Project Overview

Reports

Commodities

• Agronomic: sorghum (milo)

Target Pests

• Target Pests: aphids

Practices

• Pest Management: biological control, chemical control, forecasting, host resistance, modeling, pesticide application timing

• Crop Production: cropping systems

• Natural Resources/Environment: biodiversity, grass waterways

• Production Systems: agroecosystems

The sugarcane aphid (Melanaphis sorghi [=Melanaphis sacchari]) is an important and outbreak-prone insect pest of sorghum. It is suppressed by a complex of natural enemies although suppression varies across the southern and central U.S. Unrestrained, this aphid causes yield loss and harvesting difficulties. Since initial outbreaks in 2013, sugarcane aphid has spread throughout U.S. sorghum production. This aphid and its natural enemies are particularly relevant to the southern U.S. and the 13 states of the Southern IPM Center region where over 2 million grain sorghum acres valued over $500 million are planted annually (USDA NASS 2020) The challenge (Problem) is that sugarcane aphid and natural enemy activity varies across the states making applying IPM tactics to supplement natural enemies challenging.

The purpose (Opportunity/Approach) is to synthesize previously acquired spatial data on sugarcane aphid and its natural enemies to develop a quantitative spatially explicit model to forecast risk and guide use of IPM tools. This project links to a recent course (regional scale) model designed to assign region-specific outbreak risk of sugarcane aphid as affected by natural enemies and influences by agro-landscape and weather conditions (Brewer et al., submitted). Our capstone products will be production of a region-specific IPM guidance document and a more local risk/guidance tool as our data allow. Our current empirical analysis indicates that sorghum and other crops, riparian areas, and non-crop elements affect aphid and natural enemy interactions. A courser-grain data set across four states indicates that sugarcane aphid and natural enemies are variable as are crop and noncrop elements of the landscape. For example, sorghum is a dominant feature along the Texas Gulf Coast and is associated with non-crop habitats where aphids and their natural enemies have strong interactions. In contrast, sorghum in Alabama is planted into smaller fields occupying a smaller proportion of the landscape with greater amounts of non-crop lands. Here, sugarcane aphid populations on average are higher and aphid-natural enemy relationships are weak. Capstone project objectives include:

Objective 1: Refine our existing empirical models of the relationships between sugarcane aphids and natural enemies within the context of surrounding landscape. Field research was conducted along the Texas Gulf Coast into central Texas in 2019 and 2020. Companion coarser-scale data (2015 to 2019) is now archived from this area as well as from central and north Texas, Oklahoma, Kansas, and Alabama (Brewer et al., submitted). First, we will refine our existing quantitative empirical model of aphid-natural enemy interactions sensitive to landscape context by incorporating additional landscape metrics.

Objective 2: Convert the empirical models into a spatially-explicit quantitative model to forecast risk. This spatially-explicit risk tool will be derived from objective one and validated with data used to generate the coarse-grain (regional scale) model to forecast region-specific sugarcane aphid outbreak risk (Brewer et al., submitted).

Objective 3: Develop IPM guidance tools useful to practitioners. The results (anticipated Impact) will help guide best strategies for deploying IPM tactics, conditioned on local agro-landscape features and predicted levels of aphid suppression. The first guidance tool will be a written document on best strategies to insert IPM tools region by region (e.g., sampling intensity to time insecticide use and planting partially aphid resistant hybrids) which can be developed with the regional scale model (Brewer et al., submitted) in hand. The second product will use the quantitative modeling tool to forecast sugarcane aphid outbreak potential at a finer scale with special attention to southern Gulf Coast region, where our empirical models were developed and most applicable. The coarser-grain regional data (five years, four states) will be used to consider expansion of the modeling tool regionally based on consistencies discovered (Expanding Impact).

1.Refine empirical models of relationships between sugarcane aphids and natural enemies within the context of landscape composition and configuration surrounding sorghum fields.

2.Convert empirical models of aphids and natural enemies into spatially-explicit models that forecast aphid and natural enemy abundance in sorghum which is used to assess risk of aphid outbreaks and best strategize use of IPM practices to supplement natural enemies.

Objective 2a: Develop spatial models extrapolating the landscape’s relationship to aphid and natural enemy abundance to forecast abundance of sugarcane aphids and natural enemies for sorghum in the southern Gulf Coast and regionally as guided by Obj 1 results.

Objective 2b: Combine aphid and natural enemy sub-components of the modelling effort to estimate risk of aphid outbreaks considering level of aphid suppression from natural enemies as related to the landscape.

3.Develop IPM guidance tools on best strategies to insert IPM tools based on forecasts of sugarcane aphid outbreak potential within the southern Gulf Coast and regionally to the extent possible as guided by our refined empirical models and validation.

Objective 3a: Establish regional sorghum IPM recommendations for aphid monitoring and planting partially-aphid resistant hybrids based on sorghum agroecosystem influence on forecasted aphid and natural enemy levels.

Objective 3b: Generate local recommendations based on landscape structure and environments influence on aphid abundance and natural enemy activity for sorghum producers.