How to Manage Pests
UC Pest Management Guidelines
The most important bird pest in lettuce is the horned lark. Horned larks are about 6 to 7 inches long, smaller than robins, but slightly larger than sparrows. They are brown to gray with a distinctive pattern of yellow, black, and white bands on the face and throat. Their name comes from the small tufts of erect, dark colored feathers behind the eyes of mature males. From a distance, they appear to walk rather than hop, distinguishing them from finches and sparrows. They have high pitched, distinctive songs and often sing while flying.
House finches are small, gray-brown birds with stubby bills and narrow dark streaks on their belly and flanks. They are about the size of a house sparrow. Mature males have red orange coloring on the breast, head, and at the base of the tail. Females and immature birds lack red coloring.
Crowned sparrows are migratory birds. They reside in lettuce-growing regions of California primarily in autumn, winter, and early spring. Crowned sparrows can be distinguished by their gray breasts and by the prominent white stripes on their heads.
Birds can reduce stands in direct-seeded lettuce by feeding on seeds and young seedlings.
Seedlings may be nipped off, or small holes may remain in the soil where the seedling was pulled. Most damage occurs before seedlings have two or three true leaves.
Horned larks feed on seeds of wild plants and on insects in open grasslands. They move into lettuce when natural forage is scarce or when the lettuce crop is planted closely to their habitat. They feed in flocks and can create bare spots in a lettuce field in a few hours. They tend to feed well out into the field and do not concentrate along fence rows or wooded areas. In contrast, house finches and crowned sparrows feed along the edges of fields.
Although house finches feed primarily along the field edges, they are often seen in open areas and tend to scatter to high, open perches when alarmed.
Crowned sparrows feed on seedlings and mature plants. Damage to lettuce heads will make produce unmarketable. Much of their damage occurs along the field edges.
Bird management is crucial during the seedling stage of lettuce to prevent stand reduction. Once the plants are beyond the three-leaf stage, they are more tolerant of feeding damage. The best approach to management depends on the species feeding in the crop, but often involves combining several cultural practices, such as habitat removal, scare tactics, trapping, and the use of lettuce transplants.
Removal of large brush piles, stacks of boxes, wind breaks, or other sheltered areas will limit the nesting and resting areas for house finches. When these sites are removed, the birds are less likely to spend time in the area, although they are not as timid as crowned sparrows and will feed in areas some distance from shelter.
Horned larks do not depend on sheltered areas for nesting or resting, so habitat modification is not effective for their management.
Birds from Fields
Mechanical noisemakers such as gas cannons are not very effective for scaring horned larks or house finches, but may help in scaring crowned sparrows. For best results, frequently change the timing of the noises and the position of the devices to make the sound as random as possible. Noisemakers are more effective when combined with an occasional shotgun blast in the direction of the birds. Like other kinds of repellents, noise works best when it is used before damage occurs. Once birds have established a feeding pattern, it is hard to force them to change it.
Some growers have used helium-filled balloons with suspended hawk-shaped kites to scare birds away from their fields. Move balloons and kites to a new part of the field each day. Little experimental information is available on their effectiveness. In many cases they have not been effective. If utilized, use them in combination with other bird deterrents.
UC IPM Pest Management Guidelines: Lettuce