Slugs Damaging Corn & Soybean Seedlings
The recent cool wet weather has been perfect for slugs in reduced and no-till fields. The cloudy conditions allow them to be out all day feeding on plants. Neither corn nor soybeans are safe. Slugs are predominately night feeders, so we usually only see their feeding injury and sometimes the telltale slime trail. I have had a couple calls on slugs and replanting soybeans. The picture below was taken yesterday. These were banded slugs. Another species, the gray garden slug, can be our more predominant problem but I have not seen them yet. There is no established economic threshold for slugs in soybeans or corn. Look at population reduction and injury based on upcoming weather conditions. There are a couple of pelletized baits with different active ingredients that can be effective: Deadline M-Ps (metaldehyde), Sluggo (iron phosphate) and Ferroxx (sodium ferric). Just a word of caution. Deadline is restricted use in NY and can be fatal to domestic animals/pets if ingested. Lannate LV insecticide also has a 2(ee) label in NY for slugs in soybeans and corn. It is recommended to apply from evening to early morning when slugs are exposed and out feeding.
Black Cutworm & Armyworm Update
We continue to catch high numbers of cutworm adults in the Wyoming, Livingston & Yates County traps. I am still hearing some reports of cutworms cutting corn plants. Some of the earlier planted corn is at the V6 growth stage and is safe from cutting. At this stage, the cutworm will stay within one plant and feed up into the stalk. Look for plants that are wilting or the upper leaves have turned brown. All corn smaller than V6 should be scouted.
I really expected to hear more reports of armyworm infestations in winter grains. I know of one field of malting barley that was over threshold and sprayed last week. At our Tag team meeting in Yates County on Monday, we were able to find a couple in a spelt field. In both situations, blackbirds were flying into the fields and gave us a heads up that armyworms were present. When walking fields, armyworms will fall to the ground and curl up in a C-shape. The yellow stripes running down the sides are a clear indication that it is an armyworm. Thresholds vary but are from 3-5 larvae per square foot. Look for flag leaf reduction and possible head clipping.
Winter Wheat Update
All the wheat should be pollinated now. I believe we had a good period for pollination, but I am concerned because conditions were also ideal for Fusarium head scab (FHS). I know many of you sprayed a fungicide at flowering which reduced the risk of VOM. Early wheat is changing fast, and the heads are starting to change color. Now is the time to look closely at the heads and individual kernels for any pink/orange coloration from FHS. This will determine how aggressive to be during harvest and possibly increase fan speed to blow out shrunken kernels. Cereal leaf beetle larvae are still out there feeding and getting larger. Keep an eye out for flag leaves turning white from feeding injury. I have not seen or heard of any armyworm infestations in wheat, but I know they are out there. Keep watching for the blackbirds!
Alfalfa Insect Update
We have had quite a few storms moving up from the south in the last week. Potato leafhoppers (PLH) are definitely coming up with them. We were easily able to find PLH adults in a field in Yates County this week. We were not at threshold yet but there were no nymphs present. Once the first eggs hatch, the nymphs will drastically increase population counts and feeding injury. PLH feed by piercing and sucking the plant sap from the plant. The resulting hopper burn (yellow leaves) and stunting means that we missed our opportunity for timely management.
PLH management is based of plant height and leafhoppers per sweep. Cornell recommends taking five sets of sweeps with a sweep net (10 sweeps per set) per field and calculating a PLH (adults & nymphs, see picture) per sweep for each set. The economic thresholds for PLH are listed below. Many NY growers are now utilizing PLH resistant alfalfa varieties to protect against quality and quantity losses. Many university researchers are recommending increasing PLH regular thresholds by 3X. However, use regular threshold numbers (chart) for first year PLH resistant stands. After the first cut, use the 3X numbers.
PLH nymph (left) and adult (right). Photo Credit, M. Rice
Next report will be June 19.
