Nematodes are very small roundworms. They liveeverywhere - PDF document

Nematodes are very small roundworms. They liveeverywhereÑin soil, plants, water, and animals, includ-plants, and animals. Afew thousand species attackplants; most nematodes feed on dead or decaying organ-ic matter. Many nematode species are beneficial becauseThe life cycle of a nematode is egg, four juvenilestages, and adult. Adult females lay eggs that hatch intoadults. First and second stage juveniles are usually foundnile stage. After a total of four molts (shedding of theirare present, they mate and produce more eggs. Typically,the life cycle of a plant-parasitic nematode is completedAbout 95 percent of plant-feeding nematodes live inthe soil and feed in or on roots. Some consume above-ground plant parts. Plant-feeding nematodes feed byinserting a needlelike structure () into plant cells.They inject an enzyme into the cell that dissolves the cellremove the liquid cell contents. Nematode root feeding directly interferes with aplants wilt and appear to be suffering from a lack ofnematode populations result in plant stunting, yellow-ing, a general decline in plant health, and sometimesThough nematodes are small, they can easily dispersemove approximately 1 inch per year. However, they canbe transported from field to field or within a field byflood waters, dust storms, contaminated machinery, andNematode populations are identified and located fromfield soil samples. Soil and root samples can be submittedto MSU Diagnostic Services for identification. After prop-er identification, a site-specific nematode managementprogram can be developed. Details on how to collect andsubmit a proper soil sample are found in current MSUNEMATODE MANAGEMENTNematode management tactics can be grouped intothree types: prevention, containment, and chemicalcontrol. are intended to prevent nematodeproblems. Some are: practicing crop rotation, usingnematode-free seeds and transplants, planting nema-tode-resistant or -tolerant varieties, keeping farmequipment nematode free, and maintaining good farm After completely studying this chapter, you should:Know the three groups of control tactics specific totode, corn needle nematode, the root-lesion nema-tode, and the northern root-knot nematode. CHTERNEMATODE MANAGEMENT from spreading to other fields or other areas in theremove a nematode population from a field after it hasbecome established. Prevention tactics such as croprotation and planting nematode-free seeds and trans-plants can reduce the nematode population, however.are not often recommendedfor nematode control. However, both fumigant andcides) are available. Chemical control of nematodestode management strategies. For pesticide recommen-dations, refer to current MSU Extension bulletins.SOYBEAN CYST NEMATODE Host plants:crops (green beans, green peas) and weeds (henbit, fieldpennycress, shepherdÕs purse).with a male and produces 150 to 500 eggs. Shortly aftermating, she dies. But first she deposits a few eggs on theoutside of her body. The other eggs remain in her deadbody, which is called a . In the cyst the eggs are pro-tected from predators and environmental factors that Nematode life cycle. under cool, moist conditions. The juveniles emerge fromthe eggs and immediately begin searching for food -- soy-bean roots. Once the juveniles find a soybean root, theyenter the root and begin to feed. Ajuvenile soybean cystnematode molts four times before becoming an adultwith large soybean cyst nematode populations. Soil fumi-gants are available but very expensive. Non-fumigantnematicides applied at planting may reduce soybean cystnematode populations. In many situations, they, too, arevery costly.SUGAR BEET CYST NEMATODE ground symptoms of soybean cyst nematode damage arestunted and yellowed plants. Plant symptoms are usual-ly not evenly distributed in a field. In early July, whitefemale soybean cyst nematodes are found attached toplant roots. As the nematodes age, they become yellow.The attached females are the only visible sign of a soy-infestations can reduce soybean yields by 30 percentwithout plants showing symptoms. Severe infestationscan reduce soybean yields as much as 80 percent. To prevent soybean cyst nema-tode infestations, practice crop rotation, plant nematode-free seed, and maintain clean machinery. Nematode-resistant and -tolerant soybean varieties are available.ulations can be managed by practicing a three-year croprotation. Longer rotations may be necessary for fields Soybean cyst nematodes on soybean roots (G. Tylka,Iowa State University). Soybean field infected with soybean cyst nematodes. Asugar beet infected with sugar beet cyst nematode.Host plants:Sugar beets, cabbage, mustard, cauliflower,All cyst nematodes develop in the same manner. Therefore, the sugar beet cyst nematode is very After mating, females lay single eggs in rootsor soil. Second stage juveniles (J2) hatch from the eggs.Like all nematodes, the root-lesion nematode goesthrough four molts before reaching the adult stage.Adults and the last three juvenile stages can enter theroots to feed at any time. Root-lesion nematode may takefrom 30 to 86 days to complete its life cycle.Female corn needle nematodes produceroughly