DIAGNOSTIC LAB HIGHLIGHTS Julie Beale and Brenda Kennedy, Plant Disease Diagnosticians
Figure 3. Trial III, white corn (Pioneer P32B10) on 30‐inch rows. Pesticide application at R1 included Headline® AMP 6 fl oz, + Protyx 0.5 fl oz (surfactant) + Warrior with Zeon 1.5 fl oz (insecticide).
Conclusion Across the country, corn pathologists agree that fungicides are most likely to provide a benefit under conditions of moderate to severe pressure from key disease diseases. Our results from 2013 affirm that guideline. This is because two of our three trials had enough disease pressure that fungicide application very likely provided an economic benefit in corn grown for grain, especially for the test in white corn. In contrast, in 2011, we saw that substantial increases in yield and stalk health were sometimes (but not always) possible from a fungicide application even in the absence of significant disease. This is consistent with the experience of some producers, who believe they are getting substantial agronomic benefits rather consistently.
Only a few diagnostic samples have been submitted over the past few weeks, which is no surprise given recent weather conditions. A few notable disease samples have been seen, however: namely, Swiss needle cast on Douglas fir in a Christmas tree planting; and Dothistroma needle blight on Austrian pine in a large landscape planting. Symptoms of needle browning from each disease were severe. In addition, we have seen samples of winter desiccation in landscape evergreens (broadleaf and conifer); tomato spotted wilt virus on greenhouse tomato; and Pythium root rot, whitefly and spider mite infestations in greenhouse plants (various research plantings).
If a producer is still undecided about whether fungicide applications have a place in their production system, they should consider leaving several untreated strips in an otherwise treated field. This will help them see for themselves whether yield is increased under their
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