PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Management (IDM)
For commercial growers IDM is essential.
1.Planning is essential and may start 12 months
before planting, eg after previous final harvest ploughout
affected crops to expose roots to wind and sun. In
greenhouses root knot should not be a problem where
routine hygiene and soil-less media are used. Plan the
new crop to include appropriate non-chemical methods:
Carry out a pre-plant nematode analysis.
Use resistant varieties and cover crops as part of
your IDM program if available
Treat affected areas with a recommended nematicide
before planting only if monitoring indicates that it
can be justified.
Fumigation by appropriately trained and licensed
operators may be appropriate for seedbeds.
Utilize soil conditions suppressive to nematodes, eg
minimum tillage, crop rotation, green manuring
organic amendments and mulches to enhance
biological activity of organisms against nematodes.
2.Crop, region. Obtain information from local
departments of agriculture on root knot on your crop
in your region. Recognize variations.
3.Identification must be confirmed. Galls caused
by root knot nematodes are easy to identify (page
268). Species identification is difficult and is only
important when resistant varieties and crop rotation
are being used as control methods. Check to see if a
test for growers has been developed. If not consult a
diagnostic service (page xiv).
4.Monitoring strategies include:
Pre-plant nematode soil analysis, including
nematode counts of the top 15cm of soil is
necessary where root knot has been a problem.
Monitoring when growth is generally unthrifty,
examine washed roots under the microscope for
evidence of galls. Record results of monitoring.
Checking if conditions favour root knot.
Assessing end-of-season galling in the field to
indicate infestation liability for the following crop.
Remember know when, where, what and
how to monitor.
5.Specific thresholds are available for some
crops, especially tomatoes. For other crops, how
much damage can you accept?
6.Action. Interpret monitoring. Only apply nematicides
if monitoring has shown that numbers would cause
economic damage unless it was applied.
7.Evaluation. Review IDM program to see how
well it worked. Recommend improvements if required.
Control methods
Once the presence of root knot nematodes in the
field is confirmed, it is almost impossible to
eradicate them. Chemical control is not practical for
home gardeners or persons with few resources,
non-chemical control methods including
sanitation are their preferred options.
Cultural methods.
Cultural care. Affects of root knot can be
offset to some degree by protecting plants from
stress. Regular water and fertilizer, the use of
mulch and the control of other diseases and pests
tend to reduce damage caused by nematodes.
Summer fallow. Keep all vegetation, including
weeds, off the infested area for one growing
season. This is a cheap and effective means of
reducing numbers. Cultivate soil after each period
of rain to prevent weed growth. Fallowing does
not stop nematode eggs from hatching but without
food plants, the young nematodes die. Fallowing
may lead to wind and rain erosion.
Apply organic amendments and adequate
fertilizer to minimize losses.
Crop rotation. Where root knot nematodes
are a problem, avoid planting susceptible crops
continuously in the same area. Rotate crops
with resistant, immune or non-host crops such as
some grasses, cereal, cabbage, cauliflower,
maize, sorghum and sweetcorn and onions which
may have some resistance to some root knot
species. Rotation crops must have a high level
of resistance otherwise sufficient nematodes
may carry over to damage the next susceptible
crop. Crop rotation is useful in management but
the difficulty is in determination of host range.
– Nemfix is a cultivar of mustard selected for its
glucosilinates (which interfere with the breeding
cycle of nematodes) and its potential as a biofumigant.
Nemfix can be a useful green manure
crop used in rotation with Coolabah or Swan oats
if root knot suppression is desired.
– Some growers use rotation in combination with a
weed-free fallow to reduce nematode numbers.
– Cover crops such as sorghum have proven
effective in some vegetable growing regions due to
its resistance to the common nematode species of
root knot nematode.
Repellent plants. Asparagus roots secrete an
exudate which is toxic to root knot nematodes.
Trap plants. French marigold (Tagetes patula)
cultivars, produce exudates that stimulate hatching
of nematode eggs. The larvae then enter marigold
roots but die shortly afterwards before completing
their life cycle. Plant marigolds in 15 cm wide
rows about 15 cm apart and grow for about 90-120
days (a whole growing season) to sufficiently
reduce the nematode population to grow annuals
without further treatment. Often not practical.
Providing peat and other components of
potting mixes are obtained from sources free of
root knot and are not contaminated prior to use,
treatment before use is unnecessary.
Sanitation.
Burn all diseased plants. Do not throw infected
crop refuse onto compost heaps or manure heaps.
Do not feed infected potatoes, carrots and other
plant material to stock unless it has been boiled
first to kill the nematodes as they can pass
through the digestive tract of animals unharmed.
Stand pots and other containers on wire mesh
rather than solid benches to prevent nematodes
swimming from pot to pot in drainage water.
Wash and disinfect equipment prior to using.
Boots and other footwear worn in contaminated
areas should also be cleaned thoroughly after use.
Immediately after final harvest plough-out
affected crops to expose roots to wind and sun.
Maintain high levels of hygiene at all times to
prevent introduction of contaminated cuttings,
personnel, potting media, water and roots.
Control volunteer crop regrowth and weeds .
Biological control.
Many bacteria, predatory fungi and nematodes,
exert some control of root knot nematodes,
and are being researched for commercial use
(page 263.
Suppressive soils prevent nematodes from
establishing and from causing disease, and they
diminish disease severity after initial nematode
damage when hosts are continuously grown
(page 263).
270 Nematode diseases