Eric Bohnenblust

A comparison of various mating disruption technologies for control of two internally feeding Lepidoptera in apples

Sex pheromone mating disruption (MD) is an approach used to control several moth pest species of pome fruit by disrupting the ability of the males to find females and consequently prevent mating. The following experiments were performed to determine the effectiveness of several new and experimental sex pheromone MD technologies, and dispenser densities for simultaneous control of the codling moth (CM), Cydia pomonella (L.), and the oriental fruit moth (OFM), Grapholita molesta (Busck) (both Lepidoptera: Tortricidae), in Pennsylvania apple orchards. In one study, three MD approaches to control CM and oriental fruit moth – CM and OFM Disrupt Micro‐Flakes, Isomate CM/OFM TT, and both a CideTrak OFM and a CideTrak CM dispenser containing both codlemone and pear ester – and an insecticides‐only treatment were compared over the course of 2 years. In the other studies, the efficacy of several CheckMate Duel dispenser densities (i.e., 250, 375, 425, and 500 dispensers ha−1) were compared against Isomate CM/OFM TT, and an insecticides‐only treatment. The CideTrak CM/pear ester combination and Isomate CM/OFM TT treatments both substantially reduced CM captures in traps in 2007 and 2008. Meanwhile, OFM trap shutdown was highest in the CheckMate Duel densities of 375 (99.9 ± 0.08%) and 500 dispensers ha−1 (98.9 ± 0.07%) and the Isomate CM/OFM TT treatment (98.0 ± 1.13%), and lowest in the 250 dispensers ha−1 density treatment (94.3 ± 3.23%). In orchards where OFM is the dominant pest species, a CheckMate Duel dispenser density of 375 ha−1 is necessary for effective control, whereas higher densities are needed to control CM.

Current European corn borer, Ostrinia nubilalis, injury levels in the northeastern United States and the value of Bt field corn†

BACKGROUND Recent evidence indicates that some populations of European corn borer (ECB), Ostrinia nubilalis (Hübner), have declined to historic lows owing to widespread adoption of Bt corn hybrids. To understand current ECB populations in Pennsylvania field corn, the authors assessed larval damage in Bt and non-Bt corn hybrids at 29 sites over 3 years. The influence of Bt adoption rates, land cover types and moth activity on levels of ECB damage was also considered. RESULTS Bt hybrids reduced ECB damage when compared with non-Bt, but these differences inconsistently translated to higher yields and, because of higher seed costs, rarely improved profits. No relationships were detected between land use or Bt adoption and ECB damage rates, but positive relationships were found between plant damage and captures of Z-race ECB moths in pheromone traps in the PestWatch network. CONCLUSIONS ECB damage levels were generally low and appear to be declining across Pennsylvania. In many locations, farmers may gain greater profits by planting competitive non-Bt hybrids; however, Bt hybrids remain valuable control options, particularly in the parts of Pennsylvania where ECB populations persist. Moth captures from PestWatch appear to provide insight into where Bt hybrids are most valuable.

Corn Earworm (Lepidoptera: Noctuidae) in Northeastern Field Corn: Infestation Levels and the Value of Transgenic Hybrids

ABSTRACT Corn earworm, Helicoverpa zea (Boddie), is apolyphagous noctuid pest of agricultural crops across the United States that is gaining attention as a pest of field corn. Before the introduction of transgenic insect-resistant hybrids, this pest was largely ignored in field corn, but now many Bacillus thuringiensis (Bt) corn hybrids have activity against corn earworm. However, the value of control in the northeastern United States is unclear because the risk posed by corn earworm to field corn has not been well characterized. To understand the threat from corn earworm and the value of Bt hybrids in field corn, we assessed corn earworm injury in Bt and non-Bt hybrids at 16 sites across four maturity zones throughout Pennsylvania in 2010, and 10 sites in 2011. We also used corn earworm captures from the PestWatch pheromone trapping network to relate moth activity to larval damage in field corn. Corn earworm damage was less than one kernel per ear at 21 of 26 sites over both years, and the percentage of ears damaged was generally <15%, much lower than in the southern United States where damage can be up to 30 kernels per ear. At sites with the highest damage levels, Bt hybrids suppressed corn earworm damage relative to non-Bt hybrids, but we found no differences among Bt traits. Cumulative moth captures through July effectively predicted damage at the end of the season. Currently, the additional benefit of corn earworm control provided by Bt hybrids is typically less than US

Effects of the herbicide dicamba on nontarget plants and pollinator visitation

4.00/ha in northeastern field corn.

Evaluating sex-pheromone- and kairomone-based lures for attracting codling moth adults in mating disruption versus conventionally managed apple orchards in Pennsylvania.

Nearly 80% of all pesticides applied to row crops are herbicides, and these applications pose potentially significant ecotoxicological risks to nontarget plants and associated pollinators. In response to the widespread occurrence of weed species resistant to glyphosate, biotechnology companies have developed crops resistant to the synthetic-auxin herbicides dicamba and 2,4-dichlorophenoxyacetic acid (2,4-D); and once commercialized, adoption of these crops is likely to change herbicide-use patterns. Despite current limited use, dicamba and 2,4-D are often responsible for injury to nontarget plants; but effects of these herbicides on insect communities are poorly understood. To understand the influence of dicamba on pollinators, the authors applied several sublethal, drift-level rates of dicamba to alfalfa (Medicago sativa L.) and Eupatorium perfoliatum L. and evaluated plant flowering and floral visitation by pollinators. The authors found that dicamba doses simulating particle drift (≈1% of the field application rate) delayed onset of flowering and reduced the number of flowers of each plant species; however, plants that did flower produced similar-quality pollen in terms of protein concentrations. Further, plants affected by particle drift rates were visited less often by pollinators. Because plants exposed to sublethal levels of dicamba may produce fewer floral resources and be less frequently visited by pollinators, use of dicamba or other synthetic-auxin herbicides with widespread planting of herbicide-resistant crops will need to be carefully stewarded to prevent potential disturbances of plant and beneficial insect communities in agricultural landscapes.

