Insects of Southern Australian Broadacre Farming Systems - Grains ...

Understanding the lifecycle of pests can be important before deciding
on control strategies
Example
Earth mites are active in the cool wet months from April to November. During the winter, they
usually pass through three generations, with each lasting about 8-10 weeks depending on
the species. During the hotter months of the year, earth mites avoid the hot dry conditions by
producing over-summering eggs (diapause).
For redlegged earth mites, the first two generations of mites lay predominantly winter eggs,
usually on the under surface of the host plant leaf. In spring, mites stop laying eggs on plants
and start producing the over-summering eggs, which are retained in the body (Figure 4.3).
This knowledge can be used to time insecticide applications more strategically. Timerite ® is a
strategy that works by controlling the number of redlegged earth mites emerging in autumn
by minimising the number of diapause eggs produced (through a carefully timed spray in the
previous spring) and therefore reducing the number of mites emerging from diapause.
However, this approach is not as effective for other mite species. For blue oat mites and several
other crop-emergence pests, a large number of diapause eggs are already present in paddocks
by spring - well before the spring spray date recommended by Timerite ® .
Summer
eggs
Diapausing eggs
III
Oct
Nov
Sep
Dec
Aug
Jan
Jul
Feb
II
Winter eggs
Jun
Termination of diapause:
summer conditions for 30-40 days
Post-diapausing eggs
Initiation of egg hatch:
< 20 o C & >10 mm rain
Figure 4.3 Typical lifecycle of redlegged earth mites in southern Australia
Mar
May
Apr
I
Source: P. Umina (CESAR)
SECTION 4 COMMON Pest, Beneficial AND EXOTIC Species
75
Insects of Southern Australian Broadacre Farming Systems Identification Manual and Education Resource © 2012