Two-legged and four-legged creatures have something in common with many of the six and eight legged creatures out there: The cold months are not well-tolerated. Some insects and mites curl up and die having completed their life’s reproductive mission. They’ve laid their eggs, but will never see their offspring. Others enter a quiescent state similar to hibernation — in other words they shut down until the warmer months return. (I know some two-legged creatures that look upon this practice with a certain fondness.) Some bugs, however, seek warmth where it is available and try to make a go of it during the colder months. If you’re a grower, some of these critters may be a cause for concern.
If you grow plants in a greenhouse during the colder months, you’re providing opportunity to these creatures. Some of these creatures aren’t of consequence to you, they just come in a lay low until spring. Others can actually be beneficial as they scrounge for food — assuming that is they aren’t herbivores. Some of these will even continue their reproductive processes while others enter a reproductive diapause. The ones which should concern you if you’re a grower are the active plant feeders. Winter greenhouses and other indoor plant areas including interiorscapes may see a few aphids, thrips, and whiteflies during the winter months, but the really problematic — and common — pests are fungus gnats, scale and mealybugs, and spider mites.
Fungus Gnats
Fungus gnats shouldn’t be a huge issue until closer towards spring when new bags of peat-based growing media are opened and water added. Plants in general — although it depends on variety — should be allowed to dry out a bit during the colder months and will thank you for it by not becoming diseased. Their moisture needs are typically reduced considerably during this period. Dry-out isn’t always the case, though, as some growers will water a little too aggressively despite their plants’ seasonal needs. Problems can rage out of control quickly, especially if the interior climate is on the cool side (likely) and damp. This is sometimes the case. Not always, again it depends on heating and irrigation. If you do find fungus gnats on sticky traps during the winter months, for whatever reason, a control like Hypoaspis miles might be the best choice. The primary reason for this is that H.miles don’t require water for application and won’t contribute to the problem if you are indeed an over-irrigator.
Scale and Mealybugs
Scales and mealybugs can be quite a bother. Many plants can be moved outdoors during the summer months and scales and mealybugs will often be dealt with by nature’s finest. In the winter, though, indoor plants can often become less healthy and sometimes stressed. Many become prime candidates for scale and mealybug pests. While scouting you must keep and eye open for these pests and react with manual controls like hand-picking first, and in some cases, provided you offer sufficient warmth, scale and mealybug controls like Rhyzobius lophanthae and Cryptolaemus montrouzieri can be beneficial. These biocontrols tend to work pretty well during the winter months but, again, they do require sufficiently high temperatures.
Spider Mites
If temperatures do remain reasonable, and you don’t over-water, spider mites can thrive. They like warm, dry conditions best so the drying heat of winter can make conditions suitable for them. This can be solved with a frequent light misting, but you must be careful due to the lack of sunlight as you don’t want to create conditions where plant diseases can thrive. To prevent diseases you must provide adequate air flow and make sure plants are dry before what sun you do see goes down. Spider mites are controlled quite easily during the winter with one of the common spider mite predators like Neoseiulus fallacis or Stethorus punctillum. Both have proven themselves time and time again during the winter months.
Summary
Your success with pests at this time of year can have a huge impact on your spring successes next year. Sadly, there’s no way around some pest problems; darned if you do, darned if you don’t; balance is required. This coming season be sure to scout well, maintain a rigid schedule for this activity as we recommend during any other time of year, react swiftly to anything you might find, and, as always, be a little proactive in your efforts. Pest numbers can be smaller in the SAD months, but this doesn’t make them any less of a threat. They can gain a solid foot hold now to use against you later. In fact, because you cannot put your plants outside to let mother nature and the environment help, all of the responsibility falls squarely on your shoulders. If as a winter grower you think you can take some time off or let your guard down, sorry, you’re wrong.
