PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
CONTROL
METHODS
(contd)
In Israel, some carrot
and tomato cropping
lands have been
abandoned due to
Egyptian broomrape
(O. aegyptiaca)
infestations
SANITATION.
In urban gardens diligent pruning or removal of all traces of the parasite may mean
sacrificing plants. This coupled with regular inspections can be very slow and not
practical for large areas.
Broomrape can be pulled up by hand or hoeing before seed is set to reduce damage
to the current crop and future infestations. Minimize weed hosts, eg skeleton weed.
Tangled masses of devil’s twine can be pulled off host stems as early as
possible before seed is set. Prune off badly affected sections of host. It may be
necessary to sacrifice whole plants.
Dodder. Prune off infested plant parts. If this is done before the dodder produces
seed this may eradicate it from a small area. Destroy patches of dodder and host
plants as soon as noticed, by mowing, and burning the cut material where it lies or
killing the standing crop plants by spraying with a herbicide and then burning.
Infested crops can also be grazed by sheep and residual clumps of dodder later
slashed. Control weeds between crop rows.
Prune out large mistletoes early on isolated plants well below the point of
attachment to the host branch to prevent regeneration. It may be necessary to
remove the whole branch if damage is severe, cutting off the mistletoe where it joins
the host branch is not sufficient. After removing the mistletoe improve tree vigor by
fertilizing and watering. Cherry pickers have been used in large areas. Occasionally
whole trees, eg silver birches, may have to be removed.
Clean equipment before moving from infested to dodder-free areas. Similarly
limit movement of domestic animals.
BIOLOGICAL CONTROL.
Like other plants, parasitic flowering plants have natural enemies, eg
Broomrape (Orobanche spp.) has been controlled overseas to some extent, in some
crops by a fly (Phytomyza orobanchiae), myco-herbicides, eg Fusarium spp., and by
the fungus Trichoderma when combined with a herbicide spray.
Dodder (Cuscuta spp.) has been controlled in soybeans in China by the fungus
(Colletotrichum gloeosporioides). Fusarium spp. have been used overseas to control
dodder in cranberry crops (Brown and Ogle 1997).
Mistletoe (various species).
– Mistletoe browntail moth (Euproctis edwardsii) larvae are banded light and dark
grey, up to 40 cm long and have irritation hairs. Other moth larva and beetles can
infest mistletoe wood but none of these offer any control.
– Long term mistletoe management strategies should encourage formerly
abundant predators such as possums and gliders, or hyperparasites, such as harlequin
mistletoe (Lysiana exocarpi), to help control some mistletoe species.
RESISTANT, TOLERANT VARIETIES.
Although resistance has been bred into some crops, there are few examples of success,
and it has been overcome.
Broomrape. Sunflowers resistant to broomrapes are grown in Russia.
Witchweeds. Cowpea in West Africa and sorghum in India have shown high
levels of resistance to witchweeds (Brown and Ogle 1997).
Mistletoes. Eucalyptus nova-anglica and E. viminalis appear to have some
resistance to some species of mistletoe in some localities.
Dodder. Wheat, barley, oats and cereal rye crops are poor hosts. Summer grain
crops, eg maize and sorghum are resistant to golden dodder (Cuscuta campestris).
PLANT QUARANTINE.
AQIS (Australian Quarantine and Inspection Service). Because of
difficulty in controlling parasitic plants after establishment, all broomrapes,
witchweeds and dodder are prohibited imports (page 383). If some become
established even in small areas, Australian export markets could be affected as many
of our trading partners prohibit their import. Although seeds of these plants are a
prohibited import, seeds could enter undetected via contaminated soil, machinery
livestock clothing. Northern Australian Quarantine Strategy (NAQS) monitors for
exotic witchweeds and other target weeds during regular surveys of land across
northern Australia and in neighbouring countries.
PaDIL - Pests and Diseases Image Library www.padil.gov,au
Target lists www.daff.gov.au www.daff.gov.au/aqis
State/Territory quarantine.
– The recently introduced branched broomrape (Orobanche ramosa) is a prohibited
species in WA and SA. There are protocols for the movement of horticultural
produce, grain, straw, soil, conservation fodder, machinery and livestock in the
quarantine area. There is a Code for the Control of Branched Broomrape on the
GRDC website with prescribed treatments to eradicate infestations and prevent
spread and seed set. www.grdc.com.au/
– Pest-free status for dodder weed (Cuscuta sp.) must be demonstrated for henbane
(Hyoscyamus niger) seed grown in the Ord River Irrigation Area in North WA for
export to the US without need for treatment.
Local quarantine. Prevent spread of seed to areas where temperature and other
environmental conditions favour the parasitic plant in question.
384 Parasitic flowering plants