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42 Cards in this Set

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What are the 3 hypotheses given to explain the sudden increase in problems in managing spider mites after World War II? And which one was most often correct?
- Stimulation of mite populations by pesticides and fertilizers.
- Destruction of natural enemies by pesticides
- Escape of prey from predators in time and space due to disruption by pesticides and fertilizers
* pesticides destroyed natural enemy populations (both insect and mite predators) which led to the subsequent escape of spider mite populations from their control
Define hormoligosis.
a stimulatory effect on spider mite reproduction from some pesticides (especially carbaryl and DDT); a general physiological phenomenon that can occur when living organisms are exposed to very low concentrations of otherwise toxic materials
What is IPM?
Involves the use of tactics that are most compatible with each other and have the least negative effect on nontarget organisms and the environment while allowing the crop to be produced economically
What are the components involved in IPM?
- Host plant resistance
- Cultural controls
- Biological controls
- Genetic controls
- Biorational control
What is IMM?
Integrated Mite Management; it is information intensive, requiring considerable knowledge about the biology, ecology, economics, and cultural practices associated with crop production in a specific geographic region
Define economic injury level.
The lowest pest level that will cause economic damage or loss.
Define economic damage.
the amount of injury that will justify the cost of control measures; one must include the cost of applying the control
What is included in biorational controls?
- genetic control of pest species
- use of mating disruption methods
- mass trapping
What is included in cultural controls?
- timing of planting
- harvesting
- dust management
- irrigation
- crop rotations
- quarantines
What is biological control?
The use of parasitoids, predators and pathogens to manage pests
Define the following terms: classical biological control, augmentative biological control and conservation.
Classical biological control - the importation, evaluation, release and permanent establishment in the environment of natural enemies from the area of origin of a foreign pest
Augmentation - involves the mass rearing and release of natural enemies to control a target pest. The natural enemies must be capable of being mass reared and must be released at an appropriate time and in sufficient numbers that they can achieve effective control before the economic injury level has been exceeded.
Conservation of natural enemies involves changing agricultural production practices to enhance the effectiveness of natural enemies in the cropping system.
What are the genetic assumptions for mixtures as a potential method or model of "managing" resistance?
Mixtures
- resistance to each product is monogenic
- no cross-resistance occurs between products in mixture
- resistant individuals are rare in the population
- products have equal persistance
- some of the population remain untreated (refuge)
- resistance is functionally recessive (only homozygotes survive exposure)
What are the genetic assumptions for mosaics as a potential method or model of "managing" resistance?
Mosaics
- susceptible individuals are maintained and able to move into surrounding patches
- may require negative cross-resistance or fitness costs associated with resistance
What are the genetic assumptions for rotations as a potential method or model of "managing" resistance?
Rotations
- the frequency of individuals resistant to one product will decline during application of the alternative product, which is true if there is negative cross-resistance (rare), a substantial fitness cost associated with resistance, or immigration of susceptible individuals occur
What are the genetic assumptions for natural-enemy/pest system as a potential method or model of "managing" resistance?
Natural-enemy/pest system
- food limitation are sufficient to constrain the ability of natural enemies to develop resistance in the field
What are the genetic assumptions for high-dose strategy as a potential method or model of "managing" resistance?
High-dose strategy
- assumes complete coverage, effective kill of all individuals, ignores negative effects on secondary pests, natural enemies, or the environment
What are the 2 approches taken in augmentation?
Inudation - involves releasing large numbers of natural eneimies for immediate reduction of a damaging or near-damaging pest population; analogous to an insecticide; most expensive option
Inoculation - involves releasing smaller numbers of natural enemies at prescribed intervals throughout the pest period, starting when the pest population is low; less expensive
In what crop system is augmentation a good control technique?
greenhouses
Why can augmentation be difficult?
it requires the pest manager to have considerable information on pest and natural enemy biology, an understanding of pest-natural enemy dynamics, and the availability of adequate numbers of high quality natural enemies for release at the right time
How is conservation most often achieved?
by modifying pesticidee applications, including the rates applied, the product type, and the timing of application
Why is dust management an important cultural practice for managing spider mites?
Dust on foliage makes it easier for spider mites to become serious pests by possibly making the foliage more suitable for spider mites or interfering with predators. Dust can be managed by oiling dirt roads or using cover crops or grass. Cover crops may also add nitrogen to the soil and provide shelter, alternative prey or hosts, and nectar for adult parasitoids.
How can pesticide applications be made selective?
- intrinsically selective in that their chemistry makes them more toxic to pests than to beneficial species
- use of systemic pesticides applied to plant roots
- treating only a portion of the field
- bait sprays
- leaving portions of fields unsprayed to provide a refuge for natural enemies (i.e., apple orchards in Penn with alternate rows sprayed to control codling moth but preserve ladybugs that control European red mite)
- pesticid-resistant natural enemies
As a pest manager, what do you need to know or do if you are going to use specific pesticides in a selective manner?
need to know the past treatment history of the field or test the population yourself
What is an acaricide?
a pesticide that provides economic control of pest mites and ticks
Define mode of inheritance.
how the trait is inherited
How are acaricides classified?
