Category Archives: Insects and Disease

Pests, Beneficial Insects and Plant Diseases

Summer Watering

Now that the hectic pace of spring has come and gone, it’s easy to think that all the hard work is over.  The planting, fertilizing, trimming and clean-up are all complete, shouldn’t we just sit in our Adirondack chairs and gaze serenely at the garden? We can’t forget one of the most difficult tasks a gardener faces, summer watering. With our Northwest summer drought, plants need consistent and thorough watering to grow and stay healthy.

I’ll never forget a Myrica californica that is growing in the arboretum.  When I first noticed it a few years back it appeared healthy. The leaves were green. It had new growth, but it was small.  We added irrigation to its bed and within a year it had doubled in size.  After two years it has tripled in height and width.  It’s a changed plant now, like it has a new breath of life with regular and consistent watering. I see its potential.  It’s interesting that we might think a plant is doing just fine.  It’s green.  It grows a bit every year.  And then suddenly when all its needs are met…wow! It can take off.

There are many methods available, sprinklers, watering cans, drip irrigation and in-ground irrigation systems with timers.  Water is a precious resource and we should always be thinking about conservation.  Setting up a home irrigation system such as drip irrigation may seem complex, but is really quite manageable. The main thing to remember is that plants prefer a thorough deep watering to a light superficial sprinkling.  When we spray the surface, the soil may appear dark and moist, but underneath the roots have no moisture. We have to allow time for the moisture to reach the root zone. Water when the soil dries out, more often when it’s hot and less when it’s cloudy and cool.

It’s happened so many times.  I think I’ve watered a container really well, whether a small four inch pot or a large patio container. I might have to dump the soil out or dig into the container, and I’m shocked to find out it’s dry at the bottom!  A good method is to water a container until the water runs out of the bottom.  I also like to give a container as much water as I think it needs.  And then do it again. Give it twice as much.  If the soil is too dry it can become hydrophobic and it takes a long time to absorb the water.  Then the container will have to be watered two or three times.  Over-watering can be a problem too, but only if the soil constantly remains wet and is never given the chance to dry out.

Planting similar groups of plants together can also help conserve water.  Annuals and big leafy perennials take more water than established shrubs and trees.  Keeping them in separate beds will make watering easier. Many of our Northwest native plants are tough and drought tolerant, but remember this is only after they have had a few years to grow a good root system. So when you add any new plants, even if they are ‘drought tolerant’, remember to water for the first two summers.  Mulching is a good idea as it helps retain moisture. Rhododendrons are usually ignored all summer, but these plants will really benefit from a consistent supply of water. Remember, a healthy plant that has been well watered and fertilized will more easily fight off insects and disease. Just like us, if we aren’t getting enough sleep or eating well we tend to get sick. So enjoy your summer garden and don’t forget to give your plants a drink. And then do it again.

Ladybug Summer

Today I was so excited to find ladybug larvae on my roses.  I was making the usual weekly rounds, dead-heading, checking things out, snipping out leaves with black spot and scouting for aphids.  Normally when I find a cluster of aphids I strip them off the leaves with my fingers (yes, I wear gloves).  Today as I was brushing them off I noticed a few ladybugs nearby.  And then I noticed there were still a few insects tenaciously hanging onto the stem, but they weren’t aphids.  Upon closer inspection I discovered they were the larvae of ladybugs, little aphid-munching machines. I was thrilled that beneficial insects were hard at work in my garden. I was also glad that I hadn’t sprayed any chemicals, not even Neem oil, onto the roses. The circle of life, happening in my yard! When people don’t have a lot of time it’s just easier to get a bottle of something and spray the roses when insects appear.  But if you really love your plants, you have to take a close look at them.  Spend time with them. Give them an afternoon.  That’s when you see what’s happening in the garden.

 

The Moth Dance

Yesterday was the summer solstice, the longest day of the year.  It’s a bittersweet feeling for me, because for the last six months I’m longing for this day of light and for the next six months I’m reminiscing about this summer light.  Early morning light and late evening light.  Light that wakes me up with its bright intensity and light that puts me to bed with its soft glow.  It says, you don’t need the moon or the ‘faults in the stars’, because I’m still here, perfect sunlight, light unsurpassed. For a gardener it’s the best day of the year.  The plants have 16 hours of sunlight to work the wonders of photosynthesis.  We have 16 hours to pull weeds, plant and fertilize.  I rarely see moths feeding in my garden and this one didn’t seem to mind the sun shining radiantly still, at 7 pm, as it danced around my erysimum.  It’s collecting nectar, I”m gathering light.

