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. 

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?

Galls on the Peach Tree

Galls growing around the nodes of a peach tree

My peach tree suffered much from pest and diseases this season.  Due to the prolonged period of rains, the tree suffered much from leaf curl  (Taphrina deformans).  Now there are galls on the twigs (see picture).  The nature of these galls are unknown to me...if you know what they are please let me know.   They look like dark brown shiny beads with starch-like substance inside.  I have been doing research to identify them but I guess the most scientific step would have been to submit samples for pathological analysis.  It is my guess that these are caused by the fungal damage from the leaf curl.

Plant galls are not uncommon.  They are likened to a tumor that results from abnormal cell growth due to irritation caused by insect infestation and fungal or bacterial infection.  They grow on different plant tissues such as the roots, stems, branches, fruits and leaves.   The nature of the gall is not only affected by the organism that is causing it but also the location of gall formation on the plant.  Galls growing on leaves tend to be softer than those growing on bark of trees.   Galls growing on hairy leaves tend to be fuzzy while those growing on the branches are hard and shiny (such as the ones in the picture). 

Although they look very severe, galls are not detrimental to the plant.  They can interfere with the growth of the particular part where they are growing but not the whole plant.  

Detached galls.

Since I am not sure of the true nature of these galls,  I thought of removing them by hand to avoid further proliferation.   Luckily they were concentrated in a couple of branches only. 

If you know what these are please let me know.

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.  :)

Beneficial Insectary Plants

Santa Barbara Daisy (Erigeron karvinskianus)

Beneficial insectary is a term that refers to plants that attract and host beneficial insects.   In other words they are the plants that provide a habitat for predatory insects.  Beneficial insectary plants often have nectar and pollen to offer to the good insects.  Their flowers offer a flat landing place for insects and sometimes they exude an unusual scent as an attractant.   The list of beneficial insectary plants continues to expand with the increasing research work and interest in organic farming.     

Beneficial insects on the other hand are insect predators that prey on many common garden pests.  Indirectly they benefit gardening by helping eliminate the destructive plant-feeding insects.   For example lady bugs don't eat plants; instead they feed on aphids that are destroying plants in the garden.  For the gardener, beneficial insects offer a biological control of pests.  Effective biological pest control is a safer alternative to pesticides. 

In My Garden.  There are some plants growing in my garden right now that are known to be beneficial insectary.  The Santa Barbara daisy (Erigeron karvinskianus) as I mentioned before is a very versatile perennial.  In addition to its aesthetic contribution in the garden, it is also valued for the role it plays in biological control of pests.  Among the herbs that double as insectary are spearmint (Menta spicata), coriander or cilantro (Coriandrum sativum), flat-leaf parsley (Petroselinum crispum).  Although my marigolds (Tagetes patula) are newly planted and recently damaged by birds, they are also known to harbor some beneficial bugs including lady beetles.  Hence, they are recommended to be planted near tomato plants.  Even English ivy (Hedera spp.) is supposed to harbor some beneficial wasps. 

What then?  Not all insects are gardeners' enemies.  In fact some of them are our allies.  They eliminate the real enemies.  This is like having your own army protecting your plants while you sleep and play.  However, their loyalty is dependent on the fringe benefits we give them. Some gardeners provide a dedicated habitat (Beneficial Insectary garden) for these allies.  However, if your garden is small, you can diversify your plantings to include the ones that attract them.  

Finally, do not be deceived - not all pests can be eradicated by biological means.  An effective pest control involves an integrated approach based on numerous factors.  Read more about integrated pest management approach (IPM). 

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.