I have received many inquiries lately about the Rocky Mountain pine beetle and whether or not I thought we were going to lose all our ponderosa pines, whether we should spray and with what, and, the real panic question, will we lose all our forests?
I am not an authority on RMPB, but our good friend Dave Leatherman is. He spent many years with the Colorado State Forest Service, and much of his professional life has been spent dealing with RMPB. One fact that he has faith in is that during the many years he has worked with pine beetle outbreaks, there have been only three incidents where he has seen RMPB jump from lodgepole pine to ponderosa pine or vice versa. Yes, they have already come over the Continental Divide, but so far they are in thick stands of lodgepole pine.
Leatherman feels we should not hit the panic button quite yet, as they may not make the jump into ponderosa pine. The only areas where they did this in the past were three forests where the two species were intermingled. This is unusual in itself, as lodgepole pines are generally found in pure stands of same-age trees.
As to when to spray, the time is now. The spray should be applied to tree trunks only, as that is where the beetles land. Spraying should be done on the entire trunk up to 30 feet high, or to where the trunk becomes less than 6 inches in diameter, whichever comes first. Beetles start to emerge from trees by early July, and prevention spraying must be done before they fly. The current sprays adhere to the trunks well and are effective for many weeks. Therefore, spray as soon as you can set up a date before their early July flight. Once the beetles have entered a new tree, spraying is of little help. Three sprays approved by the EPA for use on RMPB are carbaryl, also known by the trade name Sevin; permethrin, trade name Astor; and bifenthrin, trade name Onyx. These sprays have been tested and approved. They are listed as safe for use and as not being highly toxic to birds or other forest animals. One word of caution, however: These tests are done on specific amounts, properly applied. Most problems arising from the use of these sprays are the result of three things: improper dispersal, overuse and deliberate contamination.
Improper dispersal includes aerial spraying or high-powered spraying into the crown of trees. RMPB do not go into the crown of small branches; they are only in the trunks, and the trunks are all that should be sprayed.
The second problem, overuse, is caused by those who think that if a little is good, more will be better. Follow all label instructions and do not increase quantities or proportions. Spray only the trunk, not the surrounding countryside.
The third problem of deliberate contamination is caused by improper cleaning and washing of spray equipment and allowing leftover spray or cleaning water to run into streams or water supplies. Dispose of such water properly or, better yet, don’t try to spray your own trees. Hire a reliable spray company that is known locally to be cautious, honest and concerned about the environment.
One other possible means of deliberate contamination of water supplies is an attempt by a few sick people who have deliberately contaminated water supplies in an attempt to stop all spraying. Such extremist methods are unforgivable, and the entire community of sane environmentalists should make it known they do not approve and will not tolerate such, acts as well as assisting in any way possible to expose such extremists and aid in their arrest and imprisonment.
Of necessity, spraying for RMPB must be done just at the peak of the bird-nesting season, for that is when the beetles emerge. Therefore, some precautions are in order. If nest boxes or natural cavities contain nests with eggs or young, cover the opening tightly just before spraying and uncover it immediately after spraying. This will keep the spray out of the nest itself and allow the adults to return immediately. It seems to work well, for I have known several broods of chickadees that have fared well with this treatment. No crown spraying and careful trunk spraying keeps the spray from nearby shrubs and small limbs where most birds place their nests.
The most serious problem caused by overuse of spraying is most often caused by aerial spraying, which kills many species of both good and bad insects in the crown and on open areas between trees. Such spraying over large areas leaves few insects for the birds to gather to feed their young. If they cannot collect enough insects each day, the young may actually starve in the nest.
RMPB are always present in our forests. We will never get rid of them entirely, but we can and usually do keep them under control. In the early ‘80s, RMPB were here in epidemic numbers, but we survived. Most people sprayed their most precious yard trees and removed infected trees before the beetles could fly, but we most certainly did not “lose all our ponderosas.”
It would seem we need to be vigilant, do preventive spraying before the early July flight time, and not hit the panic button. If we do develop a serious problem, then we need to re-access the treatment and disposal of dead trees. But, never forget: Nature is a powerful force that is constantly changing. If trees do die, they will be replaced by flowers and shrubs. Eventually the trees will return and grow into a mature forest. However, nature loves the color green; at first the growth may not be as tall or stately, but the mountains will be green.
One bright spot in the control of RMPB lies in their own body. When these beetles fly to a new tree they emit a pheromone (scent) that notifies other beetles that “this is a good place; come join me.” Then when as many beetles have entered the tree as can comfortably live there, the beetles emit a second pheromone which seems to tell the other beetles, “This place is full; go find your own tree.” Scientists have been working on duplicating this second phermone synthetically, and it holds promise for the future. One brand known as verbemone is available but expensive. The idea is that packets of this scent could be tied to the trunk of a perfectly healthy tree and the scent would tell beetles to go elsewhere, thus preserving the healthy tree. This may be the perfect answer for preserving our most precious yard trees, but there has not been much work done on large-scale use. Perhaps down the road it may be possible to save even large forests.