Monday, February 25, 2013

Loose Heads on Napa Cabbage

There are two main reasons why the napa cabbage does not form a tight head – variety and temperature.  Some varieties will simply produce a firmer head than others. The best approach is to plant several varieties and see which is best for your area. In tropical locations, obviously plant the tropical varieties.

Going hand-in-hand with the proper variety is temperature.  Napa cabbage prefers cooler temperatures.  Some area may be too warm to produce a firm head, especially if they are grown during the warmer months. For warm climates, try different planting seasons - fall, winter and early spring.

Concerning insect pests, aphids are quite common on cabbage and other crucifers.  A soap or oil spray should work well.  If worms are eating holes in the leaves, use BT (Bacillus thuringiensis).

Monday, February 18, 2013

Beetle Attacks Poha Berries


Poha berries, also known as ground cherry, cape gooseberry and husk tomato, are often invaded by the threelined potato beetle (Lema daturaphila, previously named trilineata).  Currently there are no pesticides registered in the State of Hawaii for the treatment of this pest on poha berry.  Yet there is good research for the nonchemical control of a related beetle in other crops.  Consider pursuing some of these methods: 

1. Yellow sticky cards – most insects are attracted to yellow.   Obtain some yellow cards, preferably something that will not deteriorate in wet weather. The next step is to apply a sticky material to the cards. A commercial spray preparation called Insect Trap Coating is effective. Put the cards on small stakes and place them in the midst of the berries. The beetles will be attracted to the cards and will stick to them. This method of control is especially effective when applied while the beetle population is still low.   

2. Plastic reflective mulches seem to ward off some insects like whitefly and perhaps these beetles, too.  The mulch can be placed on the ground as a cover, or strips hung over the crop; some gardeners have hung old CD’s and aluminum foil.   

 3. Row covers - thin woven cloths are placed over the plants to simply exclude the beetles. The covers, of course, must be put on before the beetles arrive.  

 4. In some cases, wood chip mulch applied to the ground may disrupt the insect’s life cycle and minimize its population.  

 5. Vacuum- if you’re really frustrated send off for a special ‘crop- vac’ (crop vacuum) called a D-Vac.  This cleaning devise is not for rugs but actually sucks the bugs with minimal damage to the plant. (see for interesting information) 

Monday, February 11, 2013

What Good Are Insects?

 I have often written about the good insects in the gardens such as  lady bugs eating aphids and tiny wasps parasitizing scale insects.  But what else are insects good for?  Here are a few other benefits:
   Pollination – crops like apples, pears, berries, coffee, melons, cucumbers and squash are dependent upon insects for fruit production.  Their work is estimated to be worth at least 8 billion dollars annually. 
 Honey and wax - besides the pollinating services of bees, they also provide us with honey and beeswax which is used in candle making, polishes, inks and cosmetics.
 Dyes - many species of scale insects provide dyes that are used in products like cosmetics, medicines, beverages and coloring in cakes.
  Genetics - Fruit flies have long been used in genetic studies.
  Decomposition – fly maggots and beetles breakdown carcasses, dung and other organic matter.
    Soil improvement – insects like beetles and springtails excavate and aerate the soil.
 Aesthetic value – there are many beautiful butterflies and colorful beetles.
 Skeleton cleaning –   a group of insects called carpet beetles are utilized by museum personnel to clean mammal skeletons as they feed.
 And last, but not least, insects are a food source.  Many cultures utilize insects for their nutritional value and as a condiment. Commonly eaten insects include crickets, ants, grasshoppers, termites, beetles and caterpillars. If your gastronomic juices are flowing, check out,  search ‘entomophagy’ 

Monday, February 4, 2013

Fungal Leaf Spot on Hydrangeas

There are a couple different fungal species which cause a brown to copper colored leaf spotting on hydrangeas. In general, these diseases are not serious.  They may make the plant look unsightly but will not kill the plant. Like many of the diseases in rainy areas, the reality is the more the rain, the worse the disease. (This is due to the rain droplets spreading the spores from leaf to leaf and plant to plant).  Leaves that are badly affected should be removed.  A copper fungicide spray could be used to help prevent the spread. Keep in mind that after several inches of rainfall, the protective copper will wash off.