Last Thursday, I received a series of pictures showing a soybean field with small plants, and blank patches, plants with stems severed by apparent feeding by deer, and stripped blister beetles feeding on the leaves. I visited this field the following day.
On Friday, I visited and inspected this 68-acre commercial, double crop soybean field. The soybean plants were in a very bad shape:
- most of the soybean plants were in the R6 stage, and less than 4 ft tall (~10 cm), and the rows had many skips,
- all plants with stems cut by deer (stem cuts had a ragged appearance compared to 45-egree clean cuts made by rabbits),
- abundant wheat stand residue with areas having more than a two-inch height straw "cushion",
- slugs found under this cushion of wheat residue
- many vole mounds,
- foliage with holes caused by bean leaf beetles, and
- a good number of yellow striped blister beetles.
What Caused All of These Problems? Solutions ....?
In this case, the identification of a single issue that caused such a devastation in this field was not possible. However, there are some issues that in combination might have caused the damage to this field.
Environmental conditions
The absence of rain in Western Kentucky may have contributed to the size of the plants; rain was scarce in June and July causing delays in emergence, low seed emergence, and slow plant growth. Also, lack of rain contributed to the low production of forages or grasses that could have reduced the impact of deer feeding in soybeans.
Slugs
Wheat residue on this field may have contributed to the presence of slugs, although the farmer or the company that takes care of this field did not report any damage by mollusks; the presence of rains by the end of July and beginning of August may have contributed to an outbreak of slugs that went unreported. I found between 3 to 6 slugs per square foot while searching for slugs under wheat residue. The ground under the residue was moist and temperatures were probably 10 to 15 degrees lower than the air temperature (these temperatures are based on unpublished studies conducted by my group under similar circumstances in 2022). Under these conditions, slugs may have been feeding on soybeans plants at night, whereas during the day, they were well protected under the wheat residue, escaping from the tallies conducted by scout agents.
Rodents
Many rodent species, such rabbits, groundhogs, and voles, may feed on soybeans. Here, voles were partially responsible for plants skips; I found several mounds in this field. In addition, voles had been reported in this same region (Christian County) causing severe damage to soybean fields.
Insects
I observed several bean leaf beetles and a little higher number of striped blister beetles during the time I was in this field. Blister beetles feed on the foliage; in addition larvae of these insects are predators of grasshopper eggs. However, the foliage was not heavily damaged by feeding of any of these insects. The impact of insects on the state of this field may have been minimal to none.
Final Thoughts
Although there is a chance that plants may grow, the pods and flowers in these plants are near the soil, and number of pods per plant are low. As a consequence, combines won't be able to harvest this field.
For the management of voles there are no products that are currently registered in Kentucky. Disking or some minimal tillage may be an option to reduce or disrupt nests.
Cover crops are important for soil conservation, prevent soil erosion, protect water quality, keep soils moist, reduce soil compaction with fewer trips and less tillage, save fuel, labor, and time with reduced field operations, and sequester carbon in the soil. However, for full-season or double crop soybeans, residue management from the previous crop is critical. Mollusks (snails and slugs) have been observed causing severe injury to several soybean fields, even when environmental conditions were not feasible for their development (see Snail Outbreak during the Drought and Hot Conditions Affect Soybeans). Mollusks found very favorable environmental conditions under residues from the previous crop (corn, wheat, or cover crops); these conditions are conducive to cause outbreaks if residues are not properly managed.
All of the combined issues described above may have contributed to the poor conditions observed in this field. Thus, in this particular case, yield from this field may be entirely lost. If the loss of yield is calculated at 55 bushels per acre at $15 per bushel (price as of 9/2/22), the total amount of loss would be around $56,000 for the 68 acre-field.
Categories: Kentucky, Crops, Soybeans