The crop is one of the most important crops under the protected and open environment. The plant is a favourite of many herbivores such as , spidermites, thrips, etc. Quite often, growers have to resort to using pesticides to manage these pests because thetomato plant is not a suitable host for many of the natural enemies; the list of natural enemies that can be used PREDATOR on tomato crops is miniscule. During warm summer months, Encarsia and Eretmocerus work well to control whiteflies, is Tough on but they do not work for winter crops due to lower temperatures and short day lengths. There are few natural enemies available to control pests like whiteflies, spider , and thrips on protected hesperus has shown a high potential to tomato crops in particular and specially during control whiteflies and other pests of greenhouse winter; therefore, growers try to control these pests by using chemicals. tomato crops. It is native and wildly distributed Over the years, these pests have developed in North America and has a big appetite for all resistance against almost all the chemicals registered the pests on a variety of crops. to use in Canada. Because of these difficulties encountered with current IPM systems, introduction of mirid bugs like Dicyphus hesperus can be a valuable tool to add to their arsenal for fighting pests during the winter months.

IMPORTANT PREDATORS, ESPECIALLY IN THE WINTER Milid bugs are important predators of these pests, especially whiteflies. Nine species of mirid bugs BY have been recorded in North America, but only DR. ABIDA NASREEN Dicyphus hesperus has shown a high potential to BELOW control whiteflies and other pests of greenhouse Dicyphus hesperus adult feeding on thrips tomato crops. It is native and wildly distributed in

14 GREENHOUSE CANADA - February 2016 LEFT Dicyphus hesperus adult feeding on whitefly eggs

Similarly, natural enemy producers face challenges including long life cycle, laborious collection process, and high cost of alternative prey food to mass- produce this predator.

RESEARCH HAS LED TO IMPROVED COMMERCIALIZATION Due to these factors, this predator was previously not easily available on me market for use, but researchers have overcome this problem with their extended knowledge of the biology and ecology of D. hesperus. Over the years, they have developed methods to mass-produce this predator at a Norm America and has a big appetite very affordable price for commercial for all me pests on a variety of crops growers. including tomatoes. The most controversial aspect of its Canadian scientists have explored use is that as an omnivorous , D. many facts about D. hesperus, a strong hesperus requires both plants and prey predator, and established information food to complete its life cycle (except about its potential to control insect where the mullein plant is used as a and pests on greenhouse crops, host plant on which it can reproduce including winter crops. It appears to without food). be particularly useful when crops are According to a Canadian scientist grown under lights during me winter (McGregor, 2000), D. Hesperus does months. not feed on fruits, particularly on As a general predator, D. hesperu.s tomato and pepper plants, in the can prey on all stages of whiteflies, presence of leaf material and prey mites, as well as me larvae and and does not damage fruit unless its adults of thrips. Moreover, it predates number increases up to 100-150 per on the eggs and larvae of moths and plant in combination with a shortage It can prey on all stages butterflies. Dicyphus hesperus does of prey: More importantly, all stages of of whiteflies, mites and not undergo obligatory diapause; it D. hesperus can easily move on all parts only undergoes facultative diapause of a tomato plant including parts with aphids; also the larvae which is triggered when the light hours long extensive hair. and adults of thrips, are less than 13 or the temperature To conclude, the use of generalist is below 15 C. The diapause in D. natural enemies can help farmers hesperus is also highly modified develop successful IPM programs by temperature. Under normal that are needed to reduce the use greenhouse conditions, more than of chemicals and insect resistance. 60 per cent of females continuously Moreover, the presence of generalist reproduce during winter months natural enemies in greenhouses can without me use of artificlal hght. provide a first line of defence against Most growers that have tried using invasion. Understanding the D. hesperus are frustrated because of biology and ecology of such predators the long time it takes for it to develop is pivotal for their mass production from an egg to an adult (around six and use in biological control programs. to eight weeks). This causes a delay Dr. Abida Nasreen is director of in D. hesperus response time, which research and development with GrowUv results in an increased pest population. Ud. - www.growliv.com.

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