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Crop Sci Test 4
| Question | Answer |
|---|---|
| viruses can be controlled by genetic resistance and crop rotation | true |
| three symptoms of bacterial infection are scabs, wilts, and leaf spots | true |
| bacteria are spread only by insects | false |
| fungal pathogens are different from others because they can penetrate a host without the presence of a wound | true |
| the most effective use of fungicides is to us it preventatively | true |
| nonpathogenic nematodes have stylets while pathogenic nematodes do not | false |
| the 2 classes of parasitic higher plants detrimental to their hosts are hemiparasites and true parasites | true |
| nematodes are microscopic animals similar in appearance to worms | true |
| LD50 is the dosage that will kill more than 50% of a test animal population | false |
| safe handling of pesticides is important to protect the application, the wildlife, and the environment | true |
| what does tolerance mean in terms of genetic host resistance | a plant can withstand pest attacks without a decrease in yield |
| why is knowing the lifecycle of a pest and host plant important for managing the pest | it helps identify the most vulnerable stage of the pest for control |
| what does threshold level mean in pest management | the level of infestation below which there is no economic impact |
| which of the following is not an impact of weeds on cultivated plants | increasing the rate of photosynthesis in crops |
| what is an invasive weed species | a weed species that is particularly aggressive and spreads rapidly |
| why does tillage often help to control annual weeds but spread creeping perennials | tillage disturbs annual weeds but cuts creeping perennials, spreading them |
| which of the following is an example of an invasive weed species that was deliberately introduced into the United states | garlic mustard |
| at what stage in a crops development do weeds cause the most loss | weeds that emerge early |
| why is maintaining a healthy, actively growing crop that quickly closes its canopy a weed management strategy | it blocks light from reaching weed seedlings, preventing their growth |
| what is a seed bank, and why is it important in controlling annual weeds | a group of seeds dormant in the soil that determines how many weeds will emerge |
| why is applying a systemic herbicide to perennial weeds when carbohydrates are flowing to underground structures usually very effective | the herbicide moves with the plants carbohydrates to the root, inducing whole plant control |
| how does herbicide resistance occur, and how can it be prevented | resistance occurs through the overuse of herbicides with the same mode of action |
| why is rotating crops of different lifecycles helpful in controlling weeds | weeds thrive when crops have the same lifecycle. rotating crops disrupts weed growth |
| what is allelopathy, and how can it help with weed control | the toxic effect of one plant species on another, which can help cover crops control weeds |
| how does mowing help control weeds | by eliminating seed production and depleting carbohydrate reserves in weeds |
| what are the four classifications of herbicides based on the timing of application | burn down, preplant, preemergence, postemergence |
| what does exclusion mean in insect control | preventing pests from entering an area using physical barriers |
| how do insect growth regulators work | they disrupt a pests ability to molt or develop properly, preventing growth |
| what is the advantage of neonicotinoid insecticides over other neurotoxins | they have low toxicity to vertebrates |
| what are microbial insecticides | insect toxins produced by fungi, bacteria, and viruses |
| to what type of commodity do rodents cause the most damage | stored grains and other products in open storage |
| what is the primary difference between a disease and an injury in plants | a disease is caused by a continuous irritant, while an injury is caused by a more instantaneous event |
| what is the difference between a biotic and abiotic disease | biotic diseases are caused by living organisms (pathogens) and are contagious, ..... |
| which of the following is NOT a type of plant pathogen | water |
| what three conditions must be met for an infectious disease to develop in plants | susceptible host, favorable environment, and pathogen present |
| which of the following is the correct sequence of the six steps of the disease cycle | survival, inoculation, penetration, establishment, growth and reproduction, dissemination |
| delicate low bulk crops are cooled by forced air while crops like corn are cooled by hydrocooling | true |
| solar, forced air, and freeze drying are ways of drying plant material for storage | true |
| drying works as a preservation method only because it kills mold | false |
| modified and controlled atmosphere storage works because it increases the oxygen content of the air to reduce respiration of the stored crop | false |
| ethylene is both beneficial and problematic when handling produce because it can aid in ripening fruit, but causes damage in other produce | true |
| spoilage organisms are controlled by sugar due to the change in osmotic pressure reducing water availability to microbes | true |
| the major components of marketing are assembly, distribution, exchange, financing, storage, transportation, and social media campaigns | false |
| Agriculture cooperatives are groups of producers who join together to reduce costs through volume buying | true |
| marketing boards are ineffective because they destabilize producer prices | false |
| the rapid exchange of products between many distant markets has introduced pests and diseases to areas with no natural predators or defenses | true |
| which of the following best describes conventional farming | a farming system that heavily relies on non-renewable resources and external inputs |
| which of the following is a characteristic of organic farming | use of natural methods and low dependence on non renewable resources |
| what is the main goal of sustainable farming | to meet current agricultural needs without compromising the ability of future generations to meet their needs |
