There were some real challenges In getting on fungicides for scab this year. And in case you think it was all a waste of time, it wasn't, as indicated by non-sprayed trees at the Hort. Research Center last week, where fruit scab averaged 61% and cluster leaf scab 82%. In spite of that, barring any mistakes in timing, there is no significant scab in commercial orchards.
Fire blight is also a non-issue in the state so far. Apparently,
fire blight activity didn't ever really start.
Obviously, we think it is a good idea to apply calcium to apples
on a regular basis over the summer. It develops fruit firmness,
controls cork spot on susceptible cultivars, and even helps reduce
flyspeck and sooty blotch. If you haven't started yet, anything
you do from here on out will still be very beneficial. The recommendations
are in the table below.
Applications should begin three weeks after petal fall and continue at two-week intervals until harvest.
| Calcium source | ||
| Actual calcium | ||
| Calcium chloride (29% calcium)* | ||
| Calcium nitrate (19% calcium) | ||
* Add 2/3 ounce vinegar per pound CaCl2.
Use of a surfactant in CaCl2 sprays may reduce the potential for
foliar injury.
Leaf injury may be greater when captan or guthion is mixed with
CaCl2.
Do not mix CaCl2 with SoluborTM.
The recent rains have stimulated apple maggot fly emergence from
pupae in the soil and trap captures on red sticky spheres have
begun occurring in most monitored blocks. Trap-capture treatment
thresholds have been developed over the course of years of study,
largely in New York. For unbaited sticky red spheres, the treatment
threshold is a cumulative average of 2 AMF per trap. For spheres
baited with the fruit odor butyl hexanoate, a treatment threshold
of 5 AMF per trap is recommended. If these thresholds are reached,
an application of Guthion or Imidan is advised. We do advise use
of a reduced rate of Guthion or Imidan as the first AMF cover;
waiting until the AMF season has progressed a bit before applying
a full rate of either material. Soon after treatment, all AMF
should be removed from the monitoring spheres, and accumulation
of AMF toward the treatment threshold will begin again at zero.
In order to maintain capturing power, sticky spheres should be
cleaned of all debris at least every two weeks, as the spheres'
ability to capture AMF is reduced by 25% for every week of exposure
without maintenance.
Flight of second generation adults continues, and the first wave
of second generation sap-feeding mines has been observed. Treatments
against the first generation appear to have turned out very positive
results; blocks treated at petal fall or soon after show very
low LM infestation. For treatment options against the second generation
LM adults and larvae, refer to last week's issue of Healthy Fruit.
As noted in last week's issue, mites are beginning to appear in
moderate numbers in many blocks, even some which received an early
season miticide application. At this point in the year there are
4 miticides available for use, aside from summer oil. Pyramite
was recently registered for orchard use in Massachusetts; its
recommended usage is discussed in the July 2 issue of Healthy
Fruit. Kelthane, Carzol and Vendex are also available for summer
use, but each has drawbacks. ERM resistance to both Kelthane and
Carzol has been noted, and both (particularly Carzol) are especially
toxic to predaceous mites. Vendex has been demonstrated as being
less effective when used as a July-August miticide than when applied
in May. In studies performed in New York, summer oil applications
were effective as a maintenance treatment; they slowed increases
in mite populations but did not significantly reduce the adult
population already present. As with early-season oil applications,
one must avoid applying Captan within a week or so of a summer
oil treatment to avoid the foliar damage caused by material incompatibility.
Potato leafhopper adults have immigrated in large numbers this
year from the midwest. Given these patterns of movement, no orchard
in Massachusetts is immune to infestation of PLH. Nymphs have
appeared in moderate numbers thus far, up to 10 nymphs per leaf.
There are no data which indicate that PLH cause detectable injury
to semi-dwarf or standard fruit-bearing trees. New plantings are
most prone to PLH damage, and some research suggests that dwarf,
fruit-bearing trees can also be damaged by PLH infestation. If
the level of infestation warrants a treatment, Provado, Thiodan
and Sevin are all available for use against PLH.
Woolly apple aphid colonies are now moving from the basal areas
of pruning cuts to new terminal growth. Most monitored orchards
are showing some WAA colonies, but numbers to date have remained
relatively low.
Buildup of second-generation pear psylla is continuing, hardshell
nymphs are present, and effective psylla control at this stage
of the season is a real challenge. As would be expected, most
control measures exercised against the first generation have been
fairly successful, and areas which received no first-generation
treatment show the greatest psylla populations.
Healthy Fruit is written by Dan Cooley, Ron Prokopy, Starker Wright, and Wes Autio, except where other contributors are noted. Final copy is edited by Dan Cooley. Publication is funded in part by the UMass Extension Agroecology Program, grower subscriptions, and the University of Massachusetts IPM Program. Please cite source if reprinting information.