Feeding damage to host plants does not always result in economic losses to the final crop yield. In many cases plants can recover from or out-compete the effects of the feeding injury, particularly if it happens earlier in the season. Economic feeding damage is the measurable loss to the final crop yield or quality.
For example, seedling establishment pests such as earth mites and lucerne flea cause visually obvious injury to plants but this does not always result in measurable yield loss unless seedlings are actually killed. Even when a percentage of seedlings are killed, some plants such as canola can survive without a measurable yield loss if the remaining plants are able to express compensatory growth.
Legume crops are also able to compensate for considerable damage during flowering and early podding but their ability to compensate decreases as the pods develop.
Mungbeans can compensate for early damage by setting new buds and pods to replace those damaged by pests. However excessive early damage can delay harvest.
Soybeans compensate for insect damage at flowering/early podding by calling on their ‘reserve pods’. These are viable pods that remain dormant on the plant after flowering if there is no subsequent damage to the ‘main’ pods.
- If excessive early pod damage occurs, the plant diverts energy to the reserve pods to fill them.
- Where developing seeds are damaged the plant can divert more energy to the undamaged seeds making them bigger and heavier.
For a crop to compensate sufficiently to avoid economic yield loss, there must be enough time, water and nutrients available during the remaining growing period.