| can conventional growers use practices from organic or sustainable systems | yes, many organic and sustainable practices can be used in conventional farming systems |
| which agency certifies organic farms in the United states | USDA |
| why do some organic growers label their crops as organic based instead of organic | organic certification is expensive and complex, and not all growers wish to pursue it |
| what is one of the oldest forms of sustainable crop growing | slash and burn |
| under what condition can slash and burn farming lose its sustainable characteristics | if the land is not left to fallow long enough |
| in sustainable certification, which two areas are commonly assessed | irrigation and water use efficiency, wildlife habitat preservation |
| what is a growing degree day | a measure of the accumulated heat above a baseline temperature |
| how many growing degree days would there be if the base temp is 50 and the average temp for the day is 78 | 28 growing degree days |
| how are growing degrees days used to predict harvest time | by tracking the number of growing degrees days needed for a crop to reach maturity |
| which two types of lights are most commonly used in greenhouse and indoor crop production | LED and HID |
| how are plants protected from high light intensities in a greenhouse | by using shade cloth |
| what is the primary function of a combine in a grain harvest | to reap and thresh at the same time |
| why is hand picking preferred for some high value crops rather than mechanical harvesting | it avoids physical damage to the crops |
| how do yield sensors on harvesters help improve efficiency | by adjusting harvesting speed based on the yield in different parts of the field |
| which of the following has the shortest post harvest life | a cut tulip flower |
| what is a common problem that can occur during plant harvesting | damage from breakage and bruising |
| why is striking and object quickly more likely to damage a soft fruit than striking slowly | a sharp impact applies pressure more suddenly, which the fruit cannot absorb as well |
| why are many cut flowers and potted plants sleeved before shipping | to protect the plants from damage during shipping |
| what is a major issue when storing plant structures like bulbs and tubers | sprouting |
| why are immature structures such as green peas and sweet corn more perishable than mature ones | immature structures spoil more quickly due to their high metabolic activity and lack of nutrient reserves |
| what is a climacteric fruit | a fruit that produces ethylene during ripening and can affect other produce nearby |
| why do pathogens that attack harvested plants differ from those attacking growing plants | pathogens that attack harvested plants are often opportunistic and attack only after the plant has been weakened |
| what is hedonic quality in relation to plants or produce | a quality based on the consumers appeal to the products |
| what is the purpose of curing crops after harvest | to allow wounds to heal and enhance storage life |
| the best regions for growing dry bean seeds are areas with warm temperatures with a sufficiently long growing season | true |
| dent corn has a hard starch layer overlaid with soft starch while flint corn is mostly soft starch | false |
| the main uses of sorghum are molasses, forage/silage, and feed grain | true |
| the root of sugar beets is harvested for its sugar content, compared to sugar cane which has its stem harvested | true |
| the only classifications of wheat are hard red Winter and soft red winter | false |
| the native areas of plants high in unsaturated oil are tropic and subtropic areas | false |
| unsaturated oil is more likely to cause high cholesterol in humans compared to saturated oils | false |
| plant oils are used in fuel, ink, fabrics, and cosmetics (to name a few uses) | true |
| the source of fiber from cotton is its seed coat | true |
| the source of fiber from agave is its leaves | true |
| what are cropping sequences primarily based on | agronomic and economic considerations |
| what is the main difference between monoculture and crop rotation | monoculture involves growing large areas of the same crop continously, while crop rotation involves changing the crop species grown each season |
| which of the following is an advantage of growing two different types of crops in rotation, such as corn and soybeans | better weed control, reduced disease and insect problems, and less nitrogen fertilizer needed if one crop is a legume |
| which of the following is not a reason for using a monoculture system | to increase soil biodiversity |
| which of the following describes ratoon cropping, double cropping, and intercropping | ratoon is regrowing a crop after harvest for a second harvest in the same season, double cropping is planting a 2nd crop after the 1st is harvested |
| which of the following is NOT a factor in selecting crop variety | the distance to the nearest market |
| what is the advantage of using growing degrees days over the days to maturity system for determining corn maturity | GDD is directly tied to the accumulation of heat, making it more reliable for predicting maturity |
| what is lodging in crops | the falling over of a crop before harvest |
| which of the following are considered major transgenic crops | corn, soybeans, cotton, canola, and sugar beets |
| what are the two major traits placed into transgenic crops | herbicide resistance and insect resistance |
| what is a potential risk of continually growing transgenic crops | development of resistance in insects and weeds |
| what is one potential problem when planting in soil that is too wet | poor seed-soil contact and soil compaction |
| what are the main factors to consider when determining planting date in temperate regions | soil temperature and moisture |
| when are winter crops typically planted compared to spring crops | winter crops are planted in the fall; spring crops are planted in the spring |
| why would a newly germinated soybean field be more likely to need replanting after a late frost than a corn field | the soybean growing point is above ground, making it more vulnerable to frost |
