Bionomics and Intergrated Control of the Sunflower Seed Maggot (Neotephritis finalis) and the Sunflower Bud Moth (Suleima helianthana) in the Nothern Plains Sunflower Production Region. 2009 Results.

Abstract

In the past several years, sunflower producers, field scouts and seed companies have expressed concern about the injury to sunflower resulting in deformed and misshapen areas in the head. The head damage was unlike that caused by sunflower midge and was attributed to feeding injury caused by the sunflower seed maggot, Neotephritis finalis (Loew) (Fig. 1) and/or sunflower bud moth, Suleima helianthana (Riley) (Fig. 2). Although reported from a number of sources, the exact extent and economic loss from these insect pests are not known. Although sunflower seed maggot and sunflower bud moth have been reported in the literature as insect pests of sunflower, a better understanding of their economic impact and potentially useful pest management strategies is needed. This research determined the biology of sunflower seed maggot in North Dakota, and examined two different pest management strategies for control of sunflower seed maggot and sunflower bud moth in North Dakota: 1) Planting dates, and 2) Insecticide timing and insecticide mode of action. Biology of Sunflower Seed Maggot: The bionomics of sunflower seed maggot was determined and findings are summarized in this report. Planting Dates: Late planting date (early to mid-June) was effective in reducing the damage ratings and percentage of damaged heads for sunflower seed maggot at three of the five locations examined in 2009 in North Dakota. Overall, population densities of sunflower seed maggots were low in 2009 and decreased from previous years (source NSA Sunflower Survey) making damage assessments between early (early to late May) and late (early to mid-June) planting dates difficult. For sunflower seed maggot, the late planting date had a lower percentage of damaged heads than the early planting date at three of the five research sites examined. For sunflower bud moth, the late planting date also had a lower percentage of damage heads than the early planting date at two of the five research sites examined. However, sunflower bud moth also had very low population levels and was reported only in sporadic ‘hot spots’ in 2009. Yield differences were attributed to other agronomic factors or bird damage, and not due to head damage caused by sunflower seed maggot or sunflower bud moth. Efficacy of Insecticide Timing and Mode of Action: Neither insecticide timing nor mode of action had any significant effect on the sunflower seed maggot damage ratings, nor the percentage of heads damaged from sunflower seed maggot or sunflower bud moth at any location. The lack of differences could be due to low population densities of adults or missed application timing. Therefore, future plans include the addition of insecticide applications at the R1 growth stage in addition to the R3 and R5 stages. For insecticide mode of action, the pyrethroid insecticide (Asana) and the organophosphate + pyrethroid insecticide (Cobalt) typically had higher yields than the organophosphate insecticide (Lorsban) alone. This is probably due to organophosphate insecticide having a shorter residual effect than pyrethroids. Given that the lowest yields were those treatments with insecticides applied at R3, yield differences are probably due to later (R5.1) infestations of other insect pests, like banded sunflower moth and/or red sunflower seed weevil. In conclusion, it was difficult to assess the insecticide efficacy and mode of action due to low population densities of adult insects. 2009 results indicate that there is no insecticide treatment correlation to damage assessment for sunflower seed maggot and sunflower bud moth and yield. Additional research is necessary to determine viable pest management strategies for control of sunflower seed maggot and sunflower bud moth.