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PCA - Nematodes Describe the relative size of plant feeding nematodes. - Answer Great variability. Range from 0.25 um to 12 mm in length. Name five to six life stages of plant-parasitic nematodes. - Answer Egg, juvenile 1, J2, J3, J4, adult Shape and size of root-knot nematode - Answer Females are round and lose their veriform shape as adults, males retain veriform shape Shape and size of cyst nematode - Answer Adult female is swollen, eggs retained inside of cyst and cyst is left behind after female dies Shape and size of lesion nematode - Answer Small, needle-like Describe how nematode shape affects the choice of extraction method. - Answer Larger nematodes that are swollen may be observed on the root system, but smaller nematodes require actual extraction. Define veriform. - Answer Worm-shaped Describe the major difference between the veriform stage and other nematode life stages. - 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. - 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. - Answer Cyst and root-knot nematodes Describe the differences in shape between males and females in nematodes that exhibit sexual dimorphism. - Answer Males are veriform, whereas females are swollen. Describe how nematodes move. - 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. - Answer Temperature, moisture, availability of food from the host. Identify the host(s) of some non-plant parasitic nematodes. - Answer Animals, humans, insects
Ectoparasite - Answer Nematode that feeds on the outside of the plant. Endoparasite - Answer Nematode that feeds on the inside of the plant. List three ways ectoparasitic and endoparasitic species differ. - Answer Ectoparasites move to different plants. Endoparasites move inside the plant tissue. Ectoparastites are sampled from the soil, endoparasites are sampled from the plant. Identify by genus and common name the major ectoparasitic nematode groups. - Answer Xiphinema spp. - Dagger Belonolaimus spp. - Sting Trichodorus spp. - Stubby-root Longidorus spp. - Needle Paratylenchus spp. - Pin Criconemoides & Mesocriconema spp. - Ring Helicotylenchus & Rotylenchus spp. - Spiral Tylenchorhynchus spp. - Stunt Identify by genus and common name the major endoparasitic nematode groups. - 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. - Answer Pratylenchus vulnus & Pratylenchus penetrans List the two economically important cyst nematodes in California by genus and species. - Answer Heterodera schachtii & Heterodera cruciferae List five major root-knot nematodes in California by genus and species. - Answer Meloidogyne Incognita (southern)
Ex: Lesion nematodes (Pratylenchus spp.) Sedentary endoparasites - Answer Nematodes that feed within the plant in one location for most of their life cycle. Ex: Cyst nematodes (Heterodera spp.; Globodera spp.) Survival stage of stem and bulb nematodes - Answer Dried fourth juvenile stage to survive drying. Facilitates survival and dispersal, reactivated with moisture. Survival stage of foliar nematodes - Answer Some juveniles may adapt to drying and be able to survive adverse conditions, reactivated with moisture. Survival stage of cyst nematodes - Answer Eggs within the cyst may remain viable for several years. Survival stage of root-knot nematodes. - Answer Overwintering juveniles and hatching eggs. Survival stage of pin nematodes. - Answer Fourth stage juvenile shows some resistance to unfavorable environmental conditions. Describe how and why distribution patterns of different nematode species vary. - 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. - 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. - 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. - Answer Stubby root nematodes predominate in soils with a high sand content. List three reasons why root-lesion nematodes are widely distributed in California - 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. - 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. - Answer Host requirement; host range is confined to citrus, olives, persimmons, grapes, and ornamentals. Identify the major distribution determinant of cyst nematodes. - Answer Areas of host production, such as sugarbeet Describe the impact of host preference on the distribution of the common root-knot nematode species. - 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. Understand that different nematodes are adapted to different soil types. Give an example of a nematode that is more problematic in sandy soils. - Answer Stubby root nematodes List two ways that irrigation practices can influence nematode patterns. - Answer Irrigation may spread nematodes throughout a field and reactivate some surviving nematodes. Lack of irrigation could dry out some nematodes. How does initial introduction site influence distribution of some nematode species within the field? - Answer Eggs introduced by equipment, water, animals, wind, etc., will lead to a higher distribution in the field. How does soil type patterns influence distribution of some nematode species? - Answer Some species will not do well in specific soil types, whereas some species will be more attracted to other soil types.
