By Ron Hammond and Andy Michel, The Ohio State University Extension
Normally, we have always said that Ohio seldom gets cold enough to be a factor in causing significant mortality during the winter months. However, the severe cold spell last week does have the potential to change this, at least for those pests that overwinter in Ohio. A good example of what can happen occurred during a similar cold spell in 1983 that caused significant mortality to the Mexican bean beetle, which killed off our state-wide problem that was beginning to occur in soybeans.
However, we will not be able to tell what might happen until we actually see possible lower numbers during the growing season. And remember that all these insects are capable critters; they tend to overwinter in protected places, and growers also need to consider heavier snow cover is a good insulator. Also remember not to include pests such as true armyworms and black cutworms in early summer, and potato leafhoppers later in the summer in these thoughts. These pests migrate into Ohio during the growing season, and what happened with the weather in states much further to our south has more impact on them.
Finally, there are situations to remember concerning a few specific insect pests. There first is with the soybean aphid. Because we expect the two-year cycle to continue, 2014 is already expected to be a very low year. So if soybean aphids are extremely low this year, it is probably because of the two-year cycle, and not the cold spell. But it will be interesting to see what happens then in 2015 with this aphid and if there is an impact and carry over for the two years.
The other insect is the western corn rootworm. We have had low numbers of this pest the past few years, including last year. There is no reason at this time to expect anything different this summer. Thus, if numbers of rootworms are again low, will it be from having had low numbers already, or was it the cold spell?
The main pests that we will need to watch are bean leaf beetles and Mexican bean beetles on soybean. Japanese beetles and slugs on both soybean and corn, and then newer concerns, western bean cutworms and Asiatic garden beetles on corn. All these overwinter in Ohio, and perhaps the cold spell will have an impact on them.