"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.

Save and Celebrate the Pollinators

In the course of any given season, we plant and water, we fertilize and weed but for most of our crops someone else has taken the responsibility of performing the key job that result in a good harvest.  The pollinators are our partners in the backyard or in the fields.  They are the bees, butterflies, hummingbirds, moths, flies, beetles, and bats. 

This week (June 21-27, 2010) has been designated as the National Pollinator Week by the USDA.  This post is not that late - you still can check out their website and see what you can do.  

One small step at a time counts.  As gardeners, we can make deliberate attempts to make our backyards a favorable habitat for pollinators.  It does not take much from us to help improve this "world of pollinators".   In my garden for example, I allow my herbs and vegetables (cilantro, parsley, sage, mint, rosemary) to flower.  These are insectary plants - they harbor insects including pollinators.  Now as the season progresses, the annual and biennial herbs dry out - but the bok choy (in the picture) and radishes which were purposefully left to flower are hosting the insects.  These are just plants from my kitchen garden.   There are so many ornamental plants that can provide pollen and nectar for them.   Different plants attract different pollinators.  Diversify your crops to provide a continuous food source throughout their active season.  If you want to take action for pollinators there is a specific recommendation for your area. 

In food production, the pollinators are our allies. 

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.

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). 

Seven-spotted Lady Beetle

Lady Beetle (Coccinella septempunctata) on Flat-Leaf Parsley (Petroselinum crispum)

This seven-spotted lady beetle (ladybug or ladybird beetle) has been spotted in my yard.  Fortunately, this lady is a gardener's friends. Scientifically it is called the Coccinella septempunctata.   Being a predatory insect, the C. septempunctata plays an important role in the biological control of aphids.  Both the adult and the larvae feed voraciously on aphids.  Adults hibernate or overwinter in protected areas.  In the spring when temperatures get warmer, they come out and feed on aphids before they lay eggs.  The females can lay up to 1000 eggs within a three month beginning in spring.  The females are very strategic in their choice of a place to lay their eggs.  They prefer areas with a high insect population such as in gardens, fields and tree canopies. 

Close-up on the Lady

The C. septempunctata is commonly identified by the seven black spots on the bright red elitra (singular elytron: are the tough fore wings of beetles and earwigs).  It undergoes a complete metamorphosis.  This means that it has to undergo four stages of change to complete its life cycle:  Egg; Larvae; Pupa; Adult. 

Although most ladybugs are beneficial to plants, some of them are considered pests.  In a future post I will name those bugs and describe why they are not so "lady-like."