|Disease (causal agent)
||Survival of pathogen and effect of environment
||Comments on control
|Botrytis disease (Botrytis blight,
Neck rot, Corm disease)
(Botrytis gladiolorum, B. cinerea)
leaf spots develop; spots may expand or coalesce. Brown water-soaked spots
appear on flower petals. Basal stem infections (neck rot) may penetrate corm;
corm decay may continue in cold storage. Woolly gray fungus spores may form on decayed tissues. Black seedlike sclerotia may form on underground parts.
||In corms and on crop refuse.
Spores are airborne. Favored by moist conditions and low temperatures (50° to 70°F).
||Complete control program essential
in coastal areas: cure and treat corms as outlined at end of this section;
protect foliage with chlorothalonil, iprodione, mancozeb, or
thiophanate-methyl. After harvest and before packing, spray flower spikes with
a fungicide. more info *
(Fusarium oxysporum f. sp. gladioli)
|Leaves tend to turn downward,
yellow progressively, and die prematurely. Brown rot of corms begins in basal
plate and core, and extends upward into the leaf bases via vascular strands.
Corms may rot in ground or while in storage. Cultivars vary in symptoms and susceptibility. Infection without obvious symptoms is common.
||In diseased corms and in infested soil for many years. Favored by temperatures of 70°F or above.
||Plant disease‑free corms in
clean soil, or grow resistant cultivars. Hot water treatment of cormels
eliminates the fungus from infected stocks. Cure and treat corms as outlined
at end of this section. Fumigate infested soil with methyl bromide‑
chloropicrin combination. Disease is less severe if soil pH is 6.6 to 7.0 and 80 to 90% of nitrogen is the nitrate form.
|Penicillium corm rot
|A firm brown corm rot develops in
storage; frequently in association with other corm rots. If conditions are moist, greenish blue spore masses appear over rotted areas.
||On corms and corm debris and as
spores on storage‑room equipment. Rot develops rapidly when humidity is high.
||Cure and treat corms as outlined at end of this section.
|Rhizoctonia neck rot
|Stem below ground and husks at
harvest appear shredded. Brown fungus strands (mycelium) visible with a hand lens.
||Common soilborne fungus with wide host range. Favored by warm, wet conditions.
||Corm dips help control the fungus.
Treat soil with PCNB before planting. Sprays of iprodione or thiophanate-methyl should reduce spread of the fungus down the row.
(Pseudomonas gladioli pv.
|Mainly seen on corms as irregular
or round sunken brown spots with a shiny, brittle, varnishlike material (bacterial exudate) on the surface.
||On corms and in soil refuse for 2
years. Favored by heavy, wet soils and warm weather. Encouraged by heavy nitrogen fertilization.
||Rotate every 3 years. Control
measures for other diseases usually take care of scab. Control chewing insects in the soil.
|Stemphyllium leaf spot
|Small round or
angular yellow spots with a red dot in the center appear on green parts of plants. Spots are larger on some cultivars. Cultivars differ in susceptibility.
||Carried over on gladiolus foliage
and refuse. Favored by warm, wet weather, especially sprinkler irrigation and rain.
||Spray mancozeb at 10- to 14-day intervals. Plow under gladiolus crop residues.
|Leaves yellow and die. Leaf
sheaths rot at soil level (neck rot). Rotted tissues appear shredded.
Numerous, very small black fungus resting structures (sclerotia) are imbedded in dead tissue. Corm lesions are dark brown and sunken with raised margins.
||On diseased corms and in soil for 10 years or more. Favored by wet soil.
||Cure and treat corms as outlined
at end of this section. Use uninfested or chemically treated land. Fumigate soil with methyl bromide‑chloropicrin combination.
|* For additional information, see section on Key Diseases.
|Virus or viruslike disease
||Host range and natural spread
||Comments on control
(Aster yellows phytoplasma)
|Current season infection results
in early maturity, small corms, and arrested root development. Next year, the
corms produce numerous thin, weak shoots—grassy top. Flowers produced by grassy top plants are green.
||Leafhoppers. Many kinds of plants, including some weeds.
||Destroy infected plants.
(Bean yellow mosaic virus)
|A faint leaf mottle and sometimes
a pencil‑stripe color break of blossoms. Disease is common in nearly
all gladiolus cultivars but symptoms are more severe in some cultivars. Blossoms may fail to open all the way.
||Aphids. Mechanically transmitted by harvesting tools. Legumes (beans, peas, vetch).
||Propagate from selected disease‑free plants grown in isolated areas.
(Tobacco ringspot virus,Tomato
|Yellow or white ring patterns and blotches on leaves.
||Nematodes. Mechanically transmitted by harvesting tools. Many kinds of plants, including weeds.
||Destroy infected plants.
||Plants are stunted and produce
short spikes. Virus nature not proved. Disease commonly affects 'Chamouny', 'Spic and Span', 'Elizabeth the Queen' cultivars.
||White blotches on flowers. Flowers open poorly and may shrivel prematurely.
||Corm-propagated. Vector unknown.
||Propagate from selected disease‑free
plants grown in isolated areas. Rogue infected plants at flowering time, or as soon as virus symptoms appear.
(Cucumber mosaic virus)
|White streaking or flecking of
leaves and a white blotch or color break in petals. Flowers sometimes fail to open completely.
||Aphids. Sometimes transmitted by harvesting tools. Cucurbits (melons, cucumber, squash).
||Rogue infected plants at flowering time, or as soon as virus symptoms appears. Control aphids.
leafspot (Septoria gladioli) and leaf smut (Urocystis gladiolicola) are rare diseases in California. Curvularia leafspot (Curvularia lunata)
appears occasionally as a neck rot, particularly in cormel stocks.
||The major gladiolus pathogens can be carried on
the surface of or inside corms. To control the pathogens, it is essential to correctly cure, store, and dip corms before planting.
|Curing: Immediately after digging, place corms in shallow
trays in storage rooms maintained at 95°F (35°C) and 80% relative humidity.
Use fans to circulate air through and around corms. When old corms break off
easily, usually after 6–8 days, clean the new corms. Return corms to storage at 95°F and 80% relative humidity for 4 more days.
|Storage: Store cured corms at 40°F and 70–80% relative
humidity. In mild climates, clean corms can be replanted if Fusarium yellows is not a problem.
|Preplant dip: Before planting, dip corms in iprodione or
thiabendazole plus 4–6 fluid ounces of wetting agent/100 gal water. The
water should be at a temperature of 80° to 90°F. Allow corms to dry before planting.
|Sanitation: Maintain sanitary storage facilities. Burn all gladiolus refuse. Steam treat or disinfect trays, tools, and the like.
|Hot water treatment of cormels: (1) Select sound, hard, fully
dormant corms grown in warm soil and harvested before cold weather. Cure as
outlined. (2) Presoak corms for 2 days in water when the air temperature is
60° to 80°F. Discard any corms that float. (3) Immerse 30 minutes in water
heated to 131°F. (4) Cool immediately with clean, cold water. (5) Dry
thoroughly and quickly in warm air or sunshine. (6) Dust with a fungicide and store at 40°F and 70–80% relative humidity.