Cabbage-worm on Kale

Cabbage Worm (Pieris rapae) on kale.

The leaves of my kale and broccoli are disappearing.  I thought that they were being eaten by some earwigs but upon close inspection I saw a multitude of velvety green larvae that are camouflaged on the leaves.  These are the larvae of the adult moth Pieris rapae. 

Pieris rapae is a beautiful small-sized butterfly known as the Cabbage White butterfly.  If you see a dainty-looking white butterfly with black dots on the wings flying around your garden, be extra observant.  While the adult is harmless, the larvae (commonly known as Cabbage-worm) are voracious and they feed on most brassica crops. At the early stages of the larvae, the damage happens slowly but once they reach a substantial size, they can defoliate the plants quickly.

There are a number of effective and safe biological control for the cabbage worm.  Basillus thuringiensis (Bt) and spinosad.  Ask your local nursery for these active ingredients and they will lead you to the right products.  These are both biological and considered organic pesticides.

As for me, since I do not have a huge garden, I prefer to do it by hand - picking the worms every morning. This is also biological and organic method, mind you. :) But this requires that I have to be vigilant.  

Stroll in your garden, and squash all the cabbage-worms you see :)

Rose Growing is No Bed of Roses

Fig. 1   Aphids

When it comes to roses, the peak of flowering in our area is now. During this time, plants have large leaves; the flowers are huge; and their colors are intense.  The weather is optimum for plant growth and even for pests.  As a general rule, I do not use pesticide in my garden.  We live or move around so close to the plants in my yard, that I'd rather have them look a little bit damaged and disease-infected than having to inhale the fumes of chemicals when I smell their flowers.  Pest and diseases attack my plants but since I am not selling the flowers, I don't mind that they show signs of pest damage.  I have tried some practical solutions to the problems that may not necessarily eradicate but slow down the spread of the pests. 

Aphids

Observation:

Young and succulent parts of roses are often very appealing to aphids (Fig. 1).  Early in the spring, a thick blanket of aphids is a common sight on the basal part of flower buds.  Although, there might be varieties that are more resistant or less attractive to aphids than some, I still have not seen a rose that has not been infested by the pest.

Simple Solutions: 

 1.  Feed the finches; they eat aphids in between meals of seeds.

 2.  Buy and release lady bugs in the garden; they are voracious aphid eaters.

 3.  Blast off the aphids with water. 

 4.  Regulate nitrogen application.  Too much nitrogen coupled with excessive water result in fast growing tissues of plants.  Such plant tissues are soft and loved by tiny sucking insects.

Fig. 2     Powdery mildew (Sphaerotheca pannosa)

Fig. 2a   Powdery mildew and aphids on flower buds.

Powdery Mildew

Observation:
Powdery mildew always starts as spots of scattered powder on the leaves (Fig. 2 and Fig. 2a).  As favorable conditions persist, the powdery spots increase coverage.  Roses that are well watered and growing in a shadier part of the garden tend to be more susceptible to powdery mildew.  In shady areas, leaf surfaces take longer time to get dry that those that are exposed to sunlight. Most fungi thrive on moist spaces.  The spores can be carried by air from one vulnerable leaf to the other.
Practical solutions:
1.  Avoid watering the leaves of plants. 
(This conflicts with my recommended solution for aphids but there's a remedy for that: hose off the aphids in the morning so that the leaves can get dry quickly.)
2.  Prune infected branches to prevent further spread of the disease.
3.  Treat pruners and clippers with a bleach solution. 
4.  Remove all fallen old leaves from under the rose bushes.
5.  Spray a mixture of baking soda (1tsp) and dishwashing soap (2 tsp) and water (1 cup).

 Fig. 3   Black spots (Diplocarpon rosae)

Black Spots

Observation:  

Black spots are really ugly  (Fig. 3).   They start are dark spots on leaf surfaces and eventually the surrounding areas turn chlorotic (yellowish).  Early in the spring when the temperatures are cooler (>75 degrees F) and precipitation is at its peak (here in our area) black spots are prevalent.  They also appear later in the year when the weather gets dry.  It appears to me that roses that are water stressed are vulnerable to infection.  

