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Genus Ditylenchus Filipjev
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Control
Control
The control of
stem and bulb nematode is based mainly on basic
principles which emphasize the use of clean planting stock and
denematization of propogative materials, either through fumigation or
hot water treatment. Methyl bromide fumigation of seed
and bulb at atmospheric pressure of 70
g/ma for 20 hours (CT=1400), SOg/m8 for 16
hours (CT=1280) and in a vacuum at 50 g/m3 for 20
hours, 60 g/ma for 16 hour, I00g/ma for 8 hours
(CT= 1000, 980 and 800 respectively) has proved successful6".
Germination of planting material is reportedly not affected even two
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years after
treatment. In the past, DBCP, applied at the time of alfalfa
seeding, was found quite effective in reducing reproduction of the
nematode. Good to excellent control of the nematode has been
obtained with non-fumigant chemicals, like aldicarb on narcissus,
onion, tulip; carbofuran on narcissus, onion; dazomet on onion,
demeton on narcissus; oxamyl on narcissus and onion; phenamiphos on
narcissus and onion; phorate on narcissus and onion; scbaradan on
narcissus; thionazin on narcissus, onion, tulip, oat, hydrangea, red
clover and white clover; and Shell OS 1836 on narcissus and tulip60.
Potassium metabisulfate tablets (at 400 mg/1000 cm3
distilled water) have provided effective control of the nematode in
onion and garlic".
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Infected seeds
and bulbs of several plant species can be successfully treated for
denematization by immersing them in hot water. In general, exposure of
dormant bulbs to hot water bath at 44-45°C for 3 hours, yields
satisfactory results. Pre-soaking plus wetting agent and addition of
fungicides aid in better control of the nematode. Soaking at 100°F for
30 minutes in a formalin (1 per cent)—detergent solution (0.1 per cent),
followed by a treatment for 20 minutes at 120°F in the same solution
eradicates the nematode in garlic cloves.
Crop rotation
is also an effective method and has been recommended for many crops
like oat, rhubarb, strawberry clover, narcissus, alfalfa, onion and
teasel. The success of crop rotation, as a primary means for the control
of the nematode, depends on knowledge about existence of biological
races, host range including crops and weed hosts, environmental factors
like temperature, relative humidity and soil types. A rotation of 3-10
years, with non-host crops, has been recommended for teasel, narcissus,
onion and alfalfa.
Sources of
resistance against the nematode have been identified in some cases
Alfalfa is one of the several crops which bas been extensively studied
for incorporation of stem nematode resistance in commercial cultivars.
Employing original source of resistance from Turkey or Iran, nematode
resistant lines, Turkistan, Nemastan, Lahontan, Keyseri and Talent have
been developed
which have
subsequently served as parental lines for breeding D. dipsaci
resistant alfalfa cultivars.
Although
host resistance provides an useful method for the management of the
nematode, it is important to keep in mind that not all populations of
nematode respond uniformly to a given resistant variety. For example, 'Wando'
pea is susceptible to D. dipsaci population from Raleigh, North
Carolina (RNC population), but resistant to Waynesville N.C.
population.
Inheritance
of resistance has been studied in few crops. Resistance in alfalfa is
tetrasomic while in oats it is governed by a single factor pair and in
clover by few genes.
Nematophagous fungi, Arihrobotrys anconia, A. oligoSpora, Dactylella
sp. and Catenaria aiguiliulae offer some potential as
biological agents for controlling the nematode. One to 5 conidia of
Hirsmella rossilisnsis kill D. dipSad after 5 days by
invading the body cavity. In another study, two strains of
Monacrosporium salinum have been recorded effective in trapping the
nematode.
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