Clinic Update: Early Spring Samples Submitted to the Plant Diagnostic Clinic

Spring is now beginning to progress rapidly, and we are beginning to see more samples in the extension plant diagnostic clinic. What follows is a description of what we have received in recent weeks.

Boxwood leafminer Photo provided by Simeon Wright

Many of our samples this year have been from trees. We have received a number samples and calls about sapsucker damage, rows of small holes in larger branches and trunks of trees. There have been a lot of problems with various pines, including sphaeropsis tip blight and dothistroma needle blight on Austrian pines, and pine wilt nematode associated with Scott’s pine. More information on Missouri pine problems and control measures can be found at http://agebb.missouri.edu/pdc/trees/pine.htm. While we have not received any positive samples in the clinic, I have also observed Junipers with kabatina blight in central Missouri. Kabatina blight and other juniper information can be found at http://agebb.missouri.edu/pdc/trees/juniper.htm

Damage caused by boxwood leafminer Photo provided by Simeon Wright

We have also received some greenhouse and ornamental plant samples, including New Guinea impatiens infected with impatiens necrotic spot virus (INSV). While nothing can be done to save infected plants, this virus is frequently spread by thrips, so thrips management is very important in preventing spread to healthy plants. We have had greenhouse tomatoes with botrytis blight. This fungus with a gray, moldy appearance is often present in moist, humid environments on dead plant tissues and can cause cankers and dieback on healthy plants especially when air circulation is poor and leaves remain wet overnight.

Also of interest is a boxwood sample we recently received infested with boxwood leafminer (Monarthropalpus buxi). Larvae of this insect cause a blotchy brown, slightly blistered appearance on the leaf surface. When you tear open a leaf and separate the upper and lower leaf surfaces, the tiny yellow to orange larvae are observed inside. Tiny flies (adults) are often observed swarming around infested boxwood in the spring. The females will lay eggs inside the leaf, which hatch and feed in the leaf to emerge the following spring - one generation each year. Chemical control is necessary when damage is severe. Labeled chemical controls include acephate, carbaryl, dimethoate, imidacloprid or malathion. Systemic chemicals such as imidacloprid and acephate should work for the larvae inside leaves, while contact chemicals such as carbaryl and malathion should be applied when the adult insects are seen hovering around the plants in the spring. Be sure to read and follow chemical labels.

We look forward to receiving your samples. Please see our website at http://agebb.missouri.edu/pdc/ or refer to the February issue of Missouri Environment and Garden for more information on sample submission.

Simeon Wright Plant Diagnostic Clinic 573-882-3019