Susceptibility of corn to stink bug (Dichelops melacanthus) and its management through seed treatment

We determined the susceptibility of vegetative corn stages to Dichelops melacanthus damage, and how seed treatment can reduce damage and yield loss. Two field trials were carried out. In the first, corn plants were artificially infested with D. melacanthus male/female pairs at rate of 0.5 pair per plant at different vegetative stages and infestation periods lasting 7-28 days (V1-V3, V1-V5, V1-V7, V1-V9, V3-V5, V3-V7, V3-V9, V5-V7, V5-V9, and V7-V9), plus a control without infestation. In the second, corn plants were artificially infested at a rate of one male/female pair per plant at different vegetative stages and infestation periods (V1-V3, V1-V5, V1-V7, V3-V5, V3-V7 and V5-V7) and treated with two pesticide seed coatings: (i) fungicide [carbendazim + thiram (150 g i.a. per L and 350 g i.a. per L)] + insecticide [clothianidin (600 g i.a. per L)] or (ii) only fungicide (carbendazim + thiram), plus three controls without infestation and with only fungicide-treatment (V1-V7, V3-V7 and V5-V7). In both trials, plants were caged during the entire period in order to hold stink bugs in contact with plants and to avoid injury from other arthropods. The most stink bug susceptible corn growth periods were from V1-V5 and from V1-V7. Seed treatment with clothianidin at the rate of 3.5 mL per Kg during the most susceptible infestation periods increased yield gain of 37.8 to 61%. Treatment with clothianidin during V1-V5 and V1-V7 caused 40% to 50% D. melacanthus adult mortality, respectively.