In one of my many-a-day strolls through the garden, I was looking at one of the tomato patches, lamenting the loss of most of the leaves on my calabash tomato to some sort of wilt (I hesitate to says its one thing, I am guessing various things are going on here) and I found, hanging from a tomato branch, this caterpillar beset by eggs and what looked like flying ants.

My first reaction was revulsion (OK, that remains my reaction) but I left it there because:

1. I could not help myself with wanting to take a shot,
2. I knew that someone over at the flickr group “ID Please” would be able to help me identify these two creatures (flies and caterpillar¹) and
3. I had a sneaking suspicion that something so revolting must be good some how (just like when I see an antique .. if I find it hideous it is bound to be expensive and in demand … like a reversed fashion compass of sorts)

My friends Mean and Pinchy and aw c’mon at flickr helped my identify this as a tomato² hornworm (Five-Spotted Hawkmoth - Manduca quinquemaculata) being consumed by braconid wasp³s, a VERY good thing. Once these wasps hatch they can go on and parasitize⁴ more hornworms.

From the wiki entry on braconids, relating to their parasitism:

“Most braconids are primary parasitoids (both external and internal) on other insects, especially upon the larval stages of Coleoptera, Diptera, and Lepidoptera, but also some hemimetabolous insects like aphids, Heteroptera or Embiidina. Most species kill their hosts, though some cause the hosts to become sterile and less active. In the case of endoparasitoids, species often display elaborate physiological adaptations to enhance larval survival within host, for example the co-option of endosymbiotic⁵ viruses for compromising host immune defenses. These polydnaviruses are often used by the wasps instead of a venom cocktail. These viruses suppress the immune system and allow the parasitoid⁶ to grow inside the host undetected. The exact function and evolutionary history of these viruses are unknown. It is a little surprising to consider that sequences of polydnavirus genes show the possibility that venom-like proteins are expressed inside the host caterpillar. It appears that through evolutionary history the wasps have so highly modified these viruses that they appear unlike any other known viruses today. Because of this highly modified system of host immunosuppression⁷ it is not surprising that there is a high level of parasitoid-host specificity. It is this specificity that makes Braconids a very powerful and important biological control agent.

Parasitism on adult insects (particularly on Hemiptera and Coleoptera) is also observed. Members of two subfamilies (Mesostoinae and Doryctinae) are known to form galls on plants.”

So these hymenoptera order members are in good in my book. I will just have to look the other way cause they make me nauseous!

Here are a couple shots of a couple of my tomato plants are seem to have a wilt. This first one is a calabash tomato plant with MANY fruits.

The fruits look fine and so many and so heavy that they need to be braced or the branch gets very stressed (see photo)

This is a different tomato (small salad tomatoes)

This also has abundant numbers of small cherry like tomatoes.

I took some new shots of the whole garden today and it seems to become this sort of embarrassing overgrowing crazy green entity! Makes one think of a green version of tribbles.

If you have any ideas of how best to minimize this wilt business next year, I would love to hear it. I plan on planting each tomato far from it’s neighbors and give them abundant space.

I am also definitely going to plant tomatillo⁸s again (and more, disbursed everywhere) because they bring in the bees like crazy, very good for pollination⁹.

Radish leaf.

To a plant, water management is personal, very personal.

Capturing and managing the use or loss of water is not an idle activity, its not passive. For the plant it is hardwired. Just as we have arteries and veins to conduct blood, our little ocean, throughout our bodies, so too does the plant have tubing to route water across it’s body plan.

Corn sprout.

Plant physiology is fascinating and I may explore it’s complexities further later but today I am going to tell you one simple thing - those water routes in the plant are composed of Xylem cells. You may have heard of phloem cells, they make the tubing that routes the food or carbohydrate laden water.

This is a triptych of stained xylem cells from a ficus plant. (Photos of vessels at (Ficus sp). taken at sept 2002 in university of Sidi Bel Abbes/Algeria. Shoots are treated in HCl (15N,40mn) solution,then stained with Toluidine-Bleu (5%). All photos have been taken under the Carl Zeiss microscope, by Youssef Bouterfes for the Wikipedia Project. This is a creative commons photo from the Wikipedia.)

Collard greens.

As in my pictures, you may see leaves that have these ordered arrays of water droplets. Some of these may be the result of water collection as mediated by the architecture of the leaf or may be the release of water from a water-logged plant through hydathodes (a process called guttation).

“At night, transpiration usually does not occur because most plants have their stomata closed. When there is a high soil moisture level, water will enter plant roots, because the water potential of the roots is lower than in the soil solution. The water will accumulate in the plant creating a slight root pressure. The root pressure forces some water to exude through special leaf tip or edge structures, hydathodes, forming drops. Root pressure provides the impetus for this flow, rather than transpirational pull.

Guttation fluid may contain a variety of organic compounds, mainly sugars, and mineral nutrients, and potassium.^[1] On drying, a white crust remains on the leaf surface.” Source

I borrowed this micrograph, showing a hythode, from the UW-Madison BotWeb

image clearinghouse. There is so much there to see and learn about!

“Hydathodes, often found at the end of vascular bundles, are other derivatives of stomatal complexes. Their guard cells cannot be closed, unlike those in normal stomatal complexes. Water secretion by the hydathodes is called guttation; salts, sugars, and organic compounds dissolved in the guttation water crystalize on evaporation, forming a white powdery substance.” Source

Droplets on collard sprouts.

Take some time one sunny morning, after a stretch of wet days, and go into your garden and see these drops for yourself!

Carrot tops.

Learn More:

• Plant Structure from MJ Farabee at Maricopa College
• Guttation on the Wiki