Direct and Indirect Effects of the Synthetic-Auxin Herbicide Dicamba on Two Lepidopteran Species

BACKGROUND Effectiveness of different types of commercial sex-pheromone- and kairomone-based lures for attracting codling moth adults may vary under different pest management practices. The attractiveness of four types of codling moth (CM) lures (CM L2 Long-Life(®), CM 10X Megalure(®), Pherocon CM DA(®) and Pherocon CM-DA Combo(®)) was evaluated in commercial apple orchards either treated with sex pheromone mating disruption (MD) or only conventional insecticides (non-MD) in Adams County, Pennsylvania, in 2006 and 2007. RESULTS CM DA Combo lure was most effective in terms of mean seasonal weekly moth capture as well as mean cumulative moth capture in MD orchards. In both years, the CM L2 lure was as attractive to adult moths as the CM DA Combo lure in non-MD orchards. The CM DA and CM 10X lures caught significantly fewer moths in both MD and non-MD orchards compared with the CM DA Combo lure. CONCLUSIONS ON the basis of mean seasonal weekly moth capture as well as mean cumulative moth capture, the CM DA Combo and CM L2 lures were found to be significantly more effective for monitoring CM adults in both MD and non-MD orchards. In contrast, the CM DA and CM 10X lures were not as effective in either type of orchard.

Capture of Two Moth Species in Traps Placed at Different Heights in Sex Pheromone Treated Apple Orchards

ABSTRACT Herbicides are the most commonly applied pesticides in agroecosystems, and therefore pose potentially significant ecotoxicological risks to plants and insects. Glyphosate is the most common herbicide worldwide, and glyphosate-resistant weeds are quickly becoming serious challenges in some agroecosystems. Because of this resistance epidemic and the recent development of crops with resistance to dicamba or 2,4-D, herbicide-use patterns are likely to change. Presently, dicamba and 2,4-D cause most herbicide-drift damage to nontarget plants despite limited agricultural usage, but the effects of these synthetic auxin herbicides on insects have been poorly explored. To understand the influence of dicamba on insects, we applied several sublethal, drift-level rates of dicamba to soybean, Glycine max L., and Carduus thistle, and measured growth and survival of Helicoverpa zea (Boddie) and Vanessa cardui (L.) larvae, respectively. For thistle, we measured percent nitrogen content before and after dicamba application. We also performed direct toxicity bioassays on the two caterpillar species with several rates of dicamba. Dicamba was not directly toxic to larvae of either species, and H. zea showed no negative effects when feeding on soybeans dosed with dicamba. We did, however, detect significant negative, indirect effects of higher rates of dicamba on V. cardui larval and pupal mass, total nitrogen of thistles post application, and thistle biomass in the presence of V. cardui larvae. Notably, thistle biomass was not related to dicamba dose in absence of larvae. Our results indicate that dicamba can indirectly influence the performance of some caterpillar species, possibly by altering plant nutritional content.

Corn pith weevil, Geraeus penicillus (Coleoptera: Curculionidae), in transgenic, insect‐resistant and conventional field corn hybrids

Studies were conducted to compare the effect of trap placement above and below sex pheromone mating disruption (MD) dispensers on captures of codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck), in apple orchards. Traps were placed at a height of 1.8 m or 4.5 m in the tree canopy whereas MD dispensers were placed at 3.1 m within the tree canopy; an adjacent set of plots were treated similarly with only insecticides (nonMD). All trees were approximately 4.8 - 5.1 m in height. Capture of codling moth adults in traps was highest in traps placed at 4.5 m in both MD and nonMD plots and lowest in traps placed at 1.8 m in MD treated plots. Reduction in adult codling moth capture was low to moderate (< 64%) in traps placed above dispensers and higher (>70%) in traps placed below dispensers over both years. Oriental fruit moth adult capture in 2007 was lowest in traps placed at 1.8 m in plots treated with MD. In 2008, capture of oriental fruit moth was highest in traps placed at 4.5 m.

Herbicide drift can affect plant and arthropod communities

The corn pith weevil Geraeus penicillus (Herbst) is occasionally found boring in corn stalks throughout the eastern and Midwestern United States. Injury caused by G. penicillus is not typically economical, but may be confused with that of the European corn borer Ostrinia nubilalis (Hubner), an important economic pest throughout the United States. During efforts to assess European corn borer infestations, we discovered G. penicillus in field corn in south‐eastern Pennsylvania, including hybrids genetically modified (i.e. Bt hybrids) to control European corn borer among other herbivore species. Our analysis across sites indicated that tunnels of G. penicillus were significantly more abundant in transgenic Bt hybrids than non‐Bt hybrids, but comparisons of Bt hybrids and their near isolines revealed mostly similar numbers of G. penicillus tunnels, suggesting other hybrid features might be affecting the distribution of G. penicillus. Tunnels of G. penicillus were equally distributed among the three transgenic trait packages represented in our study. In plants where we found G. penicillus, tunnels were more abundant in stalks free of European corn borer damage. Our report appears to be the first to note G. penicillus feeding in Bt corn hybrids. These findings are notable because they document insect damage in Bt hybrids that may be mistaken for European corn borer damage and may provide evidence of an insect herbivore proliferating following a mild winter or possibly even moving into competitor‐free space.