As we begin this growing season where most of us have not had appreciable rain in over 200 days, it might be useful to review what things look like on the pest insect front. Of course there is no way to know what will happen and I don’t have a crystal ball. Here is what it looks like through the bottom of a Dr. Pepper bottle.
Overwintering
Our winter was fairly mild, so we did not get high insect mortality from deep and sudden cold. Winter insect kill is greater when there is rain or melted snow and we had neither. Both things taken together mean that more insects successfully overwintered than in a “normal” year (whatever that is).
Early season host plants
Entomologists think in terms of early season “non-crop host plants”, meaning anything in the system that can support pests until the crop hosts become available. A common example would be tansy mustard that serves as an excellent false chinch bug host. Years with rain and lots of tansy mustard almost always mean we will have more false chinch bugs. Of course the lack of rain has meant a lack of early season hosts, so many of the insects emerging from overwintering will have little to no food. Populations of pests that overwinter here will start the growing season at lower overall levels than in wetter years.
Fewer insects but fewer crop acres
Starting at lower pest levels is good, but fewer crop acres mean mobile insects will concentrate on those acres. If we cut the number of restaurants in Lubbock by 1/3, then those restaurants still in business would have around 1/3 more customers. Most overwintered insects that find themselves with no food or poor food host plants will leave, either by using their wings or catching a ride on the wind. They are able to detect healthy plants either by color or odor or both, so they will navigate to healthy crops.
Immigrant pests
Crop conditions in the southern part of Texas are not as bad as ours here, so it is reasonable to expect a somewhat typical northern movement of cotton bollworm (corn earworm), fall armyworm and other migrants. These too will seek out, and concentrate on, the reduced number of healthy crop acres. Moth eggs are fairly susceptible to drying out and dying before they hatch, so high temperatures with low humidities will reduce the next generation to some extent. Those same conditions will affect the health of their crop hosts, especially dryland crops, which might in turn also mean less survival of their larvae. We can expect higher concentrations of migrant pests on our reduced acres, but how well their offspring survive is a tossup.
Biological control
Most of our beneficial insects overwinter here and build up on our pests slowly at first, then faster as we get more pests. Given that we are starting with fewer pests, it is likely that our beneficial insects will get a much slower start this year. There will be fewer of them around to deal with any large influx of immigrant pests arriving from the south.
Wildcards
Insects have many ways to survive hard times, and some of them are really good at it. When one species is heavily favored by some climate/host plant condition, it is common that other species that would normally compete with the favored species will be at a big disadvantage. Any insect that is wildly successful on the few weeds and non-crop vegetation that we have in our system can be expected to be at higher levels this year than in a “normal” year.
Future years
What is happening now will likely affect our insect situation in future years. A good example might be Mozena obtusa, one of those wildcard pests. This big true bug hit us hard in 2013, but in fact its populations started building up in the drought of 2011. Mozena thrives on mesquite, which, all things considered, was not as heavily affected by the drought. Mozena has tough skin and is relatively free from biological control agents, so it got way ahead in 2011, those populations kept getting bigger and bigger on mesquite in 2012, and then they overflowed to our crops in 2013.
That is what things look like through the bottom of a Dr. Pepper bottle. Field scouting will be very important this year; our overwintered pests might concentrate on the healthy crop acres, and the immigrant pests might be worse than normal.
