Abstract
Citrus and palm trees’ extracts, commercially formulated as ProAlexin PNSTM and AgrisprayTM, were studied against the pistachio psyllid, Agonoscena pistaciae, in field conditions. Generally, foliage spraying application against the pistachio psyllid may cause severe reduction on the honeybee forager population, which visits infested trees to collect honeydew. ProAlexinTM products have the same formulation with Provigoro 14 WA Bee Care®, a natural water acidifier, which not only has negative action on the honeybees, but also shows disinfectant action against Nosema spp. The scope of the present study was to determine any effect of ProAlexin products on the reduction of the population of the pistachio psyllid, Agonoscena pistaciae. Experiments were performed at the orchard of the A.U.A., with two mixtures sprayed on psyllid infested pistachio trees, the first with ProAlexin PNSTM and AgrisprayTM and the second only with AgrisprayTM. They were both applied with the addition of APG25TM non-ionic surfactant. Results showed that mortality on the trees treated with ProAlexin PNSTM + AgrisprayTM mixture and AgrisprayTM was significantly higher compared with the control. This could be explained due to the phytoalexins that these products elicit, which are part of the plant mechanism against insect herbivores. These products are potentially promising methods to be used in sustainable agriculture approaches against the pistachio psyllid and they should be tested for their effects on the biological control agents of this pest. Beyond this, the results of this study encourage to test their effects on other pests of pistachio and other tree species.
Highlights
Honeydew is a sugar-rich sticky liquid, secreted by insects feed on plant sap
Results showed that mortality on the trees treated with ProAlexin PNSTM + AgrisprayTM mixture and AgrisprayTM was significantly higher compared with the control
The mortality on the trees treated with ProAlexin PNSTM + AgrisprayTM mixture was significantly higher compared with the control (Figure 3)
Summary
Honeydew is a sugar-rich sticky liquid, secreted by insects feed on plant sap. Many piercing-sucking, sap-feeding insects, except for tapping into the phloem of plants, where water transports sugars and other nutrients around the plant, have a filter chamber, a bypass of part of the midgut, to allow excess fluid to be quickly passed through the system. But not all; so insects with a filter chamber tend to excrete copious amounts of fluid, still containing a good deal of sugars and amino acids, but especially sugars. This sugarladen sticky secretion is called honeydew [1]. Honeybees collect the honeydew from the living parts of the plants, transform it by combining it with specific substances of their bodies and deposit, dehydrate, store and leave it in honeycombs to ripen and mature [2]
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