Refining Management of Apple Powdery Mildew in New York State with Weather-Based Fungicide Application Timing Programs.

In the absence of durable host resistance among commercial cultivars, chemical management continues to be an essential component of disease control in apple production. Apple powdery mildew, caused by the ascomycete Podosphaera leucotricha, is largely managed with regular fungicide applications from the host phenological stages of tight cluster to terminal bud growth set, with applications typically being made in a prophylactic manner irrespective of existing disease pressure. Here we evaluated two management programs that aligned fungicide applications to specific weather thresholds conducive to powdery mildew development using a rotation of single-site fungicides and sulfur. In three separate orchards among four cultivars, we compared powdery mildew disease progression over the growing season for each of the weather factor-based programs and a typical calendar-based application program. In each year of the trial, we found that management programs with weather-based fungicide applications provided levels of disease control similar to the calendar program but required 50 to 83.3% fewer mildew-specific fungicide applications throughout the growing season. Our results provide a framework with which to evaluate future weather-based management programs for apple powdery mildew management. This knowledge could be implemented in the creation of a powdery mildew disease management decision support system to better inform and aid fungicide application programs for continued sustainable apple production in the northeast United States.

Optimizing Cercospora Leaf Spot Control in Table Beet Using Action Thresholds and Disease Forecasting.

Cercospora leaf spot (CLS), caused by the fungus Cercospora beticola, is the dominant foliar disease affecting table-beet production in New York. CLS epidemics occur annually and, if uncontrolled, will rapidly lead to defoliation. In broad-acre production, season-long maintenance of healthy leaves is important to facilitate harvest by top-pulling. Fungicides are the dominant means of CLS control and applications are initiated at an action threshold of 1 CLS lesion/leaf. Regular fungicide application occurs thereafter without regard for scheduling based on weather-based risk. The current action threshold was evaluated with selected fungicides in two replicated field trials. Copper oxychloride + copper hydroxide and propiconazole significantly improved CLS control if initiated prior to infection. Pydiflumetofen + difenoconazole significantly reduced area under the disease progress stairs compared with other fungicides tested and was most efficacious when applications began at 1 CLS lesion/leaf. Six replicated field trials also evaluated the utility of scheduling fungicides on weather-based risk rather than a calendar approach. Two risk thresholds (moderate and high) integrating the accumulation of daily infection values based on temperature and relative humidity from a forecaster for CLS in sugar beet were evaluated. Applications of pydiflumetofen + difenoconazole were reduced from three to two by using the forecaster at either risk threshold compared with calendar applications without affecting CLS control. For propiconazole, the moderate risk threshold provided CLS control equivalent to calendar applications and saved one spray per season. Thus, there was substantial scope to reduce spray frequency by scheduling based on weather-based risk rather than calendar applications. The optimal risk thresholds for pydiflumetofen + difenoconazole and propiconazole were high and moderate, respectively. In these trials, periods of high risk occurred less frequently than moderate risk, increasing the reapplication intervals and, hence, represented a less conservative approach to disease management.

Tri-trophic studies using Cry1Ac-resistant Plutella xylostella demonstrate no adverse effects of Cry1Ac on the entomopathogenic nematode, Heterorhabditis bacteriophora.

The potential impacts on natural enemies of crops that produce insecticidal Cry proteins from Bacillus thuringiensis (Bt) are an important part of an environmental risk assessment. Entomopathogenic nematodes are important natural enemies of lepidopteran pests, and the effects of Bt crops on these nontarget organisms should be investigated to avoid disruption of their biological control function. The objective of this study was to investigate the effects of Cry1Ac-expressing transgenic Bt broccoli on the entomopathogenic nematode, Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae), under tri-trophic conditions. Using CrylAc-resistant Plutella xylostella L. (Lepidoptera: Plutellidae) larvae as hosts, we evaluated the potential impact of Cry1Ac-expressing Bt broccoli on several fitness parameters of H. bacteriophora. Virulence, reproductive potential, time of emergence, and preference of H. bacteriophora for the host (P. xylostella) were not significantly affected when CrylAc-resistant P. xylostella larvae were reared on leaves of Cry1Ac or non-Bt broccoli. Also the aforementioned parameters of the subsequent generation of H. bacteriophora did not differ between nematodes obtained from P. xylostella reared on CrylAc broccoli compared with those obtained from P. xylostella reared on non-Bt broccoli. To the best of our knowledge, the current study provides the first clear evidence that Cry1Ac does not affect important fitness parameters of H. bacteriophora.

Degree-day models for predicting adult Delia platura (Diptera: Anthomyiidae) spring flight and first emergence in New York State.

