Insects in Illinois.
Prof. Forbes, State Entomologist, makes the following report to the State Board of Agriculture:
"Now that our year's entomological campaign is completed, a brief review of some of its most important features and results will doubtless be of interest. Early attention was given to the insects attacking corn in the ground, before the sprout has appeared above the surface. A surprising number were found to infest it at this period, the results of their injuries being usually attributed by farmers to the weather, defective seed, etc. Among these the seed corn maggot (Anthomyia zeæ) was frequently noted, and was received from many parts of the State. A small, black-headed maggot, the larva of a very abundant, gnat-like fly (Seiara), was excessively common in ground which had been previously in grass, and attacked the seed corn if it did not germinate promptly and vigorously, but apparently did not injure perfectly sound and healthy grains. A minute yellow ant (Solenopsis fugax) was seen actually gnawing and licking away the substance of the sound kernels in the ground, both before and after they had sprouted. The corn plant-louse (Aphis maidis) was an early and destructive enemy of the crop, often throttling the young shoot before it had broken ground. It was chiefly confined to fields which had been just previously in corn or grass.
"The chinch-bug was found in spring depositing the eggs for its first brood of young about the roots of the corn, a habit not hitherto reported.
"With the increasing attention to the culture of sorghum, its insect enemies are coming rapidly to the front. Four species of plant-lice, two of them new, made a vigorous attack upon this crop in the vicinity of Champaign, and two of them were likewise abundant in broom-corn.
"The corn root-worm (Diabrotica longicornis) was occasionally met with in sorghum, but does not seem likely to do any great mischief to that plant. It could not be found in broom-corn. In fields of maize, however, it was again very destructive, where corn had been raised on the same ground a year or two before. The Hessian Fly did great damage throughout the winter wheat region of the State, many fields not being worth harvesting in consequence of its ravages. Several facts were collected tending to show that it is three brooded in the southern part of the State. Nearly or quite all the last brood passed the summer as "flax seeds" in the stubble, where they might easily have been destroyed by general and concerted action. Fortunately, the summer weather was unfavorable to their development; and the drouth conspired with their parasites to greatly diminish their numbers. In the regions under our observation, not one in a thousand emerged from the midsummer pupa-cases, and numbers of the larvæ were found completely dried up.
"The wheat straw-worm (Isosoma tritici), a minute, slender, yellow grub, which burrows inside the growing stem, dwarfing or blighting the forming head, was abundant throughout the winter wheat region of Southern Illinois, causing, in some places, a loss scarcely exceeded by that due to the Hessian Fly. Our breeding experiments demonstrate that this insect winters in the straw as larvæ or pupa, emerging as an adult fly early in spring, these flies laying their eggs upon the stems after they commence to joint. As the flies are very minute, and nearly all are wingless, their spread from field to field is slow, and it seems entirely within the power of the individual farmer to control this insect by burning or otherwise destroying the stubble in summer or autumn, and burning the surplus of the straw not fed to stock early in spring. A simple rotation of crops, devoting land previously in wheat to some other grain or to grass, will answer instead of burning the stubble.
"The life history of the wheat bulb-worm (Meromyza Americana) was completed this year. The second or summer brood did decided injury to wheat in Fulton county, so many of the heads being killed that some of the fields looked gray at a little distance. This species was also injurious to rye, but much less so than to wheat. It certainly does not attack oats at all; fields of that grain raised where winter wheat had been destroyed by it, and plowed up, being entirely free from it, while wheat fields adjacent were badly damaged. We have good evidence that postponement of sowing to as late a date as possible prevents the ravages of this insect, in the same way as it does those of the Hessian Fly.
"The common rose chafer (Macrodactylus subspinosus) greatly injured some fields of corn in Will county, the adult beetle devouring the leaves.
"The 'flea negro-bug' (Thyreocoris pulicarius) was found injurious to wheat in Montgomery county, draining the sap from the heads before maturity, so that the kernel shriveled and ripened prematurely. In parts of some fields the crop was thus almost wholly destroyed.
"The entomological record of the orchard and the fruit garden is not less eventful than that of the farm. In extreme Southern Illinois, the forest tent caterpillar (Clislocampa sylvatica) made a frightful inroad upon the apple orchard, absolutely defoliating every tree in large districts. It also did great mischief to many forest trees. Its injuries to fruit might have been almost wholly prevented, either by destroying the eggs upon the twigs of the trees in autumn, as was successfully done by many, or by spraying the foliage of infested trees in spring with Paris green, or similar poison, as was done with the best effect and at but slight expense by Mr. David Ayres, of Villa Ridge. Great numbers of these caterpillars were killed by a contagious disease, which swept them off just as they were ready to transform to the chrysalis; but vast quantities of the eggs are now upon the trees, ready to hatch in spring.
"A large apple orchard in Hancock county dropped a great part of its crop on account of injuries done to the fruit by the plum curculio (Conotrachelus nenuphar). There is little question that these insects were forced to scatter through the apple orchard by the destruction, the previous autumn, of an old peach orchard which had been badly infested by them.
"In Southern strawberry fields, very serious loss was occasioned by the tarnished plant-bug (Lygus lineolaris), which I have demonstrated to be at least a part of the cause of the damage known as the 'buttoning' of the berry. The dusky plant-bug (Deræcoris rapidus) worked upon the strawberries in precisely the same manner and at the same time, in some fields being scarcely less abundant than the other. I have found that both these species may be promptly and cheaply killed by pyrethrum, either diluted with flour or suspended in water, and also by an emulsion of kerosene, so diluted with water that the mixture shall contain about 3 per cent of kerosene.
"The so-called 'strawberry root-worm' of Southern Illinois proves to be not one species merely, but three—the larvæ of Colaspsis brunnae, Paria aterrima and Scelodonta pubescens. The periods and life histories of these three species are curiously different, so that they succeed each other in their attacks upon the strawberry roots, instead of competing for food at the same time. The three together infest the plant during nearly the whole growing season—Colaspsis first, Paria next, and Scelodonta last. The beetles all feed upon the leaves in July and August, and may then be poisoned with Paris green.
"The season has been specially characterized by the occurrence of several widespread and destructive contagious diseases among insects. Elaborate studies of these have demonstrated that they are due to bacteria and other parasitic fungi, that these disease germs may be artificially cultivated outside the bodies of the insects, and that when sown or sprinkled upon the food of healthy individuals, the disease follows as a consequence. We have in this the beginning of a new method of combating insect injuries which promises some useful results."