Tuesday, July 29, 2014

Good mulch brings good bugs


Leaves under butternut squash and tomatoes

A gentleman of my acquaintance asked me what to do about squash bugs.  I said that I never really have a problem with squash bugs.  Turns out that the people he is helping with their farm are using plastic mulch to control weeds and row covers to try to control insect pests. 
I pointed out that what controls bad bugs are good bugs, predators that eat the plant eaters, and the most effective ones require good mulch like leaves to live under.  When you have plastic mulch or bare soil, you lose all the spiders, centipedes, ground beetles, and soldier beetles, to name a few of the most effective predators in the garden.

Warming rocks under peppers.  They warm the soil at night, cool it during the day.

Almost all of these predators live exclusively under loose mulch and rocks.  Soldier beetles spend the spring month of their adult lives flying, eating aphids, mating, and laying their eggs under mulch, where their larvae live under the mulch the remaining 11 months of the year, eating anything they can catch and kill.  If you have no loose organic mulch, you will have no soldier beetles laying eggs, and few or none of the others.
He said that the plastic mulch is needed to keep weeds down.  I said that leaves do that.  Not only do they keep sun off the seeds that need light to sprout, but they are a poor sprouting surface, as they dry out quickly, so seeds that land on top cannot sprout either.  Only larger seeds can get through 2 inches of leaves, and they are easily pulled; it is the tiny seeds that need sunlight on soil that are hardest to control without mulch.

4x8 sand and rocks under peppers and melons.  Insects are not under sand, only under rocks.  Sand is too hot.  Walk-on fir bark is beyond.

Plastic mulch cannot feed soil, while leaves are the natural food of worms and other detritus eaters, who turn them into soil.  One eater of detritus is the earwig, which many think of as a pest.  They are rather creepy in their habit of hiding in flowers and foliage during the day and coming out when they are brought into the house, but they don’t generally eat live plants; they eat the fungus out of dead or living leaves and can actually eat fungus, like rust on hollyhocks, out of your plants. 
Wikipedia considers earwigs omnivorous and says that they eat insects and plants.  Scientists seem to have missed that they love the fungus-infected parts of leaves.  They are said to eat corn silks as well, but I always have many earwigs and no corn silk damage.  Without fungus-ridden rotting leaves to eat, earwigs have only the softer parts of live plants to eat.
Two inches of leaves is great for stopping weeds and feeding soil.  12 inches or more can make wonderful soil and grow huge plants as they decompose.  Start next year’s garden by gathering your leaves this fall, rather than giving them to the trash company for compost.  They will make wonderful compost in your garden if you just let them lie there, and add to them.