| why are winter and spring types of grains not usually interchangable in planting times | spring types cannot survive mild winters, while winter types cannot tolerate frost |
| what determines the seeding rate of a crop | the population density required for optimum yield |
| what are the main factors that determine the optimal plant populationw | water and nutrient availability |
| how does plant population affect lodging, tillering, and seed head numbers | dense planting increases the chance of lodging, reduces tillering, and reduces seed head numbers |
| why is some increase in plant height an advantage for crops like soybeans and cotton | it allows harvesting machinery to be set higher, reducing damage from rocks and residue |
| why is the seeding rate for late plantings increased for small grains and soybeans but decreased for corn | corn has less seedling mortality in cold, wet soil, so the rate is decreased for late plantings |
| what is the rule of thumb for seed planting depth | 4 to 5 times the seed diameter |
| how do seed size, soil texture, and soil temperature affect planting depth | smaller seeds are planted more shallow and heavier soil requires deeper planting |
| why is a seed with hypogeal emergence planted deeper than one with epigeal emergence | hypogeal emergence allows the cotyledons to develop below ground, requiring deeper planting |
| what is the maximum allowable grain moisture for most crops | 14 percent |
| to which family do true cereal grains belong | poaceae |
| why are cereal and pseudo cereal grains the principal food source for humans | they can adapt to many climates and soils and are easy to handle |
| which of the following is NOT a genius of fabacease beans important to human nutrition | cucurbita |
| biodiversity is important to forages and rangelands because it helps provide fewer losses of nutrients to streams and groundwater | true |
| endophytes that lack the ability to produce the toxic alkaloids but provide other benefits have been available since 1995 | false |
| some benefits of endophytes are that they provide increased production of the host plant, as well as heat and drought tolerance | true |
| population dynamics in a grassland are the cycling of groups of plants and the species in a grassland | false |
| during summer droughts, bare areas may appear when there is insufficiency water for seed germination of Poa annual in grasslands | true |
| stolons are above ground stems that grow horizontally and rhizomes are underground stems that grow horizontally | true |
| overgrazing can reduce pasture growth rate because it results in the loss of leaves at the base of the canopy due to crowding | false |
| the main difference between nutrient cycling and grazing systems is that nutrients are recycled back in the same area through manure | false |
| most of the nutrients deposited by livestock through manure are usually in the open, middle area of the pasture | false |
| other than pastures, grasslands can also be used for wildlife habitat, conservation, soil preservation, and carbon sequestering | true |
| what is forage | the edible parts of plants that can be fed directly or after storage to animals |
| how much land worldwide is devoted to forages compared to other crops | about 26 percent |
| what types of species dominate forage fields and rangelands | grasses, legumes, and forbs |
| what is the typical range in the number of species in a forage crop or rangeland system | 5-50 species |
| how do forages and rangelands have value for humans | by providing feed for domesticated animals |
| what is the key difference between a grazing and a confinement system for raising livestock | in a confinement system, forages are brought to the animals, while in grazing systems, animals feed directly off of growing plants |
| what is the most important objective of grazing | to match the supply of forage production to the nutritional requirements of the animals |
| what is stock rotation in a grazing system and what are its benefits | the movement of stock between pastures - benefits include regular livestock inspection, uniform manure dispersal, etc |
| what kind of rotation system is used with intensive grazing vs extensive grazing | intensive: rotational; extensive: continuous |
| what is hay and how is it used as forage | shoots, leaves, and sometimes flowers of forage plants that are preserved by field drying |
| in the United States, which species usually makes the best quality hay and which makes up the greatest quantity of hay | best quality is alfalfa, greatest quantity is grasses |
| when is the best time to harvest hay | usually just prior to heading (seed development) |
| what determines hay quality | plant maturity, color, odor, and amount of foreign material |
| why is proper dehydration necessary when preserving hay | to preserve quality and prevent barn fires |
| what is silage | moist forage preserved by bacterial fermentation |
| how does the process to make silage work | silage is stored in airtight structures where anaerobic bacteria ferment carbohydrates into lactic acid, lowering pH...... |
| how can forage production be incorportated into a crop rotation system | by planting a short term annual forage after an early harvest of a cereal crop or by following several years of grain crops with forages |
| what is the primary factor affecting forage quality | the amount of fiber in the forage and its digestibility |
| what are the types of fiber found in forage and how digestible is each | pectin and hemicellulose (moderately digestible), cellulose (poorly digestible by non Ruminants), lignin (indigestible) |
| how do species, leaf to stem ratio, and maturity affect forage quality | species affects fiber type, leaf to stem ratio affect digestibility, and maturity decreases quality due to higher fiber content |
| which of the following are considered antiquality factors in forage | leaf saponins, ergot alkaloids, nitrates |
| what are the three main ways that forage systems can be established | full cultivation, no till planting, and frost seeding |
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