Whats eating your trees when summer heats up?


There's an 'all-points bulletin' at the zoo for mulberry leaves. Got any?

Yes, it's kind of a strange request, and it sure caught my attention when the Oregon Zoo reported that mulberry leaves were being chewed almost to extinction there. People are always asking me to identify what kind of bug, slug or thug is eating the ravaged edges of their favorite plants.

At times, figuring it out is kind of like reading tea leaves because there are so many possible culprits. With a little detective work, though, it's often clear what the problem is.

At the zoo, the problem is simply a matter of supply and demand. Turns out the staff already knows what's eating their mulberry trees, and they actually want to encourage the predator.

The zoo needs a constant supply of fresh, pesticide-free leaves for its silkworm collection. It seems the silkworm caterpillars are close to exhausting the leaf supply. And the horticulture staff is worried that the zoo's two mulberry trees will be damaged if they prune off any more leaves to feed the critters.

Kasey Jakien, assistant coordinator of education services at the Insect Zoo, has never seen anything like the silkworms' appetite.

'The silkworms are totally voracious eaters,' she says. 'They don't look like it, but they need a lot of food. That's all they do, eat.'

No wonder! It takes several hundred silk cocoons to make just one silk scarf. And no manmade fiber has ever come close to the luxurious thread spun by the lowly silkworm caterpillar.

So this got me to thinking about what bugs us this time of year in the garden. I mean, here the Insect Zoo is putting out a desperate APB for the favorite food of one 'worm,' and we home gardeners are fighting like heck to fend off the summer insect surge. Let me count the ways.

Aphids: The best solution to get rid of aphids is also the cheapest. Turn the hose on full blast and douse the plant with water.

Apparently, aphids are strong enough to suck the life out of plants, but once they are soaked and a strong jet of water catapults them to the ground, they can't get up. So repeat this trick as necessary or use an insecticidal soap. You'll find products such as Safer insecticidal soap almost everywhere. Experts say it works best on soft-bodied insects. It coats their respiratory system, which drowns them.

Cutworms: Just when you are intensely proud of how your summer annuals are filling in so nicely, you'll wake up one morning to find an entire plant cut to the quick. Cutworms slice off the stems at ground level and leave the plant felled like timber. To make matters worse this month, the climbing cutworm will now start buzz-sawing even more of the plant.

The best defense is a keen eye. Because cutworms feed at night, you can pick them off in midbite using a flashlight to illuminate them (but who has time for that?). Luckily, during daylight hours you'll find them curled up in the soil. Search and destroy, or ask for an insect spray with Bt (Bacillus thuringiensis, pronounced: 'thur-en-gen-sis') at the garden center.

This bacterium spray is more environmentally safe than other chemical controls. Caterpillars or budworms (which eat geranium flower petals in the buds) will eat leaves sprayed with Bt and die in maybe three days. The bacterium makes them unable to eat anymore. Ha!

If all else fails, maybe superstition can prevail. Make an offering to the insect gods by donating insecticide-free mulberry leaves to the exotic silkworm caterpillars at the Oregon Zoo (503-226-1561, Ext. 5242), and just maybe the garden-variety bugs will leave you alone.

'Your Northwest Garden with Anne Jaeger' airs at 7 p.m. Saturday on KGW (8). Contact Jaeger at www.gardengal.tv.