Nematode groups likely associated with citrus - Answer Citrus, sheath Nematode groups likely associated with grapes - Answer Root-knot, dagger, needle, citrus, root lesion, ring, sheath Nematode groups likely associated with vegetables - Answer Needle, root- knot, spiral, stunt Nematode groups likely associated with tomato - Answer Root-knot Nematode groups likely associated with alfalfa - Answer Alfalfa stem, root- knot, Lesion Nematode groups likely associated with cotton - Answer Southern root-knot Nematode groups likely associated with sugarbeets - Answer Sugarbeet cyst, root-knot Nematode groups likely associated with turfgrass - Answer Lesion, ring, root- knot, seed and leaf gall, spiral, sting, stubby root List the resources available to help PCAs determine what nematodes affect a given crop. - Answer UC IPM guidelines, California Nematode Host Associations, NEMAPLEX, lab tests Describe the plant damage symptoms caused by foliar nematodes on ornamental and strawberry plants. - Answer Killing of either a flower or leaf bud, a growing point that produces a blind plant, distorted, crinkled, or twisted stems and foliage, discoloration in interveinal regions, malformed strawberries Describe the general plant damage symptoms caused by stem or bulb nematodes. - Answer Twisting, distortion, discoloration of stems and foliage. Multiple crowns in sugarbeet and increased tillering in oats. Swelling of tissues on lower stem region. Crown rot. Discolored bulbs. Describe the primary aboveground symptoms associated with root-parasitic nematodes on field and vegetable crops. - 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. - 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. - 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. - Answer Nutritional and soil physical effects, poor drainage, fungi, bacteria, viruses Describe the root damage symptoms associated with root-knot nematodes. - Answer Root galls, knots, swollen roots List other pests or conditions that can cause root symptoms similar to root- knot nematode damage. - 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. - 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. - 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. - Answer Reduction in root system. Encrusted appearance of roots due to egg matrix. Describe the damage on roots induced by root-lesion nematodes. - Answer Necrotic lesions. General necrosis and root rot. List the nematode species that can induce root proliferation. - Answer Heterodera spp. (Cyst nematodes) Describe the association of root rotting and wilting organisms with root-knot nematode symptoms. - 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. - Answer Root-knot infection can predispose resistant cultivars to severe Fusarium infection. Common in warm irrigated soils of California's interior valleys.
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. - 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. - Answer Identify symptoms, take soil and plant symptoms, send to lab. Describe how PCAs can detect potential nematode problems before planting.
- 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. - 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. - Answer Numerous soil, plant, management and ecological factors Identify the appropriate time of sampling for annual crops - Answer At harvest Identify the appropriate time of sampling for vineyards or orchards - Answer Same time every year Identify the appropriate time of sampling for ornamental plantings or turf - Answer If annual, sample at plant maturity. If turf, sample same time every year. List the background information that should be included when sending a sample to a lab. - Answer Crops of interest, cropping history, name, location, soil type, symptoms, last treatment type, any other growth limiting factors List the factors that determine the size of the sample to be take. - Answer Time to process the sample is lengthy, so a good sample is worth the effort.
Factors include soil variations, plants of interest, roots or just soil Define sample size and list the number of soil cores that make up a basic minimum sample. - Answer 15-20 cores is the basic minimum sample. Sample size is the amount of field covered with soil samples. List factors to consider when stratifying the field. - Answer Differences in soil texture, soil moisture, drainage patterns, healthy vs unhealthy plants, cropping history List the minimum cores/5 acres and core depths for samples taken in field or row crops - Answer 15-20 cores/5 acres taken to a depth of 12-18 inches List the minimum cores/5 acres and core depths for samples taken in vineyards or orchards - Answer 15-20 cores/5 acres taken to a depth of 36 inches Describe how to take a sample in nursery stock - 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 - Answer Randomly taking single subsamples from all over the field and making a composite sample. Identify the tools necessary to take a soil sample - Answer Oakfield tubes, soil augers, Viehmeyer tube Identify the tools necessary to take a root sample - Answer Shovel Describe how to package a soil sample - 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 - Answer Soil or root samples taken. Use soil auger around the planting area. Describe how to collect field samples for trees and vineyards - Answer Collect soil samples near drip lines. Describe how to collect field samples for fallow fields. - Answer Collect soil samples all over the field Describe storage and shipping requirements to send a soil sample to a lab. - Answer Needs to be kept cool and moist. List the major limitations of using soil sample results for practical nematode predictions. - Answer There is a lack of correlations between actual numbers
List factors to consider in conjunction with every nematode sample - Answer Suitability of sample, efficiency of extraction method, pathogenicity of nematodes present, biological and environmental factors that might influence pathogenicity Define damage threshold. - Answer Level at which the pest is expected to damage the crop Describe the factors that influence the damage threshold for nematodes. - Answer Temperature at time of planting List the resources for finding out methods for controlling nematodes in specific crops. - Answer UC IPM Pest Management Guidelines Describe the role of the California Nursery Certification program in preventing the spread of nematodes - Answer Keeps devastating nematodes out of state, certifies nurseries as having nematode-free stock so that they may sell in California. List methods used to prevent the spread of nematodes - Answer Quarantine, certified planting materials, check suspect materials before planting, nematodes may be present in manure, clean equipment before moving, avoid contaminated irrigation water Describe the importance of cleaning equipment to limit the spread of nematodes - Answer Nematodes spread among fields mostly by dirty equipment. Cleaning equipment eliminates the possibility of spread. Describe the feasibility of eradicating 100% of the nematodes from a field. - Answer Not feasible. But, it is feasible to manage nematode problems. Describe how crop rotations can be used to manage nematode populations - Answer Rotating to a non host can help reduce problematic nematode populations Identify an example of a successful crop rotation program against a nematode pest in California - Answer Rotating sugarbeet with tomatoes because of the sugarbeet cyst nematode's narrow host range Describe the use of degree-day models and how the manipulation of planting or harvest dates can be used to limit nematode damage. - Answer Planting at temperatures colder than minimum needed for infection can lead to reduced damage. Early harvest may reduce damage and nematode populations as well. Degree-day models give an indication of when nematodes will develop into their infections stage of development.
