The recent appearance of the disease known as huanglongbing (HLB) in Colombia has caused the demand for alternative control methods for Diaphorina citri (i.e., the disease vector). Specifically, the use of nutrients, such as calcium (Ca), potassium (K) and silicon (Si), may provide some degree of plant defense against herbivory. One set of experiments (in the form of two separate experiments) was conducted on two different farms in the municipality of Jerusalén to study the effects of foliar and soil applications of nutrients (Ca, K and Si) on controlling the population dynamics of Diaphorina citri. Tahiti lime trees were treated as follows: i) untreated trees (absolute control); ii) clothianidin at a dose of 50 g active ingredient per hectare (chemical control); iii) Ca, K and Si foliar applications (at doses of 3 mL, 3 g and 2 mL of the commercial compound used per liter of H2O, respectively); and iv) soil application of potassium nitrate and potassium silicate (1 kg of commercial fertilizer per tree). Foliar sprays were carried out at 0 and 4 weeks after treatment (WAT) began; meanwhile, soil fertilization occurred at the beginning of the trial (i.e., 0 WAT). The results showed that differences were observed only in adults at 7 WAT, and the foliar calcium and silicon applications resulted in the lowest number of individuals (i.e., 1.13 per flush) compared with untreated trees (i.e., 3.13 per flush). The foliar clothianidin, Ca, Si and K sprays also affected the total number of nymphs. Additionally, Tahiti lime trees treated with either silicon or insecticide had fewer eggs than did trees in the other treatments. The use of these mineral nutrients showed a similar efficacy when compared to clothianidin, indicating that these mineral nutrients can enhance plant resistance. These observations suggest that foliar applications of K, Ca and Si could be considered as complementary tools within an integrated management program for D. citri in Colombia.
Distribution and Biology of the Invasive Weed Parthenium hysterophorus L. in Israel
