Please click the picture below to view the effects of weathering on grain sorghum by Dr. Dan Fromme.
The EPA has granted a section 18 request for the use of Transform (sulfoxaflor) for 2016 Louisiana cotton production season. Please see the link below for information on conditions and restrictions outlined by the section 18 label.
One of the most important decisions producers must make when planting soybeans in Louisiana is planting date. Soybeans have the utility to be planted in early March to late June. This wide variation in planting dates exposes seedling soybeans to a multitude of insect pests that affect both above and below ground plant structures.
Optimal seeding dates for each maturity group planted in Louisiana are:
- Group III – April 15–May 10
- Group IV – April 15–May 10
- Group V – March 25–May 5
- Group VI – March 25–April 30
Soybean seedlings possess an exceptional amount of vigor and can tolerate a substantial amount of insect injury during the seedling stage. However, early planted soybeans may also encounter greater amounts of environmental fluctuations that affect air and soil temperature. Cool conditions can negatively affect vigor and under the right conditions stall plant growth and development. The addition of insect injury, to the aforementioned environmental conditions, increases stress the plant encounters resulting in loss of stand and yield potential. Therefore, the inclusion of an insecticide seed treatment (IST) provides growers a risk management tool when soybeans are planted early. The primary insect pests of early planted soybeans are bean leaf beetles, wireworms and grape colaspis.
On the opposite end of the spectrum are soybeans planted late i.e. behind wheat or are late due to unforeseen circumstances such as inadequate or excessive soil moisture. These beans are more at risk for insect injury due to the potential for large insect populations to build in neighboring fields and generally more insects present in the environment. As a general rule with all agronomic crops, the later the crop the more insect pressure that will be encountered throughout the season. This is particularly evident when soybeans are planted into wheat stubble. Wheat stubble is favorable for the development of threecornered alfalfa hoppers and thrips. Thus, an IST is a sound investment when soybeans are planted late.
However, soybeans planted in a timely manner that being within the recommended planting window, under optimal soil conditions and low pest densities will often not benefit from the addition of an IST. Insecticide seed treatments typically produce the most benefits when environmental conditions are sub optimal as outlined in the prior paragraphs. With the current economic climate and many ag professionals looking at areas to cut inputs, justifying the use of an IST on soybeans when planted under optimal conditions becomes harder to support. Saving the cost of an IST can go to making a stink bug application later season that may provide a greater economic return.
Outside of early or late planted soybeans are situations where ISTs are justifiable. These include weedy fields with incomplete burn down applications, reduced tillage field arrangements, fields with historically problematic early insect pests (wireworms and/or threecornered alfalfa hoppers) and continuous plantings of one crop. Each field is unique and the use of ISTs as a blanket treatment over every acre may not be justifiable with $8 soybeans.
Cover crops can provide producers a variety of benefits from nutrient cycling and soil cover to nitrogen fixation and pollinator food sources. Cover crops come in many varieties including grasses, legumes and brassicas, however; cover crops maintain a “green bridge” throughout the fall and early spring that may facilitate the movement of pest insects into above and below ground plant structures.
Seedling corn, in Louisiana, is often adversely affected by many factors including excess moisture, cold temperatures and a complex of above/below ground insect pests. The complex of underground insects includes southern corn rootworm, wireworms and white grubs, while the above ground complex includes sugarcane beetles, chinch bugs and cutworms. Most of these insects require a food source that is present in fields for them to successfully overwinter and subsequently begin reproduction when temperatures begin to warm in the spring. The inherent benefits of cover crops often include the presence of large volumes of biomass and an abundant root structure that anchors soil or penetrates a hard pan. Yet, these attributes make cover crops an ideal source for the buildup of yield limiting insects.
Insecticide seed treatments (ISTs) are neonicotinoid based insecticides that coat the outer layer of the seed offering protection from below and above ground early season insect pests. The systemic nature of ISTs make these compounds water soluble and facilitate the vascular movement of the insecticide into the plant tissue. The value of ISTs in Louisiana varies among crops and environmental conditions, most agricultural commodities will usually not benefit from ISTs when planted under optimal environmental conditions (adequate soil temperature, optimal soil moisture and low pest pressure). However, insecticide seed treatments will typically produce an economic benefit when conditions are sub-optimal including very late or early planting, reduced tillage field arrangements, double cropping systems (soybeans behind wheat), pests that are present every year and consecutive plantings (i.e., corn behind corn). In addition to the above mentioned situations, data from the LSU AgCenter’s Macon Ridge Research Station confirmed the need of an IST when corn is planted behind cover crops (Figure 1). A statistically significant increase in yield was observed in corn treated with Poncho 500 IST in Berseen Clover, Crimson Clover and Hairy Vetch while a significantly lower yield was measured in corn planted behind Tillage Radishes treated with the IST (Figure 1). No fungicide seed treatment was used in this study. The measurable difference in yield may be due to the presence of below ground insects that also produced a notable decrease in vigor (Figure 2). Unfortunately for producers, there are no rescue treatments available for below ground insect injury in corn or any other agriculturally managed crop in Louisiana. Therefore, the use of an IST can help safely and effectively control below above and below ground insect pests in corn planted behind cover crops.
Aside from the use of ISTs, there are other management practices that can be done to minimize the effects of pest insects, from cover crops, on corn. Burning down cover crops in a timely fashion (6 weeks before planting) will provide enough time for available biomass above the soil to dessicate and force any harbored insects off of the plants. Yet, this timing may not allow enough time for below ground insects to cycle out or succumb to a lack of forage. Earlier burn down timings and the use of minimum tillage may allow enough time for insects to cycle out or be physically removed or destroyed with implements. If you elect to destroy your cover crops earlier than intended, check with your local NRCS representative or LSU AgCenter county agent to ensure enough time has passed that your preplant intentions are met (ie. Nitrogen fixation, nutrient cycling, etc.).
The use of ISTs is a best management practice recommended by the LSU AgCenter and will help ensure your crop is protected from yield limiting insects. The use of ISTs is highly recommended if you choose to plant corn behind cover crops particularly Berseen Clover, Crimson Clover and Hairy Vetch. If you have any questions or concerns please contact your local LSU AgCenter extension service.
Please see the article below by Dr. Dan Fromme on the impact of flooding on Louisiana corn.
Please see the link below by Drs. Steve Harrison, Boyd Padget and Trey Price.
Please click the link to access the March edition of the Louisiana crops newsletter.
Please follow the link above to access the section 18 letter. The approval letter outlines the effective and expiration dates for the use of Transform in sorghum, as well as specifics regarding number of applications and maximum acreage treated in Louisiana.
If you have any questions or concerns about sugarcane aphids or use of Transform in Sorghum please contact:
Sebe Brown at 318-498-1283 (cell) or 318-435-2903 (office)
Dr. David Kerns at 318-439-4844 (cell) or 318-435-2157 (office)
Dr. Julien Beuzelin at 337-501-7087 (cell) or 318-473-6523 (office)
Please see the link below for more information.
Dr. Ronnie Levy: LSU AgCenter Soybean Specialist
For more information please contact Dr. Ronnie Levy at firstname.lastname@example.org