attack 5. Biological Control: through the use of parasites, predators, & diseases 6. Regulatory Control: through plant, animal, & vehicle quarantines & inspections @ national, state, & even local borders
What methods of weed control are available to you? Define/describe them
1. Preventive: using weed-free seed & transplants; cleaning tillage, harvesting, & transport equipment before leaving an infested area 2. Mechanical: hand pulling, hoeing, rotary hoeing, cultivating, & mowing 3. Cultural: making the crop more competitive w/ weeds; manipulating planting & harvesting dates, planting rates, & row widths to maximize crop competitiveness 4. Biological: insects, diseases, or parasitic plants can be used as control agents to reduce weed competitiveness 5. Chemical: using herbicides to control weeds
What are the 4 major steps in disease diagnosis?
1. Scout the field & note problem areas 2. Examine the plants & note the plant part effected, symptoms of disease, & signs of pathogens 3. Observe the field & note the infestation pattern, field conditions, field history, & weather conditions for the past 10-14 days 4. Consult references to assist you in disease identification or consult your county extension advisor
List the 4 conditions necessary for a plant disease to occur
1. Susceptible host plant 2. Disease-producing agent 3. Favorable environment 4. Time for the disease to develop
What information do you need to determine economic threshold for weeds?
1. the market price of the product 2. the cost of all control measure 3. the value of product loss (yield & quality) caused by weeds 4. the value placed on ease of harvest, cleaner field, & less weed seed returned to soil
Describe the 2 main objectives of an IPM program
1. to keep pest populations below the economic injury level 2. to avoid adverse effects to humans, wildlife, & the environment
What are the basic types of grass growth habits & inflorescences?
Basic types of Grass Growth Habits: bunch-type, rhizomatous, & stoloniferous Inflorescences: Raceme, Panicle, & Spike
Why is it important to identify insects correctly?
Before you can control an insect, you must identify the insect & understand its life cycle so that the correct control measures can be applied/used @ the appropriate time
What are some examples of beneficial & injurious insects?
Beneficial Insects: dragonflies, praying mantids, soldier bugs, ground beetles, lady beetles, hornets, wasps, & robber flies Injurious Insects: European corn borer, corn ear worm, some grasshoppers, bagworm, & tent caterpillars
Name the different types of insect mouthparts. What are some examples of insects w/ these types of mouthparts? What do these insects feed on?
Different types of insect mouthparts: chewing mouthparts & sucking mouthparts Chewing Mouthparts: dragonflies, grasshoppers, mantids, eetles, caterpillars, ants, & wasps -plant material, must be chewed up prior to swallowing Sucking Mouthparts: bees, butterflies, & moths -nectar,liquids, & juices
Describe the characteristic parts of a grass weed seedling. Distinguish between barnyard grass & yellow foxtail in the seedling stage using these characteristics.
Collar region: where the leaf blade & sheath join, includes the ligule & the auricles; the ligule extends upward on the inside of the collar region & appears as an extension of the sheath where it joins the blade Barnyard Grass: ligule is absent Yellow Foxtail: ligule is hairlike Auricles if present are earlobe extensions from the base of the blade around the shoot; either are long & clasping or short
Name the life stages in a Complete Development aka 4 Stage Life Cycle of an Insect
Egg, Larvae, Pupa, & Adult
Name the life stages in an Incomplete Development aka 3 Stage Life Cycle of an Insect
Egg, Nymphs, & Adult
Name some common contact herbicides. Are they applied to the soil, the foliage, or both? What are the injury symptoms of these herbicides? Where do these symptoms appear on the plant?
Examples: Gramoxone, Basagran, Blazer, Tackle, Cobra, & Reflex: damage the membranes that absorb them by destroying cells in the leaves; activity is increased by high volume sprays & surfactants which increase herbicide coverage on the leaf surface applied post emergence: symptoms of injury are rapid death of the tissue covered w/ the spray (necrotic spotting); occurs faster in bright sunlight when temps/humidity are high
Name some common photosynthetic-inhibitor herbicides. Are they applied to the soil, the foliage, or both? What are the injury symptoms of these herbicides? Where do these symptoms appear on the plant?
Examples: triazines, ureas, & uracils: Atrazine, Bladex, Princep, Sencor, Lexone, Lorox, & Sinbar applied to the soil: injury symptoms appear first on the oldest leaves & progress to the youngest leaves; begins after the seedling depletes food reserves in the cotyledons applied to foliage: act as contact herbicides causing necrotic spotting where the herbicide droplets are deposited on the leaves
How do temperature, moisture, & sunlight affect herbicide activity?