The seedcorn maggot, Delia platura (Meigen), is a pest affecting many crops, including corn. The early spring emergence of adults and belowground seed damage by maggots leave no room for rescue treatments during the short growing season in New York State. Degree-day (DD) models play a crucial role in predicting insect emergence and adult peak activity and are essential for effective pest management. The current D. platura DD model was launched on the Network for Environment and Weather Applications (NEWA) in 2022, using existing scientific literature from other North American regions. The NEWA model predicted adult D. platura first emergence at an average of 471 (39°F) DD in 2022. To gain an accurate and precise understanding of D. platura adult spring emergence and activity, we used interpolated temperature data to calculate the DD for each specific location where adults were captured in the field. DD calculations were performed using the average method, setting a biofix on January 1st and a base temperature of 39°F. In 2023, overwintering adults emerged at an average of 68 DD, and in 2022, adult activity was registered at an average of 282 DD. Accurately predicting the emergence of D. platura could contribute to informing integrated pest management strategies that incorporate timing and cultural practices over chemical solutions to protect crops and the environment.

Invasive Tipula (Diptera: Tipulidae) in turfgrass of the northeast United States: geographic distribution and local incidence three years after detection.

Two species of invasive crane flies are damaging pests of turfgrass in the Great Lakes region after their inadvertent introduction and establishment. In New York, where Tipula paludosa Meigen and Tipula oleracea L. (Diptera: Tipulidae) were first detected in 2004, baseline data on the extent of establishment is needed to monitor range expansion, make predictions about pest status, and guide management efforts. The incidence of both species was therefore addressed at two spatial scales to ascertain how widespread they were across the state and across sites of recent local establishment. Based on divergent natural history, T. oleracea was predicted to be more widespread both geographically and locally than T. paludosa. To delimit the current area of occurrence, surveys were conducted from 2004 to 2006. T. paludosa was detected in four counties and T. oleracea in 12 counties. In western New York, T. oleracea was established in more than a six-fold greater area than T. paludosa. T. oleracea was additionally detected on Long Island, shown to be a geographically disjunct area of establishment. To measure local incidence, putting greens and tee boxes were scouted on golf courses. Contrary to predictions, 56-97 and 22-56% of those surfaces were already infested by T. paludosa and T. oleracea, respectively, within one or two seasons after initial detection. Because damage thresholds are relatively high, scouting for the insect, rather than its injury, will promote earlier detection. Given the impact of invasive Tipula across diverse turf habitats, continued range expansion will have serious repercussions for regional turfgrass management.

Application timing and efficacy of alternatives for the insecticidal control of Tipula paludosa Meigen (Diptera: Tipulidae), a new invasive pest of turf in the northeastern United States.

BACKGROUND: Two invasive crane flies, Tipula paludosa Meigen and Tipula oleracea L. (Diptera: Tipulidae), were detected in New York State for the first time in 2004. Both are damaging pests of turfgrass and other horticultural systems in North America where establishment has already been documented. To develop management recommendations for the Northeast and define opportunities for preventive (autumn) and curative (spring) control, four insecticide trials targeting T. paludosa larvae were conducted over a 2 year period. RESULTS: The most efficacious (>or=70% control in both trials) products against early instars in autumn were bifenthrin, carbaryl, chlorantraniliprole, clothianidin and trichlorfon. Results varied for azadirachtin, Beauveria bassiana, cyfluthrin, dinotefuran, imidacloprid, imidacloprid + bifenthrin and indoxacarb. Clothianidin and dinotefuran were most efficacious against fourth instars in spring; results varied for imidacloprid, indoxacarb and trichlorfon. CONCLUSION: Several insecticides offer alternatives for preventive and curative control of T. paludosa, but, because there is little overlap with application windows for scarab larvae pests, management may entail an entirely new insecticide treatment window, implying new economic and environmental burdens to the turfgrass industry. Moreover, curtailing the impact and spread of these invasives may be severely hampered because the best performing alternatives (clothianidin, dinotefuran) are not registered in New York.

Biology, Ecology, and Evolving Management of Helicoverpa zea (Lepidoptera: Noctuidae) in Sweet Corn in the United States.

The corn earworm, Helicoverpa zea (Boddie), is a polyphagous pest found throughout the United States, where it attacks many field and vegetable crops. Although H. zea has long been a traditional pest of sweet corn, its importance to this crop has increased dramatically over the past two decades. In this review, we summarize information critical for current and future management of H. zea in sweet corn production in the United States. First, we discuss the pest status of H. zea and its life history, including migration, infestation and larval development, diapause, overwintering, and abiotic factors that affect its biology. Next we describe monitoring methods, crop protection decision-making processes, chemical control options, and the use of genetic technologies for control of H. zea Alternative H. zea management options including biological control, cultural controls, host plant resistance, and pheromone disruption are also reviewed. The role of climate change and its effects on H. zea and its ecology are discussed, as well as the recent invasion of its relative, Helicoverpa armigera (Hübner), which is a major pest of corn in other parts of the world. To conclude, we suggest future research opportunities for H. zea and H. armigera management in sweet corn.