Late Season Leps
This year's harvest is quickly approaching so there are a few pests that
we need to be aware of. The unseasonable warm weather this year has caused
insect flight and development to be earlier than expected. So which worms
should growers worry about this late in the season?
Oblique-banded leafroller (OBLR)
Although both larvae and damage will be found in orchards now and up to
harvest, we have passed the point where managing this pest is worthwhile.
Late season OBLR development is not synchronized, and sprays affect only
the small portion of the population that is active at this time. Instead
of spraying, keep an eye out for late season damage during harvest (Fig
1). If damage is found at harvest, consider applying a petal fall spray
targeting OBLR next spring.
Figure 1. Oblique-banded leafroller damage
This year we have seen very high trap counts for CM, and the 2nd generation
emerged earlier than normal. There are usually two generations of CM in
most of Ontario (except near Georgian Bay), but in warm seasons, it is
possible to see a third generation of CM (often known as a suicide generation)
in some orchards. CM larvae normally diapause during the third week of
August. However in warm years and locations, some CM pupate instead, and
adults then emerge to produce a third generation. If this occurs, use
pheromone traps to establish a third biofix when flight activity increases
(around 611 to 666 DDC after the second biofix) and apply a spray when
111 to 138 degree days accumulate from the third biofix.
Oriental fruit moth (OFM)
While OFM has been less of an issue in recent years due to increased adoption
of mating disruption and timing of sprays to manage this pest, it is still
an important pest in orchards. Adult flight of OFM can last into early
October, and damage can occur up to harvest. Monitor pheromone traps in
orchards into September to keep an eye on populations. Remember that late
season sprays may be needed especially on light skinned varieties. For
growers using mating disruption, the Rosso product should take care of
OFM through harvest. However the combined CM/OFM mating disruption ties
do not last as long for OFM and late season sprays may be needed.
In summary, codling moth and oriental fruit moth are the main late leason
lepidopteran pests to keep an eye out for before harvest. Following these
tips will ensure that a worm-free harvest.