High temps/humidity increase herbicide activity so that less herbicide is needed for weed control Low temps may cause some post emergence herbicides to be ineffective Too much rain may wash the herbicide out of the target area or off treated plants Adequate soil moisture + high temp aids herbicide activity buy may also increase the rate @ which soil-applied herbicides break down, thereby reducing the duration of residual activity Dry soil doesn't allow for adequate uptake of soil-applied herbicides or rapid breakdown of the chemicals Sunlight breaks down some pesticides: photodegradation/photolysis
What 2 general types of infection do diseases cause?
Localized Infections: pathogens only infect certain parts of the plant; leaf blights, leaf spots, stem cankers, galls, & root rots Systemic Infections: diseases that affect the entire plant; wilting, yellowing, & stunted growth; often kill the plant
What are some examples of insect relatives? Name @ least one characteristic that makes them different from insects
Mites, ticks, spiders, centipedes, & millipedes -Ticks dont; attack plants
How can a plant disease be distinguished from an injury?
Plant diseases differ from nonparasitic injury in the length of time during which they affect the plant -disease usually consists of a series of harmful processes that occurs over a fairly long period of time -injuries are disorders that occur over a short period of time
When is it appropriate to use preplant, early preplant, preemergence, post emergence, & directed post emergence herbicides?
Preplant: applied before the crop is planted Early Preplant: applied several weeks before planting Preemergence: applied either before or after the crop emerges, but must be applied before the weeds emerge Postemergence: applied to the foliage for serval hours to be effective after the crop or weeds have emerged Directed Postemergence: less selective herbicides are directed away from the crop & onto the weeds to minimize crop injury
What is the 1st step in disease control?
Prevention
At what stage of growth are weeds, regardless of life cycle, most susceptible to control?
Seedlings
Compare & contrast selective & nonselective herbicides. In what situations should each be used?
Selective Herbicides: control certain plants (broadleaves or grasses) w/ little or no injury to others -useful for row crops, pastures, lawns, & other areas w/ desirable vegetation -2,4-D, Banvel, & Basagran (examples) Nonselective herbicides: are toxic to almost all plants -useful in areas where total vegetation control is desired (along fences, around buildings, & in other non crop areas) -Roundup & Gramoxone/Paraquat (examples)
Compare & contrast systemic & contact herbicides. When should each be used?
Translocated (systemic) herbicides: move through the plant from the site of uptake (can either be roots or emerging shoots for soil-applied herbicides or the foliage or stem for post emergence herbicides) -the plant must be actively growing for these herbicides to move to the sites of action; older weeds or weeds that are growing under dry or cool conditions may require a higher herbicide rate than weeds that are actively growing Nontranslocated (contact) herbicides: are active @ the site of absorption (they don't translocate w/in the plant) -kill actively growing foliage on contact; can be effective in controlling annual plants if all the growing points are aboveground & receive a thorough spraying -used before no-till planting to burn back existing vegetation -used to desiccate or defoliate plants in order to improve harvesting conditions
What is the definition of a weed?
a plant growing where it is not wanted or "a plant out of place" -reduce crop yields by competing with more desirable plants for moisture, nutrients, light, & growing space
What is Chemical Control?
an integral part of an IPM program; with scouts monitoring the pest situation in the field, pesticide applications can be timed more accurate for more effective control -integrated pest mangement should optimize control of pests, NOT maximize control -chemicals should be used only after economic, sociological, & ecological concerns have been carefully considered
What are the important characteristics used to identify broadleaf plants?
the arrangement of the leaves along the stem (alternate, opposite or whorled), leaf & cotyledon shape, type of leaf margins, & other characteristics (color, root system, flowers) can be used to identify broadleaf weeds
What is economic threshold?
the number of insects per plant or the amount of damage to a plant that economically justifies the use of control measures
What is Regulatory Control?
can often be attained through plant, animal, & vehicle quarantines & inspections @ national, state, & local borders; have helped prevent the entry & spread of destructive insects & pathogens -many common destructive pests were imported from other countries
What is Variety Selection?
choosing plant material that is resistant or tolerant to damage caused by insects or disease pathogens; you can select varieties adapted to local conditions & compatible with your cropping practices that consistently produce high yields
What is an annual weed?
complete their life cycle w/in 1 year; -reproduce from seeds only -most easily controlled in the seedling stage -to minimize the seed source in the soil, annuals should be controlled before they produce seeds
How should you scout for weeds?
early season weed scouting should be conducted w/in 2 weeks after crop emergence to evaluate the performance of soil-applied herbicides & to determine whether rotary hoeing, cultivation, or a post emergence herbicide application is needed -identify & record the level of infestations of all the weed species found -determine the intensity of each species present by counting the number of weeds per 3 feet of row in all of the areas sampled -rank species from the most to the least commonly found -make weed map for each field to indicate the location of the weed infestations -fields should be surveyed again during late July or August to determine the locations & extent of weed infestations
When must weeds be controlled in order to prevent yield reduction?
