There are numerous things I have learned about the Mojave Desert from my studies of the Joshua tree. I could write several articles detailing these alone, and I might add several articles from now. But for now, we're discussing the Joshua tree as a species. I have donated a copy of "Joshua is a Tree" to the Hesperia Star, for the benefit of those people interested in knowing more. There are also copies available at the Victor Valley College Library and probably other libraries.


There are far fewer Joshua trees present now than there were in 1964. The encroachment of civilization has greatly disturbed the desert's delicate ecosystems. Many thousands of Joshua trees have been cut down to build homes, businesses and roads. The desert has been further disturbed, by off-road vehicles and careless planting, of landscape, that does not adapt to the desert. All of these are minor, compared to mankind's greatest disturbance, the rise in relative humidity.


I am convinced that the rise in humidity, perhaps by at least fifty percent in the past twenty to thirty years, is the root cause of the Joshua tree's demise. The yucca beetle infestation has increased, to out-of-control proportion and endangers every Joshua tree alive. The female yucca beetles lay eggs in the open Joshua tree blossoms. The eggs hatch and the emerging larva (or grubs) burrow into the blossom stalk, and thence into that branch, and in a really serious outbreak, all through the Joshua tree. That destroys the tree. Most of the time, however the tree's death is gradual, requiring several years until a strong wind snaps the tree at ground level.


The yucca beetle is endemic to the Joshua tree. Without them, the Joshua tree would displace all other desert species, because of its superior adaptation to the desert. My studies prove, beyond any doubt, that the yucca beetles have always been a clear and present danger to Joshua tree. One, watches old movies from the 1940s and '50s, and sees Joshua trees with the same symptoms of yucca beetle infestation as now. Those signs include dead and fallen branches and whole dead trees.


And yet my studies have also reveled, apparently healthy trees that obviously went through this "trial," yet survived. One of the methods, Joshua trees use to limit the infestation, is to "wall off" the affected areas, with what I call silica wood. This wood "patch" is so hard that nothing can penetrate it. It's present in a lot of downed Joshua trees. It probably takes years to fully develop, so it didn't occur recently. It's old infestation.


Signs of infestation are various, such as: Dead branches. Low tree vitality. Blossom stalks that flow but fail to produce seed pods. Some of the stalks will have holes bored into them, a sure sign that the stalk was visited by yucca beetles. The larva bore into the blossom stalks and is now present in that branch. After they mature, the adult beetles bore through the branch and fly away, to infest another tree. Insecticide doesn't control them either, except for a systemic soil drench. This saturates the entire interior of the tree, and kills the beetles, without damaging the rest of the Joshua tree. I used a preparation called "Cygon," recommended by Cal Herbold's Nursery and it worked splendidly. But Cygon was banned in California. It was feared it would get into the ground water, and it couldn't be sprayed on the tree. After the blossom was fully developed, the mixture was dumped around the base of the tree, where it was absorbed systemically into the tree.


What's to be done? There isn't much civilization can do to reverse the problem (namely the rise in humidity) that we caused. We can break off the blossom stalks to separate the developing larva from the tree. Or let nature take its course. As the yucca beetles spread, they destroy the hosts, and will eventually have no place to develop. There are thousands of young Joshua trees out there, and given the opportunity, they will one day (hundreds of years from now) be giants like the ones we've lost. And Joshua trees are not infested by yucca beetles until and unless they blossom. But don't cut down any more trees. Just respect them for what they are - natural inhabitants and very successful inhabitants of the desert.