one egg per day over several months. In thespring after the eggs hatch, the juvenile nematode feedson young corn roots. As the soil temperature increases,the corn needle nematode migrates deeper into the soiland may stop feeding. In Michigan, it completes approx-imately one generation per year. The corn needle nema-of corn production and poor crop rotation. Unlike cystnematodes, the corn needle nematode will not surviveCorn needle nematodes do notenter the root but feed close to the root tip, preventing theroot from developing normally. The damage includes roottip swelling, stunted plants, small and barren ears at har-vest, and a reduction (10 to 75 percent) in grain yields. Thecorn needle nematode prefers to live in coarse-textured orsandy soils. As the soil moisture decreases and tempera-ture increases, the corn needle nematode moves deeperinto the soil. During the summer, the corn needle nema-Soil sampling should be done inspring or fall, when the corn needle nematode is close tothe soil surface. Sampling in the root zone during thesummer will not detect it. Crop rotation, especially withsoybeans or alfalfa, will reduce corn needle nematodepopulations. It is also important to maintain soil quality.Non-fumigant nematicides do not provide control of cornROOT-LESION NEMATODE Host plants:More than 350 recorded host plants, includ-similar to the soybean cyst nematode. After hatching, theroots to feed. As the nematode grows, it bursts from theroot. The white to yellow adult females are exposed onthe root surface. With ideal soil conditions, the sugar beetTypically, the sugarbeet cystnematode is found in the fibrous roots, but it can alsofeed on the storage root. Infected sugar beet plants arestunted, have yellow foliage, and wilt in warm weather.The wilting can be persistent even in soil with high mois-ture levels. You can see female sugar beet cyst nematodeson the plants roots without a hand lens. Severe nematodeinfestations may reduce yields. Sugar beets are the only majorhost of sugarbeet cyst nematodes in Michigan, so croprotation provides sufficient control. Typically, at least athree-year rotation out of sugar beets is recommended.However, in heavily infested fields a longer rotation (fiveto eight years) may be necessary. Currently, there are nosugar beet varieties that are resistant to the sugar beetCORN NEEDLE NEMATODE Plant symptoms of a sugar beet cyst nematode infestation. Root lesion nematode. Acorn needle nematode infestation can stunt a plantÕs feed on the smaller plant roots, killing them. The feedingenter the root system. Root-lesion nematode infestationscause plants to grow poorly and have yellow leaves thatmay wilt in hot weather, and can reduce crop yields.Infested seedlings are often stunted.a wide number plants. Therefore, crop rotation will usu-ally not sufficiently reduce their populations.Nematicides are available but should always be used onprogram.NORTHERN ROOT-KNOT NEMATODEMore than 300 recorded plants, including The female northern root-knot nematode pro-slime like mass on the outside of her body. In earlyspring, second stage juveniles hatch from the eggs andbegin to feed on roots. Their feeding causes the roots toswell. The northern root-knot nematode completes its lifecycle in one to two months. There are at least two gener-Northern root-knot nematodefeeding produces small root swellings called galls.Nematode-infested plants do not compete well for waterstressed even though there is sufficient soil moisture. Crop rotation is the most effectiveway to manage the northern root-knot worm. Usually aone-year rotation out of the host crop is necessary toreduce nematode populations. Soil fumigants effectivelycontrol northern root-knot nematodes and may be neces-sary when populations are high. Write the answers to the following questions and1.Nematodes are small roundworms.A.TrueB.False2.Plant-parasitic nematodes usually cause crop damageA.LeavesB.StemsC.FlowersD.Roots3.Ayoung nematode is called a:A.NymphB.JuvenileC.LarvaD.None of the above4.Nematodes can move across a field or from one fieldA.Dust stormsB.Contaminated machineryC.FloodwaterD.All of the above5.What type of mouthparts does a nematode have?A.ChewingB.SuckingC.Piercing/suckingD.Rasping6.List three types of management tactics used to control7.Nematicides are applied to plant leaves to controlroot-feeding nematodes.A.TrueB.False8-11.Match the following characteristics with the B. Corn needle nematodeD. Northern root-knot nematode8.___Cannot be detected by sampling in the cropÕs root zone during the summer.9.___Feeding results in the production of root 10.___Usually managed by practicing crop rotation and planting resistant varieties.11.___Extremely difficult to control with crop rotation.12.The eggs of a soybean cyst nematode can continue toA.1 weekB.10 hoursC.8 yearsD.12 days Review QuestionsChapter 8: Nematode Management CHTER 13.Which of the following nematodes does NOT enter the root to feed?A.Soybean cyst nematodeB.Corn needle nematodeC.Sugar beet cyst nematodeD.Root-lesion nematode14.Using crop rotation to stop a nematode population from growing and moving to other areas of a field is A.Chemical.B.Prevention.C.Containment.D.Biological.15.What is a cyst?