Just like powdery mildew, black spot is a fungal diseases  .Again, those plants in the shade are more prone to infection because they leaves takes longer to dry up allowing time for the pathogen to grow.  Infected leaves drop off and sometimes roses get denuded.  

Practical Solutions:

1. Avoid watering the foliage of the roses.

 2.  Clean underneath the plants from fallen leaves because they are likely to be carrying the pathogen.

3.  Remove all obviously infected leaves.

4.  If you are not very emotional- discard varieties that are susceptible to black spots and replace them with resistant varieties. 

Final Note:

There are fungicides and insecticides that are recommended for these pests but as I have said earlier - I deliberately avoid using them as a personal preference. 

For more information:

Black spots: http://umaine.edu/ipm/ipddl/publications/5097e/

Black spots: http://www.ipm.ucdavis.edu/PMG/GARDEN/PLANTS/DISEASES/blackspot.html

Powdery Mildew : http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7493.html

Aphids: http://www.ipm.ucdavis.edu/QT/aphidscard.html

Pests will always be a part of gardening; gardeners have to set their personal tolerance level and adjust management techniques accordingly. 

My Orange Trees

Fig. 1  Valencia Oranges in the winter. 

While other plants are starting a new season of production, most citrus plants are at the end of a season.   When the garden looks bare and unproductive, the citrus plants remind us that their deciduous counterparts are just taking a break.  They give us a glimpse of summer in a time when the frigid temperatures seem to freeze all possibilites in the garden. 

Fig. 2    First harvest:  Good eating quality, mildly tart, and medium-sized.

 I have two 'Valencia' orange trees that are growing in large pots.  Currently, they are laden with ripe and juicy fruits.  Two weeks ago we harvested some of the fruits in preparation for the supposedly cold snow storm. We did not have the snow but at least the fruits (Fig. 2) got into the kitchen where they are now a regular part of our daily meals.   Soon I will have to harvest them all so that the plant can start another season to produce. 

In my garden I also have a prolific 'Ponderosa' lemon tree where we harvest bags and bags of fruits every winter.   This year I also received a small 'Meyer' lemon tree in a five gallon pot as a present from my mother-in-law.  

Fig. 3    Scale insects on orange fruits.

Last summer these trees were infested with scale insects.   Since the trees are of manageable sizes, I decided to mechanically remove the insects off the branches, patiently.  However, it was battle between me and the ants.   As I demolished colonies of scale insects, the ants literally relocated the "pioneer" scale insects into new territories.  No insecticide was applied.  Some of the branches were severely damaged that I cut them off during the growing season.  The ones that I missed are seen as leafless branches on Fig. 1.  I hoped to win the battle against my wingless enemies (scale insects) the humane or organic way but I lost!   I saw them on the fruits (Fig. 3).  Those black dots on the rind are scale insects.    Somehow, I fear that even after harvesting all of the fruits, some ants somewhere will protecting another "pioneer" to settle on the next spring leaves.

Fig. 4  Limited growing space require regular pruning of plant.

Soon, I will have to harvest ALL the fruits in order to relieve the tree from these demanding "sink".   In a plant the sink is the destination of synthesized food substances from the source which is the leaves.  In families, the young kids can be paralleled to a sink and the parents are the source. :)  

The tree will need to be replenished with all the lost nutrients soon.  Fertilization is more important in potted plants than their in-ground counterparts since there is a limited hunting area for the roots. 

Pruning will also be necessary to remove as much of the damaged branches as possible.   Since the trees also serve as ornamental plants, they will have to be trimmed and cut back to maintain a shape and size that is suitable for the limited space on that side of the yard (Fig. 4). 

"A man ought to carry himself in the world as an orange tree would if it could walk up and down in the garden, swinging perfume from every little censer it holds up to the air."

