Friday, May 22, 2015

Update on SCA in the Lower Rio Grande Valley : May 22, 2015


This week and last week I received reports of some fields being sprayed with high SCA populations mainly in the eastern Cameron reaching all the way north to the Willacy county line and in the mid Valley area in Hidalgo and Cameron counties.  However, in a lot of the LRGV grain sorghum fields we are finding SCA but in Very low numbers.  We have yet to reach the threshold of 100 SCA/leaf here at the station in Weslaco as we have had continuous SCA presence and presence of winged SCA; but natural predator populations have been seen keeping SCA numbers low below 20 per leaf or lower counts.  It is quite a difference from last year when here on the experimental fields in the AgriLife Center at Weslaco and some commercial fields in the RGV we had SCA populations of 700-2,000 per leaf.  Also this year environmental factors such as the continuous rainfall and overcast days we believe has also inhibited the SCA from reaching soaring populations. Last year we had rainfall but it was not continuous and we also had intense sunlight beaming down, while this year the rain has kept coming with overcast days and pleasant working weather conditions outside (aside from the muddy fields and mosquitos).  With that said I’d advise you to please check your fields before you spray.  Many have had the pressure to spray these last 3 weeks given the recent rainfall and potential for more rain, however I would strongly recommend that if you are not seeing an average SCA population of 100 SCA/leaf then you should wait if possible so as not to decrease the beneficial insects present keeping the SCA in check.  Please CONTINUE CHECKING your fields because it is possible a second outbreak of SCA around the harvest time as occurred last year. What we have been observing in the field is continuous predation from beneficials even as new winged aphids fly into fields and reproduce.