GIVE

Dr. Phil Stansly

Research: Entomology

Our main objective is to conduct novel research on the entomological related problems encounter by producers of the Southwest Florida region. Our research is focused on best management practices (BMP) looking for the most environmentally friendly, yet effective ways to manage insect pests. Citrus and vegetables are the two main components of our research.

Asian Citrus Psyllid
 

Citrus greening disease or “huanglongbing” (HLB) is caused by bacterium Candidatus Liberibacter asiaticus, vectored by the Asian citrus psyllid (ACP), Diaphorina citri. The bacteria are acquired primarily by the immature stage psyllid (nymph) when it feeds and develops on infected trees. Eggs are laid on young flush were nymphs develop to adults which spread the disease. Acquisition by adults occurs but at a much reduced rate. The psyllid was first found in Florida in 1998 and the disease in 2005. Both have spread rapidly throughout the state and are also found throughout Asia and the Neo-tropics. The first sign of infection is often one or more yellow shoots from whence the name huanglongbing in Chinese. Symptoms spread throughout the tree and a gradual decline ensues resulting in dieback, leaf and fruit drop. The process is hastened by continual inoculation by infected psyllids and appears to be mitigated by foliar applications of micronutrients that seem to somewhat compensate for reduced efficiency of the phloem that ultimately impacts the tree’s ability to absorb and transport these materials from the soil.

HLB represents the greatest plant health problem to ever challenge the Florida citrus industry. Vector management is the primary means of slowing spread of the disease from tree to tree and even within trees. Our focus then is on the integrated management of ACP using a combination of tactics aimed at economical pest suppression with minimum impact to beneficial insects and mites. The major elements of this program include the “dormant” spray directed against a declining, overwintering adult ACP population at a time when much of the beneficial fauna is absent from the orchard. Significant reductions of ACP of up to 6 months have been observed following a single application in January. We are also working to improve the performance of systemic insecticides applied to the soil, especially to protect young trees, and other selective alternatives such as frequent, low volume application of horticultural mineral oil. We have also developed a “tap” sampling method for efficiently monitoring pest and beneficial populations to help with decision making during the growing season, and are working with other scientists at University of Florida, USDA-ARS, DOACS-DPI, and several institutions outside of Florida on methods of mass rearing and release of the parasitic wasp Tamarixia radiata and other psyllid natural enemies to reinforce or in some cases reestablish biological control. We are working with the industry toward area wide application of these tactics beginning with a successful cooperative dormant spray program in Southwest Florida during the 2008-09 and 2009-10 seasons. Information on all this and more can be found on this website as part of our strong commitment to actively inform a citrus community in the search of solutions for this and other pest problems that impact citrus production.

Resources

Citrus Leafminer
 

The citrus leafminer is a Gracillariidae moth also known as Phyllocnistis citrella. It was first reported in 1993 from nurseries in south Florida. The moth is approximately 4mm in wingspan. The wings are white with a black spot on the tip of the forewings. The observable damage is inflicted by the larvae, which mines the citrus leaves constructing their characteristic tunnels. The pupa forms a pupal cell usually close to the margin of the leaves. Sue to the size and mobility, adults are difficult to see; however, they ca be found actively flying during the evenings.

The host plants for this species include all citrus and related Rutacea plants. Eggs are laid individually on the abaxial surface of the leaves. When the larvae emerge they get into the leaf and begin to feed forming the characteristic serpentine mines. Older trees (>4 years) can tolerate citrus leafminer damage. Smaller trees can be affected by the distortion of the affected newly growing leaves. In places where canker is a concern, such as Florida, opening left by the emerging adults are considered to be a place where citrus canker can access the plant.

Our lab conducts research on citrus leafminer management using natural enemies and chemical alternatives.

Resources

Silverleaf Whitefly
 

Silverleaf whitefly (SLWF) Bemisia tabaci biotype B, is a small sucking insect (Homoptera) so named for the silvering effect on foliage of squash and pumpkin caused by feeding of the immature “nymph” stage. Another physiological disorder caused by nymphal feeding of SLWF is tomato irregular ripening that caused major losses during the 1988 and 1989 seasons. Biotype B is an invader from the Old World first detected in Florida in 1986 following a whitefly explosion in greenhouse poinsettias that quickly spread to vegetable fields and eventually to a large number of agronomic and horticultural crops. A native biotype or race of B. tabaci had been known in Florida since the late 1800’s but had a limited host range and caused few problems. By 1989 the previously unknown tomato mottle virus (ToMoV) vectored by the whitefly had appeared and spread through tomato fields in south Florida, soon to be followed in 1995 by the more severe tomato yellow leafcurl virus (TYLCV) first seen in the Middle East. More recently, three new whitefly-borne viruses have appeared in cucurbit crops in Florida, the most severe, squash vein yellowing virus (SqVYV) also previously unknown and causing watermelon vine decline that devastated that crop in the early years of the present century.

All these problems have earned SLWF the dubious honor of key pest in fruiting vegetables throughout the southern tier of the state, often spreading north to Georgia and beyond. An early breakthrough in SLWF management was the realization that a host free period, especially in summer was key to successful management of the pest and associated viral diseases in South Florida. Prompt crop destruction and field sanitation to eliminate hosts of whiteflies and viruses for at least 3 generations serves to reduce inoculums sources and provide a clean start the following season. Insecticidal control, especially with the systemic “neonicontinoid” insecticides has also been a powerful tool with which to manage whiteflies, but is under constant pressure from selection for insecticide resistance that continues to increase. We are constantly testing new products as they appear as well as urging growers to conserve those they have by rotating modes of action and refraining from unnecessary use. We are also conducting an active program of research in biological control and have had good success controlling whiteflies as well as thrips and broadmites in eggplant and to a lesser extent pepper using the commercially available predaceous mite Amblysieus swirskii. We believe that biological control offers a safe and effective alternative in these and other crops such as cucumber that can serve to reduce pressure on key insecticides that are needed in more difficult to manage crops such as tomato.

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Professor, Entomology