Banker Plants and Aphid Mummies

Normally growing aphids is a bad thing, but in respect to our beneficial insect program, it’s a good thing.  At the Environmental Horticulture Program at Lake Washington Institute of Technology we grow and propagate thousands of plants in our greenhouses.  Each year the students put on a huge plant sale that generates money that helps fund the program.  This year we had a serious threat from aphids, which began appearing in November and stayed through the spring.  Working with Alison Kutz from Sound Horticulture, we began a biological control program, using beneficial insects.  We started to bring in good bugs to help us wipe out the bad bugs.

One of the insects that parasitizes aphids is the native wasp Aphidius matricariae.  It seeks out aphids and lays an egg inside them, killing the aphid and producing another generation of wasp.  Each female lays about 100 eggs, but may attack 200-300 aphids in the process.  That’s a lot of destruction from one tiny super-wasp.   The larvae develop entirely inside of the aphid which turn a light brown and remain on the leaf surface.  These aphid shells are referred to as  ‘mummies’.  They aren’t just found in greenhouses, I recently discovered an aphid mummy on my Japanese Maple.  I was happy that nature was helping me keep my plants healthy.

Buying Aphidius frequently, however, can get expensive, so we decided to raise our own.  A true baby wasp nursery in the greenhouse.  It’s called the banker plant system.  We raised a type of aphid that only lives on grasses, so it wouldn’t transfer to our greenhouse crops, and this provided a place for Aphidius to maintain and grow their populations.  More wasps, less aphids…healthier plants.  We had to build an exclusion cage to keep Aphidius out until the aphid populations were strong enough.  We sprouted our wheat plants and left them in the exclusion cage for 2-3 weeks and them placed them on benches around the greenhouse.  It was fascinating to watch the Aphidius we released near these plants.  We could actually see them attacking the aphids, not a good viewing activity for the faint of heart.  This is parasitism at its best.  As our wheat matured we noticed more and more aphid mummies appearing on the plants.  The system appeared to be working!  Our aphid numbers did get too high at times and we still had to spray with insecticidal soap.  Next year we will start our wheat earlier and get a strong population ofAphidius ready to engage in battle.

Following is a video of an Aphidius release as they search out aphids on the banker plants.

 

 

 

 

 

 

 

Fresh New Growth—Yum!

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Today as I was admiring the fresh new growth on my Japanese Maple and saw something disturbing.   The buds were just breaking open with our warming April weather, unfurling delicious colors that were vibrant with life.  It must have been a signal to the Japanese Maple-eating pests, the dinner bell was ringing!  There were little black dots all over these new leaves. Black spots on the tips of the branches.  Upon closer inspection I noticed that they were soft and easily scraped off.  Unfortunately the leaves were so tender that it was hard not to damage them as well as I tried to remove the little black bugs.  As I looked closer at the photo and did a little research, it seems that they may by some type of black aphid.  Could it really be aphid season already?  I’m not prepared for this!  I have been winter lazy, thinking everything was hibernating still.  But spring is here!  Even though I’m still wearing sweaters and dashing through rain showers, the pests are right on schedule.  Tomorrow I’ll try and pull off more of these little black bugs and watch them for a while.  The tree is small enough that I can easily take care of them without sprays.  What do you think?  Have the aphids arrived?

Aphidius matricariae–A Beneficial Bug

This is an amazing solution to a plant problem.  Big fat hungry aphids are gobbling away on the plants, sucking and deforming the leaves and getting out of control.  This little parasitic wasp is released and is attracted to the aphid colonies immediately.  It begins to lay its eggs inside of aphids and will attack 200-300 aphids in the next week.  Yes, parasitism is slightly disturbing, especially if you’re on the wrong end.  The wasp eggs hatch inside the aphid body and begin feeding on the aphid from the inside out.  They complete their development inside the aphid body and emerge from the ‘aphid mummy’ after 15 days as a new adult and the life cycle begins again.   More wasps, less aphids, happy plants, healthy greenhouse!

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This is the container of Aphidius that we received from Sound Horticulture to release in our school greenhouse.  We hope to use more beneficial insects for pest management and spray less chemicals.  We also released Aphidoletes, Stratiolaelaps and Ambylesius cucumeris, the subject of future posts!