Describe the role of weed control in roration programs for nematode pest management. - Answer Weeds are potential hosts for many damaging nematodes, so management of weeds is important because the program's success depends on the absence of host roots to prevent nematode reproduction and feeding. Describe the impact of solarization on nematodes. - Answer Solarization may have some success against some nematodes, but nematodes may be so deep that it is not effective. Describe how soil amendments can be used to reduce nematode damage. - Answer Some amendments reduce stress and make nematode damage less severe, some stimulate plant growth, some stimulate predators of nematodes Define "replant problem" - Answer Replant disease affects trees and vines in ground where perennial crops were previously planted, but it is not known what exactly in the soil causes the problem. Describe how cover crops can impact nematode problems. - Answer Some cover crops may be hosts or non-hosts of certain nematodes. It is important to know what nematodes are present as well as if the cover crop is a host before planting. List four types of organisms known to attack nematodes in the soil. - Answer Tardigrades, insects, mites, nematodes Resistance - Answer Plant may or may not show damage but is not overwhelmed by nematode Tolerance - Answer Plants able to withstand nematode attack Biotype - Answer Localized races of nematodes that very in host-range specificity Differentiate between host resistance and tolerance - Answer Tolerant hosts can sometimes show damage, resistant hosts will likely not show damage List factors that need to be considered when determining whether to plant a nematode resistant cultivar. - Answer Which nematodes is cultivar resistant to, will nematodes damage the cultivar, will nematodes reproduce on the cultivar Immune plants - Answer Nematodes do not attack.
Cowpea cultivar Blackeye 46, CB50, CB5 - Answer Resistant to different species of Meloidogyne Lima bean cultivar White Ventura N - Answer Resistant to M. incognita but not other Meloidogyne species Blenheim apricots - Answer Immune to root-knot nematode VFN tomatoes - Answer Resistant to different species of Meloidogyne Compare/contrast the use of fumigants vs nonfumigants - Answer Fumigants are more effective because of the ability to move throughout the soil profile, but are also volatile and dangerous Describe the factors that influence nematicide movement through the soil - Answer Soil temperature, soil type, soil moisture, rate List some of the problems associated with the use of soil fumigants - Answer Expensive, dangerous, pollution, water contamination, harm to nontargets Define nematistat - Answer Term to describe effects when nematodes are exposed to low concentrations of organophosphates and carbamates. If present long enough, nematodes eventually starve to death. List ideal field conditions for application of soil fumigants - Answer Fine textured soils, wetter soils, high rates, moderate temperatures List various methods available to evaluate soil fumigation - Answer Nemtode bags, seeds, insects, earthworms (Bioindicators) Describe methods for evaluating a postplant nematicide application. - Answer Comparing treated and untreated areas and yield Describe methods for evaluating untested materials or new control methods.
