Friday, September 6, 2013

Outbreak of Sorghum Webworms

Scott Blankenship, Kelly Ag and Chris Parker, Wiregrass Research Center, Headland, AL, report a heavy outbreak of sorghum webworms on grain sorghum in the Wiregrass region of Alabama. As many as 70 to 80 larvae per head have been recorded. Pyrethroid insecticides have given poor control. Other treatment options include: Belt, chlorpyrifos (Lorsban or generics), Lannate, Sevin or Tracer. Growers should note the “days to harvest” restrictions with the various insecticide choices. Webworm picture provided by S. Blankenship.

Wednesday, September 4, 2013

Final Insect Update of the Season

The Alabama row crop insect control season is rapidly winding down. The few areas that still need attention for a few more weeks are as follows. We need to protect bolls on June planted cotton from stink bug injury until the bolls are approximately 25 days old. We still have plenty of time left in the season to mature small bolls that are present from blooms the last week of August. On soybeans, stink bugs continue to reproduce and feed on pods. Late planted, June to early July, soybeans will be susceptible to stink bug feeding for several more weeks. Stink bug adults will leave other crops when they mature and seek out late planted soybeans as their last host before heading for overwintering sites. I expect to see high numbers of stink bugs in many of these late maturing soybean fields. The good thing is that one application to economic levels of stink bugs in both cotton and soybeans made now should hold populations below damaging levels for the remainder of the season. Stink bug populations currently contain both the brown and southern green species. A high rate of most pyrethroids on soybeans should give adequate suppression. Kudzu bug adults are still present in many soybean fields but they are not as numerous in most fields as they were back a month or so ago. Their numbers seemed to have peaked in April and May planted beans back in the late June to early August window.

Overall 2013 has been a light insect year in Alabama for most species. A summary of what I have observed is the following. For cotton, thrips were moderate to heavy. However, their movement from wild hosts to cotton occurred in May instead of April. Therefore, their damage period coincided with our mid-planting period cotton instead of the earliest planted as happens most seasons. Plant bugs, aphids and spider mites were very light overall. Bollworms and tobacco budworms were low to nonexistent, even in fields of conventional cotton. I have conventional cotton on three research stations spread across the central and southern areas of Alabama. One had to search very hard all season to find a single larva or damaged fruit. Stink bugs were the only cotton insect that occurred at damaging levels in most fields in-season.

In soybeans, Kudzu bugs were extremely heavy in many early planted soybean fields. This was the first year that many soybean growers have had to deal with the Kudzu bug. Others will likely have their first experience in 2014. When all is said and done, I believe we will be able to handle this insect with one, or at most two, well timed sprays. Late maturing beans will likely still see a big buildup of stink bugs in coming weeks as other crops mature and dry down. The foliage feeding complex of green cloverworms, velvetbean caterpillars and soybean loopers have been very light in 2013. This follows the most widespread infestations of the past 40 years last season. Podworms have been very light in soybeans for the past two seasons.

This has been a very unusual year rainfall wise. This may be the only season during my 41 years here as our Extension Entomologist where we had too much rain.

With these comments we will end our in season blogs unless something unusual shows up. I hope my comments have been helpful to those of you that are receiving them. Hopefully we can continue this blog, the Syngenta Insect Hotline, and our tweets during the 2014 season.