Featured this month:
- Biodiversity in the sweet potato patch
- Unhappy caterpillars, parts 1 & 2
- It might be a bad day to free-range the chickens when…
- Fall flowers
September was warm with sufficient moisture. Really not too much to complain about, other than some much-above-normal temperatures.
Biodiversity in the sweet potato patch
September is prime time for sweet potato digging, and that’s generally a good task for getting up-close and personal with soil life. The leafy growth of the sweet potatoes was as vigorous as we’ve ever seen it this year, fully filling in the aisle space between rows. This created a nice shady, moist environment supporting lots of interesting critters, some of which we photographed. The next 8 photo panels were all taken in the sweet potato beds.
Digging sweet potatoes lets us see life above the soil (such as the mantis egg case on one of the sweet potato vines, life), life that spends time above and below ground (such as the ants, center), and soil-dwellers (such as the earthworms of various sizes, right).
Arachnids: Three of these are spiders, but the upper left is a harvestman. The two are very different orders within class Arachnida; spiders (order Araneae) have segmented bodies and multiple sets of eyes, while harvestmen (order Opiliones) have bodies that are fused together and one set of eyes. The harvestman shown here is in genus Vonones.
Stinkhorn “egg”: The tiny bit of this thing that was poking up through the soil surface looked and felt a lot like a reptile egg, a bit leathery and similar in size to the egg of a good-sized snake. But when I unearthed it while digging the nearby sweet potato, it became clear that this was no animal egg. Peeling the surface back revealed a kind of gooey substance covering a harder white structure inside. I cut that open, revealing the cross-sectional view shown at right. A bit of search-engine work turned up the stinkhorn fungus, phallus impudicus.
Larval insects: Various bizarre-looking critters lurk below the soil surface, including these, all of which are larval insects (we think). The one on the right is a beetle. Any ideas on the other two?
Midland Brown Snake: This is our most commonly encountered snake on the farm, a cute little thing that likes to hang out in the growing areas. They often make daring escapes away from pitchforks and sharp hoe blades, but to our knowledge we’ve never hurt one.
-pedes: Millipede above, centipede (family Geophilidae?) below. Hard to photograph, moving fast; it was difficult to impede them.
Snails and slugs: Though we don’t know its species name, the land snail on the left is moderately common here in moist areas. The slug on the right, which we believe is a Leopard Slug (Limax maximus), is a species that we first noticed a few years ago. Last year and this year it has been quite common, and it seems to be getting along just fine on the reproductive front. Note the mass of eggs in the background. Though the snails seem pretty benign from a gardening perspective, the slugs seem to enjoy eating many of the same things we do. Leopard slugs are a native European species with unusually acrobatic mating behavior.
Sweet potato damage: The chew marks on the left are suggestive of rodent damage, and we saw quite a lot of that this year, though we grew so many that it didn’t really matter. We also saw quite a number of holes in sweet potatoes that don’t match the description of rodent damage; these holes are smooth, roundish, and of similar depth. The trail of what appears to be slug slime makes us wonder whether the Leopard Slugs might be enjoying the sweet potatoes, too? That’s definitely speculation, so if anyone has definite evidence about what makes that kind of hole, please let us know!
Moving along to topics other than the sweet potato patch…
Unhappy caterpillars, part 1: As often happens at this time of year, various cabbage worms, but for us especially Cross-striped Cabbage Worms, are munching on brassicas. In the September 2013 natural events post, we posted a photo of some small fuzzy things on leaves of plants that also hosted cabbage worms (left photo), and Pam Dawling identified them as the pupae of a parasite wasp in the genus Cotesia. The wasp lays eggs in a caterpillar, then multiple larvae develop in the caterpillar at the expense of the host, eventually pupating in clusters of fuzzy cocoons. The members of this genus seem to be very host-specific, and I never did figure out that year which species of caterpillars were serving as host.
This year, I spotted an outbreak of Cross-striped Cabbage Worms on our collards (one of their favorite plants), and I started to implement “digital control” (that is, squishing them with my fingers). It didn’t take long to realize that the parasites were present; see the larvae that came out of the body of the smushed caterpillar in the right photo. Upon closer inspection, it seemed that a very high percentage of caterpillars had been parasitized, so I realized that I was better off leaving the situation alone, so the parasites could reproduce instead of me accidentally killing them. Given the host specificity, I’m inferring that these are Cotesia orobenae (based on this publication and this one).
Unhappy caterpillars, part 2: Here’s another unhappy caterpillar, a Tobacco Hornworm (Manduca sexta) on a tomato plant. Not certain what is wrong with this one. Is it another case of parasitism? Or was it injured by something else (such as a bird that stopped after one peck)? I decided not to disturb this specimen, figuring if there were parasites inside that I’d be happy to let them grow and mature. Interestingly, in our 10 years here, we’ve never seen the external, white Cotesia congregata cocoons on Tobacco Hornworms that show up in virtually every gardener’s guide to beneficial insects. But we must have some kind of natural control, since in some years (like this one) we barely notice them, while in other years they can be distressingly numerous.
It might be a bad day to free-range the chickens when you find a very fresh squirrel carcass a couple dozen steps from the chicken shed. This is very likely the work of either a Sharp-shinned or Cooper’s Hawk (Accipiter sp.). Accipiter numbers go up around here during fall migration, and we try to be attentive to their presence. When the danger is high, it usually works pretty well to keep the chickens cooped up during the morning, let them roam in the afternoon hours, and lock them in again by early evening.
Fall flowers: Goldenrod (yellow) and asters (white) combine with red sumac leaves to make a traditional fall palette of colors. In contrast, Blue Lobelia seems to buck the autumn color trend with pretty flowers in some of the moister woodland edges.