July 3-July 6, 2017
We have made reference over the years in our newsletters about how we depend on certain insects to combat the insects that prey on our plants. Let’s take a closer look at some of the insectivores we raise at Elmwood Stock Farm, along with the herbivores, omnivores, fruits, and veggies. We grow flowering plants along with the vegetables and elsewhere around the farm to provide food and housing for these insect-eating insects and spiders, to encourage them to proliferate and rear their young. We also purchase some “bugs” from one of several insect farmers, complete with educational catalogues. You may want to consider seeding your own landscape with some of these beneficial insects.
Everybody’s favorite, and most well-known, is the Convergent Lady Beetle, aka Ladybug. Adult females may consume as many as 5000 aphids in her one year lifespan, laying 1500 eggs as well. Ladybugs are unique in that the adult and the larvae are predacious, meaning they chew up and eat the entire aphid. The larvae look like little alligators and have a voracious appetite as they are growing so fast. The adults do tend to fly away as soon as all the aphids are gone, so periodic re-stocking may be necessary, but hey, they are working a wider area reducing aphids and other tiny plant pests around the farm. This is precisely why it is so important to have refuge habitat for them on the farm.
Aphidoletes aphidimyza sounds like it is an aphid rather than an insect that preys on aphids. The adults look like a mosquito and they are very good at locating aphid populations (that gets into the fascinating realm of pheromones). The legless larvae can eat 50 aphids per day. Actually they bite the aphid, inject a toxin, and then suck all the fluid out. The life cycle is about every 2-3 weeks, depending on temperature and other climatic factors and we may see 3-6 generations per year.
Adult lacewings are a fairy-like little winged insect that lays awesome eggs. Each egg is atop a hair-like structure about half an inch tall and scattered around the plant leaf or even on fruit, sometimes in a straight line. The larvae that hatch walk down the hair and begin eating any soft-bodied insect they encounter. For this reason, the eggs hatch at differing rates to prevent cannibalism. Sometimes on a just-harvested pepper or tomato, we can see the tiny stick structures. The adults require pollen and nectar from flowering plants, hence why we plant some. One of our favorite plants, buckwheat, flowers over a long period of time, and that sappy stuff on sunflower stems is actually great nectar as well.
Trichogramma wasps are so small, they lay their eggs in the eggs of other insects without harming them. However, when the larvae hatch inside the host egg, it eats the contents before emerging and flying away. It selects caterpillar type species as these have a long egg cycle, but if hatched, can devastate a crop. These are tricky to manage as they need the host eggs to be present, but if there are too many host eggs, these little wasps cannot parasitize all the eggs in a timely manner. We monitor this threshold and release them at the most opportune time. Scouting the fields, looking at the populations of the good and bad bugs and deciding where that threshold is, is part of what makes farming such a cool profession.
Many of the pest insects have one stage of their life below ground and we have some help down there as well. Beneficial nematodes are microscopic worms that eat some 250 species of insect’s eggs, larvae, pupae, or adults. These are very effective against grubs that later would become Japanese Beetles. They can survive long periods with no host at all, and reproduce quickly when another food source becomes available. We have inoculated the fields with these over the years with great success.
Non-organic farmers may use some toxic chemical if the pest threshold is exceeded, eliminating all of the insects in the field, bad and good alike. Certified organic farmers have a few botanical compounds we can use on the herbivorous insects that have no effect on the insectivores. We are only allowed to use these sprays when all other means have failed and document this in our records for the inspector to see.
There are lots of other beneficial insects on the farm and we try very hard to harbor them and give them safe haven. By releasing fresh generations, we are augmenting our host population, and we are establishing a new equilibrium with the pest population, with a much lower threshold of pest pressure. So, you may consider adding flowering and nectar generating plants in your landscape, and who knows, maybe one of our Convergent Ladybugs may take up residence in your garden. – Mac Stone