About 10 days ago we harvested a few pumpkin trials at the research station. After weighing and grading the fruit, they were set back in the row but not in the leaf canopy. Last week I drove by some of the plots and noticed some fruit were sunburned. Such is the fate of many pumpkin fruit exposed to direct sun and not covered by leaf canopy. Sunburned fruit have a reddish area facing the sun which will eventually soften and rot.
Reddish area on near fruit, sunburn.
Over the year’s growers have asked me, how long into the season should they treat the foliage with fungicides? I would respond as long as you plan to harvest fruit. Avoiding sunburned fruit is the primary reason to keep the foliage healthy later into the season. Given our increasingly warmer and sunnier fall season, growers should expect to incur significant losses if the foliage is degraded by bacterial or fungal pathogens.
Conditions that favor sunburn include thin leaf canopies, fruit that have been clipped off of the vine but left in the field to cure or be packed at a later date, and clear sunny days with highs above 80-85F. The weather forecast for the next week in southwest Ohio include max temperatures in the mid 80’s to low 90’s…let’s hope periodic cloud cover spares growers from excessive fruit losses.
Despite the late planting dates, we did not escape many of the late season diseases that attack soybeans.
Sclerotinia stem rot – we found this disease in our research plots today in a field that was planted on June 19th. Sclerotinia is caused by a fungus that survives from season to season and over several years from sclerotia. The infections actually occurred during flowering when the canopy was closed, and cool nights can really enhance and favor this disease.
Sclerotinia Stem Rot
Sudden Death Syndrome – this disease is also beginning to develop and symptoms typically start just after soybean growth stage R5. Symptoms include irregular yellow spots, which turn brown or necrotic between the veins. Interestingly the veins are surrounded by green. The center of the stem or pith is bright white in this disease. This is a fungal pathogen and infections most likely occurred shortly after planting. Even though we planted in mid-June, soil temperatures were still relatively cold this year and I won’t relive how much rain we had, but suffice it to say, this field received over 3” the weekend after we planted. These conditions greatly favor infections. Note in the picture the resistant cultivar.
Sudden Death Syndrome
Diaporthe stem canker (northern and southern) have both been problems, but I have not received any samples to date. On susceptible cultivars the plants will die early in patches. For Northern, there is a canker at the third node which girdles the plant. For Southern, there can be several reddish cankers on the stem and the internal tissue is a reddish brown.
Diaporthe Stem Canker
Phytophthora stem canker – we are finding this way too often this year and in places that have not reported it very frequently. The plants will wilt first, turn yellow, and a chocolate brown canker will form from the bottom of the plant to almost mid-height. The key difference between this and Northern Diaporthe stem canker is the length of the canker and where it originates. If the canker begins below ground, it is Phytophthora.
Phytophthora Stem Canker
Another look alike symptom on soybean leaves that you might be seeing is potash deficiency. We have had a number of calls late this summer asking what might be causing discoloration of soybean leaves – see the photos of a leaf and of the field edge. What appears to be happening is #1 – it’s dry, or root systems are compromised is some other way (think excessive wetness and compaction) or #2 the symptoms tend to be at the edge of the field. Here the guess is that with larger high capacity fertilizer applicators, we may not be getting that full rate all the way to the edge of the field. As a result, we run low on K there when we likely have adequate amounts across the rest of the field.
ABOUT THE C.O.R.N. NEWSLETTER
C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.
Don’t forget to register for our upcoming Hemp Workshops. You do not have to be a producer to attend these meetings. These meetings are open to the public and to anyone who has questions about what hemp is or how it is grown. Both programs are free to attend but RSVP is required. You can find more information on the flyers below. More programs will be announced later this fall. Please contact the Brown or Adams County Extension Offices if you have any questions.
Brown County Extension Office: 937-378-6716
Adams County Extension Office: 937-544-2339