Search

An alternative approach for suppressing ACP populations which has not been tried before, is the use of pesticidal proteins that are produced by bacteria. The soil-dwelling bacterium, Bacillus thuringiensis (Bt) produces lots of proteins that are insecticidal against certain types of insects. These proteins allow Bt to enter the insect host, divide inside the body of the insect ultimately killing it. Bt is a valuable natural product for insect control and is widely used to control mosquito larvae residing in pools of water, and in organic agriculture for example. Drawing on the use of Bt pesticidal proteins for management of other insects such as the western corn rootworm in maize and the pink bollworm in cotton, researchers at the University of Florida tested multiple Bt pesticidal proteins for toxicity against ACP. To date, we have also produced citrus seedlings that express the Bt pesticidal protein and verified that these can kill feeding ACP. However, the selected Bt pesticidal proteins showed only moderate killing of ACP and by themselves may not represent a major advancement over the efficacy which could be obtained with insecticides. The next step has been to test the effects of the pesticidal protein in combination with gene silencing RNAs. Gene silencing RNAs are small molecules that reduce or block the expression of ACP genes that are essential for survival of the psyllid. Although our project has met several pre-determined milestones with success in a laboratory setting, we recognize that several challenges must be overcome to deliver a field ready technology to growers who need new tools now. We are therefore frequently sharing our results with industry personnel to receive feedback on how to minimize potential regulatory challenges to acceptance of a field ready product. A field ready tool that combines Bt pesticidal proteins with gene silencing RNAs will not by itself solve the problem of citrus greening. We envision this technology to work in concert with an integrated program that simultaneously focuses on plant health and potentially targets the pathogen itself. However, this novel two-pronged approach for managing psyllids is expected to reduce our reliance on insecticides and increase our capabilities in wiping out psyllids on a large scale.

Several studies have documented the positive effects of controlling the Asian citrus psyllid (ACP, Figure 1) for citrus tree health and sustainability in Florida. The mature blocks established before and after the discovery of huanglongbing (HLB) in 2005 continue to benefit from psyllid control. Peer reviewed through UF/IFAS Citrus Research and Education Center; published in Citrus Industry Magazine

Weed management is a crucial component in Florida’s citrus production. Recent research from our group shows that weed management may have pest management benefits for citrus growers in addition to traditionally known horticultural gains. Maintaining a ‘weed-free’ grove and perimeter areas can potentially help improve the management of the Asian citrus psyllid (ACP), the insect vector that spreads pathogens causing HLB.

Getting rid of Asian citrus psyllids (ACP) from your grove is almost like trying to remove the sand off of a beach. You can bulldoze the great majority and make a huge noticeable impact but getting every last grain of sand will be impossible. What makes the prospect of ACP management more complex is that we want to achieve it in a manner that’s both economical, and environmentally sustainable. This article presents a recap of the basic steps that should facilitate the job. Peer reviewed prior to submission through UF/IFAS Citrus Research and Education Center; published in Citrus Industry Magazine January 7, 2020.

Management of the Asian citrus psyllid (ACP) is needed in multiple environments, such as organic and conventional production systems and urban areas. However, the tools and approach may be different depending on the circumstances. Peer-reviewed prior to submission through UF/IFAS Citrus Research and Education Center; published in Citrus Industry Magazine November 13, 2019.

As a practical alternative to chemical controls, development of knowledge-based and efficient biological control strategies to disrupt HLB spread by current technologies (i.e., RNAi) in the ACP vector itself represent our strategy to control the disease without relying solely on chemical applications. The necessity of a precise and specific biological control for Florida ACP populations initiated our ongoing study, with hopes to provide additional molecular tools. In order to decrease or eliminate major dependence on broad-spectrum chemical controls, our study aims to investigate the Florida ACP body (i.e., gut) for identifying an ACP-associated virus with the potential to be manipulated into a biocontrol agent against the HLB insect vector. The endemic establishment of both HLB and the ACP in Florida has greatly increased the need for alternative control options.

