Documenting Potential Sunn Hemp (Crotalaria juncea L.) (Fabaceae) Pollinators in Florida

Monocrotaline presence in the Crotalaria (Fabaceae) plant genus and its influence on arthropods in agroecosystems

Abstract Crotalaria (Fabaceae) occurs abundantly in tropical and subtropical regions and has about 600 known species. These plants are widely used in agriculture, mainly as cover plants and green manures, in addition to their use in the management of phytonematodes. A striking feature of these species is the production of pyrrolizidine alkaloids (PAs), secondary allelochemicals involved in plant defense against herbivores. In Crotalaria species, monocrotaline is the predominant PA, which has many biological activities reported, including cytotoxicity, tumorigenicity, hepatotoxicity and neurotoxicity, with a wide range of ecological interactions. Thus, studies have sought to elucidate the effects of this compound to promote an increase in flora and fauna (mainly insects and nematodes) associated with agroecosystems, favoring the natural biological control. This review summarizes information about the monocrotaline, showing such effects in these environments, both above and below ground, and their potential use in pest management programs.

Effects of Fabaceae and Poaceae Pollen Accessibility and Traits on the Pollinivory of Adult Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae)

Pollen is a food source for adult Chrysoperla externa (Hagen), whose larvae are biocontrol agents against pests. However, adults may face challenges in foraging for pollen due to differences in pollen accessibility and variability in pollen morphology and chemistry. In the laboratory, we investigated the ability of adult C. externa to consume pollen from flowers of Cajanus cajan, Canavalia ensiformis, Crotalaria juncea, Flemingia macrophylla, Avena strigosa, Pennisetum glaucum, Sorghum bicolor, and Zea mays, and we explored whether adults chose any of these pollens based on their quantitative and qualitative features. Cajanus cajan and F. macrophylla pollen were the only ones not consumed by adults when confined to flowers. Pollen removed from the preanthesis buds was offered simultaneously for 24 and 48 h. In both periods, adults consumed more of the medium-sized P. glaucum (with the second largest exine thickness) and large-sized Z. mays (with the thinnest exine) pollen, even though they had significantly less crude protein than Fabaceae pollen, whose sizes varied from medium (C. juncea, with the thickest exine) to large (C. ensiformis, whose exine thickness was equal to that of P. glaucum). Overall, adults consumed more Poaceae pollen than Fabaceae pollen, but the palynological features and the protein contents did not affect this choice. Our results highlighted that C. juncea, P. glaucum, S. bicolor and Z. mays are good pollen sources for adult C. externa and should be considered promising candidates in the selection of insectary plants to deploy in biocontrol programs aimed at the conservation of this lacewing.

Sorghum cover crop and repeated soil fumigation for purple nutsedge management in tomato production

BACKGROUND

Purple nutsedge (Cyperus rotundus L.) is one of the most common and troublesome weeds. Field research trials were conducted in Florida to evaluate the effects of repeated fumigation and a sorghum sudangrass [Sorghum bicolor S. bicolor var. sudanense (Piper) Stapf.] cover crop on purple nutsedge (Cyperus rotundus L.) populations over time in tomato (Solanum lycopersicum L.) production.

RESULTS

Among the soil fumigants, DMDS + metam potassium was consistently the most effective treatment in terms of in-crop purple nutsedge control. Plots with a sorghum cover crop during the fallow period exhibited higher purple nutsedge density during the tomato growing season as well as higher purple nutsedge shoot and tuber densities during the fallow period compared to the chemical fallow.

CONCLUSION

DMDS + metam potassium was the most effective fumigant for purple nutsedge control. Unexpectedly, a sorghum cover crop during the fallow period was less effective than chemical fallow for purple nutsedge management, and therefore we do not recommend the use of sorghum cover crops for weed management in fields where purple nutsedge is the major weed species.

