Wheat Freeze Again

On Sunday morning May 11th temperatures dipped below freezing again over a wide area of southwest Kansas.  Impact on the wheat is still unknown but there is likely incremental damage.  Evaluating damage will be a little easier at these growth stages than earlier ones.  At partial heading, temperatures below 32 degrees can cause partial or total head sterilility. Normally only the top portion of the head is impacted.  Awns or entire spikelts will turn white within a few days of the freeze.  If the wheat was fully headed damage may be harder to evaluate.  Flowering parts within the spikelets could be damage and there may be no outer signs of damage.  At this point it appears that this latest freeze may have caused as much as 20% damage in individual fields but no more than 5% damage to the area as a whole

Fungicide Decisions on Wheat

We are at a point where wheat growers need to decide on the use of fungicides.  Cut offs for using fungicides are prior to pollination and we will be there within days.  You would think with a better wheat price than past years it would be easier to decide but the conditions in the fields make it more difficult.  As of today, we still have no leaf rust or stripe rust anywhere in the area.  The other important disease, Powdery Mildew is a problem in some of the thick canopied Jagalene.  In many cases Jagalene has already been sprayed in irrigated wheat but not dryland.  It is probably not a matter or if we'll get the rusts but when will we get the rusts and that will determine the amount of yield loss that we can expect.  If these foliar diseases cause 20% leaf loss at heading or pollination we can probably expect to see 20% yield reduction.  If this same leaf loss doesn't occur until the milk stage, the yield loss is probably only 2% to 3%.  It is obvious now that we won't have heavy pressure prior to pollination so the decision is much more marginal than past years.  Yield potential, varietal resistance, wheat price and the cost of the treatment all come into play. 

Alfalfa Weevil

Many of the Pyrethroid treatments that were applied for alfalfa weevil control have been much less effective than past years.  It doesn't seem to matter which product was used.  The only common factor associated with these failures has been temperatures at the time of application.  In many cases these failures had the product applied when temperatures were in the 30's.  Two weeks post treatment some of these fields have as many as 70 to 80 larva per 10 sweeps.  In those cases if harvest is still more than 10 days away it may be necessary to come back with a knockdown treatment.  Probably the most effective would be .5 pt Furadan.  This won't give much if any residual but it should give quick knock down for what is in the field.  There is a 7 day harvest interval required with this rate of Furadan.

Corn Conditions

The freeze on Sunday morning also impacted a low percentage of corn fields.  In some cases all of the leaves were burned off and the plants are starting over.  It doesn't appear that the growing points were affected so in theory these plants will recover with no loss in yield.  In past freezes however even though the growing point was not affected the new growth struggled to emerge from the damaged whorl and many plants tend to buggy whip or wrap.  This caused a significant delay in recovery and probably did have an impact on yield.  If it is just scattered plants in a field that are affected I would do nothing but if it is 20% plus of the plants in the field I would probably consider replanting.  We don't have the luxury of watching this corn for a week or two to make a decision and it is still only May 13th and this planting date still has the potential to produce high yielding corn