CORN AND SOYBEAN CROP INFLUENCE
The influence of tarnished plant bug on corn and soybean populations in cotton.
General description of research:
Corn may play an important role in the dynamics of tarnished plant bug populations that infest mid- late-season cotton. Prior to research conducted at the USDA-ARS Southern Insect Management Research Unit (SIMRU), consultants and researchers had collected nymphs and adult stage tarnished plant bugs from corn; however, it was unknown if the insect was able to reproduce on the crop.
Our objectives at SIMRU are to: Determine if the pest can develop on corn tissue Quantify egg production for plant bug adults reared on corn tissue Determine the location and timing of plant bug oviposition on corn Study the life history of plant bug development on corn Quantify the population densities of plant bugs developing on corn that could potentially move into mid- to late-season cotton Determine the association between corn earworm damage to the corn ear and tarnished plant bug development on developing corn seed.
The ultimate goal of this research is to determine if plant bugs reproduce in corn at sufficient levels to warrant control of the pest before it infests mid- to late-season cotton.
In the laboratory, we have discovered that tarnished plant bugs can develop successfully on pollen-shedding corn tassels (75.0% developed to adults) and blister- and milk-stage kernels collected from corn ears. Development on these tissues was not different when compared to the broccoli control. When adult female fecundity was checked, the female tarnished plant bugs that were reared on broccoli produced significantly more eggs than those females reared on milk-stage kernels, but not those reared on corn cob tips which contained blister- and milk-stage kernels. Because developing corn seed from healthy ears is unavailable to plant bug feeding, ear damage by the corn earworm/bollworm may be important for the tarnished plant bug to feed and complete its normal development.
In the field, we found tarnished plant bug eggs oviposited on the leaf sheath, leaf mid-rib, tassels, and silks of corn (Photos 1-3). We examined whole corn plants for tarnished plant bugs throughout the corn growing season and discovered the greatest number of plant bugs on R2 (milk stage) corn. During this stage, we recorded an average of 6.2% tarnished plant bugs/plant. The highest number of plant bugs infesting corn (12.7% of plants) occurred on 20 June, 2003 on R2 stage corn that was planted 18 April, 2003. For irrigated corn grown in the MS Delta, normal plant populations for corn are at 40,000 plants/acre. If we assume 6.2% of these plants will produce one tarnished plant bug, 2,480 tarnished plant bugs may be produced per acre of field corn. Additional research will be needed to determine if this level of reproduction in corn is occurring and if it is economically significant for cotton producers.
Notice how the eggs below were not inserted into the tissue, but were laid on top. These eggs may not hatch properly.
Photo 1. Eggs laid in corn sheath.
Photo 2. Egg laid in corn silk.
Photo 3. Eggs laid on corn tassel.
Large scale strip-plots of cotton planted next to corn, cotton or soybean will be either sprayed unsprayed with insecticide to determine the relative differences in plant bug densities emerging and infesting mid- to late-season cotton.
The development of tarnished plant bug on soybean will be investigated in 2004 and 2005. A study to determine the life history of the pest on soybean will also be conducted during these two years.
For more information contact:
PO Box 346
141 Experiment Station Rd
Stoneville, MS 38776
Abel, C. A. and G. L. Snodgrass. 2003. The development of tarnished plant bug on various corn tissue. In Proc. Cotton Res. Conf. Natl. Cotton Council Amer. Nashville TN, www.cotton.org/beltwide