CEU Series: Mitigate Pesticide Resistance

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Several questions come to the mind of crop protection professionals as they ready to transverse a given field and scout for potential threats to a crop. Whether it is a field of sweet corn, a block of crisp leafy greens, rows of seedlings just emerging or transplants flowering, the history of previous observations and actions are both considerations that should be made before setting foot in the field.

Knowing what the situation was during the most recent scouting excursion and the consequent decision made is essential to gauging how effective the action taken was and influences the next step to take. Once boots are on the ground and in the field, careful inspection of the crop is another critical component of the decision making process. Only thorough scouting methods like turning over leaves, inspecting blossoms with a hand lens, digging up roots, checking traps, soil moisture and the like can the severity of threats to the crop be determined. A pesticide application may not be needed and therefore can be conserved for future use when actually warranted.

Sometimes, however, a spray is justified and proper identification of pests, diseases and abiotic disorders becomes of the upmost importance to crop protection professionals so they can make the best management decision. Crop consultants and managers rely on scouts to confidently and accurately report what is found standing, crawling, creeping, hopping, flying or trying to hide within the crop. These decision makers depend on scouts to know whether what they find is friend or foe as well as the developmental stage of the crop and potential pest. Frequency of occurrence and spatial distribution within the field are also needed to access the threat to the crop. Consultants and managers can begin to determine the best action to take with such information in-hand.

How immediate the threat of damage to the crop may be plays a significant role in the consideration of a pesticide application or whether another means of management should be implemented. An accurate, complete and timely scouting report allows the examination of alternative measures and appropriate pesticides. Therefore critical inspection of the crop is essential so unnecessary sprays are avoided. This is especially true since there are cases where abnormal looking plants are the result of abiotic factors such as a nutrient deficiency, improper soil moisture, high winds, temperature extremes or herbicide damage. Other times symptoms of a sickly plant may be very similar in appearance but the result different biotic causal agents.

One case in point includes symptoms of distorted new growth commonly seen in peppers. New growers are delving into pepper production as the popularity of fresh farmers and green markets increases. Broad mite damage caused by Polyphagotarsonemus latus is commonly misdiagnosed as virus symptoms or herbicide damage.

Broad mites feed using piercing-sucking mouthparts, which inject a toxin causing leaf petioles to elongate and leaves to become twisted, hardened and shrunken. Their feeding can also result in vegetative and flower buds abscission. The new foliage should be examined thoroughly with a hand lense when such symptoms are discovered. Early detection and treatment will mitigate any impending damage and minimize the use of unnecessary pesticide applications due to an inaccurate identification.

Refer to EDIS publications EENY-183 and ENY-658 for more information on broad mites and thrips management respectively.

Christian F. Miller is a UF/IFAS commercial vegetable production and tropical fruit Extension agent based at the Palm Beach County Cooperative Extension Service office in West Palm Beach, FL.

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