Problems With Tomato Plants With Yellow Crystals

Psyllid Sugar Crystals

• What appears to be a collection of yellow crystals on a tomato plant is the result of infestation by an insect known as a tomato or potato psyllid. The immature form of the insect secretes tiny balls of what is commonly called "psyllid sugar," a substance that looks like granulated sugar crystals. The pest also produces a condition called psyllid yellows, the result of a toxic saliva being injected into the leaves of the plant, turning the foliage yellow.

Identification

• The psyllid sugar crystals may completely cover the leaves during heavy infestations. The eggs of the tomato psyllid are also a yellow or orange color and deposited along the margins and each side of the leaves before hatching within six to 10 days. The immature psyllids are yellow before turning greener as they age. Adult psyllids are a dark green with alternating dark and light stripes and normally appear on tomato plants late in the growing season.

Damage

• The most significant damage is caused by the immature nymphs as they produce the "psyllid yellows" and the leaves yellow and curl. The entire top of the plant can turn a yellowish-green and, if feeding occurs early in the growth of the tomato plant, the setting of fruit may be retarded. A late infestation forces an abnormally large number of fruits to develop; however these are rarely of good size or quality.

Management

• Several generations of psyllid are born each year and because the insect is so tiny, damage to the tomato plant is often well underway before the presence of the insect is known. The collection of psyllid sugar crystals is the most meaningful sign that psyllids are present. Insecticides are effective in controlling the pest and should be applied preventatively as soon as the tomato plant reaches 6 inches in height. Continue this treatment through mid-summer.