Root-knot nematodes are sedentary, soil-dwelling parasites that infect plant roots to disturb their nutrient and water utilization, causing significant yield losses. Avermectin is widely used in the field because of its excellent nematicidal activities; however, it is adsorbed by organic matter near the soil surface, resulting in poor migration in the soil, limiting its field performance. Many organic compound pesticides suffer from the same challenge. Six avermectin B1a (AVB1a) derivatives with phenyl carbamate groups were obtained and found to have increased water solubility and significantly decreased oil−water partition coefficients (K ow ) and soil adsorption coefficients (K f ). Two soil mobility experiments verified that all derivatives could move to a farther location compared with AVB1a. These derivatives could reduce nematode viability, though the nematicidal activities were lower by nearly 1.5−5-fold compared with AVB1a. In the field, the six derivatives exhibited excellent efficacy, 20−30% higher than that of the control compound. This research emphasizes the significance of uniform distribution in the soil by hydrophilic modification with phenyl carbamate that increased the delivery efficiency and bioavailability of the agent, thereby improving its efficacy.
The
fungicide pyraclostrobin is highly toxic to aquatic organisms.
Microencapsulation is an effective way to reduce the exposure of pyraclostrobin
to aquatic organisms but it also reduces the contact probability between
the fungicide and plant pathogens. Hence, winning a balance between
the toxicity and bioactivity of pyraclostrobin is very necessary.
In this study, triethylenetetramine (TETA), ethylenediamine (EDA),
hexamethylenediamine (HAD), and isophoronediamine (IPDA) were selected
as cross-linkers to prepare the pyraclostrobin-loaded polyurea microcapsules
(PU-MCs) by interfacial polymerization. TETA formed the shells with
the highest degree of cross-linking, the slowest release profile,
and the best protection against ultraviolet (UV). In terms of MCs
fabricated by diamines, higher leaking, weaker UV resistance of the
shells was observed with increasing carbon skeleton. TETA-MCs showed
the highest safety to zebrafish (LC50 of 10.086 mg/L),
whereas EDA-MCs, HAD-MCs, and IPDA-MCs were 5.342, 3.967, and 0.767
mg/L, respectively. TETA-MCs had the best long-term disease management,
while the control efficacies of other MCs were higher at the early
stage of disease development. Overall, a balance between the aquatic
toxicities and fungicidal activities of pyraclostrobin-loaded PU-MCs
could be reached through a simple selection of polyamines in the fabrication.
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