The yield loss estimates in the calculator assume that spraying results in a 100% kill and that there is no midge damage prior to chemical application. It also assumes that you will receive the same average midge pressures over 4-5 days. In reality research has shown that one well timed insecticide for midge (put on from panicle emergence and before midge even enter the crop) will still only prevent 70-80% damage protection in lower rated sorghum hybrids. In 8 rated hybrids, yield losses can be reduced by over 90% with this spray timing.
Collecting data to use in the calculator
Generally, peak midge activity occurs between 9-11am, and this is the best time to look. Sorghum heads are most attractive to midge at mid flower. Midge flies are only 1-2 mm long and the easiest way to ‘get your eye in’ is to look at the top half of mid flowering panicles and look for movement of the small red flies against a still sorghum panicle looking from side on and slightly above side on one section of the sorghum panicle at a time. Keep your eyes focused over a couple of branches of florets for several seconds at a time to detect female midge walking around the branch or bobbing up and down probing their ovipositor into each floret. On windy days shelter the panicle for 10-20 seconds before scanning each panicle, to allow you to more accurately see midge movement. Monitor for midge over 10 metres of row in at least 4 different locations in your crop. It may be necessary to spray only one section of crop at a time, or the whole crop accordingly.
View our Sampling for insects in sorghum video on the BeatSheet’s YouTube channel.