“May you live in interesting times,” is a curse that seems to dog gardeners this summer. If late snow, shredding hail, and humid conditions weren’t enough, Mother Nature is now sending a wave of insects to perk things up in the tomatoes.
Tomatoes top the list for most kitchen gardeners, ranking number one in popularity across the country in a recent National Garden Bureau poll. With thousands of love apples blanketing the area, it’s no wonder the Front Range is a hot place for psyllids to take their summer vacation.
These tiny tomato boogeymen have begun assaulting plants this season in what may be the vanguard of thousands of migrating psyllids (Bactericera cockereli). Dr. Whitney Cranshaw, Professor of Entomology at Colorado State University, has seen large numbers of these insects several parts of the state, including Larimer county. Sightings of the insect have also been reported in Louisville and north and south Boulder gardens.
The aphid-sized adults are lovely, with jewel-toned eyes and dark abdomen banded in white. Their young, yellow at hatching, gradually turn green with each molt; being flat and elliptical they look like scale. Though adults move about actively and fly in migration, the young are sedentary, content to sit quietly, feed, and excrete white, waxy frass that resembles sugar. This is their waste, called lerps, and is an easy to see clue that your plant is being attacked.
We should prepare for their arrival in our area soon, since these small, winged sap-feeding insects have toxic saliva that causes the plant to grow oddly. Look for leaves turning yellow with purple veins, fruit that’s small and tasteless, or the plant appearing as if sugar were spilled on it.
Start scouting your plants, carefully checking them for insects or disease every three days until you spot signs of trouble. Psyllids can mean big problems for tomatoes, severely stunting fruit; so at the first sign of them begin spraying plants with insecticidal soap to keep them at bay. Coverage of both upper and lower leaf surfaces is crucial to control, and may not be enough.
Dusts of sulfur can help, if care is taken to cover all leaf surfaces, but should the insects get the upper hand, stronger products with pyrethrin or esfenvalerate can be used.
Several diseases show up in gardens at this time. Green plants turning blonde by yellowing from the lower leaves upward should be closely examined. If they have brown spots with concentric rings, suspect early blight (Alternaria solani).
Water, insects, and gardeners spread this fungus. Pick off diseased leaves and keep the ground free of debris. Dust healthy leaves with sulfur to shield them from infection. Once the plants have gotten three feet tall, pluck off leaves in the lower foot to prevent the spreading climb of the fungus. Give plants room to grow without crowding them, and use drip irrigation to prevent splashing water.
Black, sunken, rotten spots on the bottom of fruit are blossom end rot, a disorder caused by poor uptake of calcium. Though calcium is plentiful in our soil, irregular watering and excessive heat prevent the plant from using it. The key to control is watering consistently, so use a timer to automatically turn on and off the irrigation. Mulch plants to keep the soil from drying out too rapidly.
More information on tomato troubleshooting can be found on the Colorado State University Extension website.