Gardeners and homeowners have been calling to find out what are the large green or tan hairless caterpillar-like worms they are finding in their yards. These intriguing hairless green, yellow-brown, or brown caterpillars are called achemon sphinx caterpillars. (Fig. 1)

The achemon sphinx caterpillars (a member of the hornworm family) begin to appear in early summer and persist into fall. They begin a bright green color and progressively change to yellow-brown and eventually brown as they reach maturity. True to their family name they have a “horn” on the rear end of their body, which turns to an eye spot. Another identifying characteristic is the diagonal white bars along the sides of their abdomens. Full-grown caterpillars can be 2.5-3.5 inches in length and are about the diameter of an average person’s thumb. These larvae feed on the leaves of elm, apple, grape, and other plants, which include woodbine vine or Virginia creeper. Those found here in the county have been found on woodbine vines.

Although considered garden pests, achemon sphinx caterpillars are rarely observed and do not cause significant injury to plants. If particularly disturbing or problematic to homeowners, the hornworm larvae can be handpicked and submerged in soapy water. It will be easier to notice them near dusk and dawn, as they become active feeding on exterior plant parts. Due to their protective coloration, they can be hard to detect.

Achemon sphinx caterpillars are the larvae of the hawk moth or sphinx moth. Hawk moths are some of the largest moths in the world capable of having a wing span of >5 inches. They are important pollinators and are also one of the fastest flying insects reaching speeds of up to 30 miles per hour. These moths are also called “hummingbird moths” due to their resemblance to hummingbird flight patterns and feeding habits. The moths will feed on nectar from deep-lobed flowers.

September is

Best Month to Improve Lawn

NOW is the best time to improve your lawn. Consider the following: Fill in bare spots. Now through mid- September is the best time of the year to sow grass or lay sod. The ground is warm and the seeds will germinate quickly. As a bonus, weeds are less likely to germinate in lawns established in fall compared to lawns established in spring. Choose a quality seed mix with a variety of grasses. Most seed mixes will include cultivars of Kentucky bluegrass, fine/red fescues, and perennial ryegrass. Kentucky bluegrass is a hardy grass that is recommended for sunny areas. The fine/red fescues are best for shade. Perennial ryegrass is especially useful since it germinates rapidly and stabilizes the soil while the other lawn grasses emerge. If you plan on using sod, you’ll be pleased that it grows actively in fall and will quickly “knit” into the ground.

Fertilize the lawn. Fall is the most important time to fertilize your lawn. Lawns grow vigorously and will develop most of their roots this time of year. If you fertilize your lawn only once a year, do so in September. Fertilizer has three major components: nitrogen, phosphate, and potash. Nitrogen is most important for turf growth; look for a fertilizer that has over 20% nitrogen. Select a fertilizer with slow-release nitrogen. This will gradually feed the grass until the ground freezes. As for the other major nutrients, phosphate is least important because it is already abundant in most soils. Potash will help the lawn become hardy for winter; look for a fertilizer that is at least 10% potash.

Kill broadleaf weeds. Mid to late September is the best time to kill broadleaf weeds, including dandelion, creeping charlie, thistles, and clover. As days get shorter, the weeds will begin channeling their nutrients down into their roots to prepare for winter. This is great, because a herbicide sprayed on a weed at this time will naturally be channeled down into the weed’s root system, killing the entire plant. Aerate. If your soil is hard and compacted, fall is the best time to aerate it. Aerated lawns will respond with vigorous root growth until the ground freezes. Many persons overseed immediately after aeration. If overseeding, do this by mid-September. Dethatch. Lawns with thatch layers exceeding one-half inch will benefit from a power raking. This is best done in September, while recuperate from this operation.

For more information on either of these topics you may contact the NDSU Extension Service Pierce County office by calling 776-6234 ext. 5 or by email at yolanda.goodman@ndsu.edu.