Aphids, SLWF spoil the party
Hopes of a bumper 2011-12 cotton season, coupled with good
prices, risk being soured by the emergence of Cotton Bunchy Top
(CBT) disease outbreaks in all major cotton growing areas.
This is the warning of agricultural researchers and extension
officers from Queensland's Department of Employment Economic
Development and Innovation (DEEDI), CSIRO and other pest and cotton
biosecurity experts.
A 2011 industry-wide pathology survey conducted post flowering
by DEEDI's Industry Development and Delivery Team and reported in
CRDC's 'Winter Spotlight' 2011*, confirmed a startling
50% of cotton fields showed presence of CBT.
Compounding the risks has been the wet and mild weather -
including floods in Queensland and the wettest winter in NSW for
more than 50 years in some areas - which have provided ideal
conditions for weed growth and over-wintering insect survival.
CBT is spread by cotton insect pests such as aphids - which in
themselves are problem sucking pests in cotton, and which are
becoming increasingly resistant to many current chemical control
measures including newer expensive products.
The clear message from entomologists and agricultural advisors -
remove overwintering weed hosts, volunteer and ratoon cotton and
also be cautious when double cropping to reduce the 'green bridge'
which allows pests such as aphids to survive and infest next
season's cotton crop.
Technical and Marketing manager for Caltex Precision Spray Oils,
Dr David Johnson, said growers had an invaluable tool to help
manage the latest pest and disease threat by using a carefully
targeted early season spray of Canopy® to control sucking pests
such as aphids and mirids in cotton.
Unlike the widely used neonicotinoids, carbamates,
organophosphates and synthetic pyrethroids - each of which was
suffering varying levels of insect resistance problems -Canopy's
mode-of-action offered an effective alternate class of chemical to
clean up problem pests.
"Even the cleanest crops with no overwintering weeds in the
fallow or crop margins, can still suffer migrations of
disease-carrying and potentially insecticide-resistant insects from
neighbouring crops, channels and native vegetation," Dr Johnson
said.
Canopy has the added advantage of being an oil-based
formulation, which largely controls sucking insect pests via
suffocation - a mode-of-action that has no known resistance
problems. Canopy also acts as an ovipositional and feeding
deterrent, effectively reducing the attractiveness of new growth to
pests.
At the same time, Canopy has an extremely low beneficial
disruption index (BDI), which means it is soft on predators of
sucking pests which alleviates the risk of late season silverleaf
whitefly or mite flaring caused by the use of broad spectrum
chemicals.
"Many seasons of field experience have demonstrated the value of
using Canopy as the basis of integrated pest management to control
problem pests without contributing to resistance problems or more
costly outbreaks later in the season," Dr Johnson said.
Best results are achieved when using Canopy early in the season
and as a partner spray with other products at other opportune times
based on insect monitoring and a recognised insecticide resistance
management strategy.
Canopy has existing registrations for cotton aphids, Heliothis,
green mirids, cabbage /diamond back moths, and work is progressing
on anticipated additional registrations for silverleaf whitefly in
cotton and other summer and winter crops. It is also used as a low
rate defoliant aid, giving another strategic advantage to achieve
additional insect control on crop residues.
"The advent of CBT is a worrying development, but we believe the
impacts will be significantly reduced through a combination of good
crop hygiene and an informed use of Canopy as a key plank of any
chemical control measures," Dr Johnson said.
* As reported in CRDC's
'Winter Spotlight' 2011