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PCA – Nematodes EXAM WITH CORRECT ACTUAL
QUESTIONS AND CORRECTLY WELL DEFINED ANSWERS
LATEST ALREADY GRADED A+ (2025/2026).
Describe the relative size of plant feeding nematodes. - CORRECT ANSWER- Great variability. Range from 0.25 um to 12 mm in length.
Name five to six life stages of plant-parasitic nematodes. - CORRECT ANSWER- Egg, juvenile 1, J2, J3, J4, adult
Shape and size of root-knot nematode - CORRECT ANSWER- Females are round and lose their veriform shape as adults, males retain veriform shape
Shape and size of cyst nematode - CORRECT ANSWER- Adult female is swollen, eggs retained inside of cyst and cyst is left behind after female dies
Shape and size of lesion nematode - CORRECT ANSWER- Small, needle-like
Describe how nematode shape affects the choice of extraction method. - CORRECT ANSWER- Larger nematodes that are swollen may be observed on the root system, but smaller nematodes require actual extraction.
Define veriform. - CORRECT ANSWER- Worm-shaped
Describe the major difference between the veriform stage and other nematode life stages. - CORRECT ANSWER- Veriform stages are mobile, swollen stages are not.
Describe the feeding apparatus of plant-parasitic nematodes and how it is used to feed on plants. - CORRECT ANSWER- Stylet is used to feed. It pierces the plant, and draws nutrients from the plant.
List two groups of nematodes by common name that exhibit sexual dimorphism. - CORRECT ANSWER- Cyst and root-knot nematodes
Describe the differences in shape between males and females in nematodes that exhibit sexual dimorphism. - CORRECT ANSWER- Males are veriform, whereas females are swollen.
Describe how nematodes move. - CORRECT ANSWER- Nematodes move with snake- like movements in short distances. For long distances, they move with infected material, water, and equipment.
List the major environmental/ecological factors that influence the time it takes a nematode to complete its life cycle. - CORRECT ANSWER- Temperature, moisture, availability of food from the host.
Identify by genus and common name the major endoparasitic nematode groups. - CORRECT ANSWER- Meloidogyne spp. - Root-knot
Heterodera & Globodera spp. - Cyst
Pratylenchus spp. - Lesion
Radopholus spp. - Burrowing
Rotylenchulus reniformis - reniform
List the two most economically important species of root-lesion nematodes on perennial crops in California by genus and species. - CORRECT ANSWER- Pratylenchus vulnus & Pratylenchus penetrans
List the two economically important cyst nematodes in California by genus and species. - CORRECT ANSWER- Heterodera schachtii & Heterodera cruciferae
List five major root-knot nematodes in California by genus and species. - CORRECT ANSWER- Meloidogyne Incognita (southern)
M. hapla (northern)
M. javanica (Javanese)
M. arenaria (peanut)
M. chitwoodi (columbia)
M. naasi (barley)
Egg laying habits of ectoparasitic nematodes - CORRECT ANSWER- Eggs are laid singly in the soil around the roots, and females may lay up to 2,800 eggs
Egg laying habits of root-lesion nematodes. - CORRECT ANSWER- Female lays one to two eggs a day for many days
Egg laying habits of stem and bulb nematodes. - CORRECT ANSWER- After fertilization by a male, a female lays up to 10 eggs a day within host tissue and up to 500 eggs in a lifetime.
Egg laying habits of foliar nematodes. - CORRECT ANSWER- Relatively few eggs laid. 20-30 total eggs has been observed in one species.
Egg laying habits of citrus nematodes - CORRECT ANSWER- Egg masses of about 100 eggs are deposited into a gelatinous matrix.
Egg laying habits of root-knot nematodes. - CORRECT ANSWER- Eggs are laid in a gelatinous matrix at posterior end of the body, which may be within the root partially or completely. Low survival.
Sedentary ectoparasite - CORRECT ANSWER- Nematodes that feed on the outside of the plant in one location for most of their life cycle.
Ex: Ring Nematode (Criconemella, Macroposthhonia)
Migratory ectoparasite - CORRECT ANSWER- Nematodes that feed on the outside of the plant, but will move to different locations in their life cycle.
Survival stage of root-knot nematodes. - CORRECT ANSWER- Overwintering juveniles and hatching eggs.
Survival stage of pin nematodes. - CORRECT ANSWER- Fourth stage juvenile shows some resistance to unfavorable environmental conditions.
Describe how and why distribution patterns of different nematode species vary. - CORRECT ANSWER- Climate may be unsuitable, distribution may reflect association with vegetation, climatic variations in california are diverse enough to influence pattern of different species distribution, farming factors such as equipment movement, soil type, crop
Describe how nematode population levels fluctuate in an annual crop from harvest of one crop in fall to planting of another in spring and harvest of that crop in the next fall. - CORRECT ANSWER- Nematode levels are typically low during planting and increase during first harvest, then decrease in winter and spring and then increase again at the second harvest.
Nematode levels are easier to detect immediately following harvest than several months after harvest.
