by Lis Friemoth
Resistance to Disease
Plants reaction may be too slow
Are you confused about what is meant by plant resistance to disease and insect invasions?
First of all, resistance is just that — resistant to damage. All plant material is susceptible to disease and insect invasions. Most often, different plant species will have a differing range of specific problems. Within each species, there may be some plant varieties that are more susceptible than others to diseases and insects.
If a healthy plant (of any species) proves to be resistant, that means it is susceptible to damage but has been found to successfully repel certain diseases/insects at or near the time of initial invasion.
Nature provides a complete environment of interacting components in the plant world. Some of these components attack, some defend and some are just oblivious.
Insects and diseases often, but not always, attack. Plants will naturally defend themselves, projecting an oblivious attitude.
When those naturally interacting components are allowed to evolve simultaneously, there will be a race of sorts as one tries to outwit the other. The pathogens and insects often evolve faster than the plant material in response to changes in either the plant system or in the surrounding environment. Even though the plants are slower to respond, the invaders don’t often completely exterminate the host in one generation. Complete destruction would reduce the ability of the invader to successfully survive without an immediate replacement host plant.
The first line of defense in this resistance game is the waxy exterior surface, which repels physically as well as with a microbial response. If the first surface is breached, the cell walls provide another stopping point. Insect damage occurs during feeding. Some critters chew, some pierce and suck, and others will tunnel and feed.
But no matter the feeding method, the best line of defense is a very healthy plant. Early damage detection in these plants will trigger a genetic response that repels pests. Those insects that have evolved with the plant material are the easier ones to control without chemical intervention.
However, we have many insects that have been imported out of their natural habitat and thrust into ours. These are the most difficult to control because our plant material is quite palatable to them and the plants have not had an opportunity to evolve any genetic protections from these insects. Japanese beetles are a great example of this type of problem critter.
Although much work has been done to select, breed and develop resistant plants, as soon as they are developed, nature is working to break that resistance down. Remember, insects and pathogens evolve very quickly but nature will find ways to protect its own.
However, with the demands we place on plants, production, ornamentation and global movement, we push things too fast for nature to keep up without additional human intervention.
— Lis Friemoth is a horticulture diagnostician. Contact her at (262) 745-2904, P.O. Box 58, Springfield, WI 53176, visit online at www.thegardenhoe.com or e-mail her at gardenhoe@tds.net. Listen to Liz from 9 a.m. to 10 a.m. every third Saturday on WISN AM1130 radio. |
