In Maine, potato yield is consistent, 38 t·ha−1, for last 10 years except 2016 (44 t·ha−1) which confirms that increasing the yield and quality of potatoes with current fertilization practices is difficult; hence, new or improvised agronomic methods are needed to meet with producers and industry requirements. Normalized difference vegetative index (NDVI) sensors have shown promise in regulating N as an in season application; however, using late N may stretch out the maturation stage. The purpose of the research was to test Trimble GreenSeeker® (TGS) and Holland Scientific Crop Circle™ ACS-430 (HCCACS-430) wavebands to predict potato yield, before the second hilling (6–8 leaf stage). Ammonium sulfate, S containing N fertilizer, is not advised to be applied on acidic soils but accounts for 60–70% fertilizer in Maine’s acidic soils; therefore, sensors are used on sulfur deficient site to produce sensor-bound S application guidelines before recommending non-S-bearing N sources. Two study sites investigated for this research include an S deficient site and a regular spot with two kinds of soils. Six N treatments, with both calcium ammonium nitrate and ammonium nitrate, under a randomized complete block design with four replications, were applied at planting. NDVI readings from both sensors were obtained at V8 leaf stages (8 leaf per plant) before the second hilling. Both sensors predict N and S deficiencies with a strong interaction with an average coefficient of correlation (r2) ~45. However, HCCACS-430 was observed to be more virtuous than TGS. The correlation between NDVI (from both sensors) and the potato yield improved using proprietor-proxy leaf area index (PPLAI) from HCCACS-430, e.g., r2 value of TGS at Easton site improve from 48 to 60. Weather data affected marketable potato yield (MPY) significantly from south to north in Maine, especially precipitation variations that could be employed in the N recommendations at planting and in season application. This case study addresses a substantial need to revise potato N recommendations at planting and develop possible in season N recommendation using ground based active optical (GBAO) sensors.

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BACKGROUND: The Colorado potato beetle (Leptinotarsa decemlineata Say) is a major agricultural pest of commercial potatoes, partially due to its ability to rapidly develop resistance to multiple insecticide modes of action. Patterns of L. decemlineata insecticide resistance in the contiguous United States have been linked to geographic location and regional management practices. Several previous studies have classified enzymes that are overexpressed following L. decemlineata exposure to commercial pesticides, many of which have been linked to xenobiotic metabolism. Studies have further associated geographic disparities in resistance patterns to cross-resistance driven by fungicide exposure in the East Coast and Midwest.RESULTS: In this study, our objective was to investigate transcript expression of 38 previously classified detoxification enzymes induced by imidacloprid (an insecticide) and chlorothalonil (a fungicide) within five discrete populations of L. decemlineata obtained from areas in the USA representing eastern, midwestern and western production regions. We found unique patterns of transcript expression in different geographic locations, including overexpression of transcripts related to insecticide metabolism within insecticide-resistant populations. CONCLUSION:The results suggest the genetic response of these populations may be partially linked to geographic location and corresponding management practices.

White mold or Sclerotinia stem rot (Sclerotinia sclerotiorum (Lib) de-Bary) was first observed on soybean varieties in a variety trial at the Maine Agricultural and Forest Experiment Station, Presque Isle, and in commercial soybean fields in late July and August 1997. Symptoms and signs included stem bleaching, fluffy white mycelial growth on soybean stems and foliage, and presence of sclerotia typical of white mold. Disease assessment, based on symptoms, was conducted on the varieties in the trial in the experiment station. Field observations on disease occurrence were also conducted in commercial soybean fields in northern Maine. In the variety trial experiment, mean incidence (%) of white mold ranged from 0 to 6.8% on Lambert, APK007, P9092, P9132, and Stine varieties. No white mold was detected on P9071, P9007, Korada, Bravor, Ugo, APK020, and Aquillon varieties. Of the infected varieties, incidence of white mold was detected in 10 of 33 fields examined. This is the first report of the occurrence of white mold on soybean in Maine. Because of large-scale commercial potato production in the region, and previous occurrence of white mold on potato, it is likely that the pathogen is present in soils of various commercial potato fields in Maine. Precautions should, therefore, be taken in introducing resistant varieties and ensuring proper rotation and cropping sequences as soybean production increases in Maine.

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