Describe how nematode populations fluctuate throughout the year on an established perennial crop. - CORRECT ANSWER- Nematode populations will fluctuate with the timing of crop and location fluctuations. This makes year-to-year sampling critical to sample at the same time each year.
Identify a nematode group whose distribution is mainly limited by soil texture in California. - CORRECT ANSWER- Stubby root nematodes predominate in soils with a high sand content.
List three reasons why root-lesion nematodes are widely distributed in California - CORRECT ANSWER- They are adaptable to many climactic regions of the state.
They have wide host ranges.
They have species that show preferences for many soil types in California.
Describe how stem and bulb and foliar nematodes are distributed to new areas of the state. - CORRECT ANSWER- These nematodes are primarily distributed through the movement of infested planting material and infested propagative material.
Identify the major distribution determinant of citrus nematodes. - CORRECT ANSWER- Host requirement; host range is confined to citrus, olives, persimmons, grapes, and ornamentals.
Identify the major distribution determinant of cyst nematodes. - CORRECT ANSWER- Areas of host production, such as sugarbeet
Describe the impact of host preference on the distribution of the common root- knot nematode species. - CORRECT ANSWER- Most species have a wide host range, however some species have host preference so land with that host crop will have that species more commonly.
How does movement of agricultural equipment influence distribution of some nematode species? - CORRECT ANSWER- Nematodes can be spread by equipment and tractor wheels, so movement of equipment between fields without cleaning between fields could lead to nematodes being distributed among the fields.
Know the distance most plant-parasitic nematode species can move through the soil in one year. - CORRECT ANSWER- 3-6 feet in a season, depending on species
Describe how nematodes move from field to field. - CORRECT ANSWER- Infested planting material, irrigation water, infested equipment
Describe the role of irrigation on inter-field distribution of nematodes. - CORRECT ANSWER- Many nematodes can hitch a ride in the irrigation water to different areas of a field.
Describe the value of quarantine in limiting the distribution of nematode species.
- CORRECT ANSWER- Quarantine of plant material can limit nematode species because many need moisture, temperature, and food to survive. A quarantine can reduce the ability of the nematodes to survive.
Identify the primary factor that determines the vertical and horizontal distribution of nematodes in the soil. - CORRECT ANSWER- Pattern of distribution of a plant's root system
Identify the site of greatest nematode population levels in established orchards and vineyards. - CORRECT ANSWER- Within the vine row, and in the horizontal plane under the edge of the leaf canopy
Identify the site of greatest nematode population levels in annual field and vegetable crop rows. - CORRECT ANSWER- In and around the plant row
Nematode groups likely associated with deciduous fruit trees - CORRECT ANSWER- Citrus, sheath, dagger, root knot, root lesion, pin
Nematode groups likely associated with deciduous nut trees - CORRECT ANSWER- Dagger, ring, root lesion, root-knot
Nematode groups likely associated with citrus - CORRECT ANSWER- Citrus, sheath
Nematode groups likely associated with grapes - CORRECT ANSWER- Root-knot, dagger, needle, citrus, root lesion, ring, sheath
Nematode groups likely associated with vegetables - CORRECT ANSWER- Needle, root-knot, spiral, stunt
Nematode groups likely associated with tomato - CORRECT ANSWER- Root-knot
Describe the primary aboveground symptoms associated with root-parasitic nematodes on field and vegetable crops. - CORRECT ANSWER- Retarded growth. Lagging plants. Plant height and canopy reduced. Fewer fruits. Heightened plant stress.
Describe the primary aboveground symptoms associated with root-parasitic nematodes on sugarbeets. - CORRECT ANSWER- Stunting of top growth and discoloration of leaves. Loss of stand may occur. Root system damage resulting in stunting. Patchwork effect.
Describe the primary aboveground symptoms associated with root-parasitic nematodes on grapevines. - CORRECT ANSWER- Nonspecific with other diseases. Reduced vine vigor, yield. Slight yellowing of leaves. Rarely vine death. N and water deficiency symptoms.
Identify other stresses that can cause the same symptoms of root-parasitic nematodes. - CORRECT ANSWER- Nutritional and soil physical effects, poor drainage, fungi, bacteria, viruses
Describe the root damage symptoms associated with root-knot nematodes. - CORRECT ANSWER- Root galls, knots, swollen roots
List other pests or conditions that can cause root symptoms similar to root-knot nematode damage. - CORRECT ANSWER- Dagger, needle, and sheath nematodes. Nodules on the roots of legumes can bear a resemblance to root-knot galls.
Describe the damage symptoms associated with cyst nematode and root-knot nematode on sugarbeets. - CORRECT ANSWER- Cyst: root proliferation, stunted top growth, discolored leaves
Root-knot: secondary rot infection, stunting of top growth, discolored leaves, some root proliferation
Describe the damage to roots caused by ectoparasitic nematodes. - CORRECT ANSWER- Reduction in root growth. Short, stubby, malformed roots. Swelling and cessation of elongating growth. Halting of taproot elongation.
