Below are some favored weed hosts of bean thrips and some stages
of their development you might see during fall. The winter annual
species may be present as seedlings after fall rains arrive and
where irrigated. In fall, the perennial hosts will typically
be mature plants and may be flowering. Note that although late
summer to early winter are critical bean thrips monitoring and
management times, better times to monitor and control weeds may
occur earlier in the growing season.
Names link to more information on identification and biology.
Click on photos to enlarge
(Sonchus oleraceus): Sunflower family; summer or winter
annual; seed leaves markedly stalked, almost spoon-shaped, rounded
at tip and often have grayish powdery bloom; injured tissue bleeds
milky white latex.
Little mallow (Cheeseweed) seedling
(Malva parviflora): Mallow family; winter annual; seed
leaves heart shaped, sometimes with red tinge; true leaves
roundish with wavy, shallow-toothed margins.
(Erodium moschatum): Geranium family; winter annual
or biennial; seed leaves 3- to 4-lobed, center lobe largest;
true leaves arranged as opposite or alternate; leaves and
stems bristly and hairy.
Prickly lettuce seedling
(Lactuca serriola): Sunflower family; winter annual or biennial;
seed leaves about 2 times longer than wide; first true leaves with
rounded margins; injured tissue bleeds milky white latex.
Prickly lettuce mature
Mature plant grows erect and bears numerous creamy yellow
flowers on branches off the main stems; leaves are alternate,
clasp the stem, and may be lobed or entire with prickly margins.
Russian thistle mature plant
(Salsola tragus): Goosefoot family;
summer annual; mature plants are spherical bushes up
to several feet tall. After they turn grayish brown,
the plants break away from the roots at the soil line.
(Cynodon dactylon): Grass family; perennial that becomes
dormant during cool weather; mature plant forms dense mats
with spreading and branching stolons that root at the nodes;
flowering spikes radiate from a single point at the tip of
(Paspalum dilatatum): Grass family; perennial; flower head consists of
3 to 6 spikes that arise apart on the stem and often droop.
Mature plants form loose bunches, 1 to 4 feet (0.3–1.2
m) high, or low and spreading; leaf sheath somewhat flattened.
(Sorghum halepense): Grass family; perennial; persists and spreads via
underground stems (rhizomes), which are thick, fleshy, and segmented; roots and
shoots can rise from each rhizome segment; leaves have a prominent whitish midvein.
Mature plant grows in spreading, leafy patches that may
be as tall as 6 to 7 feet (1.8–2.1 m). Most any grass
can host bean thrips, including crop grains such as wheat
(shown in the background).
(Nicotiana glauca): Nightshade family; perennial
broadleaf; grows to become a small tree; foliage has
strong, unpleasant scent; plant highly toxic if ingested;
yellow tubular-shaped flowers spring through fall.