Subtropical Fruit Crops Research & Education
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Subtropical Fruit Crops Research & Education

Posts Tagged: insecticides

New online course from UC IPM helps growers prevent illegal pesticide residues

UC Statewide Integrated Pest Management Program

The California Department of Pesticide Regulation (DPR) runs the most extensive Pesticide Residue Monitoring Program in the nation and is hard at work ensuring that the fruit and vegetables we purchase and consume are free from illegal pesticide residues.  Just last month, DPR detected residues of a pesticide not registered for use on grapes and fined the grower $10,000 for using a pesticide in violation of the label and for packing and attempting to sell the tainted produce.

Cases like this are rare in California but remind growers how important it is to apply pesticides correctly by following all pesticide label directions. Understanding and following label instructions is the focus of a new online course developed by the University of California Agriculture and Natural Resources Statewide Integrated Pest Management Program (UC IPM).

Proper Pesticide Use to Avoid Illegal Residues is targeted to those who apply pesticides or make pesticide recommendations.  It explains what pesticide residues are, how they are monitored, and highlights important residue-related information from several sections of pesticide labels.  In addition, the course identifies the following as the most important factors leading to illegal residues:

 

  • Using a pesticide on a crop or against a pest for which it is not registered

  • Applying pesticides at an incorrect rate

  • Ignoring preharvest intervals, re-treatment intervals, or plantback restrictions

     

Course participants are presented with several real-life scenarios. They must search through actual pesticide labels to determine if the scenario illustrates proper use of pesticides or if the described situation could potentially lead to illegal residues.

The overall goal of this course is to have participants follow pesticide label instructions when they return to the field. Following the label can eliminate incidences of illegal pesticide use.

Proper Pesticide Use to Avoid Illegal Residues is published just in time for pest control advisers and pesticide applicators who are still a few units short to renew their licenses or certificates with DPR.  The course has been approved for 2 hours of Pesticide Laws and Regulations continuing education units (CEUs) from DPR and costs $40.  If you don't need CEUs, but are still interested in viewing the course content, check it out for free on YouTube.

DPR recommends that renewal packets be submitted before November 1 in order to receive your renewed license or certificate by December 31, as the processing time can take up to 60 days. For additional online courses that UC IPM offers, visit the online training page.

weed label screen
weed label screen

Posted on Thursday, October 13, 2016 at 5:09 AM
Tags: bacteriacides (1), herbicides (15), insecticides (2), pesticides (23)

Organic Control of Asian Citrus Psyllid is Challenging

With the detection of Huanglongbing (HLB) in California in 2012 and 22 additional cases reported during 2015 through June 2016 there is a major concern among citrus growers about the spread of this incurable bacterial disease. The vector of the disease, the Asian citrus psyllid (ACP), is a hardy insect with good dispersal capabilities and can be found in many southern California citrus groves today. With no direct cure for HLB at present, the only option for growers to combat the disease is to control the psyllid. This can prove difficult for conventional citrus growers with broad spectrum insecticides, but for organic citrus growers, which grow an estimated 7% of citrus in California, the task is even more difficult with the currently available options.

Entrust (spinosad) + oil, Pyganic (pyrethrin) + oil, and oil alone are currently the recommended and most widely used insecticide options for organic growers (UC IPM Guidelines for Citrus). While these insecticides are fairly effective in killing ACP if they make direct contact, the residual life of these pesticides is very short (days) compared to conventional insecticides (weeks to months). For example, in our petri dish studies, 10 fl oz/acre Entrust SC + 0.25% Omni supreme spray oil caused 89% mortality, 17 fl oz/acre Pyganic 5.0 EC + 0.25% Omni supreme spray oil caused 73% mortality and 0.25% Omni supreme spray oil caused 42% mortality when 1st-2nd ACP nymphs were exposed to treated leaves one day after application. Nymphal mortality continued to decline for the Entrust + oil treatment (69% mortality) and even more severely declined for Pyganic + oil (27% mortality) 3 days after treatment. In contrast, one-day-old residues of a conventional insecticide, the neonicotinoid 5.5 oz Actara (thiamethoxam), resulted in more than 95% mortality of nymphs and mortality remained high for more than a month.

Studies of grower orchard treatments confirmed laboratory studies that showed a short residual effect of organic treatments (Entrust + oil and oil alone) compared to conventional insecticides (Actara). We monitored changes in population densities of ACP (adults by tap, nymphs and eggs by flush examinations) in the fall of 2015 before and after a grower sprayed separate orchards with one of three insecticides; 1) 1.25% 440 Supreme Spray Oil by ground application (400 gpa), or 2) 9 fl oz Entrust SC + 1% oil by air (50 gpa), or 3) 5.5 oz Actara by air (50 gpa). The oil treatment had little effect on the adult population, but significantly reduced psyllid nymph densities for 17-24 days. Entrust was completely ineffective in controlling psyllid nymphs, but suppressed adult and egg populations for about 14 days. Actara, a conventional insecticide, was the most effective treatment in the study and provided more than 5 weeks of both adult and nymph control. Because of the short residual effect of organic insecticides in citrus, repeat treatments are needed at a frequency of about every 2 weeks for ACP control.  

Tamarixia radiata wasps released for biological control of ACP provide 20% to 88% parasitism depending on geographical location and time of year. If there were no disease to be concerned about, this level of parasitism by Tamarixia would be sufficient to protect citrus from the feeding damage of the psyllid. However, the disease spreads rapidly with just a few psyllids and so a greater level of control is needed. Generalist predators, such as lady beetles, lacewings and assassin bugs, also assist with control. Argentine ants can severely disrupt this parasitism by protecting psyllids from natural enemies. Unhappily, Entrust + oil, thought of as a very selective insecticide combination, was found to be highly toxic to adult Tamarixia wasps exposed to 3 day old residues. Thus, the organic insecticide that is the best for controlling the psyllid pest is not compatible with the parasitoid natural enemy, limiting our ability to use integrated strategies to control the psyllid.

At present, it is not mandatory, but is strongly recommended, that all southern California citrus growers treat their orchards in an area wide manner. The area wide program consists of coordinated treatments twice a year (winter and fall), and additional treatments in between. Due to the short residual nature of organic insecticides, organic applications should be applied twice within 10-14 days of each other for every single conventional insecticide application. This is especially important for younger groves as ACP nymphs thrive in new flush. Organic growers have a tough decision to make between treating frequently for ACP and the high cost associated with those treatments or transitioning into conventional management in order to more effectively control ACP. Additional solutions are needed for organic citrus.

UC IPM Guidelines for Citrus: Asian Citrus Psyllid. http://ipm.ucanr.edu/PMG/r107304411.html

ACP adult and nymph
ACP adult and nymph

Posted on Monday, July 25, 2016 at 4:57 AM
  • Author: Nastaran Tofangsazi and Beth Grafton-Cardwell, Department of Entomology, UC Riverside
Tags: ACP (75), actara (1), Asian Citrus Psyllid (51), entrust (2), HLB (58), huanglongbing (58), insecticides (2), neonicotinoid (1), oil (3), organic (12), pesticides (23), pyganic (1), Tamarixia (5)
 
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