| How do these insects harm their target weeds?
Each species we sell is able to harm their weedy hosts. Some do so by feeding as larvae inside the flower heads thereby destroying seed production. This type of feeding usually does not influence plant density. Rather, it reduces the amount of new, viable seeds going into the seed bank in the soil.
The larvae of other species feed inside the stem of the plant. This can disrupt the vascular tissues that move moisture and nutrients within the plant.
Other species feed on the exterior and interior of the primary and secondary roots and the fine root hairs. Root feeding can be very destructive to a weed. Small plants may be killed outright and the larger plant's growth may be severely stunted. Again, the vascular tissues of the plant are damaged.
Gall forming insects have a unique evolutionary relationship with their weedy hosts. The adult gall former will lay their eggs into specific parts of the plant. The feeding larvae will stimulate the plant to form a structure (the gall) to surround the developing larvae. In addition to the direct damage caused by the feeding larvae, the plant must redirect some of its energy into gall formation. Studies have found that gall formation acts as an energy drain on the entire plant, not just the attacked areas.
Defoliation is an obvious form of attack by some insects. While not particularly stressful to many weeds, it does contribute to reducing leaf area, water loss, yellowing and leaf death.
These and other forms of plant damage are important in harming your weeds and fit hand in hand with good land management. Bio-control should be an integral part of your overall land management plan. With successful bio-control, the weed's competitive ability is diminished, herbicide costs are reduced and the value of the land improves.
Biological Control of Weeds, Inc.
1418 Maple Drive Bozeman, MT 59715