Tuesday, July 24, 2012

Coconut Mealybug

A common pest that infects indoor and outdoor palms is the coconut mealybug (Nipaecoccus nipae).  They are soft-bodied insects that suck sap from plants. This can weaken the plant and cause leaves to shed.  In addition to palms, coleus, lantana, hoya, and poinsettia are preferred by the mealybug.

Some coconut mealybugs are white in color; others range from light brown to yellowish orange.  When the eggs hatch, the newly emerged insects, known as crawlers, move about the plant. At this stage they are the most susceptible to pesticides, and therefore, it is the best time to treat.  Pyrethroid insecticides and insecticidal soaps are usually quite effective.  Spraying the insects off the plant with a strong spray of water will also help. For light infestations, wipe the leaves with a cloth or tissue dipped in rubbing alcohol. 

Friday, July 13, 2012

Cuban Laural Thrips – Attack on Ficus!

Cuban Laural Thrips are fairly easy to identify; the damage is quite distinguishable.  They attack only a few species of Ficus, notably the retusa, while most others are immune.  But when thrips become abundant, they will feed on other hosts.

Using their rasping, sucking mouthparts, they feed on the tender, light green leaves causing a sunken purplish red spotting.  As the thrips feed, the individual leaves roll together with the thrips inside.  Eventually, the feeding causes a yellowing of the leaf along with some dark spotting. In the wind and rain these leaves will ultimately drop off.
With small trees, regular pruning of infested branches is often effective. Shearing off a few inches like trimming a hedge, however, should be avoided. This will stimulate new growth which is then susceptible to attack. 

Folded leaves can be unsightly but rarely become serious.  In most cases the thrips can be ignored.  If treatment is needed, common contact insecticides are of little use since the thrips are rolled up inside the leaf.  Using a systemic insecticide like acephate (Orthene) would be more effective.

Tuesday, July 10, 2012

Spinach by Any Other Name?

New Zealand spinach, (Tetragonia tetragonioides) as its name implies, is indigenous to New Zealand, but it is not spinach at all.  Not only does it look different from our regular spinach, the two are not even in the same plant family.   However, some will tell you that NZ spinach tastes better. It can be eaten fresh in salads or steamed and is especially good sautéed in olive oil and garlic.

The advantage in planting this species is that it grows in hot weather (up to 95° F) and will not bolt.  Bolting is the premature flower formation initiated by hormones within the plant system in response to high temperatures, as well as drought and starvation.  This unwelcome occurrence in leafy plants such as cabbage, lettuce and spinach,  takes the plant out of its leaf producing mode and switches over to flower and seed production.  The fact that NZ spinach is resistant to bolting makes it ideal for growing in tropical climates.

In regions with mild winters, this spinach acts like a perennial with frequent picking stimulating new growth. The plant will reach a height of 1-2 feet, spreading to 2-3 feet across. The seeds are large and germinate slowly. Soaking for 24 hours before planting will help germination. Rows need to be 24-30 inches apart, plants 12-15 inches apart. The first foliage is ready for harvest about 2 months after seeding.

NZ spinach is low in saturated fat and cholesterol. It is a good source of many vitamins and minerals: thiamin, niacin, foliate, pantothenic acid, phosphorus, potassium, zinc and a very good source of vitamin A, vitamin C, riboflavin, vitamin B6, calcium, iron, magnesium, copper and manganese.

Malabar spinach (Basella alba, B. ruba) is yet another spinach substitute, unrelated to the New Zealand spinach.  It is also known as Ceylon spinach and Vietnamese spinach. This is the one that has the mucilaginous texture (it’s slimy) and is useful as a thickener in soups and stews.

It is a fast growing vine which tolerates high rainfall. It grows best when trellised and is well adapted to high temperatures, even into the 90s F. But growth is disappointing when temperatures stay below 80 F. The plant requires consistent moisture to keep it from flowering, which will cause bitterness in the leaves.

Friday, July 6, 2012

Perils of Watering Houseplants

For those who choose to beautify their home with house plants, here are tips to help avoid some of the common causes of plant death.

Some people under water their houseplants.  This is not disastrous; the plants won’t grow as vigorously as well watered plants. And if the plant is wilting, adding water, in most cases, will revive it.

On the other hand, overwatering can often be the death of a plant.  Many people gauge watering by looking at the surface of the soil.  The problem is that the surface may be dry, but down a few inches and more, where the roots are, the soil is still wet.  This is especially true with nonporous containers.  Digging with a small trowel or even a finger will indicate if the soil is moist below the surface. 

Worse yet, some people will irrigate on a schedule. The water requirement of plants, however, will vary depending upon temperature (winter/summer), humidity (rain/shine), drafts (open windows), and the use of heaters, fans or air conditioners. The soil is the best indicator not the calendar!

After watering, the excess water needs to be disposed of.  Leaving standing water can lead to serious root rot.  

Wednesday, July 4, 2012

Tomatoes: Yellow Shoulder Disorder

What’s wrong when tomatoes don’t ripen evenly? For example, most of the tomato will turn red, but the stem end, known as the shoulder, remains green or yellow, and even whitish. This is a physiological disorder known as yellow shoulder, also known as green shoulder.  The shoulder area may also be noticeably harder than the rest of the fruit.  

Scientists have been working on this problem for many years.  They have finally come up with three potential causes.  1) Environmental – the disorder can occur when high temperatures, above 90 F, remain for a prolonged period, and the fruit receives too much direct sun exposure.  2) Nutritional – it can be triggered by insufficient potassium and a soil pH above 6.7.   3) Varieties – although no specific research has been conducted to conclusively identify the better varieties, there seem to be certain varieties that are less prone to the yellow shoulder disorder. The problem is more prevalent in heirloom varieties because many hybrid tomatoes have been bred to alleviate this problem.  

What to do – first, try some other varieties, especially the newer hybrids. In addition, you may need to increase the amount of potassium you are applying and adjust the soil pH.  If there is a heat wave, create some partial shade cover for the plants.   Letting the fruit hang longer on the vine in order for the fruit to color does not help and can increase the potential for rot.