- Answer Field trials Quarantine nematodes - Answer Hemicycliophora arenaria and Rotylenchulus reniformis Anguina spp. - Answer Seed and leaf gall nematodes Anguina spp. Host Range - Answer Wheat and Rye Anguina spp. Life Cycle - Answer Sedentary endoparasites, diploit, amphimictic
Anguina spp. damage symptoms - Answer Seedlings stunted, show rolling, twisting, and crinkling of leaves. Growth distortion. Ears are undersized, shorter and thicker than healthy ones. Anguina spp. Management - Answer Mechanical seed cleaning, avoid infested fields Anguina spp. Economic significance - Answer Rare now Aphelenchoides spp. - Answer Foliar nematodes Aphelenchoides fragariae - Answer Strawberry bud nematode Aphelenchoides ritzemabosi - Answer Chysanthemum nematode Aphelenchoides spp. host range - Answer Wide host range Aphelenchoides spp. Life Cycle - Answer Migratory endoparasites in leaves, but also ectoparasitic feeding on leaf and flower buds. Males required. Aphelenchoides spp. damage symptoms - Answer Blotches. Necrotic lesions between veins. Malformed leaves with crinkled edges. Aohelenchoides spp. management - Answer Roguing plants with symptoms. Hot water treatments. Foliar or soil chemical treatments. Ditylenchus spp. - Answer Stem and bubl nematodes Ditylenchus destructor - Answer Potato rot nematode Ditylenchus dipasaci - Answer Stem and bulb nemtode Ditylenchus spp. host range - Answer Wide host range Ditylenchus spp. life cycle - Answer Sexual reproduction. Migratory endoparasite. Survives in soil. Ditylenchus spp. symptoms - Answer Distorted and stunted plants. SPongy tissues. Reduction of internode length and swollen stems. Bulbs with dark rings. Ditylenchus spp. management - Answer Systemic insecticides (not in CA). Resistant alfalfa, fenamiphos and oxamyl for garlic. Ditylenchus spp. importance - Answer Serious problems on daffodils, garlic and alfalfa Hemicycliophora arenaria - Answer Sheath nematode
Meloidogyne hapla - Answer Northern root-knot nematode Meloidogyne incognita - Answer Southern root-knot nematode Meloidogyne javanica - Answer Javanese root-knot nematode Meloidogyne naasi - Answer Barley root-knot nematode Meloidogyne spp. host range - Answer Very broad host range Meloidogyne spp. life cycle - Answer Sedentary endoparasite. J2 infective. Males veriform, females saccate. Males not required. Sexually dimorphic. Meloidogyne spp. symptoms - Answer Reduced root systems and galling. Poor top growth, chlorotic foliage. Meloidogyne spp. management - Answer Preplant nematicides, Resistant or immune cultivars and rootstocks. Hot water treatment. Crop rotation not feasible. Mesocriconema spp. - Answer Ring nematodes Mesocriconema xenoplax - Answer Ring nematode Mesocriconema spp. host range - Answer Wide host range, generally woody plants Mesocriconema spp. life cycle - Answer Migratory ectoparasite. Feeds on root tips or mature roots. All stages feed. Mesocriconema spp. symptoms - Answer Root-pruning effect. Reduction in feeder roots, ability to withstand stress, uptake of NPK. Mesocriconema spp. management - Answer Preplant nematicides. Mesocriconema spp. importance - Answer Associated with bacterial canker of stone fruits, severe in Central Valley Nacobbus spp. - Answer False root-knot nematodes Paratrichodorus spp. - Answer Stubby root nematodes Paratrichodorus spp. hosts - Answer Wide host range Paratrichodorus spp. life cycle - Answer Migratory ectoparasite. Feeds over entire root surfact. Paratrichodorus spp. symptoms - Answer Root tips stop growing and appear stubby
Paratrichodorus spp. management - Answer Preplant nematicides, virus-free planting stock Paratrichodorus spp. importance - Answer Associated with corky ring spot of potatoes. Paratylenchus spp. - Answer Pin nematodes Paratylenchus spp. host range - Answer Wide host range Paratylenchus spp. life cycle - Answer Migratory ectoparasite, J4 survival Paratylenchus spp. symptoms - Answer Crop decline in figs, damage to celery, deforms carrots Paratylenchus spp. importance - Answer Can occur in very high numbers without causing damage Pratylenchus spp. - Answer Lesion nematodes Pratylenchus brachyurus - Answer Southern lesion nematode Pratylenchus coffeae - Answer Coffee lesion nematode Pratylenchus neglectus - Answer Root lesion nematode Pratylenchus penetrans - Answer Northern lesion nematode Pratylenchus scribneri - Answer Scribner's lesion nematode Pratylenchus thornei - Answer Thorne's lesion nematode Pratylenchus vulnus - Answer Walnut lesion nematode Pratylenchus zeae - Answer corn lesion nematode Pratylenchus spp. host range - Answer Wide host range Pratylenchus spp. life cycle - Answer Migratory endoparasite, sexual reproduction, J2-adult can invade roots Pratylenchus spp. symptoms - Answer Small roots killed, opens roots to infection. Large necrotic lesions. Chlorotic foliage, poor growth. Reduced crop yield Pratylenchus spp. management - Answer Preplant nematicides, crop rotation not feasible Rotylenchulus reniformis - Answer Reniform nematode
