Tuesday, July 5, 2016

Psyllids Are Coming! Plant lice on Tomatoes by Patti O'Neal

Adult Psyllids photo Michigan State University Extension

Reports of sightings of this insect pest in Northern Colorado has set the alert for us on the Front Range.  The potato/tomato psyllid  is a member of the family known as “jumping plant lice” and is very damaging to tomatoes in particular.  It is time to start monitoring your tomatoes on a regular basis for evidence of this pest in your garden. 

Psyllids do not overwinter here in the cold climate of Colorado.  They blow up from Mexico, Texas and Arizona.  Some years are worse than others. And because they are found in one place does not mean they are in another.  Monitoring is the key.  When they are here, they can do a great deal of damage to tomato and potato crops. The home gardener is not exempt and should be on alert to catch this pest before it gets out of hand. 

Psyllid Nymphs photo Michigan State University Extension

Psyllids nymphs are small, flat and go from yellowish to green, often matching the green of the leaf.  They have piercing, sucking mouthparts and feed on the moisture in the leaf.  The difference between this and other sucking insects is that their saliva contains toxic components that infect the plant systemically as they feed.  The leaves on the upper portion of the plant, especially the new growth, take on a purplish appearance along the midrib and margins and the margins take on a feathery, strapped appearance.  It is systemic and the infection is viral. 

This is what makes this insect more problematic than others for your tomato, in that if affects not only the green parts of the plants, but the fruit as well.  The fruits will never reach expected size and the flavor is compromised as well.  Once this has taken hold, there is no turning the plant back. 

What to look for?  Their excrement is the best clue that the insect is present on your plant. The upper surface of the leaf will look as though you sprinkled sugar or salt crystals on it.  This is the insect’s “leavings” and the best clue to spotting the problem.  When you see this, check the underside of the affected leaf and the one above it for the insects and you will likely see them.  

What to do?
  1. Keeping your plants in good, healthy condition by practicing good culture is the number one prevention against this and other pests.  Control your impulse to overwater, don’t over fertilize, and make sure your soil is healthy and that there is plenty of air circulation in and around your plants.  

2.  Monitor.  Look at plants with a critical eye and spot check the upper and undersides of leaves for signs of the insects presence. 

3.  Treat if necessary.  Younger plants are less able to tolerate an infestation than more mature plants, so routine treatment of young plants can be beneficial.  Insecticides available to the homeowner contain permethrins or esfenvalerate.  For preference dusting with sulphur is very effective.  Insecticidal soaps are very erratic in terms of effectiveness.   As always, and with any insecticide, even organic, read the label and make sure it is recommended (1) safe for food crops, (2) effective for the pest you are treating for and (3) that you apply according to label directions.

4.  Consider removing the plant if the infestation is beyond correcting so the infestation does not move to your other plants.  Do not compost an infested plant. Bag and trash it. 

5.  For additional information on this pest that is relevant to Front Range Colorado gardens, check out the CSU fact sheet http://extension.colostate.edu/docs/pubs/insect/05540.pdf