Describe the common damage symptoms on the roots of trees infested with citrus nematodes. - CORRECT ANSWER- Reduction in root system. Encrusted appearance of roots due to egg matrix.
Describe the damage on roots induced by root-lesion nematodes. - CORRECT ANSWER- Necrotic lesions. General necrosis and root rot.
List the nematode species that can induce root proliferation. - CORRECT ANSWER- Heterodera spp. (Cyst nematodes)
Describe the association of root rotting and wilting organisms with root-knot nematode symptoms. - CORRECT ANSWER- Rhizoctonia and Pythium are associated with root-knot nematode symptoms.
Describe the association between root-knot nematode and Fusarium wilt infection in cotton and tomatoes. - CORRECT ANSWER- Root-knot infection can
Describe how pockets or irregular spots of poor growth provide indications that nematodes may be damaging plants - CORRECT ANSWER- Nematode problems are usually pocketed or irregular spots. Nematode may or may not be restricted to areas of poor growth, so sample healthy areas as well.
Describe how indigenous association with crop and location provide general indications that nematodes may be damaging plants - CORRECT ANSWER- Nematodes are associated in areas that have traditionally had a host for them to feed on.
Ex: Grape growing regions are associated with Xiphinema index
Describe how sampling history provides general indications that nematodes may be damaging plants - CORRECT ANSWER- Some species are easier to control than others and sampling history can confirm what species is present.
Describe how history of nematicide usage provides general indications that nematodes may be damaging plants - CORRECT ANSWER- Response of plant to nematicide has provided a way to identify nematode presence, but this method has several limitations.
Describe how crop susceptibility provides general indications that nematodes may be damaging plants. - CORRECT ANSWER- There are cultivars that are susceptible to nematodes and some cultivars that are not.
List the procedures PCAs should follow to identify and confirm a nematode problem. - CORRECT ANSWER- Identify symptoms, take soil and plant symptoms, send to lab.
Describe how PCAs can detect potential nematode problems before planting. - CORRECT ANSWER- Looking at cropping history and previous nematode problems can indicate whether crop being planted will have a nematode problem.
List two examples of economic injury levels for California nematodes. - CORRECT ANSWER- 1. Presence of more than one sugarbeet cyst nematode egg per gram of soil in warm, clay loam soils of Imperial Valley.
- Presence of one root-knot nematode, one Pratylenchus vulnus, one citrus nematode, or one Xiphinema index in a field to be planted with grapes.
List the factors to take into account when using quantitative assays to forecast future nematode damage. - CORRECT ANSWER- Numerous soil, plant, management and ecological factors
Identify the appropriate time of sampling for annual crops - CORRECT ANSWER- At harvest
Identify the appropriate time of sampling for vineyards or orchards - CORRECT ANSWER- Same time every year
List the minimum cores/5 acres and core depths for samples taken in vineyards or orchards - CORRECT ANSWER- 15-20 cores/5 acres taken to a depth of 36 inches
Describe how to take a sample in nursery stock - CORRECT ANSWER- Taking cores from a series of pots and bulking into a composite sample. Amount of cores taken depends on the potential for loss.
Describe how to take a sample in a field - CORRECT ANSWER- Randomly taking single subsamples from all over the field and making a composite sample.
Identify the tools necessary to take a soil sample - CORRECT ANSWER- Oakfield tubes, soil augers, Viehmeyer tube
Identify the tools necessary to take a root sample - CORRECT ANSWER- Shovel
Describe how to package a soil sample - CORRECT ANSWER- Subsamples mixed well, 1 quart/liter of soil in a plastic bag, label the bag, keep cool until arrival at lab
Describe how to take field samples for established crops - CORRECT ANSWER- Soil or root samples taken. Use soil auger around the planting area.
Describe how to collect field samples for trees and vineyards - CORRECT ANSWER- Collect soil samples near drip lines.
Describe how to collect field samples for fallow fields. - CORRECT ANSWER- Collect soil samples all over the field
Describe storage and shipping requirements to send a soil sample to a lab. - CORRECT ANSWER- Needs to be kept cool and moist.
List the major limitations of using soil sample results for practical nematode predictions. - CORRECT ANSWER- There is a lack of correlations between actual numbers and field conditions which result in yield condition, and there is a lack of standardization among soil sampling and extraction procedures.
Recognize the importance of telling the lab the previous, current, and subsequent crop to help them determine the extraction method. - CORRECT ANSWER- Different nematodes attack different crops, and extraction methods vary depending on which nematodes are thought to be present
Recognize the importance of knowing the extraction procedure to interpret laboratory results. - CORRECT ANSWER- Different methods will extract different proportions of particular nematode genera that might be present.
Describe why ectoparasitic nematodes are not found in root samples. - CORRECT ANSWER- They spend their entire lives outside of roots in the soil, so they will be found in soil samples.
Describe why root-knot nematodes may not be found in a root sample that has nematode galls on it - CORRECT ANSWER- Dagger and needle nematodes also produce