if weeds are kept out of the field for 4-6 weeks after crop emergence (generally by using soil-residual herbicides) any weeds that invade later shouldn't significantly reduce yield weeds can generally grow w/ a crop for 3-5 weeks w/o causing field losses as long as the weeds are subsequently controlled & the crop remains weed free until harvest
What are symptoms? (Think plant diseases)
indications of disease that affect the external or internal appearance of the plant: these are produced when plants react to pathogens -used to help identify the pathogen & may ultimately help determine the exact cause of the disease -common symptoms: wilting, yellowing, leaf spots, blights, dropping leaves, & necrosis (death of tissue)
What is a biennial weed?
live for 2 years; seeds germinate in the spring -usually occur in pastures & fencerows that aren't mowed -reproduce from the seed only -most susceptible to chemical control as seedlings or in the rosette stage, but are best controlled beef they produce seed
What is a perennial weed?
lives for more than 2 years; classified as either herbaceous or woody, depending on wether the stems overwinter -more prevalent in no-till crops, pastures, fencerows, & other areas w/ minimum soil disturbance -complete control of perennial frequently requires more than 1 treatment
Name some common meristematic-inhibitor herbicides. Are they applied to the soil, the foliage, or both? What are the injury symptoms of these herbicides? Where do these symptoms appear on the plant?
root inhibitors: Treflan, Sonolan, & Prowl; don't translocate, inhibit root growth of seedlings growing through the herbicide layer; aboveground parts are stunted, wilted, swelled, or purpled (1st symptoms) -injury symptoms are more likely during cool, wet weather or when excessive rates are applied shoot inhibitors: acetanilides (Lasso & Dual), thiocarbamates (Sutan+, Eradicane, Genate, Eptam, Eradicane Extra, & Genep); translocate upward n the plant & inhibit shoot growth of seedlings going through the herbicide layer -injury symptoms: leaf crinkling or drawstringingn of broadleaf plants, & onion leafing, buggy whipping, & underground leafing out of grasses shoot & root inhibitors: imidazolinones (Scepter & Pursuit), sulfonylureas (Classic, Harmony, & Pinnacle), & premixes containing sulfonylureas (Preview, Canopy, Gemini, & Lorox Plus); amino acids (Roundup), & miscellaneous postemergence grass herbicides (Poast, Option, Fusilade, & Assure) -imidazolinones & sulfonylureas inhibit root development of grasses by causing pruned lateral roots; plants become stunted & occasionally the leaves appear striped (internal chlorosis) -broad leafed plants also become stunted & the leaf margins take on a chlorotic appearance similar to that caused by potassium deficiency
What is the key to a successful IPM program?
scouting
Why are perennial weeds more likely to thrive in unmowed or no-till sites than in frequently tilled areas?
soil hasn't been which allows for the regrowth of perennials via seeds, root structures, or vegetative reproductive parts
What are signs? (Think plant diseases)
structures or parts of the pathogen itself; they aren't produced by the most plant -examples: fruiting, or spore-producing structures, a mat of fungal tissue (mycelium), overwintering structures, nematode galls or cysts, & bacterial exudate
Why is it important to know the different types of development when controlling pests?
the 2 different types of development influence which measures are used to control insect pests Incomplete development: damaging stages=adults & nymphs Complete development: larval or adult stage=damaging stage (usually only has 1 damaging stage)
What is economic injury level?
the point @ which the cost of pest control equals the revenue loss caused by a pest -is determined by estimating the potential yield loss, the value of the crop, the cost of treatment -defines how much damage can be tolerated
Why is scouting important?
the scout: collects the data about which pests are causing damage, what stage of life each pest is in, & whether the pest population is increasing or decreasing
Why is it important to correctly identify weeds before implementing a control program?
the weed control method should be chosen based on the type of plant, its life cycle, & its method of reproduction -plants of all life cycles are easiest to control when they're seedlings
What is an economic threshold for weeds?
the weed density at which control is economically justified because of the potential for yield reduction
What are Mechanical Controls?
used to exclude pests; include hand destruction as well as the use of screens to keep out insects & traps to catch them; traps aren't very successful
What is Cultural Control?
used to make the crop environment unsuitable for pests to feed, live, or reproduce & to improve the health of the crop; can influence pest populations for years -cultivating, rotary hoeing, draining wet areas, changing planting dates, harvesting early, using trap crops, plowing down crop debris, using proper fertility, & rotating crops