Last weeks isolated thunder storms carried some baggage; pockets of hail destroyed some area crops. The speed at which moisture has disappeared is a testament to the current moisture demands of crops (and
weeds). Corn continues develop at a good pace; some corn is near dent while other fields are growing vigorously. Moisture demands remain near maximum in corn from tassel to milk stage but begin to decline as the crop transitions from milk to the dough stage and continue to decline at a fairly rapid pace through maturity. Much of the area cotton crop is in full bloom and is at or near maximum moisture demand. Irrigation should be carefully managed to promote earliness and maintain fruit load; many times this is walking a fine line. Lower amounts and more frequent irrigation applications will allow producers to speed maturity and maintain yield; adjustments in irrigation frequency and amount should be based on individual field conditions. Much of the grain sorghum is also at or near peak moisture demand which is from boot to heading. Using a moisture probe to monitor soil moisture levels has become futile in many fields with limited irrigation capacity as the probe cannot penetrate the soil.
Weed management has been a continual battle; weed resistance to herbicides, primarily glyphosate resistant pigweed, is a huge concern. Every effort should be made to remove suspected resistant weeds from the production system. Now through harvest will be a good time to make a few notes on field specific weed issues to refer back to as weed management plans for 2014 are developed.
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| Pigweed killed by glyphosate on right and an unaffected potentially resistant pigweed on left |
Insect pressure remains very light to non-existent in cotton but verticillium wilt has really intensified. Verticillium wilt is a soil born fungus that cause plants to wilt but does not cause root rot. The pathogen in affect plugs up vascular tissue preventing the translocation of moisture. Stalks of plants can be cut longitudinally and inspected for brown streaking for a quick in field diagnosis. There are no curative treatment for verticillium wilt in cotton, the key management tactic is to plant resistant/tolerant varieties. So, as with weed management make some field notes on “vert” pressure that can be used to help make variety planting decisions next year.
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| "Vert" symptoms on leaf. |
Spider mite pressure remains high in many corn fields and miticide applications are on going. Mite suppression has been good in some fields while others have had to be retreated. Coverage is critical to maximize miticide efficacy. Increased total volume of spray will provide better coverage and penetration into a dense canopy, 5 gallons per acre should be considered minimum. A much higher incidence of spider mite destroyers (Stethorus) have been observed feeding in in mite colonies recently. The spider mite destroyer is a very small beetle in the lady beetle family (Coccinellidae). The beetle is about 1/16 inch long and shinny black; the larvae are gray to brown with a miniature alligator type appearance (minus the teeth :-) ). Both the adult and larval forms are key predators of mites and will help stabilize mite populations. Mite management tactics should exploit these natural enemies; avoid pesticide applications which will destroy your partners in mite management.
Spider mite destroyer (Stethorus) adult left and larva right
An occasional sorghum headworm has been observed in area sorghum. As grain sorghum transitions from vegetative growth to heading whorl feeding pests will shift to feed in developing heads. Corn earworm and fall armyworm commonly referred to as the headworm complex in grain sorghum, rank as the third most damaging insect pests of sorghum in the United States. Treatment thresholds for sorghum headworms are dynamic based on grain value, cost of control, and infestation levels. We have developed a sorghum headworm calculator "app" which is available on the Google Play Store at http://goo.gl/8mXvv The app can also be found by searching for sorghum in the store. The app will run on any android device with an OS of 2.3 or above. Once the app is installed no internet connection is needed. We also have a web app for other operating systems which can be accessed at http://goo.gl/5k7ZtU. The web app will require an internet connection to work. The Android app calculates larvae/10 heads while the web app calculates larvae/head.
Some corn damaged by hail in late June is not pollinating adequately simply due to the lack of pollen production. Injury to the small developing tassel in late June has caused some tassels to be completely bare.
Injured developing tassel left, barren tassel right
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