Tuesday, June 16, 2015

Spraying for scab

   With the over-abundance of rain we have been receiving lately, I've been concerned with the spread of pecan scab onto this year's nut crop. It took me a little while to find active scab lesions this early in the pecan season. When I drove our hydraulic lift over to a Maramec tree, I knew I could find scab on this super, scab-susceptible cultivar.
   After some searching in the canopy, I found a few leaflets spotted with scab (photo at right). Notice that the disease seems to be confined to the youngest leaf on the terminal and the youngest leaflets on the leaf. Since scab infects rapidly growing tissues, is seems likely that scab infected this leaf during pollination season during last month's rainy period.
   The point of finding scab on leaves is to verify that the disease is present and ready to infect young nuts. As the nuts start to grow in the later half of this month, they will become more susceptible to the disease. Unfortunately, the weather man has promised us and entire week of rain--great for scab, terrible for making scab sprays. 

    This morning we had a break in the rain showers and I even saw the sun shine for a minute or two. So we decided to spray our high-value pecan cultivars (photo at left). I knew there was a threat of rain in the afternoon so I choose to use a systemic fungicide that could provide scab protection once the fungicide entered plant tissues. Today, we applied Headline fungicide and added an insecticide to limit the casebearer population. We also added a high quality spreader-sticker to make sure we got good spray coverage.