In central Illinois, cedar-apple rust galls
have been sporulating on red cedar since about April 21.
Galls of cedar-quince rust were seen sporulating on cedar a
few days later. To protect hawthorns from the stem-damaging
cedar-quince rust, apply the first protective fungicide
sprays when Red Delicious apples in your area are flowering.
If you use a fungicide with some systemic activity, you may
be able to delay sprays 3 or 4 days.
On May 1, apple scab sporulation was apparent on crabapples
on the University of Illinois campus in Urbana. According to
weather data, the required wetting criteria (a combination
of leaf surface wetting and temperature) for scab infection
have been met in central Illinois. This early infection and
sporulation probably indicates that we are in for a heavy
scab year. The first sprays for scab should be applied at
budbreak to target primary infection. If the first sprays
are delayed and late fungicide sprays are applied, there may
still be some efficacy on the secondary infection. Still, no
one can accurately predict efficacy of late sprays.
Fire blight has not yet reared its ugly head in central
Illinois. This bacterial disease infects under precise
environmental conditions monitored by a forecast system used
at the University of Illinois orchards. As of May 1,
conditions for infection had not occurred. Fruit pathologist
Dr. Steve Ries said that if conditions stay cool through
bloom, fire blight is not likely to be a problem in central
Sphaeropsis blight on pine has been a major problem in the
past several years. The new strain that causes oozing
cankers is particularly damaging to pines. If you have
diagnosed this problem on your trees in the past and are
considering fungicide applications, remember that three
applications are necessary. The first application is made at
pine budbreak; the second when candles (new growth) are half
elongated; and the last when needles are fully expanded.
Watch the pines in your area to know when these stages have