This post may not interest many folks, but it is really important for the work we're doing in the Road to Life Yard.
We have a problem in our Moringa plantings with aphids. We've discovered that ladybugs control them, but it often takes a good bit of a while for the ladybugs to get the upperhand. So, I sent the question to ECHO in North Fort Myers, FL (ECHO stands for Educational Concerns for Hunger Organization), and bingo! I got this information.
So read and enjoy, if this kind of thing interestst you. Or, just marvel at the kinds of connections that exist.
From a Grad student at UFL
My research interests are in enhancing natural enemies through habitat manipulation so I was excited to get your email [from the technial team at ECHO]. I would recommend starting with intercropping a nectar and pollen source or planting hedges along the perimeter of the growing area —You could interplant an insectary hedgerow or ground cover when the Moringa is coppiced to so the insectary species gets a good start.
Sunflowers are often used as an insectary hedgerow in Florida and California in vegetable production systems—In Cuba , I visited a farm where individual sunflower plants were planted throughout the garden to serve as an attractant for coccinellids in particular. I am not sure how well this worked in Cuba , but I know that (3-6ft wide) hedges of sunflowers have been used successfully to attract a host of insect predators in conventional and organic operations FL & CA. For our local organic growers, sunflowers are a major cash crop as an ornamental (people pay $10 at the Gainesville farmer’s market for a bouquet of Sunflowers)—so the hedgerows are multipurpose and offer significant economic benefit in addition to a their “eco-system service.” It would be great to find a synonymous hedgerow species that offers both economic and ecological benefit for Haitian farmers. I’m coming to Haiti this fall and would be delighted to do some investigating—in the meantime let me know if you have any suggestions. Sunflower seeds could be a secondary benefit as well.
If you google “insectary plant” you’ll get a huge list of plants—however most of them are northern species and only a few will really do well during Haiti’s cool season. The most common hedgerow species promoted to enhance the activity of natural enemies include: dill (Anethum graveolens L.), coriander/cilantro (Coriandrum sativum L.), buckwheat (Fagropyrum esculentum) is used cool season cover crop in FL and Coccinellids like it, sweet alyssum (Lobularia maritime)(definitely northern—we can’t grow this very well in FL, but look at the flower structure), Prostrate Knotweed Polygonum aviculare (a low-growing member of the buckwheat family and present in the Caribbean as a weed), and Phacelia tanacetifolia (native to the southwest).
Several organic websites promote members of the parsley family, Apiaceae; mustard family, Cruciferae (we’ve observed large populations of Ladybirds in wild mustard here), the mint family, and some members of Compositae (such as Achillea & Artemisia—Cory Thede is growing Artemesia spp. near Limbe for medicinal purposes I believe). Sustainable ag folks in California and Michigan seem to have the best resources regarding hedgerows. This is a link to a publication about hedgerows by the Community Alliance with Family Farmers http://www.caff.org/programs/farmscaping/Hedgerow.pdf . They have a long list of hedgerow species and that indicates which plants are best for hosting natural enemies. Some of these plants do well in the tropics—a few may already be present in Haiti .
I would start with sunflowers and additionally look for local flowering weeds that have characteristics similar to these known insectary plants. Small flowered low growing weeds may offer more nectar and resources than showier flowers, so keep an eye out for the more “humble” species. The insectary hedgerow(s) should provide an alternate source of non-pest prey, pollen and nectar for natural enemies throughout the year, so you’ll likely have to plant or selectively maintain a rotation of insectary plants. Ideally the alternate source of prey would be a species that is not interested in your Moringa, but will build up populations of generalist predators and aphid parasitoids that spill over into adjacent crops. Another option would be to intercrop with a known aphid host like beans or cowpea—which would perform well in the filtered shade of the Moringa.
Additional techniques you may want to incorporate into your system to enhance natural enemies include:
Strip harvesting: Alternate rows for harvest, this leaves somewhere for the natural enemies to go when they’re host plant has been chopped down. You may already be doing this, but the more conservation techniques you employ, the more likely you’ll have success.