~Henry Ward Beeher

Duck and Duckweed

This park was one of our favorite places to go when the kids were little.  There was a fountain in the middle and the water was really clear we could see small fishes in the water.  The other day I was surprised to see that it is now almost completely covered with tiny little floating plants called duckweeds (Lemna minor).   

Given the right conditions, duckweeds can be very prolific.  One reason for this fast growth in this pond could be high nitrogen content of the water.   The sloped surrounding grass area is kept green year round - meaning high amounts of nitrogen is applied on a regular basis.  It is expected that some nitrogen find their way to the pond through runoff.  A second reason for the high nitrogen content of the water could be due to the animal waste from all the ducks in area.

It appears that the duck population in the area cannot keep up with the growth of the duckweed.  I wonder what the Community Service District will do with this pond - to get rid of the duckweed infestation.  They could keep it that way or do something to remove it so that the water can be clear again.  They could increase the duck population but that will only increase the amount of animal waste going into the water.  They could skim the duckweed regularly but that would be labor intensive.  Duckweed is rich in nitrogen and would make an excellent composting material; local gardeners can be encouraged to do their part and harvest some of the duckweeds. 

Any suggestion?

"Italian" Caterpillars

Caterpillar feeding on basil

Basil (Ocimum basilicum) is one of the basic aromatic plants that I maintain.  Every summer I grow them in pots near the kitchen.  This is the first year when I had to deal with some caterpillars which were trying to defoliate my basil at a high speed.  I've never had "basil-eating caterpillars" in my garden before.  Could it be that they have migrated from Tuscany? :) 

Phytophagous insects are those that feed on plants.  We see them all the time in our gardens on different plants.  Different insects are attracted to different types of plants.  For example, the tomato hornworm which is the larvae of the Five-Spotted Hawk moth (Manduca quinquemaculata) feeds on tomato leaves as their first choice.  

How do they choose their host plant?  The adult female insect chooses the host plant before they lay their eggs.  The adult insects (moths and butterflies) are beneficial pollinators but their larval form is very destructive to plants.  Although the adult does not have the same diet as the larvae, it knows what its offspring will want to eat.  There are cues that they use to choose their host.  The first one is visual cue - they choose green (plants) instead of brown (soil).  Once they are on the right color location they start to inspect the other details such as the chemical properties of the plants that they have chosen.  Only after they have made sure that the location is right that they begin to check out the other details of the host plant.  The scent, palpability, and taste of the plant will be final test on whether the insect will decide to stay.  Otherwise it will continue to look for another plant until the perfect one is found. 

This is similar to house-hunting.  First we choose the right location or city and then we look for the house that is affordable, with a big yard to garden, or a sparkling swimming pool. We view different houses until we make an offer only on the one that meets our requirements.

The voracious larvae that are on my basil plants did not choose to be there nor did they migrate from another yard because they liked the good smell of the herb.   They were left there by their harmless parents (moth or butterfly) who made sure that their young will be fully supported.

Friends or Enemies?   Well, a couple of days ago I wrote something about saving the pollinators.  Now, I am talking about "future pollinators" eating my food.  How then should we treat them - enemies or allies?  No matter how I will answer this question it will always be wrong.  The butterflies and moths are our partners in food production and they deserve to have food during the different stages of their life cycle.  If we do not want them to feed on our own food then we need to make sure that they can find theirs somewhere.  Therefore, diversify.

  

Plant-eating larvae

Damaged basil plants.

Ants Can Farm

Ants tending scale insects on orange tree.

Have you ever wondered what in the world are ants doing on your plants?  Well, you might want to check their activities by following their trail.  It is likely that they are tending some aphids or scale insects somewhere on your plants.   This is the case with my orange trees that are in pots.   Hidden from my eyes are pests that are being farmed by the ants.  Slowly the aphids are sucking the blood out of my plants, and the ants feed from their exudates known as 'honeydew'.  Ants consume the honeydew as an important source of their nutrition.  The aphids and scale insects in turn have a greater survival rate and thus increasing their population.  As you can see, both aphids and ants benefit from this relationship but the plant is the victim.