The undeniable current facts are that HLB is present in all of Florida citrus production and ACP is endemic and very good at locating and colonizing citrus groves. With the ubiquity of both the disease-causing pathogen and vector, there is no longer a possibly for slowing spread of disease. So, it is logical to ask whether reducing vector numbers is still something that is worth pursuing, given the investment needed in such practice. Collectively, all current research data suggest that reducing psyllid pressure on trees does appear to increase tree health and productivity. Although the biological answer so far does not seem to be as simple and straightforward as the predicted: “more infected psyllids = greater pathogen titer = greater severity of decline”, it does seem to follow a pattern resembling the following: “reductions of psyllid inoculation frequency = improved tree health and yield”. Minimizing the presence of resident psyllid populations in your citrus grove appears to help maintain tree health even if your grove is periodically infested by ACP. This can be accomplished several ways and include insecticides, as well as, cultural and biological methods. An integrated approach will likely be best. This may be good news, because until there are ‘planting ready’ resistant trees, HLB is likely here to stay. Periodic invasions of psyllids will be the norm. It appears that trees can survive these periodic invasions, if we can prevent a standing long-term population from continuously causing both feeding damage and re-circulation of bacteria. The combination of these two forces appears more destructive to trees than either alone.

Citrus growers facing issues from several new diseases and pests. For example, Florida citrus growers, currently struggling with citrus greening (huanglongbing, HLB) and citrus canker diseases, now face a new economic threat from citrus black spot (CBS) disease. The CBS disease reduces the ability of Florida growers to export or move fresh fruit both nationally and internationally. On another example, the Asian citrus psyllid (ACP) is a key pest of citrus in Florida due of its role as a vector of citrus huanglongbing (HLB). There is no known cure for HLB, but vector management has been shown to be critical both for slowing spread of the disease as well as attenuating symptoms in infected trees. Therefore, monitoring the ACP population is an essential component of ACP management, both for application of economic thresholds as well as assessing effectiveness of control actions. For this purpose, the tap sample has proved invaluable and has been adopted by citrus growers. Hence, a more rapid and accurate tool for accomplishing these important pest and disease management goals is needed. Furthermore, almost all of the agrochemicals (e.g. pesticides) applied in specialty crop production are made uniformly with conventional spraying equipment despite that fact that pathogens distribution is typically patchy. Uniform applications result in the use of agrochemicals where no diseases, weeds or pests occur. This unnecessary use of agrochemicals leads to increased costs, risk of crop damage, environmental pollution and contamination of the edible products. The rapid development of new technologies and the changing landscape of the online world (e.g., Internet of Things - IoT, cloud-based solutions) provide a unique opportunity for developing intelligent agricultural systems for precision applications. Technological advances in machine vision, artificial intelligence (AI) and machine learning (ML) enabled the development of intelligent agricultural technologies for precision applications. These technologies can optimize weed, pest, and disease identification and management. In this article, several example of emerging technologies in citrus are presented.

Pest management has always been important for citrus production in Florida. It has become even more critical following invasion of the Asian citrus psyllid (ACP) and citrus leafminer (CLM), due to their association with huanglongbing (HLB or citrus greening) and canker diseases, respectively. Peer reviewed through UF/IFAS Citrus Research and Education Center; published in Citrus Industry Magazine January 31, 2018.

Citrus growers frequently inquire if Florida temperatures in the summer or winter are sufficiently high or low enough to control or suppress the Asian citrus psyllid (ACP). This question is the subject of this short article. The reason growers pose the question about how temperature impacts psyllids is because ACP is a phloem feeder that vectors citrus greening or huanglongbing (HLB). When HLB-infected psyllids feed on the citrus plant, they introduce the bacteria into the tree. The level of HLB spread is directly related to the distribution and population level of the infected ACPs within a given area. Any factors that may suppress or control ACPs would be beneficial to citrus growers to minimize the spread of HLB.