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Smart Gardening
by Dr. Ayanava Majumdar - posted 03/22/18

(Fig. 1) Details of a sticky wing pheromone trap that can be used to monitor insect pests in farm and garden. The top and the replaceable sticky bottom are held in place by wire hangers. Attractant lure is the piece of red rubber seen in the picture.


Integrated pest management or IPM is a smart way of managing insect pests for economic and environmental benefits. IPM starts with the timely detection and correct identification of pests, leading to intervention using multiple control tactics. Insect traps can be used as a tool for timely pest detection and decision-making in home or commercial settings. Pheromone traps (Fig. 1) are devices that attract and hold insects for periodic observations. Pheromone traps are available commercially from many vendors in the United States, and the cost of traps and lures have dropped considerably in the last decade. The advantages of pheromone traps include nontoxicity, environmental friendliness and ability to detect insects at very low densities. However, the problems with pheromone traps are they only capture flying insects and trap counts do not indicate real crop damage. Despite the disadvantages, pheromone traps answer the question often asked by gardeners: What insect should I look for while scouting and when? This article is based on the results of an insect pest monitoring/crop scouting project recently completed in Alabama. Since the new findings correspond to the previous work done in neighboring states, this article should serve as an important reminder for gardeners across the South to follow recommended scouting procedures and insect management tactics.

(Fig. 2) Fall armyworm activity in vegetable farms monitored using pheromone traps, Alabama, 2010. Note the differences in trap catches between organic and conventional farms.

(Fig. 3) Tobacco budworm (moth) activity on vegetable farms monitored using pheromone traps, 2010. Budworm activity was high in conventional as well as organic farms.

(Fig. 4) Season-long activity of squash vine borer on two organic vegetable farms in north (Marshall County) and south Alabama (Dale County), 2010. Note the high pest pressure detected using sticky wing pheromone traps.


Lessons from the Insect Monitoring Project
In 2009 and 2010, the Alabama Cooperative Extension System conducted a season-long insect monitoring project for pests listed in Table 1. About four organic farms also participated in the program, where small farmers were trained in the proper deployment of insect monitoring systems for IPM decision-making. The project also trained several Master Gardener volunteers in pest identification and management. In two years, this special initiative captured over 8,400 moths from 22 vegetable fields and gardens. The numbers in Table 1 provide evidence regarding the basic pest pressures in Alabama that follows trends seen in adjoining states.

Gardeners can conduct season-long monitoring of insect pests and also determine the migration path of major pests using pheromone traps. Some of the major insect pests monitored in this project had earlier-than-usual peak flight or mating in 2010, e.g., the armyworms and the squash vine borer. This was probably due to the extremely dry conditions that prevailed in early and midsummer. Plant stress due to drought conditions makes them attractive to insect pests; for example, armyworm female moths are known to prefer stressed plants for egg laying.

Other major pests of vegetables include the tomato fruitworm and tobacco budworm, beet and fall armyworm, cabbage and soybean looper. These insect pairs are closely related to each other and caterpillars are difficult to identify in the field. The tomato fruitworm, also known as the corn earworm, routinely attacks row crops as well as horticultural crops, causing economic losses. The caterpillars of the tobacco budworm appear fuzzier than the tomato fruitworm caterpillar due to greater number of microspines and hair on the body. The moths of the budworm and fruitworm are easier to distinguish with or without the use of insect traps. Fall armyworm is a dark brown or grayish caterpillar with an inverted Y mark on the head. The beet armyworm is a greenish caterpillar with a pair of black dots behind the head. Since moths are always first to arrive in your vegetable garden for egg laying, there is a lag-period between the detection of moths with traps and the presence of hungry caterpillars on suitable host plants. Thus, pheromone trapping in backyard gardens provides time to react after detection of moths.