Have you ever wondered how the ants farm aphids and scale insects? Here are some ways:

1. They protect them from their predators - For example, ants attack lady birds.
2. They prevent the proliferation of destructive microorganism (such as molds) by eating the honeydew.
3. They hunt for a favorable shelter and feeding area on their behalf.
4. They move the nymphs (young aphids or scale insects) to better parts of the host plants.

Ants cleaning/eating the wastes produced by scale insects.  On the background is a spider web.

It's a dog-eat-dog world out there.  The ants might seem very powerful in this case but there are also other living creatures that are "farming" them.  When I was scrutinizing my plants, I noticed that the ants were not the only indicator of the location of infestation.  If you look at the picture above, you can see a spider web that runs along the branch where the scale insects are.  Somewhere a spider waits for the ants to make a wrong move by stepping on its web.  The ants might be powerful to scare lady birds away but once they step on a sticky web, then they become a prey instead of a protector.

It turns out that spiders are our friends.

Aphids

Aphids on rose buds

The area has had an unusually good dose of rain this year.   Combine that with the warmth of the California sunshine and the plants can almost grow unhindered.  I said "almost" because that same weather condition can also make pests grow almost unhindered.  This year we had so many aphids - the lady bugs cannot keep up with their population growth.   I had to rely on my handy dandy "dishwashing soap spray". 

Aphids like to feed on young and tender plant parts.  They feed by piercing and sucking sap from their host.  Unlike the chewing insects where the damage can be detected easily, aphids keep the plants intact but drain them out of the nutrients that they need.  Regular close inspection gives us a better chance to eradicate them before damage is done.

Stroll in your garden, it's good for you and your plants.  :)

Aphids

Aphids on Chives

Spring is here...even aphids are having a blast in the garden.  They have infested my chives and some of my roses.  The problem with aphids is that they reproduce so quickly.  With the mild climate of California, aphids can reproduce asexually through parthenogenesis (females can have offspring even without males) even faster. 

It is important to keep checking your plants for infestation - twice a week would be a good idea.  It is difficult to get rid of them once the population gets high. They cause the leaves to curl and then use these damaged-leaves as hiding places.   When you observe a trail of ants climbing onto your plants, it is likely that they are tending some aphids somewhere.   Ants eat the honeydew that aphids excrete. 

To get rid of aphids, spray them off with water.  They can drown easily.  If your plants are delicate, hand spray them with a mixture of one pint of water and 1-2 tsp of dishwashing liquid detergent.  Repeat as necessary.

To learn more about aphids, the UC Davis IPM Online provides a good resource.

Gardening is not all beds of roses.  Challenges present themselves from time to time in different forms.  As a gardener keep your eyes open to recognize your enemies before they damage your plants.

An Enemy

Brown Garden Snail  (Cantareus aspersus)

I saw this enemy in the garden today.  Although it has not been named as a serious pest in California, snails, along with their relatives the gray garden slug (Deroceras reticulatum, formerly Agriolimax meticulatus) are annoying pests in home gardens especially during this time of the year when the herbaceous plants are just beginning to emerge from the ground.  It is easy to mechanically control the snails but I prefer to deal with slugs chemically using metaldehyde (2,4,6,8-tetramethy 1,3,5,7 tetraoxycyclo-octane) in late winter and very early spring.  This is the only time I put slug/snail bait in the garden mainly for the purpose of protecting the seedlings.  Later on I hand-pick those that survived.  This way we can enjoy slug-free strawberries.

Important Link: IPM for Snails and Slugs

Did you know?

The brown garden snail is closely related to the Roman Snail (Helix pomiata), the edible snail which is commonly known as Escargot in French cooking.

The Philippines has its own edible aquatic snails known as Kuhol or the Channeled Apple-Snail (Pomacea canaliculata).  They are aquatic; usually found in rice fields as pests.  Recently, it has been found to be good source of feed supplement for livestock and poultry.