The Madman And His Bugs

Here we go again with the madman and his bugs! He just found his third Stink Bug lumbering through the upper canopy of a citrus plant! He panicked. Unusual for him. Generally he just sucks them up with his bug vacuum and releases them near the outdoor fire pit. He learned the hard way not to squish them – they are called stink bugs for a good reason.

I can thank the Connecticut Flower and Garden Show for his panic. He’s been preparing his plants for possible entry into the Standard Flower Show, and he lives in fear of the inspectors finding a bug on one of his show plants. This got us thinking about bugs – not just the ones that would spoil the show for him, but also the ones that might spoil the gardening season.

Gardeners Know About Bugs

Anyone who gardens knows about bugs. There are good bugs and there are bad bugs. It’s all a part of nature. And, on February 22, it’s time to start thinking about them. On March 1, the Connecticut Agricultural Experiment Station (CAES) begins calculating Growing Degree Days (GDD).

Last year we introduced you to the importance of temperature on plant growth – remember chill hours? Plants need cold temperatures to prepare themselves to flower and fruit. But warm temperatures are necessary to snap plants out of dormancy. And, like plants, bugs react to temperatures.

As humans, we follow a written calendar – spring starts this year on March 20. Our calendar is based on the vernal equinox so it can vary by a day or two – but it is determined by celestial occurrences, not by anything here on the ground. Some years we welcome spring with warm weather; some years with two feet of snow.

No Written Calendar

But, plants and insects don’t have any such calendar. Their calendar is internal, so for many years, scientists have been studying what drives their biological calendars. Phenology is the study of relationships between climate and life cycle stages. Accumulated warmth drives plant and insect development, and this accumulated warmth varies from year to year. So, making calendar related decisions can be somewhat less than accurate. How do you measure heat accumulation? Simple, by relying on Growing Degree Days.

Growing Degree Days

The concept of GDDs was introduced back in 1730 by a French scientist named Rene A. F. Reaumur. But, it really didn’t become an important agricultural tool until 1959 when Integrated Pest Management (IPM) entered the mainstream in response to problems often caused by the overuse of chemical controls.

By using GDDs, growers can more easily target pests. Unlike us, insects are cold blooded and cannot regulate their own body temperature. According to the University of California IPM, their development is dependent upon accumulated temperatures they are exposed to in their environment. Insects go through a number of stages from egg to adult, some of the stages more destructive than others: but the larval stage or stages are the worst, that’s when those bugs are crawling around and eating like crazy. But, it is also when they are most vulnerable to control. The real interesting thing about insects is that each species has a different mechanism that will help them get through cold Connecticut winters.

Survival Strategies Depend On Heat

Some species lay eggs that will survive the winter. When the eggs accumulate a certain amount of heat they hatch. Others spend the winter as larvae, huddled under leaf litter or burrowed deep in the soil. They may even use a rotting tree trunk for shelter. As heat starts to accumulate in spring, the larvae will emerge – hungry and looking for food.

Still others survive the winter as pupae, patiently waiting for enough warmth to appear as an adult. And, then there’s the “snowbirds”, those species who fly south for the winter only to return when it’s warm enough.

Like us, a bunch of adult insects hunker down and do their best to survive the cold. That explains why the madman is finding these Stink Bugs – they’ve actually been here all winter. Some adult insects will overwinter in your house, but others will seek shelter in out buildings, tree holes, under logs – you get it. And, they are counting the Growing Degree Days to tell them to get active, so if you pay attention to Growing Degree Days (GDD) you know when to expect these critters to show up.

Calculating GDDs

Growing Degree Days are calculated daily by subtracting a base temperature from the mean daily temperature (high + low/2). The base temperature in Connecticut is 50˚, because very little grows below this temperature. The madman thinks this is a lot of work, so he prefers to let CAES calculate it for him. By checking this frequently, the madman will have a good idea of when he can expect the arrival of some of his biggest headaches, including the Colorado Potato Beetle.

These monsters overwinter as adults burrowed in the soil or buried on the edge of fields. These adults are laying eggs at around 120 GDD and at 400 GDD the fourth instar larvae are doing their greatest damage, munching on leaves of potatoes and other Solanaceae (the madman has noticed that they love his eggplants). By 675 GDD, the larvae are back underground transforming into adults for the next cycle. Armed with this knowledge, the madman can come up with a good strategy for management.

Not Playing By The Rules

Wouldn’t it be nice if all insects followed the rules? The most troublesome insects have their own sets of rules which confound us. We’re talking mosquitoes and ticks. First, mosquitoes. Mosquito overwintering mechanisms vary by species and in Connecticut, we have 52 different species. Some overwinter as eggs, some as larvae, some as adults, but according to Cornell Entomology they start emerging after 230 GDD. Since they emerge at all stages, some are ready to bite, some are just turning into wigglers looking forward to biting.

Then there’s the tick. Anyone who wanders outdoors in Connecticut lives in fear of Lyme disease. Ticks in general don’t do much when the temperature is below 32˚, but as the weather becomes warmer, they become more active. During the winter, ticks have developed the habit of latching onto a warm blooded mammal to make it through, spending warm days actively feeding. I’m sure the madman’s friends, the Three Musketeers are transporting those Arachnids all over the place.

Because ticks are always active, using a GDD model won’t help us. But we do know that when spring gardening season begins, we have to be diligent. We have tick gaiters, arm guards and other permethrin-treated clothing that we plan to wear in the garden. The madman just told me that he heard hot cocoa helps ward off tick bites, however, he can’t verify the source – sounds fishy to me.

I guess he’s just looking for a nice cup of hot cocoa.