A Sporadic Pest in the Greenhouse:
The Squash Bug
University
of Florida
Horticultural Sciences Department
Protected Agricultural Project
Drs. Silvia I. Rondon, Daniel. J. Cantliffe, and James F. Price
The Florida/Israeli Protected Agriculture Project (http://www.hos.ufl.edu/ProtectedAg/) is seeking the implementation of biological tactics as part of an integrated pest management program for vegetable crops, including new crops such as Beit alpha cucumber, Cucumis sativus L., and the Galia muskmelon, Cucumis melo reticulatus L. In the spring of 2001, a sporadic pest in greenhouses, the squash bug, Anasa tristis DeGeer (Heteroptera: Coreidae), caused damage in a Beit alpha cucumber trial. Studies were conducted to evaluate two predators, Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae), the pink lady bug, and Geocoris punctipes Say (Heteroptera: Lygaeidae), the big eyed bug, for control of this pest. The early instars of the squash bug were controlled by C. maculata adults, which seem to be more effective than the 3rd instar C. maculata larvae. Thus, the greenhouse vegetable growers may have a viable alternative to pesticides for the control of this pest. Further studies including the use of other predators such as Orius insidiosus Say, or the combination of all predators are still needed. Details of the experiment will be published on an entomological review journal.
General Overview of the Pest
Scientific name: Anasa tristis (DeGeer), Family Coreidae, Order HETEROPTERA (Fig. 1)
Hosts: Squash, pumpkin, cucumber, melon, and other cucurbits.
Fig. 1 The squash Bug, A. tristis, in a Beit alpha cucumber cultivar.
©
Elio Jovicich
Description and Biology: The squash bug is a true bug which utilizes its piercing-sucking mouthparts to remove plant juices. Recently, it has been reported that while feeding, the insect injects a toxic substance into the plant causing a wilting known as “Anasa wilt of cucurbits”. The symptomatology resembles bacterial wilt (www.ohioline.ag.ohio-state.edu) (www.nps.ars.usda.gov/menu.htm?newsid=1667). After wilting, vines and leaves turn brown and crispy (Fig. 2). Depending on degree of infestation, small plants can be killed, while larger plants may survive. Translocation of the toxic substance is systemic.
The ecology and biology of the squash bug has been studied extensively.
Eggs. In open fields, females deposit brownish-red eggs (Fig. 3) in clusters on the lower leaf surfaces of the plants. Eggs are yellowish-brown to brick red. Their size is approximately 1.3 mm long and 1 mm wide. In the greenhouse, a greater number of egg clusters (20 ± 3.3 eggs per cluster) can be found on leaf surfaces mainly on the upper 2/3 of the plant. Depending on temperature, eggs hatch in about 10 days. In our experiment, eggs hatched 8 ± 0.8 days after oviposited. Temperature was kept at 21oC (70oF). Without interference from biocontrol agents, almost 100% of the eggs hatched in unison.
Fig 2. Damage caused by the squash bug on Beit alpha cucumber, C. sativus, grown in a greenhouse in Gainesville, FL.
Fig. 3 Cluster of squash bug eggs in Beit alpha cucumber, C. sativus, grown in a greenhouse in Gainesville, FL.
Nymphs and Adults. Newly emerged nymphs are small and light orange (Fig. 4). Hours later, the cuticle begins to sclerotize and becomes greenish to gray. Nymphs develop through five instars requiring approximately 4 to 6 weeks to reach adulthood at 21oC (70oF). Adult females are bigger than males; males hatch before females. In protected crops, if infestation occurred from mid to late season, bugs are found on border rows. They spread to the center of the crop after they become established.
Fig. 4 Nymphs of the squash bug in Beit alpha cucumber, C. sativus, grown in a greenhouse in Gainesville, FL.
Early detection of adult squash bugs is very important since they could cause considerable damage. Cultural control includes the elimination of debris and leaves that may be potential hiding sites. If only a few vines are infested, growers can collect and destroy the bugs and crush their egg masses. In greenhouses, trap crops could be used. Potted squash plants could be set between rows. Adults will fly from the main crop to feed on the squash plants which then can be removed. Before our observations were made, no effective biological control agents were known; however, we observed in our trials that spiders such as wolf spiders (Arachnida: Lycoseidae) fed upon adults. The early instars of the squash bug can be controlled by early releases of C. maculata adults, which seem to be more effective than the 3rd instar C. maculata larvae. The number of predators needed to provide an effective control is still under study.
Use high pressure when applying insecticides to ensure penetration of the dense plant foliage. Nymphs often are on the undersides of leaves and on tops of the plants. Carbaryl (Sevin®) is listed among the insecticides that could be used in open fields. Spray according to label directions and safety precautions when bugs first appear. Rotenone also is effective on younger bugs, but not the adults (http://edis.ifas.ufl.edu/IN168).
Reference Cited