Manejo de doenças em milho

Let's talk about the main diseases, going through management strategies and fungicide placement in corn. For me, the most important thing is the choice of hybrid... this is because the difference in disease tolerance between hybrids is much greater than the difference between fungicides. Disease management begins with the choice of hybrid. Unfortunately, no company can deliver a hybrid that meets the three pillars: earliness, productivity, and hardiness (disease tolerance). This is because hardiness or disease tolerance, in the selection criteria, is antagonistic to productivity and cycle... I have a range of genes, and among these, by prioritizing earliness and productivity, it's difficult to achieve disease resistance (Photo 1). The first aspect, then, regarding disease management: very early-maturing hybrids are more susceptible to super-early-maturing hybrids, and these, in turn, are more susceptible to early-maturing hybrids. Since the selection criterion is often based on the cycle, and many opt for very early-maturing varieties, thinking ahead to the subsequent off-season crop, these materials respond to up to three fungicide applications (Photo 2). In this photo, we have a P30F53 variety on the right and a P1630 variety on the left. The difference between both materials without fungicide application was 40 sacks per hectare. Remember that these materials have a smaller leaf area, therefore, they are less resistant to diseases and have a shorter grain filling period... So, is the idea to avoid very early-maturing varieties? No, the idea is to work with more than one hybrid, and if you don't have the application technology, then yes, it's better to avoid these materials, because if I use a very early-maturing hybrid, I can already plan for three fungicide applications... And why is this productivity loss so significant? Corn reaches tasseling with its maximum leaf area index (4.5 to 5.5 square meters of leaf area per square meter of soil). At this point, the corn has accumulated around 40% of its total biomass. The remaining 60% takes about 50 to 60 days to accumulate, and the plant is extremely dependent on this photosynthetic apparatus to achieve a good grain weight. Note that grain weight can range from 250 to 450 grams, depending on the hybrid, leaf lifespan, nutritional status, etc. Therefore, maintaining live, well-nourished, and healthy leaves is fundamental to achieving high yields.