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March 12, 2015 Ohio Soybean Council
Highlighted in the Spring Magazine were a few top diseases and pests that affect Ohio crops. Continue reading to find the full lists provided by OSU researchers Dr. Anne Dorrance and Dr. Andy Michel.
OHIO’S TOP 10 YIELD BUSTERS
According to OSU’s Dr. Anne Dorrance, an internationally recognized expert in soybean diseases, the top 10 crop diseases in the state are:
1) Phytophthora sojae – P. sojae is a killer, plain and simple. When susceptible varieties are planted and infected, it means a total loss. Checkoff-funded research has found that growers should look for varieties with very high levels of partial resistance (tolerance or field resistance) combined with Rps genes 1c. 1k, 3a, 6, or 8.
2) Soybean cyst nematode (SCN) – More and more fields in Ohio now have this pest. Losses can reach up to 50 percent when susceptible and resistant beans are grown side by side. Closely monitoring these populations will help keep them low.
3) Seedling pathogens – Currently in Ohio, there are more than 20 different water molds contributing to poor stands. A seed treatment with multiple active ingredients is required to take out this complex of species.
4) White mold – This pesky mold was very present in Ohio in 2014. Focus on host resistance first but some fungicides and herbicides have been shown to be effective.
5) Sudden death syndrome – A new seed treatment is in the pipeline for 2015 but in the meantime the best course is to manage SCN populations and choose high-resistance varieties.
6) Charcoal rot – Despite being thought of as mainly a problem in the Southern U.S., we are seeing this pathogen here in Ohio. It is usually associated with drought conditions and can be indicated by early maturity in patches across a field.
7) Frogeye leaf spot and brown spot – Frogeye should continue to decrease in Ohio as susceptible varieties are taken off the market. In the meantime, a fungicide application at R3 will slow inoculum build-up. Brown spot occurs most often in fields with a considerable amount of residue. At this time, we are only seeing losses of three to four bushels per acre, which may be tolerable, depending on the cost of fungicide application.
8) Head scab fungus – Also occurring on wheat and corn, this pathogen can contribute to poor stand establishment. When soybeans follow a difficult year for corn and wheat in rotation, a seed treatment for this pathogen should help.
9) Soybean viruses – In the past few years, viruses like bean pod mottle, soybean mosaic virus and soybean necrotic vein virus have been identified in surveys across Ohio. Managing weeds and appropriate variety selections are key to keeping these viruses in check.
10) Brown stem rot – While rare in our state, it is still present in fields with pH levels below 6.0. Choosing highly resistant varieties, managing soil fertility and SCN levels will help keep this from becoming a regular occurrence.
FUN FACTS ABOUT PESKY PESTS
OSC is also funding a study by Dr. Andy Michel to develop aphid resistant soybean varieties for Ohio’s unique growing conditions. Here are eight little known facts about field crop pests:
1) Slugs are not insects and therefore common insecticides have no efficacy.
2) Some insects overwinter in homes or crop residue so cold weather doesn’t impact all insects in the same manner.
3) Bt toxins in corn don’t affect piercing/sucking insects like aphids and stink bugs and, to date, there are no naturally occurring Bt toxins for those pests.
4) Though they try to fool us by coming in a wide range of colors, from tan to brown to red, and appearing both with and without spots, the one identifying characteristic that remains the same on the bean leaf beetle is the black triangle behind the head.
5) Both corn rootworms and bean leaf beetle larvae feed on soybean root nodules. However, this type of feeding doesn’t seem to affect yields.
6) The silver spotted skipper, a common though non-economic pest in soybeans, has false eyes to fool predators.
7) The spined soldier bug is a natural insectivore that will feed on stink bugs and other common soybean pests.
8) The kudzu bug, stink bug and soybean aphid all have bacteria in their gut that provides nutrients and defends against parasitoids and predators. In fact, most of the insect order Hemiptera has a symbiotic relationship with this particular bacterium.