Crop pests are of two general kinds: indigenous and migratory. The indigenous ones are those that overwinter in your fields and are waiting for appropriate conditions to ‘start over’ once more. Almost all weeds are in this category. The migratory pests are those that are blown in on winds or storms from warmer areas where they have been feeding or reproducing earlier in the year. Some crop insects and some diseases fall into this category.
Since temperatures have been relatively mild this winter throughout most of the country, how might this affect pest levels this season?
Let’s start with weeds, as that might be the easiest question to answer. A mild winter often means that winter annuals (chickweed, henbit, some mustards) will be more vigorous as they resume growth earlier in the spring. This means their growth may be more rank and we may even see some winter annual species that are seldom noticeable become quite prominent in certain fields. For summer annual weeds, especially those that are early germinators like lambsquarters, you must be prepared to fight them earlier than usual with tillage or appropriate herbicides. The warm winter weather won’t usually change the mix of weeds we see in the spring, but it can make weeds a bit more competitive with early planted crops.
For each crop there are many indigenous insects that overwinter in our fields. Warm winter weather will favor their survival as extended cold temperatures tend to reduce the viability of eggs, larvae, and adult forms of pests. There are two factors that can suppress pestiferous insect numbers. First, if their overwintering habitat (crop residue and top soil) has been tilled in the fall, this may have helped reduce insect numbers. Second, although saturated soil conditions are not good for field operations or crop growth, soils that remain saturated in the spring for an extended period of time (5+ days) will reduce insect development and survival..
The same general advice also applies to migratory insects (i.e. cutworms, stalk borers, etc.). If the weather has been warm across the Southern US we can expect prevailing winds and storms to carry them about, perhaps landing in your fields a bit earlier than normal and in greater numbers. Of course mild winter temperatures also tend to favor the beneficial insects that feed on the crop pests, but overall mild temperatures is a signal for us to be on the lookout for high insect numbers this spring.
Similar advice applies to crop diseases. Although a direct correlation between a mild winter and a resultant outbreak in a crop disease is hard to find, there can be a rapid development of some diseases due to an abundance of airborne spores (think rusts). Some indigenous diseases like seedling blights, may actually be less of a problem if we have a warm spring and crops emerge from the soil and develop quickly.
Speaking of pests and how to stay on top of them - one of our new features, Pest Engine, will be available soon as a part of the 2016 Grower AgriBundle. This feature lets growers receive alerts for increases disease or insect pressure on specific fields. You can learn more about everything the 2016 Grower AgriBundle has to offer on our brand new website.