1) Mode of entry - stomach poisons, contact poisons, fumigants, systemics
2) Chemical structure - organic or inorganic
3) Source - botanicals
What are the most common acaricides used in IMM and what is a potential negative effect?
sulfur, petroleum oils
- can cause phytotoxicity; petroleum oils lack residual activity
Define resistance, tolerance, cross resistance and multiple resistances.
Resistance is a decreased response of a population of animal to a pesticide or control agent as a result of their application; it is an evolutionary or genetic response to selection.
Tolerance is an innate ability to survive a given toxicant dose without prior exposure and evolutionary change.
Cross resistance is a genetic response to selection with compound A that generates resistance to both compound A and other compounds (B and C).
Multiple resistances involve resistance to different compounds due to the coexistance of different resistance mechanisms in the same individuals.
Describe silk and webbing in spider mites.
Tetranychidae are called spider mites because they produce silken webbing. But not all spider mites produce silk.
Silk protects spider mites from many predator species and low RH, from rainfall and pesticides.
Silk is used by some species for dispersal, such as a silk balloon.
Webbing is used in courtship where the female deutonymph attaches herself to the leaf surface.
T. urticae may spin down when they encounter pesticide residues.
Webbing protects mites from being blown off or wetted by rain.
Webbing may help displace mites that do not produce webbing or protect them from generalist predators.
C/C hibernal diapause and aestivation in spider mites.
Hibernal diapause occurs in the adult female or in the egg. It is overwintering.
Aestivation is a form of diapause that occurs during the hot dry weather in the summer.
Describe the different acarine mechanisms of dispersal.
- walking
- aerially by ballooning on silk threads (i.e., avocado brown mite)
- balls of mites that are blown aerially (T. urticae)
- man and farm equipment
- phoresy on insects and birds (hypopi)
- aerially by standing on 2 legs (Phytoseiidae)
What types of plant diseases do Tetranychidae cause?
- Remove cell contents causing economic injury
- Loss of chlorophyll resulting in stippling
- Bartlett pear leaves appear "scorched" by feeding of one or few
- Modify developing tissue by causing deformed leaves
- Inject virus, i.e., Potato virus Y
Why are phytoseiids effective natural enemies?
- Consume large numbers of prey (high functional response)
- Can maintain plant-feeding mites at low densities
- Can be mass reared for augmentative releases
- Have a rapid developmental rate, comparable to their prey (high numerical response)
- Have a female-biased sex ratio equivalent to their prey, which allows them to respond numerically to increased prey density
Are obligatory predators better natural enemies than those species that can survive on alternative foods for augmentative releases?
If the target pest is present only during a limited part of the season, then the ability to feed on alternative foods or prey is desirable. If, however, the pest is present consistently, it is probably better to use an obligatory predator species in your augmentative releases.
How do phytoseiids find their prey?
They use several cues and sensory receptors on legs 1 and on their palps to detect prey.
Some phytoseiids detect webbing and chemical cues deposited by spider mite prey (feces, kairomones)
What are the advantages and disadvantages of insects as predators?
Advantages
- Larger than phytoseiids and thus can consume more prey per unit time (higher functional response)
- Greater longevity and fecundity than phytoseiids (greater numerical response)
Disadvantages
- Lack of specialization on mites
- Relatively slow development so there may be a delayed numerical response
- Unable to persist when prey populations are low, so rebounds of the pest can occur (they fly away)
- Mass rearing is not cost effective
Define intraguild predation.
insect predators compete with phytoseiids for prey and can also prey on them
What are the barriers to commercialization of microbial products?
1) Products are not highly reliable under field conditions.
2) The activity of microorganisms may be too specific.
3) Most microbial products have a short residual activity
4) Microbial pesticides are expensive
5) Microbial products may act slowly
What are the different mechanisms of host plant resistance?
Tolerance - describes the ability of a plant to repair or endure damage by the arthropod.
Nonpreference - affect the behavior or biology of the arthropod due to physical or chemical characteristics of the plant that repel or cause an arthropod to prefer another plant for feeding, shelter, or oviposition (i.e., spines, secondary plant compounds).
Antibiosis - achieved by physical and chemical traits of the plant that cause decreased survivorship, fecundity, and/or developmental rate of the arthropod (i.e., heavy pubescence, increased thickness of cuticle, sticky exudates)
What is hypersensitivity?
a rapid plant reaction to pathogens that result in less favorable conditions for the attacking pathogen.
Is host plant resistance to Tetranychidae useful in an IPM program?
It is very useful because it is quite effective in reducing mite numbers, but if the resistance is overcome than the plant has no protection. Multiple tactics in addition to host plant resistance must be in place.
What is a mite brushing machine?
It is often used by researchers to monitor spider mite and predatory mite densities. The mites are brushed onto a glass plate (usually covered with a thin layer of oil) and the plate is held in the refrigerator until it can be counted on a grid under a dissecting microscope.