The dust is flying with harvest finally underway in many areas of the county. Last week I spoke of safety to ourselves and others while we work on the farm, but don’t forget the equipment. Already this fall I have heard of some combine fires. Most combine fires can be prevented if we follow some simple maintenance steps throughout harvest.
The obvious is to keep the combine as clean as possible. During harvest, frequently blow dry chaff, leaves and other crop materials off the machine. Remove any materials that have wrapped around bearings, belts and other moving parts. Be sure to check those pockets that house wires or lights and where chaff accumulates.
Keep wiring and fuses in proper working condition. Check wiring and insulation for rodent damage and replace as needed.
Keep fittings greased and watch for overheated bearings.
Use a ground chain attached to the combine frame to prevent static charges from igniting dry chaff and harvest residue, letting the chain drag on the ground while in the field
Prior to fueling a hot combine, wait 15 minutes to reduce the risk of a spill volatilizing and igniting.
Don’t park a hot combine in the shed or shop. After a long day of harvesting, smoldering hot spots may be present in the combine. If those spots suddenly flare up, at least you won’t lose the building!
Be prepared if a fire does happen by:
Keep at least one fully charged, 10-pound ABC dry chemical fire extinguisher with an Underwriter’s Laboratory approval in the combine cab. Have your extinguisher checked yearly to make sure it will work when needed.
Mount a second, larger fire extinguisher on the outside of the machine at a height easily reached from ground level.
Have a plan if a fire starts. Turn off the engine; get the fire extinguisher and your phone. Get out and get help.
Stay a safe distance away.
Call 911 before beginning to extinguish the fire.
Approach the fire with extreme caution. Small fires can flare up quickly with the addition of air.
While you are harvesting you might notice some signs of disease that was present in the fields. A couple of these soybean diseases that showed up in the 2017 growing season, typically rare in this part of the U.S. — Diaporthe Stem Canker and Cercospora Leaf Blight.
According to Anne Dorrance, plant pathologist with The Ohio State University, certain soybean fields across the state have been severely affected by these two pathogens.
Diaporthe stem canker:
The symptoms seen in Ohio are large patches of early dying plants that still have their leaves attached. The canker is not as well defined but can occur from the third node at the bottom of the plant up to the top 1/3. There may be rows of small pin dots in the center of the canker or on pods that are the actual fungus. The bottom two nodes of the plant are still green — which can separate it from Phytophthora. If the stem is bleached white and has white mold — it is Sclerotinia. For Diaporthe, the internal tissue — both the pith and the stem are degraded.
Diaporthe is caused by several different fungi and can also lead to Phomopsis seed rot. The fungus survives very well on residue. Dorrance notes the fact that the most affected fields were in fields where the disease may have occurred to a smaller extent the previous year.
Infections for this disease occur in the early vegetative growth stages of the plant and these are favored by long periods of warm (72 to 86F) wet weather. This fungus takes its time, and the symptoms tend to coincide when the seeds begin to fill in the pods.
Management is highly successful with two tactics, planting resistant cultivars and reducing inoculum. The screening for resistance to this pathogen is fairly straightforward for Diaporthe, so most companies should be doing this. Tillage and rotation both are effective in reducing inoculum.
Cercospora leaf blight — and Purple Seed Stain
The reddish discoloration and leathery appearance begins to appear on the top leaves as the plants begin to fill out the seeds. Purple lesions on the petioles or stems also develop. Infected petioles remain attached to the plants while the infected leaves fall off the plants. Warm temperatures and frequent rains also contribute to this disease which can be spread by rain and wind. This can also be residue born: If found in 2017 — TAKE NOTE — residue management and planting varieties with resistance will be essential in 2018.
Cercospora can begin at flowering and repeat throughout the season, but symptoms do not develop until pod fill. Seed can also become infected and develop the same purplish-red coloration. The pathogen that causes Cercospora leaf blight and Purple seed stain produces a light-activated plant toxin, which contributes to the purple discoloration of the diseased tissue. Spores are produced on the residue or infected tissue and are dispersed by wind or rain onto nearby soybean plants. Only susceptible varieties will develop symptoms and these will be more pronounced when dry, warm conditions occur at pod fill.
Disease management strategies include planting disease free seed, tillage to break down infested residue and crop rotation to prevent inoculum build-up, and planting resistant varieties. For fields that are affected in 2017 – a timely harvest to ensure the fewest number of seeds develop purple seed stain. Secondly, for fields in 2018 that go back into soybean, if susceptible varieties are planted, a fungicide application of a triazole at R3 may provide some protection. However, infections can occur during the vegetative phase.
Tony Nye is the state coordinator for The Ohio State University Extension Small Farm Program and has been an OSU Extension educator for agriculture and natural resources for 29 years, currently serving Clinton County and the Miami Valley EERA.
