Specialists
Speaking
disease up the plant, which is dependent on favorable conditions. If we fail to meet these three requirements, then a fungicide application is generally not economically warranted. For the smuts, unfortunately, fungicide applications must be made preventatively before we know if we have the disease for certain. Fields with a history of either kernel or false smut, planted to susceptible cultivars and that received excess nitrogen fertilization are candidates for a fungicide application to prevent disease development. The optimum application timing is mid-boot as flag leaves are coming out or just out. If you delay to split boot, then a fungicide application is unlikely to be effective. Rice stink bug is always a moving target in terms of pressure each year. We recommend scouting beginning when 75% of plants are heading. The first two weeks after heading, treat when five or more rice stink bugs per 10 sweeps are found. The second two weeks after heading, treat when 10 or more stink bugs per 10 sweeps are found. An additional point to make on rice stink bugs is when to stop spraying for them. Recent Arkansas research has shown that when 60% of panicles are hard dough (straw-colored kernels) or beyond, rice stink bug can no longer cause economical damage. When we say, “hard dough, let it go,” we’re referring to the majority of the panicle being in hard dough. Good luck managing these late-season issues in 2021 — hopefully conditions will be in the crop’s favor and not the pests.
Figure 1. Feeding damage on soybean foliage by green cloverworm in September 2020.
Lessons learned for soybean rust preparation PHOTOS BY YOUNG-KI JO, TEXAS A&M
DR. YOUNG-KI JO
TEXAS Professor & Extension Specialist Department of Plant Pathology & Microbiology Texas A&M University ykjo@tamu.edu First, I would like to take a moment to mention the retirement of my mentor, collaborator and colleague, Dr. M.O. Way. The void created in his absence can be felt in many places; already I miss his monthly articles in Rice Farming magazine describing current issues and providing insightful advice for Texas rice and row crops. His contributions and care to the Texas rice industry for the past 38 years will be remembered for a long time to come. Dr. Way’s retirement has led me to reflect on our last collaborative soybean field trial in the Texas A&M AgriLife Research Center at Beaumont. Our original research plan for 2020 was disrupted by pest and disease outbreaks that seriously damaged our test crops. Our soybeans were planted in mid-May and we originally planned to test fungicide effectiveness for common foliar diseases. But later that summer, green cloverworm (Hypena scabra) caterpillars devoured most of the leaves, leaving only leaf skeletons on the field plots that were not protected by insecticides (Figure 1). This blow was worsened in October when the field spared from the insects was hit hard by soybean rust (Phakopso-
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Figure 2. Soybean rust outbreak in October 2020. Yellow leaves caused by the disease are apparent in the right row (untreated control) compared with the left row which was protected by fungicides.
ra pachyrhizi) (Figure 2). Later, the soybean plots that were not protected by fungicides were highly infected with rust and mostly defoliated, leading to 25%-30% yield loss. Green cloverworms are common in Texas and relatively easy to control with insecticide applications. The major challenge is to detect the presence of caterpillars early since young instars of pale green larvae can easily go unseen. Implementation of timely insecticide use before they cause economic damage is the key for managing foliage-feeding caterpillars. In contrast to the common cloverworms, an outbreak of soybean rust in the summer had never been observed in Jefferson County. Reports have been found of this occurring at low frequency in the late season but in southern Texas. RICEFARMING.COM
