Plant Health Brief
A Publication of the Agri-Food & Veterinary Authority of Singapore -
Diamond Back Moth infestation on Vegetables
Number of Thrips/Trap
90
80
70
60
50
2015
40
2016
30
20
10
0
Number of Diamond Back Moths/Trap
Thrips infestation on Orchids
March 2016
70
60
50
40
30
2015
2016
20
10
0
Comments:. The overall average thrips population for
Comments: The overall average Diamondback moth
March 16 was around 31 thrips/trap while in Feb 16 it
was around 19 thrips/trap which showed that there is a
significant increase in the average thrips population in
March 16 as compared to Feb 16. In comparison with
March last year, there was a moderate decrease in the
overall average thrips population from 48 thrips/trap
(March 15) to 31 thrips/trap (March 16). In general the
thrips population for the last three months was found
lower as compared with the last year.
(DBM) population for March 16 was around 61 moths/trap
while in Feb 16, it was around 35 moths/trap which showed
that there is a significant increase in the average DBM
population in March 16 as compared to Feb 16. In
comparison with March last year, there was a significant
increase in the overall average DBM population from
14moths/trap (March 15) to 61 moths/trap (March 16). In
general the DBM population for the last three months was
found higher as compared with the last year.
PULVINARIA SPECIES – SOFT SCALE
INSECT ON MURRAYA PANICULATA
been featured earlier. Pulvinaria species found on Murraya
paniculata (Fig 1 & 2) in our routine plant health surveillance in
Singapore is an example of soft scale insects to be elaborated
here. Soft scale insects (family Coccidae) like Pulvinaria
species have a smooth, cottony, or waxy surface. At maturity,
they are usually larger and more rounded and convex than
armoured scales. Pulvinaria species can produce a mass of
eggs in a cottony ovisac without mating and excrete excess
sap from the phloem as a by-product called honeydew.
Honeydew is usually the first sign that a soft scale is feeding
on the tree. Honeydew will stick leaves together and attract
many insects (e.g. ants, wasps, and flies) that will feed on the
excretions and promotes the growth of blackish sooty mould.
Insects i.e. ants can then carry scales to uninfested plants as
well as protect them from natural enemies such as predators
and parasites. The coating of sooty mould interferes with the
plant’s ability to manufacture food through photosynthesis. Mild
infestation may escape notice but heavy feeding by soft scales
cause yellowing of leaves and overall plant decline. The
ovisacs and honeydew excreted can disfigure plants. Feeding
by scales opens up wounds that provide entry sites for plant
pathogens that predispose plants to disease infection.
Important Some important species of Pulvinaria include
Scale insects are sucking insect pests on ornamental trees
and shrubs. They appear as small bumps on the foliage,
twigs and branches of many landscape trees and shrubs.
They are often overlooked as they are immobile insects that
blend in with the bark and leaves till the plant exhibit visible
symptoms i.e. yellowing. Their waxy shell or the scale cover
(where they obtained their common name – scale insects)
is secreted by the insects to protect themselves from the
environment and predators. This waxy covering is also a
barrier
to
many
pesticides
used
for
insect
management.There are two types of scales i.e. soft (or
bark) scales and hard (or armoured) scales. Both types
spend most of their life protected by the scale covering that
they produce. Characteristics of soft scales include (1)
produce honeydew; (2) highly active crawlers and (3) has a
protective body wall. Soft scales, unlike hard scales, feed
by sucking within the vascular system with their tube-like
mouthparts while hard scales rupture and destroy plant
cells they are feeding on and may bypass the vascular
system. Chrysomphalus aonidum - a hard scale insect has
species such as P. floccifera (cottony camellia scale) - an
important scale insects on Citrus, P. innumerabilis (cottony
maple scale) affecting many species in landscapes and P.
urbicola affecting many hosts such as guava, pineapple,
and frangipani, etc. Generally, scale insects begin their
lives as eggs laid under the shell of the females i.e. in high
numbers probably up to thousand per adult female. The
eggs hatch into mobile active crawlers that look for new
food source. They may be dropped off into the air currents
or dispersed over hundreds of metres to fresh hosts. Long
distance dispersal may be possible through birds. Once the
crawlers settle on a host plants, it will start feeding on plant
sap and develop into second and third instar (adult insects)
with the protective waxy covering. Regular visual inspection
of plants is required to treat localised infestations by
physical removal before they escalate. Placing doublesided sticky tape around stems could help to monitor if
crawler stage is present. Systemic insecticides, e.g.
dimethoate, imidacloprid, etc. are more effective in
controlling soft scales i.e. Pulvinaria species as there is a
stronger likelihood that the applied insecticide transported
through the plant vascular system would be ingested by the
scales feeding on plant sap in the plant vascular system.
However, severe field infestations usually comprised of
overlapping/multiple generations and multiple pesticide
applications are generally required for control. Therefore, it
is best to control mild infestation before the situation
worsens to avoid multiple pesticide applications.
PEST INTERCEPTIONS FOR MARCH 2016
There was no pest interception for the month of
March 16.
PESTICIDE INFORMATION
COMMON
Propineb
NAME
TRADE NAME
Antracol
70WP,
WendellPropineb,
Propineb
7000,Propineb 70.
TYPE
Fungicide
CHEMICAL
Nonspecific
,
multi-site
NATURE
fungicide
belongs
to
dithocarbamate group
FORMULATION Wettable powder
PROPERTIES
Foliar fungicide with protective
action. Fungal spores are killed
by contact action.
USES
Used as a foliar fungicide
against
many
leaf
boren
pathogens such as Alternaria,
Septoria leaf spots. Also used
against Phytophthora blight,
downy mildew on tobacco, rust
and leaf spot diseases on
ornamentals .
TOXICOLGY
Acute oral LD50 for rats: Around
5000 mg/kg. Not irritating to
skin and eyes. Non toxic to
honey bees
DOSAGE
2-3 gms/lit
WITH-HOLDING 2 weeks
PERIOD
CONTACT US
Fig 1. Pulvinaria sp on Murraya paniculata
Fig 2. Pulvinaria sp- Enlarged
Please report any unusual occurrence of plant pests
(new or severe occurrence) to Plant Health
Laboratory, AVA. It would help to protect our plant
industry and the garden city from new invasive
pests. Please provide the location, plant hosts
attacked and suspected pests or diseases to our
officers to follow-up and confirm the situation if
required. You can report your observations through:
Email: [email protected]
Telephone: 63165168 or 63165188 or Fax:
63161090
Visit us at: http://www.ava.gov.sg