Horne, C. Wendell

Johnson, Jerral D.

English

Texas A&amp;M Repository

~..s-JIY)~ ? -J I -Jl/L-475The Texas A&MUniversity SystemTexasAgriculturalExtensionServiceDaniel C. Pfannstiel,DirectorCollege StationTOMATO DISEASESC. Wendell Horne and Jerral D. Johnson*Tomato diseases can be controlled by followingrecommended practices. Complete eradication sel-dom is possible, but disease damage can be lessened.Change the location of your tomatoes each year.Tomatoes should not follow peppers, Irish potatoes oreggplant. Grasses, grain sorghum, corn, rye, wheat,oats and barley are immune to most tomato diseases;hence, include them in your rotation plan. Avoidareas where Southern blight, nematodes and bacterialwilt have been problems.Grow disease-resistant, adapted varieties. It isimportant to plant fusarium wilt and nematode-resistant varieties in East and South Texas. Plantverticillium wilt-resistant varieties in West Texas.Varieties designated as VFN types are resistant toverticillium, fusarium and root knot nematodes. Askyour county Extension agent about the newest dis-ease-resistant varieties. Based on soil tests, add someform of calcium to prevent blossom-end rot. Calciumforms include limestone, gypsum and calcium nitrate.Use transplants grown under disease-free condi-tions. Disease-free plants are produced as follows:• Use disease-free or chemically fumigated soil inthe plant bed each year.• Use seed treated with Arasan® or Captan®.• Water the seedbed in the morning so the sur-face can dry before night.• Where hotbeds and coldframes are used, re-move the sheets in the daytime when the tem-perature is 45° F. or higher, provided there isno severe wind or rain.• Drench the plant bed with a copper fungicideused according to label directions. Drench be-fore plants come up and again when about 1week old.• Spray the plants with a copper fungicide every 7days. Do not apply within 1 week of trans-planting.• Wash hands with laundry soap each time afterusing tobacco before handling plants.*Extension plant pathologist, The Texas A&M University System.• In areas where fruit rot is common, stake orcage tomatoes .• Follow the spra schedule. Begin when bloomsappear and continue at 7- to 10-day intervals asneeded. Follow the shortest recommended in-terval during periods of above average rainfall.Apply sprays at the rate of 50 to 100 gallons ofwater per acre, depending on plant size and rowwidth.ost cleared fungicides are compatible with in-secticides. Combinations are satisfactory if both areneeded. Always follow label directions.Vary ~he foregoing practices to fit local conditions.A spray program to prevent bacterial and fungaldiseases is more necessary some years than others.Above average rainfall increases the incidence of mosttomato diseases. Studying regional and local weatherpatterns aids in timing applications. Many diseasesdecrease in importance during drought years. Iffoliage diseases were severe the previous year, theyare more likely to be severe during the current year.Check tomato plants often for disease symptoms.Fungicides prevent diseases rather than curingplants already infected. Important steps to follow in afungicide program are:• Use a fungicide that is effective in preventingdiseases commonly occurring in the area.• Apply before plants are infected.• Apply often enough to cover new growth and toreplace fungicides washed off by rain.• Completely cover all leaves, stems and fruits.Adjust spray equipment for proper coverage. Ad-just each sprayer type so it gives the best distributionand coverage. Use enough nozzles for each row toinsure directional coverage for all leaf and fruit sur-faces.DA PI G-OFFSOUTHERN BLIGHTROOT K OTFUSARIUM WILTMain symptoms. Y ng se dlings rna bkilled before or oon er emergenc. incstem are affect d at or n ar the round Ie elseedlings ilt, th n fall and die. Affectedplants usuall are confin d to certain ectionor area in the plant b d. Smaller plant thatsurvi e rna ha e har ,discolored terns.Main symptoms. Su den wilting of the en-tire plant without noti able change in foliagecolor. At the soil line, the main stem decaysfrom a white fungal owth adjacent to theground line. Small, ark, seed-like bodiescalled sclerotia form in the white fungalgrowth. This fungus al 0 may attack fruits onor near the ground. Caused by the fungusSclerotium rolfsii, it c n live on dead organicmatter on or near the oil surface.Main symptoms. PIa ts severely affected byroot knot are stunted nd weak. They wilt indry weather but may recover at night beforedying. Roots of infested plants have swellingsor galls.Main symptoms. Lo r leaves turn yellowto brown, and the plant may wilt first on onlyone side. Then the ntire plant