The potential for armyworm outbreaks is increased when corn is planted in a grass cover crop under a reduced-tillage program. Fields adjacent to small grains also may be subject to migrating larval population.
Wireworms are the larval state of a group of beetles commonly called "click beetles." The larval stage of wireworms requires from two to five years or more to complete.
Because corn is the preferred host of corn rootworms, larvae of rootworm populations only occur in significant numbers in corn fields preceded by corn.
Seedcorn maggots are larvae of small flies that are attracted to germinating seeds, especially in situations where decaying organic matter is present. During a wet, cool spring, the corn seed may have difficulties germinating, and therefore the period of time that the maggot can attack is extended.
When the alfalfa weevil larvae are 1/4 to 1/3 inch in length, they cause the most damage to alfalfa. Both the adult and larvae stages of the alfalfa weevil beetle feed on alfalfa foilage. Adult damage to the foliage is not considered significant.
Wheat sown on or after the fly-free date indicated for each county will escape most egg deposition by fall brood of Hessian fly. Maggots of the Hessian fly extract juices from stems of wheat and other grains.
The armyworm will chew the leaves, starting from the edge, and if populations are high enough, strip the entire leaf and plant.
Cutworms or webworms may be the critters cutting off your corn plants. Such cutting may occur in corn up to the 6th leaf stage. Webworm cutting will be restricted to small plants due to their smaller size.
The wireworm can cause damage by any of the methods listed. Wireworm injury is often associated with a small feeding hole at the base of the plant.
The corn rootworm can cause damage by feeding on the corn root system or by feeding on the silks during July and August.
Wireworms and seedcorn maggots can both feed on the corn seed (Seedcorn beetles are also a predator of the corn seed.)
All of the answers are correct in this question. As a farmer, you must realize that the benefits from using an insecticide must exceed the cost of application. We are becoming increasingly aware of environmental and user safety, therefore "B" and "C" would also apply.
Bloom to pod-fill is a critical time period for the soybean plant. Defoliation at this point could greatly reduce yields. The plant is no longer growing new leaves and insect feeding will cause a reduction in photosynthesis. Loss of photosynthesis affects reproductive growth (filling of the pods).
Honey bees are least active late in the evening or early in the morning, therefore we should attempt to spray insecticides at that time.
Pod-feeding is a definite threat presented by the bean leaf beetle. Once the pod is damaged, moisture and disease organisms have a greater chance of entering and reducing seed quality.
In recent years grubs have become a problem in Ohio. They can feed on roots and root hairs, as well as the main shoot below ground level.
Weedy areas (especially where orchardgrass is present) and fields receiving minimum tillage are likely to have a higher common stalk borer population.
If alfalfa is tall enough to ensure root reserves, early cutting is an alternative. Beneficial parasite (such as the parasitic wasp) populations that control alfalfa weevil are kept at high numbers when cutting is used as the control method. Timely harvest of 2nd and 3rd cuttings reduces potato leafhopper numbers.
In some parts of the state adults of the black cutworm may originate from overwintering pupae, but most adults of the black cutworm migrate into Ohio in the spring by way of southern weather fronts.
Adult beetles cause the most foliar injury in late June, July and August. The adults emerge from the soil in late June where they have passed most of the year in the grub stage.
In late spring, wheat is subject to attack by armyworm populations. Beard and head clippings, defoliation, and consumption of the whole plant are symptoms to watch for. Corn is also subject to attack by armyworms in late spring.
Ohio does recognize the greenbug, the English grain aphid, the oat-bird cherry aphid, and the corn leaf aphid as small grain pests. Of those, the greenbug may prove to be the most serious pest. If populations are high enough, all aphids could cause damage that warrants rescue treatment.
Nearly all pesticides have preharvest limitations. Check the label before making applications.
It is the intent of the author that the preceding questions on insects will have better prepared you for the private applicator exam. The actual exam will be different and preparation on your part is essential. We recommend you spend time in each section of the book.
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868