David

Well to a point! I have found that all experienced gardeners come to a point where they take great delight in wreaking vengeance on pests that have destroyed their carefully reared plants. For me the point came this morning when I came upon one of my exotic pepper plants that I have carefully grown from a seed that I planted three months ago – it was toppled over, felled by a miniature lumberjack. I quickly unearthed the culprit, a plump grey worm about an inch long close to the ‘stump’ of my pepper – a cutworm – and swiftly dispatched it.

I led a workshop last week at the Carp library on dealing with garden pests. About a dozen gardeners were happy to share their successes and frustrations in dealing with pests, both large and small. And there was not a squeamish one in the lot – all were delighted to hurl insects into a bucket of soapy water, stomp them into the ground or squish them with bare hands!

Tent Caterpillars

You may have noticed an unseemly number of tent caterpillars this spring. The following photo shows a very active nest. I recently visited a retirement home where there were tens of thousands of these critters, hanging from defoliated trees, on the side of buildings and devouring everything in sight – it was like a scene from a horror movie!

This year appears to be a high point in their cycle. Most advice is to not be overly concerned as the trees will recover when the caterpillars move on to their next stage. I am concerned that if trees do face back to back infestations and are already stressed it may prove fatal so I do try to remove and stomp on nests that I can easily reach.

Tent caterpillars are moderately sized moth larvae that are often considered pests due to their habit of defoliating trees. They are social caterpillars and build conspicuous silk tents in the branches of host trees. The eastern tent caterpillar builds a single large tent which is typically occupied through the whole of the larval stage.

While I am not a big fan, their engineering skills are astounding. They hatch from their eggs in the early spring at the time the leaves of their host trees are just unfolding. The tent is constructed at a site that intercepts the early morning sun. The position of the tent is critical because the caterpillars must bask in the sun to elevate their temperatures above the cool ambient temperatures that occur in the early spring. Studies have shown that when the body temperature of a caterpillar is less than about 15 °C (59 °F), digestion cannot occur. The tent consists of discrete layers of silk separated by gaps and the temperature in these compartments varies markedly. Caterpillars can adjust their body temperatures by moving from one compartment to another. On cool mornings they typically rest in a tight aggregate just under a sunlit surface of the tent. It is not uncommon to find that the temperature of the aggregate is as much as 30°C (54°F) warmer than the surrounding air temperature on cold but sunny spring mornings. Later on in the spring, temperatures may become excessive at midday and the caterpillars may retreat to the shaded outside surface of the tent to cool down.

The digestive physiology of tent caterpillars is tuned to young leaves, and their need to complete their larval development before the leaves of the host trees become too aged for them to eat compels them to feed several times each day. At the onset of a bout of foraging, caterpillars leave the tent en masse, moving to distant feeding sites. Immediately after feeding, the caterpillars return to the tent and aggregate in sunlight to facilitate the digestive process.

Caterpillars grow rapidly and typically complete their larval development in seven to eight weeks. When fully grown, the caterpillars leave the natal tree and seek protected places to spin their cocoons. About two weeks later, they emerge as adults.

Tent caterpillars exhibit boom-or-bust population dynamics. Caterpillars rarely remain in outbreak numbers for more than two to three years. Factors which bring outbreaks to a close include parasitoids and disease. In some cases populations collapse because caterpillars starve to death either because trees are completely defoliated before the caterpillars are fully grown or because the quality of host leaves declines to the point where they are no longer palatable. Defoliated trees typically refoliate after caterpillar attacks and experience no lasting damage. In some cases, however, trees or parts of trees may be killed after several seasons of repeated defoliation.

(Much of the previous four paragraphs relied on information from Prof. Wikipedia)

Mayor’s Carrots Doing Well

This year’s abundant rainfall – twice the average and four times what we received last spring – has been a very mixed blessing. In chatting with the mayor at the very successful bike month potluck on Mill Street on Saturday he observed that the germination of carrots this spring has been phenomenal as compared to last year when the very hot dry conditions made it nearly impossible to start carrots.

So while it has not been great weather for planting the vegetables that like a lot of heat and that are very sensitive to colder temperatures there are many plants that do benefit from cool wet conditions. This week I have planted more peppers and tomatoes but have been holding off on the eggplant, basil and sweet potatoes until later in the week when warmer temperatures are forecast.

My advice continues to be to plant a diversity of crops. Plant some that like cooler wet summers such as kale, cabbage, carrots, potatoes, beets and chard. And also plant veggies such as tomatoes, peppers, sweet potatoes and squash that embrace a hot dry summer like the one we had last summer. Surely something will do well this summer!