An Analysis of Some of California's Major Entomological Problems

Because of the great variety of crops grown commercially in California, the economic entomologist must specialize to a large degree in order best to serve. There is much waste and injury in the use of insecticides when a proper scientific basis for action is lacking. In this, both the farmer and the entomologist are often at fault. An unbiased investigation of the fundamental principles of insect control will in some instances at least, reveal astonishing discrepancies in our present methods of procedure. Intensive laboratory experiments coupled with carefully planned field investigations are essential. Thus experiments with newly hatched codling moth larvae which attack both the apple and English walnut in California, indicate that the efficacy of lead arsenate in protecting apples in particular against side entrances and stings has been greatly overestimated. Greater attention to orchard and packing house sanitation is urged. With what appears to be a gradual development of resistance of the black scale of oranges to hyrocyanic acid gas and the well known resistance of the citrus red spiders to the same gas, oil sprays are now being used quite extensively in the citrus areas of California. A strong tendency to use oil sprays against red spiders on prunes is evident in many parts. The use of oil sprays presents many difficult problems such as possible injury to the tree and discoloration of the fruit, but much trouble has already been obviated by the development of a quick breaking emulsion of highly refined lubricating oils. The large amount of damage done by the garden centipede to asparagus and that of certain soil infesting nematodes has created a strong demand for soil fumigants. It has been found, however, that the damage to asparagus done by the garden centipede can be entirely overcome by proper flooding where that is possible. On the other hand, an effective soil fumigant is now available in the xanthates which are valuable when properly employed on account of the decomposition product, carbon disulfide. Sugar beets, one of the pioneer crops of California, have been threatened for some years by a disease known as curly-top which is carried by a very small leafhopper. The control of this insect presents much difficulty on account of its migratory habits. Cotton is one of the newer crops of California but is already valued at over $10,000,000. To keep this crop free from the pests so prevalent in the South is one of our problems, and to prevent native insects from transferring their affections from wild vegetation to this valuable crop is another. California beekeepers have long disagreed as to the nectar value of the California buckeye. It is now known that when severe droughts curtail the nectar possibilities of other plants and bees are compelled to use the buckeye alone, poisoning of the bees is pretty sure to follow, while mixed with nectar from other plants, that of the buckeye is harmless. Similar climatic peculiarities limit the use of top minnows (Gambusia) in anopheline mosquito control. Great differences in topography within a short distance, likewise ocean and desert influences within a narrow range, greatly influence climate and make it dangerous to generalize in control recommendations.