Insect UpdateInsect Ecology in Controlled Environments The Ohio State University/OARDC, Wooster canas.4@osu.edu Aphids and their control (see it in pdf) Recently there have been reports of aphid activity in different facilities. During this time of the year aphids can become problematic as the temperatures rise and they become active. Here I include general information about them and their control. Identification. Aphids are common pests of greenhouses and they include the green peach aphid (Myzus persicae), the melon/cotton aphid (Aphis gossypii), the chrysanthemum aphid (Macrosiphoniella sanborni), the rose aphid (Macrosiphum rosae), the potato aphid (Macrosiphum euphorbiae) and the foxglove aphid (Aulacorthum solani). From these, the most common aphid found on greenhouses is the green peach aphid ( Figure 1 ). Aphids can be easily recognized by their cornicles (tailpipes at the end of the abdomen; Figure 2 ). However, these characteristics need to be seen using a hand lens. Proper identification is important when selecting management options. Aphids can become a serious pests because they can transmit viruses, and can contaminate plants with the honeydew they excrete. Females of many aphid species do not need to mate to reproduce. Some aphids have wings. As aphids increase in size they shed their exoskeleton, leaving white cast skins that can sometimes be confused as whiteflies. Aphid Cycle and Damage. Most aphids found in greenhouses are females that produce live young. As such they do not produce eggs. The immature aphids are called nymphs. Aphids have a very high reproductive capability and each female can produce between 50 and 200 offspring over her life span of about one month. All offspring are females and they usually begin producing more offspring after 7 to 10 days. Adult aphids may or may not have wings. The number of winged forms increases depending on population density. Monitoring. It is very useful to monitor sticky cards for presence of winged aphid adults. However, most aphids do not have wings, therefore is really important to inspect plants, especially those that are know to be susceptible to aphid attack. Look for aphids on stems and leaves, particularly on the undersides. As plants mature, more attention need to be placed in monitoring buds and flowers since aphids prefer them. Other signs of aphid presence include leaves covered with honeydew aphid cast skins. Adults can be monitored by using sticky traps throughout the growing zones. To find nymphs it is necessary to monitor the plants. Control. It is useful to screen windows and doors to prevent aphid entrance. To successfully control aphids it is important to discover their presence before the populations grow out of hand. Monitoring is key as aphids can reach high numbers in a very short time. Sanitation and weed control are very important to limit the availability of alternate food sources. Covering greenhouses with plastic that block UV light at wavelengths below 380 nm might reduce the numbers of aphids found. For commercial operations the following options are available: Biologicals: Predators 1- Lacewings (Chrysoperla rufilabris): These insects are available from commercial biological control companies as eggs or larvae. They also feed on other insects such as mealybugs, scales, spider mites and thrips. 2- Predatory Midge (Aphidoletes aphidimyza): This insect is commercially available and is sold as adults, which need to be released in the greenhouse. The adult lays eggs near aphid colonies and the offspring (larva) feeds on aphids. Parasitoids. When using parasitoids to control aphids, it is important to properly identify the aphid causing problems, as the wasps that are available commercially are very species specific. 3- Aphidius colemani: This insect is a parasitic wasp that is commonly used to control green peach and melon aphid. The wasp lays an egg inside the aphid, develops into a larvae, finally producing a new wasp. When the wasp exits the aphid body, it leaves the carcass of the aphid in the form of a brown shell called an aphid mummy ( Figure 3 ). 4- Aphidius ervi: This species is used to control potato aphids. This parasitic wasp is bigger than Aphidius colemani. Examples of Distributors of Biological Control Agents: 1- Koppert Biological Systems, Inc 2- Plant Products USA. Representative of Biobest Biological Systems 3- Agrobiologicals 4- Rincon Vitova Pesticides: When high populations are observed it might be necessary to treat the plants with some insecticides. Always remember to rotate products from different mode of actions groups (see Volume 11; Issue 1; February 2004 from the following address Some suggested products follow (MOA = mode of action group):
* Might be available during the summer 2004. |
