Cereal Leaf Beetle Eggs Have Hatched
Found the first CLB larvae in wheat on Monday. Larvae are shiny and black and almost look slug-like. They cover themselves in their own excrement and are actually pale orange when clean (after a rain). They feed on the green epidermis of the leaf and their damage results in a windowpane appearance as the leaves have strips of white. They are not causing much injury now, but they will as they get bigger. I also saw a lot of adults still paired up and laying eggs. Threshold is three eggs and larvae per plant or one larva per flag leaf. I was able to check some oat fields this week and I was able to find just a few beetles. They may move into the oats later and should continue to be monitored.
Winter Wheat Heads Starting to Emerge
Some of the early planted winter wheat started to head this week (Feekes 10.1 (Awns pushing out of the boot). Most of the fields still had the head an inch or two down in the boot. It is time to get ready to apply a fungicide as full head emergence is not far away and flowering will begin in some fields next week. Fungicides applications at flowering (anthesis) of Miravis-Ace, Prosaro, Prosaro-Pro and Sphaerex (Caramba if you still have some) will be crucial in suppressing Fusarium head scab. These fungicides also protect upper leaves against fungal leaf blotches, powdery mildew, and rusts. There is an application window of approximately 7 days from the beginning of flowering in which reasonable FHB and DON suppression can be expected. Check the Fusarium Risk Assessment Tool as we get closer (http://www.wheatscab.psu.edu/ ) and your local weather forecast as your winter wheat crop approaches heading and flowering.
See comments above about cereal leaf beetle populations at the same time. No armyworm larvae have been detected yet and flights have been very low. Wyoming and Ontario sites have had some good flights. I’m sure there are a couple fields out there somewhere so keep watching for chewed and missing lower leaves.
Black Cutworms Larvae Injuring Corn
While armyworm flights have been really low, large numbers of black cutworms continue to fly into our region this week. Four of our five BCW traps had significant flights for a second week in a row. The traps in Monroe and Ontario counties were really high! Based on the degree days accumulated since our first significant flight on May 3, eggs laid at that time have all hatched and small larvae are active. Lots of corn has emerged and is vulnerable. Time to start looking for signs of BCW feeding. Young larvae will chew holes and cut off pieces of leaves and even the whole leaf. This picture is from a field in Castile, Wyoming county, yesterday. I dug in the soil around this plant and could not find the critter.
If 3 to 5% of the plants are missing or cut, spraying with an insecticide is warranted. Remember, BCW are nocturnal feeders and hide below ground during the day. The NWNY team has a good video on how to scout for BCW damage and find the culprit https://www.youtube.com/watch?v=51xthmslywo&list=PLBMGyzTr13dsj4Ufdu6Dle2AJtGJbyo6z&index=6
We have not hit the 300 degree days for BCW to cut bigger plants yet. Next week looks pretty warm so it won’t take them long to get big enough!
I also want everyone to be aware of another insect larva that looks very much like a black cutworm. Crane fly larvae are feeding below ground right now normally on grass roots. Sometimes we find them feeding on corn roots usually in fields following plowed down sods. They are light gray like a cutworm, but they are a fly larva, so they do not have legs and prolegs like a caterpillar and they do not have a distinct head with large eyes. They feed below ground so they are discovered when digging in the soil around plants. They can feed and damage turfgrass but are not known to be an economic pest in field crops.
- Egg hatch around 90 Degree Days
- Plant cutting around 300 Degree Days
- Degree Day data from Network for Environment and Weather Applications, NEWA
Marginal Spring Seeded Alfalfa Stands
The warm to cold back to warm temperatures left some of our regions spring alfalfa seedings marginal. An acceptable alfalfa population should have 10-20 plants per ft2 in the first year of productions. It’s not a bad time to start thinking about whether or not you need to manage these fields.
Does That Alfalfa Field Look Right?
I am seeing some fields with discoloration in areas. WNYCMA also reported fields with a yellow tint to it and went out and pulled tissue samples and are seeing nutrient deficiencies around potash, sulfur and manganese. If your alfalfa fields aren’t receiving manure applications then it is possible you may see a sulfur deficiency. Consider obtaining tissue samples if you observe discolored field regrowth so that you don’t miss the window of opportunity to apply fertilizer.
Alfalfa Weevil
Alfalfa weevil is one of the two most-damaging insect pests of alfalfa in New York. As an exotic species, it is attacked by few natural enemies native to the United States. Uncertainty surrounds the role of parasitoids in alfalfa weevil population control, and a much-needed assessment around this remains. Economically damaging populations of alfalfa weevil do occasionally build up in New York alfalfa fields and I believe we will need to be attentive with second cut regrowth. Temperatures have warmed up and weevil larvae are out feeding. For fields still standing, yield impacts will be minimal. We will want to watch our regrowth for second cutting.
Potato Leafhopper
The other damaging insect to watch out for in alfalfa is the potato leafhopper. With the rains we received last week it is time to be on the lookout for leafhopper. It would be wise to go out and regularly scout your fields because once there’s evidence of feeding, the economic damage has already occurred.
Pea Aphid
Pea aphids can be green or rose colored, winged or unwinged, large or small, and attached to leaves. Dead individuals are light tan and a result of the beneficial bugs out in the field. The economic threshold is a field average of 100 pea aphids/sweep. Under good growing conditions, spraying may not be necessary, but if the alfalfa is under stress, foliar application may be needed. Harvesting alfalfa is an excellent cultural control method and few aphids will survive.
Next report will be May 24.
