Multi-pest field tour – Western Bean Cutworm early season

Video on what we are seeing in the corn field right now inregards to Western Bean Cutworm infestation.

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Start SCOUTING for Western Bean Cutworm – egg masses being found

Contributed by Robert Moloney, NK Brand Seeds

 We are starting to see a high number of Western Bean Cutworm (WBC) moths in our monitoring traps from London through Windsor and along the east shore of Lake Huron. What does this mean to you? It’s time to start SCOUTING for egg masses. Kudo’s to Cole Cruikshank from Bluewater Agromart near Kincardine for being the first NK dealer to help OMAF researchers find egg masses. Egg masses have also been collected in Chatham-Kent. Since this is a new pest to Ontario and populations will be sporadic, OMAF is looking for any egg masses that they can collect and use to infest their research plots. These research plots are being used both to learn about this pests behavior and also to determine the proper threshold levels for spraying this pest in Ontario.

SCOUTING FOR EGG MASSES

 In some ways scouting for egg masses is relatively simple. The egg masses range in size from the size of a penny to the size of a quarter. They are laid on the UPPER surface of the UPPER leaves of the plant. Most likely leaves are going to be the ones that are still upright on the plant. There seems to be a very strong preference for the moths lay eggs on plants that have not tasseled over those with exposed tassels. Within a field the first place to look for egg masses will be later maturing plants (i.e. areas with compaction or other issues that have delayed development) or look in later planted fields next to other earlier planted/tasseling corn. Ontario experience this year suggests the eggs tend to be laid nearer to the base of the leaf than the tip.

 The easiest way to scout for egg masses is to look up such that the sun is behind the leaves you are looking at. If you see a blotch-like shadow on the leaf, pull the leaf down and likely it will be an egg mass on the upper side. The eggs are laid in a mass of individual eggs. They are round and start off pearly white. As the eggs mature and get near hatching they become purple in colour. For more details on egg scouting and egg masses check out Tracey Baute’s (OMAF Field Crop Entomology Lead) blog at www.bautebugblog.com

If you find egg masses in your field (especially white, recently laid ones) please collect them, keep them cool and let your NK rep know. OMAF is still looking to collect egg masses for use in their research and they will come and pick egg masses up.

SPRAYING FOR WBC

The threshold for spraying for WBC is 5% of plants in a field with egg masses. However, timing is the key to spraying for control of the WBC larva. There is a very small window between egg hatch/larva emergence and the point at which the larva are protected from spray under the cover of the husk on the cob to get control. Matador insecticide is registered for control of WBC (including aerial applications), but it requires contact with the larva to kill them and it will not control larva in unhatched eggs. This means that before spraying you at very least need to scout to see when eggs are hatching to get effectiveness from spraying, although you should also be scouting to determine if you are at threshold or you may be wasting your money anyway.

SUN SCALD IN SOYBEANS

Contributed by Robert Moloney, NK Brand Seeds

It looks like some soybean fields aren’t liking this heat any better than the rest of us.  There is a much higher level of sun scald showing up in soybean fields right now than we would normally see.  This is likely due to the somewhat overcast conditions we’ve had in June followed by the intense heat/bright sun that we are now getting.

Sun scald is usually pretty easy to diagnose.  You will see it on the top trifoliates of the plant, and often where a leaflet has flipped over.  It gives the leaf a brownish, rusty look to it and usually there will be a distinct line between the exposed surface and the under surface that’s not injured (see picture below).  This makes it easy to differentiate from disease which will be more scattered over the whole leaf (and usually over more of the plant).  While it may look ugly in the field, there is not likely to be a yield impact from it.

Current conditions mean we may see ozone damage (similar to sun scald but more of a bronzing) and the conditions are ideal for spider-mites to explode.

WESTERN BEAN CUTWORM – THEY’RE HERE

For 2010 Syngenta Seeds, working with our dealers, have over 50 Western Bean Cutworm (WBC) moth traps out across Ontario and Quebec. These traps have a pheromone lure to attract the WBC males and are monitored on a weekly basis. The data collected from these Syngenta Seeds traps are fed into the OMAFRA WBC trapping network (see maps at http://www.cornpest.ca).
So far in 2010 WBC moth numbers are still low, but as of the week of June 27-July 3 there are starting to be low number catches across most of southwestern and mid-western Ontario. Compared to previous years, this we are seeing earlier flights and higher numbers for this early in the season. This isn’t really surprising since we are running 100-200 Corn Heat Units ahead of normal. The catches are also showing that the range of the WBC is definitely expanding east and northwards. The number of moths caught to date this year aren’t high enough to cause significant damage but since we are still early in the season it is still quite possible that there could still be some fields that reach damaging levels by the end of the season.
If you’re out walking your corn fields be sure to keep an eye out for WBC egg masses. These egg masses are laid on the topside of the upper leaves. They are a mass of individual eggs laid together that start off pearly white and become purple in colour as they mature (see pictures below). If you find any eggs masses PLEASE collect the plant with the eggs and let your Syngenta rep know immediately. OMAFRA would like to collect as many egg masses as possible for use in their research plots. Techniques for lab rearing this insect are still being developed and since this is still an emerging pest it is hit and miss whether their plots will be infested naturally or not.

Size matters!

From Clare Kinlin – Eastern Ontario, Field Manager

Does size matter? Soybeans on the right planted 18 days earlier than the ones on the left. The early planted strip is already flowering and 2 growth stages ahead than the later planted strip. The corn crop is developing well
with these ideal growing conditions. The tassel is easily seen in the plant above while the cob is less visible but is about a 1/3 the size of a quarter. This crop was planted
April 22.(12-13 leaf).

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