Cause Several insects, including thrips, stem borers and plant bugs, cause physical damage and/or inject plant toxins during feeding. Poa species and, to a lesser extent, orchardgrass are affected. The fungus Fusarium poae is associated with silvertop but only after damage has been done.
Symptoms Affected seed heads die and bleach white, appearing to mature early. Stems of affected heads can be pulled easily out of the leaf sheath if stem-boring insects are involved. Plant bugs often cause the stem to shrivel and turn brownish just above the uppermost joint. Affected heads do not set seed.
Cultural control
- Burning fields after harvest has reduced incidence of this disease when caused by plant bugs.
Chemical control Insecticides may reduce incidence of silvertop. See the PNW Insect Management Handbook for details.