Alternatively, if you have weedy areas/ nectar sources nearby or interspersed within the Moringa, you can manipulate the movement of natural enemies, by mowing/cutting back weedy resources to encourage the dispersal of natural enemies onto your infested Moringa plants.
Aphids usually occur in clumps and will quickly appear and just as suddenly disappear due to predation, parasitism (parasitzed aphids look swollen and bronze—eventually a minute wasp will emerge), naturally occurring fungal outbreaks, declining host-plant quality, changes in weather, or dispersal etc. They prefer sheltered areas out of the wind, so perhaps even thinning the Moringa as you harvest to get more airflow through the plants would help.
Another option that has been promoted in IPM programs in Honduras and in the literature to some degree is the use of food sprays to attract natural enemies. Water mixed with honey or other unrefined and refined sugars have been demonstrated to attract predatory beeltes, ants, and wasps… The idea is simple—spray a food source for the beneficial insects to attract them to the plot and nourish them while they start looking for prey/hosts. There are some obvious potential problems—1.ants, 2.fungus, 3. Sticky-messy. However, this is a potential low-tech solution that might warrant some investigation…if not for the morninga system, perhaps for a vegetable crop or corn.
Rearing Insects: Ladybird beetles & lacewings to a lesser degree are fairly easy to rear, keeping them fed is the greatest challenge. Because of the ephemeral nature of aphids—and the quantities you’ll need to rear a colony of predators, you should plan to keep a colony of aphids to supply your brooding beetles. Ladybugs will eat pollen, and honey but in my experience they develop much faster on aphids than pollen and honey is a sticky mess that always brings ants. A few tips: We hung pieces of folded black plastic trashbag in the cage to provide a substrate for oviposition; provide ample food—well fed beeltes lay more eggs; keep it clean (get rid of dead insects etc.); from time to time add field collected adults to your colony for breeding—this keeps genetic diversity high & prevents inbreeding problems.
Releasing Insects: If you have the choice, release larvae-not adults. Use an artist’s paint brush to move larvae as they are very delicate. Alternatively you can release eggs. Larvae are voracious and will consume more aphids, mites, whiteflies, thrips etc. during their development than as adults. Additionally, they are unable to fly, so dispersal is not a problem until they become adults. With sufficient prey in the system, (either on the moringa or insectary crops etc.) adults will hopefully stick around, reproduce, and prevent further outbreaks. However, in the absence of sufficient prey, adult coccinellids will disperse. A border crop or intercrop that attracts aphids (preferably aphid species that are not interested in Moringa) may enhance the success rates of a release and establishment.
In Cuba , I observed some small-scale urban gardeners rearing coccinellids and lacewings in homemade cages. It can be done, but requires work that might otherwise be avoided through habitat manipulation alone. I am curious about Wayne Niles’experience. Rearing beneficial organisms certainly has great potential as a teaching tool for students and interested farmers. We did some interviews in the Bohoc-LaJuene area around HAFF in November to find out how farmers manage pests. None of the farmers we interviewed seem to have any knowledge of beneficial insects, although some mentioned that birds picked off caterpillars and snails from their gardens. Most of the vegetable growers were using broad spectrum conventional pesticides and fertilizers. Some were using a combination of conventional and natural pesticides (they learned about them from MPP), but complained that they required too much labor to make themselves.
Other aphid predators to look for: (I experimented with inserting photo links)
Lacewings—their immatures are sometimes called trashbugs because some species carry plant debris on their back while they scour plants, looking for aphids, mites etc. They are voracious aphid predators. Larvae
Syrphid fly/Hover fly: Adults are attracted to nectar sources and worm-like larvae are effective aphid predators. Syrphid fly larvae
Minute Pirate bug—Orius spp. Adults and nymphs are generalist predators of small prey (thrips, whiteflies, aphids, mites, etc.). They are associated with flowering plants especially sunflowers. Here are some links to photos: orius nymph;
Orius adult feeding on whitefly nymphs
Parasitoids: Minute wasps lay their eggs inside aphids. Aphids that have been Parasitized are called mummies and look like swollen, bronze, aphid-sized balls.
I hope this information is helpful. Let me know how it goes!