 

Insect 2010 Trap catches No. of sites 2009 Trap catches No. of sites Peak moth activity
Beet armyworm 978 15 606 7 July, August
Fall armyworm 733 15 674 7 July, August
Southern armyworm 46 13 167 4 August
Tomato fruitworm 120 15 290 7 July
Tobacco budworm 150 15 71 7 August
Lesser cornstalk borer 2307 15 715 1 July, August
Cabbage looper 274 15 83 3 August
Soybean looper 181 15 100 1 August
Corn rootworm 65 5 200 6 June, July
Squash vine borer 605 15 - - May, June, July
Tomato pinworm 54 15 4 6 August
TOTAL 5563   2910    

 

Can Organic Practices Affect Insect Populations?
Organic and sustainable vegetable production methods, incorporating the use of diverse cropping systems, improved crop varieties and crop rotations, can reduce pest pressures significantly. For example:

• Armyworm activity was found to be lower in organic farms compared to a conventionally-managed farm (Fig. 2). Armyworm activity on vegetables depends on the local climatic conditions. Noticeable caterpillar feeding may be seen when 10 or more moths are captured in sticky wing traps per week.

• Tobacco budworms generally occur in mixed populations with the tomato fruitworms; caterpillars of the latter species can be seen feeding with part of the body inside the feeding hole. In 2010, budworm activity was higher in the organic production system than on conventional farms (Fig. 3), meaning that this insect is highly adaptive to different farming practices.

• Squash vine borer is another pest of concern for many gardeners; organic gardens may have a high population of borers in the soil (Fig. 4). Squash vine borers overwinter as larvae or pupae, so soil preparation in the garden is critical to prevent population buildup of this species. Gardeners can monitor vine borer moth activity by using pheromone traps and then using some mechanical tactics such as row covers and manual removal of larvae if vines are infested. General use pesticides do not provide adequate protection against this insect.

Although the research above has been done in Alabama, this information should be encouraging to gardeners in other states. Thus, organic vegetable production can lead to long-term ecological benefits.
 

Brown stink bug (Euschistus servus) on okra fruit in a vegetable garden. • Squash vine borer • Tobacco budworm moth


How to Correctly Use Pheromone Traps
Gardeners should purchase pheromone traps from reliable sources, e.g., Great Lakes IPM, ARBICO Organics, Scentry Biologicals, Trécé, Suterra, etc. Purchase sticky wing traps and lures as part of a kit containing plastic tops, sticky bottoms and wire hangers. You can purchase trap kits for monitoring some specific pests that routinely invade your vegetable crops. Only one lure should be used per trap; do not attempt to trap multiple pest species with one trap. Place the active traps at a distance from the actual plot and change the lure every week (more frequently if insects are at peak activity). Hang the traps on metal or plastic poles; do not hang the traps from trees in order to avoid attracting birds and rodents to the trap. Plastic wing traps are very easy to assemble and maintain. Make sure to check traps after a major rain or storm event to replace the lure (lure degrades faster in high heat and moisture conditions). Purchase adequate quantities of wing trap sticky bottoms and lures to last you one full season. The sticky trap bottom can be photographed and stored in self-sealing bags for future reference.


Beet armyworm moth


KEY TO SUCCESS IN YOUR BACKYARD
Early detection of pests is critical to successful backyard vegetable production. Pheromone traps can be used to monitor insect pest activity throughout the season and to correctly time control efforts. Stressed plants suffer more from pest attack than normal plants, so be sure to provide the right conditions for your vegetable plants. Gardeners should avoid unnecessary pesticide sprays because chemicals disrupt the activity of beneficial insects and pollinators. Always read the pesticide label before spraying. When in doubt, seek help from extension personnel in your state.

 

A version of this article appeared in a March 2011 print edition of State-by-State Gardening.
Photography courtesy of Dr. Ayanava Majumdar.

 


Ayanava Majumdar (Dr. A) is Extension Entomologist at the Alabama Cooperative Extension System (Auburn University) and the State Coordinator for Sustainable Agriculture Research and Education. Please contact the extension service in your state before using the information provided herein. Funding for this IPM project was provided by grants from the USDA-NIFA Extension IPM and the Alabama Specialty Crops Programs.