graduallyturns yellow or brown, wilt and die . Cutstems ha e dark brown treaks on the inside.The disease is most erious during warmweather and usually appear hortly beforethe first fruit ripens.Principal control methods. To preventdamping-off u oil fre of pathogen ithgood drainag. her practical t rilize theoil. Treat the s ed and a oid 0 ercrowdingand 0 erwatering th eedling. Pro ide ade-quate ntilation and unlight in th plantbed. Appl a recommended fungicide beforeand after se dling emergence.Principal control methods. Commercialproducers should rotate tomatoes with resis-tant grass crops such as grain sorghum, rye,wheat, oats or corn. Keep crop re idue out ofthe area near the base of a plant. Deep burialof crop residue before plant establishment issuggested. Control foliage diseases with re-commended fungicides.Principal control methods. To prevent rootknot damage, use disease-free transplants andavoid nematode-infested soil. Soil fumigationmay be required where nematodes are a limit-ing factor and resistant varieties are not availa-ble. Varieties resistant to common species ofroot knot nematode include Big Set, Bon,us,Jackpot, Better Boy and Small Fry (cherrytype).Principal control methods. To preventfusarium wilt, use di ea e-resistant, adaptedvarietie . Re istant varieties include Home-stead 24, Home tead Elit Chico III, anap-aI, Floridel, Walter, Big Set, Bonus, Jackpot,Better Boy, Spring Giant and Small Fry (cher-ry type).BACTERIAL WILTBACTERIAL SPOTLATE BLIGHTGRAY MOLDMain symptoms. Plants often are dwarfed,and the ba e of stem may be a dirty gr en,brown or black and hri eled. Lea e rnawilt within 2 days aft r stem ymptom ap-pear. hen the ba e of a diseased stem i cut,a slimy, whiti h material flows from the watertubes within a few minutes.Main symptoms. Affected plants havesmall, dark, irregular greasy spots on theleaves. These spot enlarge, become black-ened and then sunken on the underside of theleaf. Affected leaves turn yellow and drop. Ongreen fruit, spots are first small; becomewhite and raised; and later are sunken, lightbrown and have a rough surface.Main symptoms. All above ground struc-tures can be affected by the late blight fungus.On leaves, greenish-black, irregular, water-soaked spots develop. Under damp condi-tions, the spots enlarge rapidly. A moldygrowth may develop on the lower leaf surface.Rainy, foggy weather with temperatures of40° to 60° F. at night and 70° to 80° F. in thedaytime favors diseas development. Elon-gated black cankers may develop on stem andMain symptoms. Gray mold occurs mainlyin greenhouse-grown tomatoes when the rela-tive humidity is extremely high and tempera-tures are cool inside. Disease symptoms in-clude gray, powdery tufts of fungus on affect-ed leaves, roots and t m .Principal control methods. To prevent bac-terial wilt, rotate tomatoes with gra e, grainorghum, corn or mall grains. Dela 4 ormore ar before planting tomatoe pep-per , Iri h potatoe or eggplants again. Re-mo ing and destroying di ea ed plants, cou-pled with insect control, prevents furtherspread.Principal control methods. When bacterialspot is found on a few plants, destroy orremove them from the field immediately.Avoid letting them contact other plants. Sprayplants with fixed copper according to manu-facturers' suggestions. Use seed from healthyplants.leaf petioles. On the fruit, water-soaked spotsdevelop, enlarge rapidly and gradually turngreenish-brown. The surface of the diseasedarea is firm and irregular, sometimes coveringhalf the fruit.Principal control methods. To avoid dam-age from late blight, use disease-free trans-plants and follow a regular spray schedule.Staking or caging helps reduce fruit losses.Principal control methods. To control dam-age from gray mold, practice good sanitationby removing dead plant parts from thegreenhouse. Utilize a preventive spray sched-ule to avoid development of high fungal sporepopulations. Shorter spray intervals may berequired to get the disease under control.Improve air circulation in greenhouses.EARLY BLIGHT A D COLLAR ROTGRAY LEAF SPOTMain symptoms. Plants affi cted b arlblight and collar rot ho larg, dark circularspot with concentric markings (targ t poteffect) on lea e and darkened pot on t m .Spots occur on the 10 er lea es first· duringse ere attack lower lea e are killed. Fruitmay d velop dark, leather pot at or n arthe stem end. This organism al 0 may cau e agirdling of plants in e dbeds (collar-rot).Main symptoms. ray leaf spot causes gray-ish-brown, shiny s ot (1/16 to V8 inch in di-ameter) to appear on leaves. Affected leavesturn yellow and drop from the plant. Thedisease usually starts on lower leaves and thenworks up the plant.Principal control