Herself’s Houston Garden

When spider mites attack a bean plant, the plant responds by producing odours which attract predatory mites. These predatory mites then exterminate the spider mite population, thus acting as a type of ‘bodyguard’ for the plant. However, if the plant is simultaneously attacked by whiteflies, insects that are related to aphids, the plant becomes less attractive to the predatory mites and therefore more vulnerable to spider mites.

The research team studied the strength of the plant’s “cry for help” through a chemical analysis of the plant odour blend and found that one of the odour components (beta-ocimene) is produced in much lower quantities if the plant is not only attacked by spider mites, but also by whiteflies. The production of the odour decreases because of a lower expression rate of the plant gene that codes for a crucial enzyme in the production chain. When the researchers added ocimene to the odour of plants which were attacked by both species, the attraction of predatory mites was restored.

This recent breakthrough demonstrates that there are also herbivores that can interfere with a plant’s “cry for help”, possibly because the whiteflies attempt to interfere with the plant’s defence system. Spider mites also produce more offspring on a plant under attack by whiteflies. For a spider mite, there are therefore two reasons why a bean plant which is being attacked by whiteflies is better than a bean plant that is not being attacked: more offspring and fewer bodyguards. It is therefore no surprise that the researchers found that the spider mite preferred plants infested with whiteflies above plants without them.

Read more Whiteflies sabotage alarm system of plants in distress

More information:
Whiteflies interfere with indirect plant defense against spider mites in Lima bean

No pigs or chickens yet. But the vast farms where leaf-cutter ants raise their fungal crops may harbor a crew of previously overlooked farmhands — nitrogen-fixing bacteria.

At least eight species of leaf-cutter ants typically live with bacteria that capture nitrogen from the air and turn it into a form that living organisms can use, says microbial ecologist Adrián Pinto-Tomás of the University of Costa Rica in San José. He and his colleagues propose that these bacterial helpers might explain how the ants feed up to 8 million workers in a single colony just by harvesting bits of nitrogen-poor leaves and letting a fungus grow on them.

Neither the fungus nor the ants, nor any other multicellular organisms, can use the atmosphere’s abundant nitrogen directly. Pinto-Tomás and his colleagues tracked the path of nitrogen through ant nests and tested inhabitants for genes active in capturing the nutrient from the air. Live-in bacteria, particularly in the genus Klebsiella, could provide an estimated 45 to 60 percent of the nitrogen in the ants’ food, the researchers report in the Nov. 20 Science.

read more . . . Classic view of leaf-cutter ants overlooked nitrogen fixing partner

More information:
Symbiotic nitrogen fixation in the fungus gardens of leaf cutter ants ( paper is here for purchase )
Farmer ants fertilize their gardens with bacteria
Video leaf cutter ants

Are ladybugs being overtaken by wasps? A Université de Montréal entomologist is investigating a type of wasp (Dinocampus coccinellae) present in Quebec that forces ladybugs (Coccinella maculata) to carry their larvae. These wasps lay their eggs on the ladybug’s body, a common practice in the insect world, yet they don’t kill their host.

“What is fascinating is that the ladybug is partially paralyzed by the parasite, yet it’s eventually released unscathed,” says Jacques Brodeur, who is also a biology professor and Canada Research Chair in Biocontrol. “Once liberated, the ladybug can continue to eat and reproduce as if nothing happened.”

read more . . . Ladybugs taken hostage by wasps

Down here on the Gulf Coast root knot nematodes can destroy gardens. Commonly people bring them home on tomato plants and once in the garden they are near impossible to eradicate.

I’ve been reading ‘Silent Spring’ in bits and pieces and tonight’s reading mentioned the use of marigolds as a treatment for root knot nematodes. After a bit of digging through old texts and online I discovered marigolds are still commonly used as a treatment for infected soils.

In ‘Silent Spring’ Rachael discusses success had planting marigolds among roses in some infected soil. Down here it’s your vegetable garden that is likely to be the problem.

The marigolds release alpha-terthienyl through the roots. The alpha-terthienyl is extremely toxic to nematodes, many insects and viruses. It works by preventing the hatching of the nematode eggs.

In addition, nematodes can not feed on marigold hosts, so you are also denying the nematodes food.

While you can always plant nematode resistant plants ( check for the N on the plant label ) Marigolds might be a nicer option.

Not all marigolds will prevent and harm root knot nematodes, do a bit of research first.

Varieties recommended for control of southern root knot nematode include: Tagetes patula, T. erecta, T. minuta.

More information:
Marigolds ( Tagetes spp. ) for Nematode Management