Did the cold kill the insects?

 

I think a lot of us are looking for a silver lining in this disastrous historical cold spell. I have been getting a lot of questions to the theme of - will this cold weather kill all the insects?  The short answer is no.  As one of the most successful groups of animals on the planet, arthropods have developed mechanisms to avoid succumbing to cold temperatures, even if they don’t often have to endure them here in the Valley.  Different species go about it in different ways.  Some more mobile life stages will seek shelter in leaf litter, other debris, outbuildings or even our homes.  Other insects can actually produce cryoprotectants like glycerol and sugar that work like antifreeze, allowing the insects to survive freezing temps without actually freezing.  This time of year, many of our important row-crop insects are overwintering while their host plants are unavailable.  Most overwintering, or off-season, life stages are already in protected stages (eggs or pupae) and/or safe locations (in the soil, under residue, etc.) and most will probably emerge as usual.  

Where we will likely see some impact of the cold temperatures is in our more tropical species such as the sugarcane aphid and with insects that were actively infesting vegetable crops.  For example, most exposed whitefly adults were probably killed as it only takes 3 hours at 21° F to kill 90% of adults.  However, whitefly eggs and nymphs must be exposed to that same temperature for 57 or more hours to get the same mortality.  Keep in mind, if the host plant dies, so do the whitefly eggs and nymphs.  

Bottom line, the insect world is diverse, and each species was impacted by the cold to a different degree.  And, while low temperatures dramatically reduced some pest populations, they will eventually make a comeback. We may not see some of our early season pests in as large of numbers as we typically do, however, their ability to produce large numbers of offspring in a relatively short time will allow them to rebound. One thing for sure, time will tell us more.