New Year's Resolution: No pest problems

Columns - Plant Health

January 20, 2011

Daniel Gilrein

1. What’s the best way to avoid most pest problems?
One New York greenhouse grower declared it’s “easier to stay clean than to get clean.” He was speaking specifically about thrips and whiteflies, although his comment applies to other pests. This grower takes sanitation (removal of weeds, older plants, plant debris, etc.) quite seriously, knowing they have clearly been the source of headaches in the past.

2. When is the best time to monitor for pests?
Detect pests early and control at an early stage well before they are noticeable or damaging. Even if crops are well developed, monitoring is time well spent. Check propagated cuttings and older plants first, especially in production areas with a history of infestation.

3. Is it really worth the time and effort to put out sticky cards?
Yellow sticky cards are a great detection tool for many insects, such as thrips, whiteflies, fungus gnats and shore flies. Place them on older plants, among newly received cuttings and in areas with air currents.

Infestation Symptoms:

  • Aphid cast skins and sometimes shiny honeydew dropping on leaves, pale speckles or yellowing on leaves or possibly edema.
  • Yellowing and brown spotting on zonal geraniums foliage from twospotted spider mites.
  • Scarring and white patches on leaves and flowers from thrips.
  • Stunting, bronzing and distortion of new growth from broad mites. There can also be a very fine white stippling on flowers of New Guinea impatiens and standard impatiens from broad mites, even before injury to leaves and terminals is apparent.

What to watch out for
Thrips, specifically western flower thrips, were likely every grower’s No. 1 pest this past year on bedding and flowering pot crops, but certainly not the only one. Broad mites generated a few surprises too. Hard-to-control whiteflies on poinsettias and a few other crops were the biggest problem in some locations. Mites tended to be more common in long-term crops such as foliage, and aphids were occasionally seen on crops like mums, lilies and vegetatively-propagated plants like perennials as well as some annuals. Anyone growing herbs from vegetative cuttings probably encountered all of the above.

Have a question?
You can write Daniel at