Patrick B. Beauzay

Pest management of wheat stem maggot (Diptera: Chloropidae) and wheat stem sawfly (Hymenoptera: Cephidae) using insecticides in spring wheat.

Abstract The effectiveness and timing of foliar insecticides and insecticidal seed treatments were evaluated for pest management of the wheat stem maggot, Meromyza americana Fitch (Diptera: Chloropidae), and the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), in hard red spring wheat in North Dakota. Treatments included: 1) untreated check, 2) foliar application of lambda-cyhalothrin at the 4–6 leaf stage, 3) foliar application of lambda-cyhalothrin at the flag-leaf stage, 4) low rate of thiamethoxam seed treatment, 5) high rate of thiamethoxam seed treatment, and 6) low rate of thiamethoxam seed treatment plus a foliar application of lambda-cyhalothrin at the 4–6 leaf stage. A foliar application of lambda-cyhalothrin at either leaf stage significantly reduced the number of white heads caused by wheat stem maggot. The combination of a low rate of thiamethoxam seed treatment plus a foliar application of lambda-cyhalothrin at the 4–6 leaf stage also resulted in a significantly lower number of white heads. However, the low and high rates of thiamethoxam seed treatment alone were not effective at reducing the number of white heads. None of the treatments reduced the percentage of damaged stems from wheat stem sawfly. No yield differences were observed among treatments for either wheat stem maggot or wheat stem sawfly.

Impact of Rag1 Aphid Resistant Soybeans on Binodoxys communis (Hymenoptera: Braconidae), a Parasitoid of Soybean Aphid (Hemiptera: Aphididae)

ABSTRACT Multiple strategies are being developed for pest management of the soybean aphid, Aphis glycines Matsumura; however, there has been little published research thus far to determine how such strategies may influence each other, thereby complicating their potential effectiveness. A susceptible soybean (Glycine max L.) variety without the Rag1 gene and a near isogenic resistant soybean variety with the Rag1 gene were evaluated in the laboratory for their effects on the fitness of the soybean aphid parasitoid, Binodoxys communis (Gahan). The presence or absence of the Rag1 gene was verified by quantifying soybean aphid growth. To test for fitness effects, parasitoids were allowed to attack soybean aphids on either a susceptible or resistant plant for 24 h and then aphids were kept on the same plant throughout parasitoid development. Parasitoid fitness was measured by mummy and adult parasitoid production, adult parasitoid emergence, development time, and adult size. Parasitoids that attacked soybean aphids on susceptible plants produced more mummies, more adult parasitoids, and had a higher emergence rate compared with those on resistant plants. Adult parasitoids that emerged from resistant plants took 1 d longer and were smaller compared with those from susceptible plants. This study suggests that biological control by B. communis may be compromised when host plant resistance is widely used for pest management of soybean aphids.

Impact of Planting Dates on a Seed Maggot, Neotephritis finalis (Diptera: Tephritidae), and Sunflower Bud Moth (Lepidoptera: Tortricidae) Damage in Cultivated Sunflower

ABSTRACT Neotephritis finalis (Loew) (Diptera: Tephritidae), and sunflower bud moth, Suleima helianthana (Riley) (Lepidoptera: Tortricidae) are major head-infesting insect pests of cultivated sunflower (Helianthus annuus L.). Planting date was evaluated as a cultural pest management strategy for control of N. finalis and S. helianthana in several production regions of North Dakota during 2009 and 2010. Results of the nine site-year study revealed that late planting date (early to mid-June) reduced damage ratings and percentage of damaged heads for N. finalis compared with early planting dates (mid- to late May). Visual observations of adult N. finalis found that the majority of flies were found in the early planted sunflower (78.2%) compared with the late planted sunflower (21.8%). Late planting date also reduced the percentage of S. helianthana damaged heads compared with early planting dates. Yield losses were reduced with late planting date when populations of N. finalis and S. helianthana were high enough to cause damage. Results of this study showed that delayed planting is an effective integrated pest management strategy that can reduce head damage caused by N. finalis and S. helianthana and mitigate yield losses.

Transgenic Bt Corn, Soil Insecticide, and Insecticidal Seed Treatment Effects on Corn Rootworm (Coleoptera: Chrysomelidae) Beetle Emergence, Larval Feeding Injury, and Corn Yield in North Dakota

Abstract Northern, Diabrotica barberi Smith & Lawrence (Coleoptera: Chrysomelidae), and western, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), corn rootworms are economic pests of corn, Zea mays L. in North America. We measured the impacts of corn hybrids incorporated with Cry3Bb1, Cry34/35Ab1, and pyramided (Cry3Bb1 + Cry34/35Ab1) Bacillus thuringiensis Berliner (Bt) proteins, tefluthrin soil insecticide, and clothianidin insecticidal seed treatment on beetle emergence, larval feeding injury, and corn yield at five locations from 2013 to 2015 in eastern North Dakota. In most cases, emergence was significantly lower in Bt-protected corn than in non-Bt corn hybrids. Exceptions includedWyndmere, ND (2013), where D. barberiemergence from Cry34/35Ab1 plots was not different from that in the non-Bt hybrid, and Arthur, ND (2013), where D. v. virgifera emergence from Cry3Bb1 plots did not differ from that in the non-Bt hybrid. Bt hybrids generally produced increased grain yield compared with non-Bt corn where rootworm densities were high, and larval root-feeding injury was consistently lower in Bt-protected plots than in non-Bt corn.The lowest overall feeding injury and emergence levels occurred in plots planted with the Cry3Bb1 + Cry34/35Ab1 hybrid.Time to 50% cumulative emergence of both species was 5–7 d later in Bt-protected than in non-Bt hybrids.Tefluthrin and clothianidin were mostly inconsequential in relation to beetle emergence and larval root injury. Our findings could suggest that some North Dakota populations could be in early stages of increased tolerance to some Bt toxins; however, Bt corn hybrids currently provide effective protection against rootworm injury in eastern North Dakota.