Agro-Ecological Management of Coffee Pests in Brazil

Coffee plants host several herbivorous species, but only few are considered pests. Brazil is the largest coffee producer of the world, and the two key coffee pests of the crop in the country are the coffee leaf miner Leucoptera coffeella and the coffee berry borer Hypothenemus hampei. However, in some regions or on specific conditions, species of mites and scales can also cause damage to coffee plants. Conventional management of coffee pests relies on chemical pesticides, and it is the most commonly used strategy in Brazil, but environmental problems, pest resistance, and toxicity-related issues have led coffee growers to search for alternatives for pest control. Agro-ecological strategies suitable to coffee cultivation can be adopted by farmers, based on plant diversification, in order to provide resources for natural enemies, such as nectar, pollen, shelter, microclimate conditions, and oviposition sites, thereby promoting conservation biological control. Here I revise these strategies and report the results from research in Brazil. I include results on agroforestry, use of cover crops, and non-crop plant management. These are complemented by curative measures based on the use of organic farming-approved pesticides that can be employed when the agro-ecological practices are not yet consolidated. I also present the cultural control method used by several coffee producers in Brazil to decrease coffee berry borer damage.

Long-term effect of fumigation and a sorghum cover crop on broadleaf and grass weeds in plastic-mulched tomato

BACKGROUND

Broadleaf and grass weeds can adversely affect growth and productivity of plastic-mulched tomato (Solanum lycopersicum L.). Two, four-year research trials were conducted in Florida to evaluate the effect of repeated fumigation and chemical fallow versus a sorghum [Sorghum bicolor S. bicolor var. sudanense (Piper) Stapf.] cover crop on broadleaf and grass weeds in tomato plasticulture.

RESULTS

1,3-Dichloropropene (1,3-D) + chloropicrin (Pic), dimethyl disulfide (DMDS) + Pic, and DMDS + metam potassium effectively controlled broadleaf weeds in-crop and reduced densities by 79-98% compared to the non-fumigated control but provided inconsistent control of grass weeds. DMDS + metam potassium was generally the most effective fumigant. During the fallow period, a sorghum cover crop effectively reduced broadleaf weed density than the chemical fallow, while chemical fallow effectively reduced grass weed density than the cover crop. The fallow program did not affect in-crop densities of broadleaf and grass weeds. In some measurements, the evaluated fumigants resulted in taller tomato plants and higher yield compared to the non-fumigated control.

CONCLUSION

We conclude that the evaluated soil fumigants effectively control broadleaf and grass weeds. Planting a sorghum cover crop effectively suppresses broadleaf weeds but not grasses during the fallow period. However, this suppression does not result in reduced weed density in-crop despite the fact that similar weed species were observed in both time periods. © 2020 Society of Chemical Industry.

The genetic characterization of fall armyworm populations in Ecuador and its implications to migration and pest management in the northern regions of South America

The fall armyworm (Spodoptera frugiperda) is a moth pest native to the Western Hemisphere that has recently become a global problem, invading Africa, Asia, and Australia. The species has a broad host range, long-distance migration capability, and a propensity for the generation of pesticide resistance traits that make it a formidable invasive threat and a difficult pest to control. While fall armyworm migration has been extensively studied in North America, where annual migrations of thousands of kilometers are the norm, migration patterns in South America are less understood. As a first step to address this issue we have been genetically characterizing fall armyworm populations in Ecuador, a country in the northern portion of South America that has not been extensively surveyed for this pest. These studies confirm and extend past findings indicating similarities in the fall armyworm populations from Ecuador, Trinidad-Tobago, Peru, and Bolivia that suggest substantial migratory interactions. Specifically, we found that populations throughout Ecuador are genetically homogeneous, indicating that the Andes mountain range is not a long-term barrier to fall armyworm migration. Quantification of genetic variation in an intron sequence describe patterns of similarity between fall armyworm from different locations in South America with implications for how migration might be occurring. In addition, we unexpectedly found these observations only apply to one subset of fall armyworm (the C-strain), as the other group (R-strain) was not present in Ecuador. The results suggest differences in migration behavior between fall armyworm groups in South America that appear to be related to differences in host plant preferences.