methods. To a oid thidi ease u di a -fre tran plant practicrotation and appl appro ed fungicide regu-larl . Pre ent collar rot in the plant b d bu ing recommen'ded fungicide pra .Principal control methods. Use the samecontrol method suggested for early blight.LEAF MOLDMain symptoms. Yellowish-green blotches Principal control methods. To prevent leafon the upper sides of the leaves, accompanied mold, follow a regular spray schedule. Im-by greenish-brown, moldy spots on the lower prove air circulation in greenhouses and avoidsides appear on plants having leaf mold. Leaf overcrowding the plants.mold may be destructive in fields in cool, wetweather and in greenhouses.MOSAICMain symptoms. Diseased plants havemottled leaves and often are stunted. Fruitmay be fewer in n mber and smaller thanthose formed on healthy plants. Wrinklingand strapping leaflets may occur when severestrain of the virus are present. The mottlingsymptoms in leaves may di appear in hotweather. The virus, present in some types oftobacco products, c n be transmitted on thehands, and it survives in crop residue in thesoil. Once the virus !is established in plants, itcan be distributed to other plants mechanical-ly.Principal control methods. To avoid con-tamination, wash hands with laundry soapbefore handling plants. Avoid excessive han-dling of plants in plant beds or in the field.Removing disea ed plant i helpful onlyif they do not contact normal plants.CURLY TOPBLOSSOM-END ROTANTHRACNOSESOIL ROTMain symptoms. Curly top is a disease oc-curring primarily in irrigated areas of Westand South Texas. Upper leaves turn grayish-green. Soon the e becom crisp, brittle androll upward. Leave then turn light green toyellow, with purple veins on the lower side.Plants stop growing fail to ripen fruit and diewithin a few weeks.Main symptoms. Dark, sunken, leatheryspots appear on the blossom-end of greenfruits. The spots vary in size, sometimes af-fecting half the fruit. This is a physiologicaldisease caused by a fluctuating moisture sup-ply and a lack of calcium.Main symptoms. Light-brown, circular,sunken spots with darker colored rings de-velop on ripe fruit. Small black specks oftendevelop in the center of these spots. Soft rotsmay develop.Main symptoms. Fruits touching wet soiloften develop large, cracked, rotten spotswith alternating bands of light and dark-brown color. The rot is caused by the fungusRhizoctonia that is common in culti ated soil.Principal control 1nethods. This virus istran mitted by the beet leafhopper. Insec-ticide use may limit the damage, but it willnot prevent all infection. The condition can.best be prevented by u ing resi tant varietiessuch as Ropac, Roza, Columbia or Salad-master.Principal control methods. Based on a soiltest, add adequate limestone or gypsum tobalance deficient soils. Use adapted varieties.The addition of calcium chloride to the spraymay be beneficial. Maintain a uniform soilmoisture supply with irrigation and mulch.Principal control methods. To control an-thracnose, apply regular sprays of approvedfungicides. Practice rotation and avoid poorlydrained soil. Caging, staking or mulching re-duces fruit infection by the fungus.Principal control methods. To prevent soilrot, cage and tie plants to stakes or wires oruse a plastic mulch. Time the irrigation tokeep soil dry under the plants a much aspossible during harvest. Follow the regularspray schedule.Fungus, Bacterial and ematode Diseasesand Their Causal OrganismsDiseaseDamping-offCollar rot andearly blightSouthern blightRoot knotFusarium wiltBacterial wiltGray moldBacterial spotLate blightGray leaf spotLeafmoldAnthracnoseSoil rotsCausal organismPythium and Rhizoctonia spp.Alternaria solaniSclerotium rolfsiiMeloidogyne pp.Fusarium oxysporum f.Pseudomonas solanacearumBotrytis cineraXanthomonas vesicatoriaPhytophthora infestansStemphylium solaniCladosporium fulvumGleosporium atramentariumRhizoctonia spp. andPhytophthora spp.Educational programs conducted by the Texas Agricultural Exten-sion Service serve people of all ages regardless of socioeconomiclevel, race, color, sex, religion or national origin.Cooperative Extension Work in Agriculture and Home Economics,The Texas A&M University System and the United States Depart-ment of Agriculture cooperating. Distributed in furtherance of theActs of Congress of May , 1914, as amended, and June 30, 1914.25M-6-80, Revision PP

Tomato Diseases.

https://oaktrust.library.tamu.edu/bitstream/1969.1/172788/8/475/Leaf0475.pdf

Tomato Diseases.

Abstract

Similar works

Full text

Available Versions

Texas A&M Repository

Tomato Diseases.

Abstract

Similar works

Full text

Available Versions

Texas A&amp;M Repository

Texas A&M Repository